PR-410: 1998 Fruit and Vegetable Crops Research Report
Introduction • Tree Fruits • Small Fruits • Vegetables • Diagnostic Laboratory • Appendix A
New strawberry cultivars adapted to matted row production are becoming commercially available with great frequency. To evaluate their performance under Kentucky conditions, we establish a variety trial with new and a few traditional cultivars every few years. In 1997 we established such a variety trial, harvested it in 1998, and have maintained it for a 1999 harvest. The first year’s results are presented here.
Beds were fumigated with methyl bromide 3 weeks prior to planting. Dormant plants were set on May 1, 1997, in rows 3.5 ft apart and 1 ft apart within the row. Individual variety plots were allowed to develop to a 5-ft length and a 1-ft width. Excess growth was removed by cultivation. Beds were watered during the year of establishment as needed and received a fall N application at 60 lbs N/acre. The beds were mulched with straw in late fall; mulch was removed in April 1998 at the first signs of growth on a majority of the plots. The earliest varieties were first harvested on May 15, and the latest were last harvested on June 19. After harvