L.W. Murdock, J.H. Herbek, J.R. Martin, and J. James
No-till wheat production has been practiced in Kentucky for many years. Currently, between 25 and 30 percent of the wheat acres in Kentucky are no-till planted. Many farmers remain skeptical of the practice and feel significant yield is sacrificed with the practice.
Previous research in the 1980s by the University of Kentucky showed favorable results. With these conflicting reports and experiences, the Kentucky Small Grain Growers Association entered into a cooperative effort with the University of Kentucky to take an intensive look into no-till wheat.
A replicated trial was established on a Huntington silt loam soil at Princeton, Kentucky, in the fall of 1992. Two small adjacent fields were placed in a three-crop, two-year rotation of corn, wheat, and double-cropped soybeans. Both no-till and conventionally tilled (chisel-disk) wheat were planted and compared with different nitrogen, fungicide, and herbicide treatments. The corn and double-cropped soybean crops were planted no-till. Stand counts, weed control ratings, disease, and insecticide ratings, as well as yield and compaction results, were obtained for wheat. The long-term effects of the two different wheat tillage practices on the succeeding soybean and corn crops and on soil changes were also measured and are included in another report.
Seven years of results (1993-99) are presented in this report.
Yields. The seven-year average yields have been high (Table 1). The conventional till-planted wheat averaged about 5 bu/A more than the no-till wheat. The yields of no-till wheat have been significantly lower than wheat planted with tillage three of the seven years, due to compaction one year (1993) and freeze damage in 1996 and 1998. The yields of no-till wheat have been similar or exceeded that of conventionally tilled wheat the other four years.
|Table 1. Summary of seven-year wheat results (1993-99).|
|Treatment Comparison||Yield (bu/A)||Wheat Stands (plants/sq ft)|
|Nitrogen Rate (lb/A)|
|No-Till Fall Gramoxone + Spring Harmony Extra||90|
|No-Till Fall Harmony Extra||90|
|No-Till Spring Harmony Extra||88|
Stands. The number of emerged plants was lower with no-till. Planting at the rate of 32 viable seeds/sq ft, the final stands averaged 26 and 29 plants/sq ft for no-till and conventional till, respectively. Both stands were high enough for maximum yields. Seeding rates may need to be increased by 10 percent as one moves from conventional till to no-till seeding.
Nitrogen Rates. No-till wheat may require more nitrogen than conventional-tilled wheat. Nitrogen in this trial was managed for intensive production with one-third applied at Feekes stage 3 (February) and the remainder at Feekes stage 5 (mid-March). The no-till wheat sometimes appeared to be slightly nitrogen deficient before the second application, but in most years this had little effect on yield. Increasing the nitrogen rate from 90 to 120 lb/A had only a small effect on yield for the seven years (Table 1). Although more nitrogen is recommended for no-till plantings, it may not always be justified. The years that the high rate of nitrogen resulted in higher yields were when late winter freezes resulted in wheat damage and when excessive amounts of rain fell after the first application of spring nitrogen.
Weed Control. Good weed control was obtained in no-till wheat by three treatments: 1) Harmony Extra applied in the fall, 2) a contact herbicide at planting plus Harmony Extra in the spring, and 3) Harmony Extra in the spring (Table 1). Yields were equivalent for all three herbicide treatments. Wild garlic, which is sometimes associated with no-till wheat, was not a significant problem when Harmony was used. Without fall or spring herbicides, weed competition was a problem (especially with common chickweed and henbit) and resulted in lower yields (no-till check).
Nitrogen Application Time. The last four years (1996 and 1999) have included treatments with different rates of nitrogen applied at different times. The first two years, the highest yield has been obtained with a 120 lb/A nitrogen rate, with half of the nitrogen applied in February and the remaining half applied in late March just prior to jointing. The last two years there has been no effect related to time of nitrogen application.
Fungicides. Preventative disease control applications of fungicides were managed for intensive production. A control treatment receiving no fungicide treatment was included the first five years of the study in both tillage systems. Diseases that can be controlled by a fungicide were of no significance during the five years of this study. Therefore, fungicide applications had little effect on either tillage system (data not shown).
Insects. Insects were monitored by use of scouting and traps. No significant insect infestations occurred. A few aphids, true army worms, and cereal leaf beetles were present but never approached the economic threshold. The wheat seed was treated with Gaucho before planting for Barley Yellow Dwarf protection from 1993 through 1996, and all treatments have received a fall foliar insecticide after 1996. In the first year, Barley Yellow Dwarf was present and was vectored by a small number of aphids.
Diseases. There was no significant disease on any treatments during the seven years except for Barley Yellow Dwarf during the first year. This is consistent with no yield increases from the use of fungicides found during the first five years. Also, head scab, which is sometimes associated with no-till, was practically absent. The Barley Yellow Dwarf Virus symptoms were significantly higher in the no-till treatments the first year of the trial (1993). This was probably one of the factors that reduced yields in the no-till plots that year.
Soil Compaction. Corn harvest on a wet soil prior to wheat planting left a compacted and depressed zone in each plot the first year (1993). This was removed with tillage in the conventionally tilled wheat but caused decreased yields in the no-till planted wheat. There has been no evidence of its continued effect after the first year.
No-till wheat can produce as well as conventionally tilled wheat when properly managed. Stand establishment and weed control appear to be where the greatest changes in management are necessary.
L.J. Grabau, J.H. Grove, and C.C. Steele, University of Kentucky; P. Needham (Opti-Crop); D.S. Jones and K.S. Van Sickle (Wheat Tech)
In 1997, the Kentucky Small Grain Growers Association established the goal of having 75 percent of the state's wheat acreage managed using no-till methods by the year 2005. Before that dramatic change can occur, producers must be convinced that they will not have to sacrifice short-term economic viability in order to gain the long-term benefits of topsoil conservation attainable using no-till methods. Hence, this project's goal was to compare some tillage (ST) and no-tillage (NT) wheat-production systems, both under intensive management, for profitability.
Table 1 compares the two tillage systems. Yields, on average across the seven tests, were 3.0 bu/A higher for ST, resulting in $8.60 greater value per acre. Tillage and stalk chopping cost an average of $25/A for ST, while extra seed, herbicide, and N fertility cost an average of $14.80/A for NT. On the whole, this resulted in a slight economic advantage ($1.60/A) for NT methods.
The footnotes for Table 1 discuss some assumptions made in this analysis. Most importantly, no dollar benefit was assigned to the topsoil saved by NT methods. Of course, another year's data could dramatically change the above profit comparison. Market price changes could help to some extent; for example, if the market price had been $4/bu across the 1998 and 1999 seasons, the comparison would have shown a $1.80 advantage for ST.
We plan to repeat this study at four locations in the 1999-2000 growing season to assess this tillage comparison under different environmental conditions. To this point, our results appear to provide some incentive for growers to consider moving toward a no-till system. However, we do note this caution: The previously funded on-farm tillage comparisons in the 1996-97 growing season resulted in an average of 65 bu/A for ST and 58 bu/A for NT. These grower-managed tests produced 12 percent less grain under NT management, while our 1997-99 consultant- (or researcher-) managed tests only produced 4 percent less grain under NT management. It appears that no-till may respond to more careful management than some growers have been willing to implement.
Based on our work to this point, it looks as if the slight yield loss for NT wheat production is more than covered by the savings producers would have in tillage costs. We are planning to continue this work for the 1999-2000 wheat production season.
|Table 1. Economic summary of on-farm tillage comparisons funded by KySGGA/KySGPB in 1997 through 1999.|
|Test||Managed by||ST Advantage||Additional ST Costs||Additional NT Costs||Net ST Benefit|
|Yield||Value||Residue Mgmt||Tillage||Seed||Herbicide||N Fertility|
|Notes and Assumptions for Table 1
1. Abbreviations: ST, some tillage; NT, no-tillage; OC, Miles Opti-Crop; UK, University of Kentucky; and WT, Wheat Tech.
2. Expenses that were in common were not considered in this analysis, as the goal of the project was to compare economic advantages of the two tillage systems.
3. No economic credit was given for the long-term economic advantage likely to result from use of no-tillage methods (through the conservation of topsoil).
4. No economic credit was given for the potential benefits of no-tillage methods to rotated corn and soybean crops.
5. We assumed that neither test weight nor harvest moisture was influenced by tillage system.
6. Both ST and NT were managed to optimize their profitability rather than to obtain the highest possible yields.
7. Specific practices employed (for example, the type and number of tillage passes) at test locations are available from the author.
8. Each location included two varieties and two replications. Calculated yield differences between tillage systems are assumed to represent real differences.
9. In five of the above tests, the later maturing variety produced higher yields than did the earlier maturing variety (within a given location). Rather than picking the better variety to paint this economic collage, we averaged across the two (to make our conclusions more supportable).
10. These data should be interpreted with some caution, as environmental conditions in coming seasons could clearly affect the outcomes of the two tillage systems. (However, some management considerations may have already helped buffer NT wheat from winterkill; for example, none of these seven tests were planted in early October, and that may have helped account for the similar survival of most NT tillers in the face of a severe spring freeze in early March 1998.)
11. In 1998, we used a market price of $2.90/bu. The income deficiency payment for 1999 tests brought the value of the 1999 crop to $2.80/bu.
12. No adjustments were made for differing speed of operations; for example, ST was not penalized for slightly slower combining, nor was NT penalized for slower speeds while drilling the crop.
The objective of this research is to determine whether the optimal N fertilizer rate for no-tillage wheat will be different among several fertilizer N sources or due to the residues of the previous crop. No-till wheat was grown after both full-season soybean and corn. The fertilizer N sources were urea, ammonium nitrate, and urea-ammonium nitrate solution (UAN). The UAN was applied with either broadcast or "stream jet" nozzles.
The experiment was located at the Spindletop experimental farm, located outside Lexington, Kentucky. The soil was a Loradale silt loam, which is a well-drained soil high in organic matter and general fertility (Mollisol). The wheat (cv. Pioneer 2540) was seeded in the fall of both 1997 and 1998 at a rate of 40 seeds per square foot using a Lilliston 9680 no-till drill. A burndown herbicide was applied prior to planting both corn and soybean. The fertilizer N sources were applied at rates ranging from 0 to 135 pounds of N per acre. The N was all applied in the spring and was split into two applications (33 percent at greenup and 67 percent just prior to formation of the first node). Fungicides were applied to control fungal diseases each year. The grain was harvested in late June of both 1998 and 1999.
Yield trends were similar for both 1998 and 1999, but yields were greater in 1999 because of an earlier fall planting date and better seasonal conditions. In 1999, fertilizer N addition and soybean, as opposed to corn, as a previous crop (Table 1) positively influenced yield. Wheat following soybean averaged 11 bu/A greater yield than wheat following corn in this year of the study. Averaged across all N rates, and regardless of previous crop, little difference due to N source management was observed. The optimal N rate was little affected by N source management but was strongly related to the previous crop. The optimal fertilizer N rate was about 27 pounds N/A for wheat following soybean and 81 pounds N/A for wheat following corn. UAN solution application management, whether broadcast or streamjet, had little effect on the yield results for wheat grown in the two rotations.
The results suggest that wheat producers need not worry about differential performance among N sources for winter wheat production. Their first consideration should be the N source price per pound of actual N. Their second priority should be to do a good job of fertilizer application, minimizing any skips or overlapping areas within their fields.
It is clear that wheat following soybean gave superior yields than that following corn, although the mechanism for this is not clear. Certainly, the greater amounts of corn residue hinder crop establishment and slow crop development. Higher levels of fertilizer nitrogen were needed to raise optimal yields of wheat following corn, but improved N nutrition was not sufficient to eliminate the yield gap between wheat yields in the two rotations.
|Table 1. Effect of previous crop, N source management, and N rate on yield of no-tillage wheat in 1999.|
|Previous Crop||Fertilizer N Rate lb N/A||Wheat Yield - by N Source Management (bu/A)||N Source Average (bu/A)|
|UAN Streamjet||Urea Broadcast||AN Broadcast||UAN Broadcast|
L. Murdock, J. Herbek, J. Martin, J. James, and D. Call
The objective of this experiment was to verify the effects of no-till wheat and tilled wheat on the subsequent yield of soybeans and corn planted after wheat in a wheat, double-cropped soybean and corn rotation and measure differences in fertility and physical effects on the soil on a long-term basis.
The experiment is at Princeton, Kentucky, on a Pembroke silt loam soil that is moderately well drained. Wheat was planted no-tilled and with tillage, and the tillage plots were chisel plowed and disked twice. The plots were 10 ft x 30 ft. The soil test was pH - 6.0, P - 39, and K - 247, and 0-60-30 lb/A of N-P2O5-K2O was applied before planting. Soybeans are planted no-till immediately after wheat harvest, and no-till corn is planted the following year, and wheat (tilled and no-tilled) is again planted after corn harvest.
Yields of Succeeding Crops. The data (Table 1) indicate that both no-till corn and no-till soybeans tend to yield more (3.3 percent for soybeans and 8.6 percent for corn) where the wheat is planted no-till. However, the differences are not always statistically significant, but the trend has remained consistent since the second year of the experiment.
|Table 1. Effect of wheat tillage systems on the yield of succeeding crops.|
|Year||Wheat Tillage System (bu/A)|
|1996||Harvest Data Lost|
|* N.S. means no significantly statistical differences.
** Statistically different at the 0.1% level.
These yield differences indicate that changes between the two systems have taken place with time, and the changes favor the system that has only no-tillage plantings in it. The reason for the difference is not clear at this time but might include residue cover, soil moisture, soil physical changes, or others.
Soil Changes. The amount of soil organic matter found in the two systems was very similar. There is also no difference in the soil test pH, phosphorus, or potassium between the two systems. The total no-tillage system has 0.24 percent more organic matter in the top 3 inches of the soil than the one with tilled wheat.
There was also no difference in the soil density between the systems. This indicates that there was no compaction of significance in either system. The soil strength, as indicated by penetrometer measurements, was higher in the exclusively no-tillage system. This indicates that the soil structure has changed and probably has larger aggregates than the system that is tilled every second year for wheat planting.
Moisture measurements taken during the 1999 growing season on the no-till corn found more moisture available for plant growth in the treatments where tillage was not used for wheat. This resulted in an 18 percent higher grain yield for these plots.
A true no-tillage system seems to have a favorable effect on the crops grown on the yields of soybeans and corn. When no-till wheat was grown, the no-till corn and soybeans had 8.6 percent and 3.3 percent greater yields, respectively, than when these crops were grown after tilled wheat. The changes that are taking place are unclear at this time, but it appears that they result in more plant-available moisture for these crops. Research is continuing to try to better understand the differences.
C. Tutt, S. Swanson, and D. Van Sanford
To determine whether wheat varieties that are superior under conventional tillage are also superior under no-tillage.
Entries consisted of 46 commercial and public soft red winter wheat varieties in 1998 and 43 in 1999. Twenty-eight varieties were common to both years. Each variety was replicated four times at each location in both years. Conventional tests were planted with a six-row cone seeder with double-disk openers in 7-inch rows. Plot area was 60 sq ft. No-till plots were seeded with a seven-row cone seeder equipped with John Deere 750 openers in a row spacing of 7.5 inches. Plot area was 240 sq ft. Seeding rates were approximately 325 seeds/sq yd for conventional tillage and 365 seeds/sq yd for no-till. Inputs such as fertilizer and pesticides were similar to those used by the cooperating farmers on their commercial wheat fields.
Variety yield means are presented in the following three tables.
There was very good agreement between no-till and conventional-till performance in terms of variety mean yield. For example, the correlation between no-till and conventional-till performance over two years in Shelby County was 0.85 (Table 1). Perfect agreement would have yielded a correlation coefficient of 1.0. When comparing no-till versus conventional-till performance in Logan County in 1998 and Caldwell County in 1999, the correlation was 0.74 (Table 2). When data from all three locations in both years were considered, the correlation was 0.88 (Table 3). The take-home message at present is that, in general, superior varieties will perform well under either tillage system. However, we will continue to test wheat varieties under conventional and no-till management in the foreseeable future.
|Location||Harvest Year||Cooperator||Previous Crop||Conventional Tillage||Stubble Condition (No-Till)||Planting Date|
|Logan County||1998||W. G. Farms||Corn||Disk-ripper, disk, cultipacker||Flail-mowed||10/8/97|
|Caldwell County||1999||Gilkey Farms||Corn||Disk-ripper, disk, cultipacker||Flail-mowed||10/9/98|
|Shelby County||1998-99||Ellis Farms||Corn||Chisel plow, disk||Standing||10/1/97; 10/12/98|
|Table 1. Shelby County no-till and conventional variety trial, 1998-99.|
|Yield (bu/A)||Yield (bu/A)|
|AG FOSTER + GAUCHO||81.0||43.5||62.3||77.6||50.7||64.2|
|TERRA SR 204||81.2||48.4||64.8||79.2||46.2||62.7|
|Correlation of Conventional, No-Till, 1998-99: 0.85|
|Table 2. Logan County (1998) and Caldwell County (1999) no-till and conventional variety trial.|
|Yield (bu/A)||Yield (bu/A)|
|AG FOSTER + GAUCHO||83.0||41.1||62.1||100.3||29.7||65.0|
|TERRA SR 204||76.3||35.3||55.8||72.0||28.7||50.4|
|Correlation of Conventional, No-Till, 1998-99: 0.74|
|Table 3. Conventional vs. no-till, 1998-1999.*|
|Variety||1998-1999 Yield (bu/A) Conventional||1998-1999 Yield (bu/A) No-Till|
|AG FOSTER + GAUCHO||62.2||64.6|
|TERRA SR 204||60.3||56.5|
|Correlation of Conventional, No-Till, 1998-1999: 0.88
* 1998: LOGAN AND SHELBY counties; 1999: CALDWELL AND SHELBY counties
J. Herbek, L. Murdock, J. James, and D. Call
A major obstacle of no-till wheat is obtaining an optimal, uniform stand. Most wheat in west Kentucky is planted following corn, which results in a large amount of residue that hinders planting. Producers debate the best method for managing corn residue for no-till wheat planting. A corn residue management study was initiated with the following no-till wheat stand establishment objectives: 1) To determine if mechanical shredding of corn residue is necessary; and 2) compare different methods of mechanical shredding of corn residue (and corn maturities) to non-shredded and no corn residue.
The experiment was established in 1997 at the University of Kentucky Research and Education Center in Princeton, Kentucky. Two corn maturities were used: a full-season corn (123 GDD) and an early-season corn (110-112 GDD). Excellent corn yields both years resulted in a large amount of residue. Corn residue management treatments included: 1) no residue (corn residue removed), 2) residue flail mowed after harvest, 3) residue rotary mowed after harvest, 4) residue after harvest as is (plant parallel to corn rows), 5) residue after harvest as is (plant at angle to corn rows), and 6) residue after harvest as is (plant parallel to corn rows with 15 percent increase in wheat seeding rate). Mechanical shredding was completed immediately after harvest of each corn variety. Wheat was no-till planted with a Lilliston 9670 no-till drill in 7-inch rows at a rate of 35 seeds/sq ft, except for the increased seeding rate (40 seeds/sq ft). Data taken included wheat yields and fall stand counts.
Results for 1998 and 1999 are presented in the table below. Wheat stand establishment was less for 1998 than for 1999 and is attributed to excellent establishment conditions for 1999. As expected, stands were high both years if residue was removed. Flail shredding of corn residue resulted in some of the better stands in 1998 but was not as apparent in 1999. Rotary-mowed residue achieved lower wheat stands than flail-mowed residue (particularly for 1998) and may be attributed to a more uniform distribution of residue with a flail mower. Planting into non-shredded corn residue achieved the worst stands in 1998, but results were inconsistent in 1999. Planting at an angle to the corn rows in non-shredded residue appeared to achieve better wheat stands than planting parallel to corn rows. Increasing the seeding rate in non-shredded residue achieved the highest stands in 1999. Although the early corn variety appeared to have less residue and more decomposition prior to planting than the full-season corn variety, wheat stands were not consistently better. The excellent wheat stands in 1999 resulted in no statistical differences between shredded and non-shredded corn residue. Wheat yields were lower in 1998 due to a spring freeze and high May temperatures. Excellent tillering in 1999 (mild fall/winter) resulted in high yields for all corn residue treatments. There were small differences in yield and almost no statistical differences among the corn residue treatments both years. There was little correlation between wheat stand and yield.
|Table 1. Effect of corn residue management on no-till wheat stand and yield.|
|Corn Residue Treatment||Corn Maturity||Wheat Stand (plants/ft2)||Wheat Yield (bu/A)|
|Removed all corn residue||Full||26.8 a||35.2 ab||55.4 ab||104.6 b|
|Flail mowed residue||Full||24.2 b||32.1 bc||60.9 ab||112.3 ab|
|Flail mowed residue||Early||22.4 bc||32.2 bc||59.4 ab||107.8 ab|
|Rotary mowed residue||Full||21.3 cd||31.9 bc||57.4 ab||107.9 ab|
|Non-shredded residue (parallel planted)||Full||16.8 e||34.1 bc||53.3 b||106.7 ab|
|Non-shredded residue (parallel planted)||Early||20.0 d||31.2 c||62.2 a||101.6 b|
|Non-shredded residue (diagonally planted)||Full||21.4 cd||32.9 bc||59.8 ab||118.6 a|
|Non-shredded residue (15% seed increase)||Full||---------||37.8 a||--------||111.2 ab|
D.A. Van Sanford, B. Kennedy, M. Hall, and C. Swanson
Entries in the 1999 Uniform Winter Scab Nursery along with a number of advanced breeding lines were planted in the field in a randomized complete block design with four replications on 29 October 1998. Each plot consisted of a single 4-ft row. The previous crop was corn, and the seedbed had been chisel plowed and disked. Entries in the greenhouse were planted in a completely randomized design with a variable number of replications.
Mason jars containing approximately 500 g of autoclaved corn seed were inoculated with the head scab fungus F. graminearum on April 5, 1999. On April 27, wheat plots were inoculated just prior to heading by spreading 35 to 40 g of the inoculated corn mixture per plot. Plots were mist irrigated daily beginning May 7 for approximately one hour during the early part of the morning, midday, and late evening throughout anthesis into early grain fill. Because of extremely dry weather and a delay in irrigation, wheat plots were inoculated a second time with more corn inoculum on May 17. Incidence of scab was reported as the percentage of scab-infected heads per total number of heads per row. Severity was determined by counting the number of infected spikelets and dividing by the total number of spikelets on diseased heads only.
Several advanced breeding lines were evaluated in the greenhouse for Type I (preventing initial infection) and Type II (reducing spread within the head) resistance.
To measure Type II resistance, at flowering, 3 µl containing approximately 1,200 spores was injected into a single floret in the middle of the head. After inoculation, plants were placed directly into humidity chambers for three consecutive nights. The final percentage of infected spikelets per spike was recorded on day 21. Type I resistance was measured by spraying a spore suspension onto heads at flowering and placing the pot in a humidity chamber for three nights. Twenty-one days after inoculation, plants were rated for disease development using a 0 to 4 scale: 0 = no disease, 1 = 1 to 25 percent, 2 = 26 to 50 percent, 3 = 51 to 75 percent, and 4 = 76 to 100 percent of spikelets infected.
Seed Assessment: Wheat seed was collected from both injection and spray test entries. Total seed number plus the number of visually scabby seed were recorded for each seed lot. Plates were incubated for seven to 10 days at 20 C. Each plate was visually inspected for F. graminearum-contaminated seed. Seed from the injection test was also assessed for the presence of F. graminearum. In this particular test, seed was visually inspected and placed in the following three categories according to appearance: l) normal, 2) small, wrinkled, and 3) tombstone. The location and category of each seed was recorded on the top of each petri plate. After incubation, those seed that were positive for the presence of F. graminearum were recorded.
Field Screening: For the first time in three years of field screening, incidence and severity in our inoculated, irrigated nursery were rather low (Table 1). Nonetheless, the resistant checks, Ernie and Freedom, actually showed some signs of resistance in our nursery, which was not the case in the previous two years. Thus, the scab pressure that we observed this year may have been closer to what would be expected under a natural infection.
Greenhouse Screening: Even with a large number of replications (15 plants), repeatability of assessment of type II resistance was low (Table 2). The most promising entry, KY 91C-022-36, ranged from 6 to 26 percent scabby spikelets. With only three plants, however, it is difficult to have confidence in this estimate.
Selective Media: We tend to regard an evaluation of scabby seed after harvest as a confirmation of our assessment of scab on the intact spike. Although visual assessment of seed seems straightforward, plating out the seed on a selective medium revealed some surprises (Tables 3 and 4). Seed of Freedom, for example, was visually rated at 17 percent scabby, yet plating the seed revealed that 82 percent was actually infected with F. graminearum.
|Table 1. Uniform winter wheat scab screening nursery, Lexington, Kentucky, 1999.|
|Cultivar||Average Severity %||Average Incidence %||FHB Index||Height (in.)||Yield (bu/A)||Heading Date (Julian)||DON Levels (ppm)|
|Table 2. Evaluation of 14 advanced breeding lines in the greenhouse for Type IIa resistance to scab.|
|Entry||N||AUDPCb||% Diseased Spikeletsc|
|a Reduction of spread within the spike. b Area under the disease progress curve.
c Percent of infected spikelets per spike recorded 21 days after injection.
|Table 3. Mean number of seed collected and percent of seed infected with F. graminearum from 14 advanced breeding lines screened in the greenhouse for Type II resistance to scab.|
|Entry||Mean Number of Seeda||Percentage of Infected Seed|
|a Visual assessment of seed by appearance. b Percent of F. graminearum contaminated seed per total number of seed by category, recorded 7 to 10 days after plating on selective media.|
|Table 4. Evaluation of 15 advanced breeding lines screened in the greenhouse for Type I resistance to scab.|
|Entry||N||Disease Scorea||Total Seed||Percent Visual Scabby Seedb||Percent of Seed Infected with F. graminearumc|
|KAS EX 108||1||4||6||100||83|
|a 21 days after inoculation plants were rated for disease development using a 0-4 scale: 0 = no disease, 1 = 0-25%, 2 = 26-50%, 3 = 51-75%, and 4 = 76-100% of spikelets infected.
b Visual assessment of seed by appearance.
c Percent of F. graminearum-contaminated seed per total number of seed, recorded 7 to 10 days after plating on selective media.
W.L. Pearce, C.G. Poneleit, and P. Shine
The Hybrid Corn Performance Test provides unbiased performance data of commercially available corn hybrids sold in Kentucky. Each year, more than 125 hybrids are evaluated for agronomic performance at seven locations in the state. At each location, separate tests are grown for early (112 days to maturity or earlier), medium (113 to 117 days to maturity), and late (118 days to maturity or later) hybrids.
In 1999 a TC blend high oil test was grown for agronomic evaluation at three Kentucky locations. Data were made available to seedsmen, county agents, and farmers on the Agronomy Web site along with the customary progress report (PR-421). The Web site has an HTML version (used as a search mechanism) and a PDF file, which is the printable version.
Also, evaluations of protein, oil, and starch were obtained from one replication of all regular corn hybrids from each location (Tables 7E, 7L, and 7M). The evaluations for protein, oil, and starch were also done on every replication of the TC blend high oil test (Table 15F). All chemical analyses were provided by the Grain Quality Laboratory. In 1998 a new combine was provided by the Kentucky Corn Growers Association. This combine uses a data collection system that provides test weight data along with yield and moisture. Other data provided in the progress report are percent stand and lodging.
C.G. Poneleit, R.C. Green, G. Swango, and W.L. Pearce
What is the benefit of examining variations of starch or protein or oil in corn grain? The answer varies from a few extra cents per bushel for grain growers or additional energy per bushel for animal feeders to several dollars of product per bushel for specialty grain processors. Most of the answers will not be available, however, until hybrids with the distinctive characteristics are available for direct testing. That is the objective of the Corn Breeding testcross trials: to select white endosperm inbreds with value-added starch, protein, and oil characteristics. Hybrids can then be made from the inbreds. White endosperm corn grain with waxy starch may provide the unique composition needed by a special industry. New waxy hybrids are now being tested for agronomic ability, i.e., yield and standability, as well as for amylose and amylopectin composition. A diallel test of white endosperm grain populations that are high in amylose, because of the amylose extender gene, is being tested for combining ability and possible use in future breeding programs.
White endosperm grain selections with hard kernels that have high lysine content, called Quality Protein Maize (QPM), are also being tested for agronomic worth. These QPM hybrids are an improved version of high lysine hybrids that were grown by many Kentucky farmers several years ago but had poor quality grain for storage. Additionally, all hybrids in the Hybrid Corn Performance Test program are routinely screened for percent composition of starch, oil, and protein through the Grain Quality Laboratory, to find those with unusually high or low values for any of the composition materials. Each of these selection programs using testcross evaluations or screening tests may provide a future value-added hybrid for Kentucky.
C.G. Poneleit and G. Swango
The Kentucky Corn Grain Quality Laboratory provides an analysis service for farmers, industry, and University of Kentucky researchers using Near Infrared Reflectance Spectroscopy (NIRS) for protein, oil, starch, and fiber. Other testing includes amino acid composition, test weight, moisture, specific density, stress cracks, kernel size, and broken corn and foreign materials (BCFM). Additionally, ELISA quick tests are done for aflatoxin and fumonisin. All tests are done free of charge to Kentucky residents.
During the 1999 harvest season we processed 370 samples for farmers and industry, 220 for special research studies, 1,500 for the Hybrid Corn Performance Test program, and 3,500 for corn breeding research. The laboratory is supported by funds provided by the Kentucky Corn Growers Association.
M.J. Bitzer, D.J. Grigson, and D. Herbst
Each year a corn hybrid silage trial is conducted on one or more farms in Kentucky. In 1999, these tests were located in Lincoln and Adair counties. The test included 17 different corn hybrids which were grown in three replications. The plots were hand harvested for yield and chopped in a chipper shredder to obtain samples for moisture and silage quality. These tests are conducted to provide unbiased performance information for corn hybrids for silage commonly sold in Kentucky. Every effort was made to conduct the test in an unbiased manner according to accepted agronomic practices. Yields were affected by the dry weather more in Adair County than Lincoln County.
The yield and quality data are presented in Table 1. TDN is an energy value that is very important for milk production and cattle gains. NEL percentage is an energy value that is important for milk production. The ADF percentage is a measure of the plant material that is highly indigestible by the animal. A low ADF percentage is desirable. Several hybrids were the highest yielders in both counties, whereas other hybrids did somewhat better under the more stressed environment of Adair County.
|Table 1. Yield and quality data of corn hybrids for silage.|
|Hybrid/Brand||Yield (T/A)||Combined Counties|
|Novartis N79-L3 Bt||23.6||17.7||8.25||29.6||63.9||0.64|
|Novartis N7639 Bt||22.7||14.4||8.00||29.0||63.9||0.65|
|ABT HTX 7639 Bt||21.3||13.3||8.23||31.2||61.1||0.62|
|Southern States SS849 IT||20.4||15.0||8.18||31.0||61.3||0.62|
|DeKalb DK720 S||20.3||15.3||8.62||30.5||62.0||0.63|
|ABT HT 4138||19.7||15.6||8.27||30.7||61.6||0.62|
|Caverndale Silage A||19.6||13.9||8.50||33.5||58.1||0.58|
|Southern States SS943||19.2||13.7||8.20||31.0||61.4||0.62|
|Garst 8222 IT||18.9||11.4||8.17||30.1||62.4||0.64|
|ABT HT 4927||18.7||13.8||7.80||29.3||63.6||0.65|
|Mycogen TMF 114||16.6||14.9||7.73||30.3||61.3||0.62|
L. Murdock, P. Howe, and K. Wells
Combine yield monitors are commonly used by many farmers. As farmers see the yield vary across the field, they question the reasons for this and wonder if the different yield zones could be managed differently to improve yields or reduce costs. To answer these questions, the reasons for the yield variability must first be determined. The yield variability within fields can be attributed to many factors. The objective of this study is to precisely map soil morphological characteristics and soil fertility factors within a field and determine if such variability is associated with yield variability of corn.
Work was conducted on two fields in the western part of the state on soils derived from limestone parent material. The two fields are located in Caldwell and Trigg counties in the Pennyrile area. The fields were typically upland sites with ridge, side slope, and basin positions. These fields had a three-year history of yield maps that showed consistent differences. Sites chosen for the study in the fields were representative of the yield ranges within the fields and were selected on a combination of factors that included past yields, topography, and soil type. There were 24 sites on the field in Caldwell County and 18 sites on the Trigg County field. Soil characteristics measured were yield, topsoil depth, Ap horizon, depth to clay accumulation, internal drainage, penetrometer measurements, slope and aspect, site position, soil type, organic matter, pH, buffer pH, phosphorus, and potassium. A correlation between yields and soil characteristic across sites in each field was performed to determine its effect on yield. For comparison of all years in both fields, the yields were normalized and correlated to soil characteristics.
It appears that topsoil depth may be the most important yield-determining characteristic on these types of soils. It alone described more than 70 percent of the yield variability in corn yield in 1996 and 1997 in the two fields in the Pennyrile area (Table 1). On the average, yields increased 10.1 bu/A for each inch of topsoil up to 8 inches of topsoil (Figure 1). Increase of topsoil depth above 8 inches resulted in only a 1.2 bu/A yield increase per inch. The depth to clay accumulation in the soil, which is closely related to topsoil depth, was also highly significant and will correlate to the yield in the fields. Both of these factors are related to water availability to the plant. The slope percentage was also significant and correlated to the yield. This is probably a reflection of erosion history because it negatively correlates to topsoil depth and is again related to plant water availability. There was a weak correlation of soil strength (penetrometer measurements) to yield variability. With only one exception, there was no correlation of yield variability to any of the fertility parameters (phosphorus, potassium, pH, buffer pH, or organic matter). Within the sites tested, the range was pH (5.6 to 6.8), P (11 to 65 ppm), and K (214 to 366 ppm). Phosphorus correlated to yields on the field in Trigg County, but this may have been at least partially due to past erosion effects.
|Table 1. Correlation coefficients of soil characteristics to yield.|
|Soil Characteristics||R2 Values|
|Depth to clay accumulation||0.63|
At this point in the study, it appears that yield variability on these types of soils is primarily related to plant available water that is controlled by top soil thickness (which is related to erosion or accumulation) and soil type.
Figure 1. Effect of topsoil depth on 1996 and 1998 corn yields.
M.J. Bitzer and J.H. Herbek
In the 1990s, corn row width studies were conducted in many corn-producing states. Responses to row widths narrower than 30 inches have occurred mostly in areas from central Illinois northward. Studies in southern Illinois, Missouri, Tennessee, and Kentucky have not shown any advantage for rows narrower than 30 inches. There has been a trend toward higher yields for plant populations up to 30,000 plants per acre. Most studies have been conducted with only one or two hybrids, but even when more hybrids were used, no difference was found between hybrids. After completing three years of data in Kentucky, which showed no advantage to rows narrower than 30 inches but an increase of yields from 22,000 to 30,000 plants per acre, a new study was initiated in 1998 that included two corn hybrids, two row spacings, and three plant populations.
A two-year study was conducted in 1998 and 1999 to determine the effect of row width, plant population, and corn hybrids on corn grain yield. Two row widths (20 and 30 inches) with three plant populations (24,000, 28,000 and 32,000 plants per acre) and two corn hybrids were studied at two locations in Kentucky. The plots were located on Bob Wade's farm in Hardin County and on Doug Wilson's farm in McCracken County. The two corn hybrids that were compared were Pioneer 33Y18 (114 day hybrid) and Southern States SS828 (118 day hybrid). These two hybrids were the among the highest yielding hybrids in the Kentucky Hybrid Corn Performance Trials in 1997 and 1998.
In 1998, the yields averaged 151 bu/A in Hardin County and 191 bu/A in McCracken County, whereas in 1999, the yields averaged only 113 bu/A in Hardin County and 143.5 bu/A in McCracken County. The lower yields in 1999 were due to the extreme drought conditions that were prevalent especially in Hardin County. Across years there were no significant differences for row width or plant population (Table 1). There was a significant hybrid by row width interaction. In 1998, the hybrid Pioneer 33Y18 yielded significantly higher in 20-inch rows, whereas Southern States SS828 was higher yielding in 30-inch rows. In 1999, both hybrids were slightly higher yielding in 30-inch rows. Pioneer 33Y18 is the first hybrid that we have studied that was higher across locations in 20-inch rows in any one year. Although there was no significant difference in plant populations, slightly higher yields were obtained at 28,000 plants per acre. In 1999, the dry weather had a greater effect on the yields of the later maturing hybrid.
In conclusion, after five years of studying the effect of row width and plant population on corn grain yields in Kentucky, there does not appear to be any advantage for 20-inch rows over 30-inch rows. For fields that have the potential of producing more than 180 bu/A, a final population of 26,000 to 28,000 plants per acre should be adequate.
|Table 1. Effect of hybrid, row width, and plant population on corn grain yields across years (1998 and 1999).|
|Southern States SS828||167.1b||120.7b||143.9b|
L. Murdock and J. James
Soil compaction has become more of a concern with producers as the size of equipment has increased. Some of the questions that producers ask are: 1) how much will compaction decrease my yield?, 2) are penetrometers a good measure of compaction?, 3) will deep tillage restore all of my yield potential?, and 4) how long will the effects of compaction last? To help answer some of these questions, a compaction experiment was established at Princeton, Kentucky, on an experimental area that had tilled and no-tilled areas.
A replicated trial was established on a Zanesville silt loam at Princeton, Kentucky, in the fall of 1996 on an area that had both no-tillage and tilled areas. There were six treatments; one no-till and one tilled treatment were not compacted. Two no-tilled and two tilled treatments were compacted. In the fall of 1999, one of the compacted no-till treatments and one of the compacted tilled treatments were subsoiled.
The compaction was accomplished by trafficking the entire plot with a 7-ton per axle large front-end loader. This was done twice in the fall of 1996. In the spring of 1997, the entire plot was trafficked four times with a 10-ton John Deere 7700 tractor with dual rear tires and extra added weight. All compaction traffic was done when the soil moisture was about 17 percent. This was found to be the optimal moisture for compaction by Dr. Larry Wells using a Proctor test method.
Severe compaction was found to exist to about a 12-inch depth on all compacted plots. This was confirmed by soil strength measurements made with a penetrometer at field capacity. All compacted plots exceeded 300 psi in the top 12 inches.
Corn was planted in 1997 and 1999 and soybeans in 1998. The tilled plots were disked to a depth of 6 inches prior to planting, and the no-till plots were planted directly into the compacted soil.
The yields for the different treatments are found in Tables 1 and 2 as relative yield (percentage of highest yielding treatment) and actual yields. The uncompacted treatments were the highest yielding, with the no-till treatment being consistently and slightly higher than the tilled treatment for both corn and soybeans. The tilled/compacted treatment yielded consistently 20 percent to 25 percent less over the three-year period than the uncompacted treatments. The no-till compacted treatment yielded very low the first year (2 percent), and then dramatic gains were made the next two years. Relative yields were 82 percent and 89 percent for the second and third years.
|Table 1. Effect of soil compaction on corn and soybean yields with and without compaction.|
|Treatment||Relative Yields* (%)|
|* Percent of highest yielding treatment.|
|Table 2. Effect of soil compaction on corn and soybean yields with and without compaction.|
The difference between yields in the tilled and no-tilled compacted treatments over the three years is thought to be due to tillage and in the ability for the increased biological activity of the no-till treatments to ameliorate compaction. The extremely low yield in the no-till treatment the first year was due to compaction of soil into the soil surface. Roots had extreme difficulty becoming established, so plants and yields were very small. The tilled compacted treatment was disked to 6 inches, so plant growth and yields were greater. After the first year, compaction was completely removed by natural means in the top 3 inches of the compacted no-till treatment.
The relative yields have continued to increase in the no-till compacted plots. It seems that this is probably due to a high level of biological activity in no-till that is actively correcting the soil compaction. This is seen in root observations made in 1999 by taking soil cores below the plants. Small channels were found in the compacted layer that were of granular structure that had a dark organic stain with a high concentration of larger active roots that traversed through the compacted zone into the uncompacted soil below. Some evidence of this can be seen in the soil penetrometer readings in Table 3. The soil strength in the no-till compacted treatment is beginning to decrease with no evidence of this in the tilled compacted treatment.
|Table 3. Effect of time on the percentage of soil penetrometer readings over 300 psi in compacted tilled and no-tilled treatments.|
|Treatment||Percentage of Measurements over 300 psi|
This experiment indicates that there is a difference in severe soil compaction between tilled and no-tilled systems. Some of the conclusions are:
M. Rasnake, L. Murdock, and F. Sikora
Currently, Kentucky poultry operations produce about 300,000 tons of litter each year. The nutrient content of this litter compares roughly with 75,000 tons of 10-10-10 fertilizer. However, the nutrients in litter are less available to crops than nutrients in fertilizer. This is especially true for nitrogen since most of the nitrogen is in an organic form that must be broken down before the nitrogen can be released. This study was designed to evaluate the availability of nutrients in litter to corn in comparison with nutrients in fertilizer.
An experiment was initiated in 1998 on a Zanesville silt loam soil at Princeton, Kentucky, to evaluate the use of poultry litter on corn. The experiment was repeated in 1999 on the same plots. The 1998 results were low due to late planting, so only the 1999 results are reported in this paper. The treatments used are shown in Table 1 and were the same in both conventional and no-till planting systems compared in adjacent plots. All the poultry litter and the 150 pounds nitrogen treatments were applied near planting time (April 26) with incorporation in the conventional-tilled plots. Nitrogen for the split treatments (3 and 4) was applied broadcast on June 11. Nitrogen was applied as ammonium nitrate. Rainfall was good until the first of July, but no rain occurred after that date. Yields were limited by the late drought.
On-farm tests were also conducted in Hopkins and Webster counties in 1999.
|Table 1. Corn yield response to poultry litter and nitrogen fertilizer -- Princeton, Kentucky, 1999.|
|1||10||590||0||137 a||149 ab|
|2||5||295||0||125 ab||153 a|
|3||1.3||77||112||114 b||137 c|
|4||3.1||183||56||120 b||145 b|
|5||0||0||150||115 b||135 c|
|* Yields within a column followed by the same letter are not significantly different (% = .05)|
Average yields for the various treatments at Princeton are shown in Table 1. In the conventional tilled plots, the 10-ton rate of poultry litter produced higher yields than nitrogen alone, or combinations of litter and nitrogen fertilizer. The 5- and 10-ton rates were not significantly different; however, the results suggest that treatments with less available nitrogen may not have had sufficient nitrogen for the corn crop.
Yields in the no-till plots were higher, although no statistical comparisons are made between no-till and conventional. The 5-ton litter rate produced the highest yields in comparison with the nitrogen or combination treatments. The 5- and 10-ton litter rates were not significantly different in corn yields produced. Nitrogen may have been limiting in treatments three through five.
Results of on-farm tests conducted in Hopkins and Webster counties are shown in Tables 2 to 4. The study in Hopkins County (Table 2) with no-till white corn showed no consistent patterns. Whether 3 or 5 tons of litter were used, it appears some extra nitrogen was needed. This field was planted later than the others (May 14) and probably suffered more from the dry weather in July and August.
Yields on the Duncan farm in Webster County showed no significant differences due to treatments, although there was a trend toward higher yields with extra nitrogen in the conventional tilled plots. Apparently, there was sufficient nitrogen in 4 tons of broiler litter per acre to grow a high-yield corn crop. The late-season drought may have limited yields and an opportunity to see differences due to nitrogen treatment levels.
The Carlisle farm yields (Table 4), although higher, show trends similar to those discussed for the Duncan farm. One difference on this farm was a large increase in yields with the 20-lb nitrogen rate on the no-till plots. This suggests that more nitrogen was lost from the litter on the no-till plots, or the decomposition of litter and release of organic nitrogen was less.
|Table 2. White corn response to poultry litter -- Osburn Farm, Hopkins County, Kentucky, 1999.|
|Litter (T/A)||Nitrogen (lb/A)|
|Table 3. Corn response to poultry litter -- Duncan Farm, Webster County, Kentucky, 1999.|
|Litter (T/A)||N (lb/A)||Conv.-Till||No-Till|
|* Yields not significantly different.|
|Table 4. Corn yield response to poultry litter -- Carlisle Farm, Webster County, Kentucky, 1999.|
|Litter (T/A)||N (lb/A)||Conv.-Till||No-Till|
|4||0||160 a||137 a|
|4||20||161 a||175 b|
|4||40||169 a||170 b|
|4||60||165 a||176 b|
|4||80||175 a||182 b|
|* Yields within a column followed by the same letters are not significantly different (% <0.1)|
These results indicate that poultry litter is a good source of nutrients for corn production. However, it is more difficult to predict the breakdown of litter and the release of nutrients to the crop. This is more of a problem in no-till since the surface-applied litter is more prone to nitrogen loss via ammonia volatilization and breakdown of the litter is more dependent on weather conditions. For these reasons and other problems, such as the difficulty in getting a uniform distribution of litter, poultry litter probably should not be used to supply all the nutrient needs of a crop. Using lower rates of litter to supply phosphorus for the crop, then balancing nitrogen and other nutrient needs with fertilizer will be more economical and effective in most cases. It may also help from an environmental standpoint in the long run.
M. Rasnake, F. Sikora, and L. Murdock
Poultry litter sometimes must be stored for varying times before it can be applied to land. Changes in nutrient concentration during storage are expected, but how soon they occur and how much they change is not known. This paper reports the results of a study on poultry litter storage that was initiated in December 1998 at Princeton, Kentucky.
Broiler litter cake (the material removed from broiler houses between flocks by a machine that picks up the litter and screens out the larger particles) was delivered to Princeton on December 21, 1998. The litter was placed in nine 8-ft x 8-ft bins to a depth of 4 feet. Three bins were covered with a roof, three with plastic directly on top of the litter, and three were left uncovered. Each bin was sampled at one week after storage and periodically for six months with the last sample taken on June 29, 1999. The samples were analyzed by the University of Kentucky Regulatory Services testing labs.
Changes in concentration of nutrients in poultry litter with storage time and method are shown in Figures 1 through 5. The method of storage had very little impact on nutrient concentration except possibly on nitrogen. Therefore, in Figures 2 through 5, the data for all methods are combined and show only the results of time of storage. Nutrient concentrations are reported on a percent dry matter basis.
Nitrogen concentrations (Figure 1) tended to decrease after two weeks of storage until 10 weeks. Then they increased over the next 16 weeks. Nitrogen losses were probably due to ammonia volatilization. Significant differences due to storage method occurred only during the last 16 weeks, with the plastic-covered litter being higher in nitrogen concentration compared to the other two treatments.
Phosphate concentrations tended to increased with storage time (Figure 2). Overall, phosphate increased from 4.8 to 5.7 percent of dry matter over the six-month storage time. Since phosphate is not expected to be lost from the system, this increase can be attributed to a loss in mass of the litter due to organic matter decomposition.
Potash concentration (Figure 3), although more variable, showed the same trends as phosphorus. The overall change was from about 3.9 to 4.2 percent of dry matter after six months of storage.
Calcium and zinc concentrations (Figures 4 and 5) followed similar trends to phosphate and potash. Calcium increased from 2.8 to 3.4 percent of dry matter, while zinc increased from 440 to about 520 ppm. As with phosphorus, these increases are due to a decomposition of organic matter rather than increases in the total amounts of calcium and zinc.
Internal temperatures of litter stacks are shown in Figure 6. Litter stacks under roof and uncovered reached a maximum temperature of 120ºF two weeks after stacking. Stacks under roof cooled to about 110ºF after about six weeks and maintained that temperature for six months. The uncovered stacks continued to cool to near ambient temperatures two months after storage. The plastic-covered stacks maintained a temperature between 100 and 110ºF throughout the experiment.
These results indicate that stored poultry litter continues to be microbially active for long periods of time. This results in a loss of mass and an increase in concentration of nutrients with the exception of nitrogen.
Figure 1. Changes in Nitrogen Concentration in Stored Poultry Litter.
Figure 2. Change in Phosphate Concentration in Poultry Litter with Storage Time.
Figure 3. Potash Concentration Changes with Litter Storage Time.
Figure 4. Calcium Concentration Changes with Litter Storage Time.
Figure 5. Zinc Concentration Changes with Litter Storage Time.
Figure 6. Effect of Broiler Litter Storage Method on Internal Temperatures.
E. Lacefield, C. Tutt, and T. Pfeiffer
The Kentucky Soybean Performance Tests annually evaluate soybean varieties being marketed in Kentucky to provide farmers and seedsmen information to use in making variety selections. Over the last three years the Kentucky Soybean Performance Tests have expanded to meet the needs of Kentucky soybean producers. In 1997 about 80 varieties from commercial companies and 25 varieties from public institutions were tested in six locations. Eight of the commercial varieties were Roundup Ready® (RR). This year (2000) 119 commercial varieties, 12 public varieties, and a number of novel soybean varieties are being tested. The number and acceptance of RR varieties has also greatly increased. Last year for the first time in Kentucky all RR soybean varieties entered by companies were tested in the five conventional tests and the double-crop test and were compared directly to non-RR soybeans. Twenty-one companies entered 78 RR varieties that now comprise more than two-thirds of the commercial varieties entered in the newly revamped tests.
A selection key was available for the first time last year at the Kentucky Soybean Performance Test Bulletin's Web site: http://www.ca.uky.edu/agc/pubs/pr/pr424/pr424.pdf. This new feature creates subsets of the summary table. The sorting of the data provides alternative views, showing those varieties selected by basic questions a soybean producer might ask and encourages the use of the summary data. The publication Web site, which was activated December 1, 1999, has been accessed more than 2,000 times.
The Kentucky Soybean Performance Tests provide multiple environments for the latter stages of testing of soybean lines considered for release by the University of Kentucky soybean breeding project; for example, the newly released soybean variety 7499 was tested in 10 environments during two years within these tests prior to its release.
Many novel soybean varieties with value-added specialty traits are emerging from both the public and private sectors. Some novel varieties will supply relatively small market niches, while others may be of much broader market value. A number of novel varieties will be tested this year to provide soybean producers with reliable data on grain yield of these value-added soybean types. These data will enable producers of novel soybeans to evaluate whether the premiums offered for a given trait offset possible yield lag/drag.
T. Pfeiffer, D.A. Van Sanford, and D. Pilcher
Soybean double-cropped after wheat accounts for, depending on the year, 20 to 40 percent of the soybean acreage in Kentucky. Double-crop soybean yield, is on average, 75 percent of full season soybean. There are numerous factors that contribute to this reduced yield, including later planting date with reduced soil moisture reserves following the wheat crop, shorter day lengths during seed filling, and more frequent dry periods during the seed filling period. Several soybean producers have commented to us that the prior wheat crop directly affected double-cropped soybean in ways such as reduced stand establishment, soybean plant growth, and soybean yield. Mike Garland, a private soybean breeder, conveyed to us that in his experience soybean cultivars were differentially affected by double cropping behind wheat. Furthermore, in a science fair project that his daughter conducted, soybean growth was reduced by watering with wheat straw leachate compared to using only water. In the 1970s Dr. C.E. Caviness at the University of Arkansas conducted research on the phytotoxic effects of wheat residue on soybean growth. He reported on greenhouse pot studies which showed 18 to 38 percent reduced soybean growth due to the addition of 20g wheat straw/kg soil (Crop Science 26:641-643, 1986). Grain crop farmers in Kentucky will continue to follow the wheat/soybean double-cropping system. We want to determine if wheat and/or soybean cultivar selection can overcome some of these obstacles inherent in double cropping. Our first question was whether, in field production tests, straw residue from wheat cultivars grown in Kentucky had differential effects on double-cropped soybean growth and yield.
This experiment was conducted at the Kentucky Agricultural Experiment Station farm at Lexington, Kentucky, in 1997 - 1999. Data are reported for 1997 and 1998 as no soybean plots were harvested in 1999 due to the severe drought. Tests in all years were conducted on a Maury silt loam soil. The University of Kentucky routinely conducts a wheat cultivar performance test which includes released cultivars and promising breeding lines. These tests are conducted with four replications planted in six row plots 10 ft long and 4 ft wide. The wheat performance test in 1997 consisted of 48 entries and in 1998 consisted of 53 entries. Thirty entries were common in the two years. Wheat was harvested when all cultivars in the trial reached maturity. Wheat cutting height was approximately 6 inches, and all straw residue from the combine remained in the field, mostly lying on the plot from which it came or in the alley between plots. Soybean cultivar Asgrow A4715 was planted with a no-till planter in 15- inch rows with a seeding rate of six seeds/ft. Planting dates were 8 July 1997 and 2 July 1998. Gramoxone and Dual were applied pre-emergence. Soybean plots were 10 ft long, and alleys between the soybean plots corresponded to the alleys between the previous wheat plots. Depending on the alignment of the no-till planter and the straw rows in the prior wheat plots, three or four soybean rows were situated entirely within a wheat plot, and three rows were harvested from each plot with a small plot combine. Three inches of irrigation water were applied in September 1998. Soybean matured before the first freeze in both years.
Data were collected on plant stand by counting the number of plants in one meter of two adjacent rows. Plant height was measured at R1 (first flower) and at R8 (maturity). Plots were harvested with a small plot combine, and yields were expressed as bu/A at 13 percent moisture.
The two-year means of soybean growth as affected by the straw residue from 30 wheat cultivars are shown in Table 1. Soybean yields ranged from 27.4 to 20.0 bu/A with a two-year mean yield of 23 bu/A. The yields differed significantly in the two years, averaging 25.8 bu/A in 1997 and 18.2 bu/A in 1998. There was no significant effect of wheat cultivar on soybean yield averaged over the two years (p>0.10), and there was no significant cultivar x year interaction (Table 2). The two-year average of soybean plant height at flowering ranged from 43 to 39 cm depending on the wheat cultivar in the plot with a two-year mean height of 41 cm. There was a statistically significant difference due to the wheat cultivar. The average soybean plant height at flowering differed significantly in the two years, 46 cm in 1997 and 33 cm in 1998, but the year x cultivar interaction was not significant (Table 2). The two-year soybean plant height at maturity ranged from 70 to 66 cm with a mean of 68 cm but did not differ significantly depending on the prior wheat cultivar in the plot. The plant height at maturity differed significantly between the two years, 79 cm in 1997 and 50 cm in 1998. The wheat cultivar in the plot did not affect the soybean plant stand, and there was no year effect or year x cultivar interaction (Table 2). The average plant stand for the 30 cultivars grown in the two years was 159,000 plants/A.
|Table 1. Two-year (1997 and 1998) means of soybean yield, stand, and plant height at flowering (R1) and maturity (R8) as affected by wheat cultivar straw residue from prior wheat plots.|
|Wheat Cultivar||Soybean Yield (bu/A)||Soybean Stand (plants/A)||Soybean Plant Height at R1 (cm)||Soybean Plant Height at R8 (cm)|
|NK Coker 9803||24.5||158,000||39||68|
|NK Coker 9663||22.4||177,000||41||68|
|NK Coker 9543||21.7||155,000||42||68|
|NK Coker 9704||20.1||158,000||41||66|
|Table 2. The levels of statistical significance are indicated for the year, wheat cultivar, and year x cultivar interaction sources of variation for soybean yield, stand, and plant height of soybean cultivar A4715 planted double-crop following 30 different wheat varieties in 1997 and 1998 at Lexington, Kentucky.|
|Source of Variation||Soybean Yield||Soybean Stand||Soybean Plant Height at R1||Soybean Plant Height at R8|
|Year x cultivar||NS||NS||NS||NS|
|** Significant at the p=0.01 probability level.
NS=not significant at the p=0.05 probability level.
We were not able to measure a significant differential effect of wheat cultivar straw residue on soybean yield. However, the mean yields were low and were particularly affected by the dry August and September in 1998. This was followed by the extremely dry summer and fall in 1999 in which irrigation was regulated, and the experiment was not harvested. We did measure a significant difference in soybean plant height at flowering depending on the wheat cultivar straw residue in which the soybean was planted. Plant height measurements are more repeatable than yield measurements, and in this experiment the CV (a measure of relative variability) for plant height was 8 percent compared to the CV for yield of 19 percent. A CV of this magnitude is common for yield measurements in double-crop soybean experiments. There was a significant correlation between the two-year means for soybean height at R1 and soybean yield (r_0.44, p<0.05). This indicates that a small differential effect of wheat cultivar straw residue that affects plant growth early may affect soybean yield. Our experimental techniques are not precise enough to quantify this effect if it actually exists. The research by Caviness et al., which showed differential soybean cultivar responses to wheat straw in greenhouse pot experiments, was also not verifiable in field-scale experiments (Crop Science 26:641-643, 1986).
Soybean has genes which produce a wide range of pubescence densities. Densities higher than normal reduce feeding by aphids and thus reduce the spread of soybean mosaic virus transmitted by the aphids. Experimental soybean lines with increased pubescence densities were developed which eliminated the yield depression associated with the genetic donors of the pubescence-increasing genes. High-yielding soybean that avoids SMV infection should be possible.
Isolates of two different soybean viruses were collected from soybean fields across Kentucky. These isolates varied in their potential to reduce soybean yields, a range of 0 - 40 percent yield reduction for the BPMV isolates and a range of 0 - 50 percent for the SW isolates. Depending on the virus isolates prevalent in an area, virus protection can be valuable.
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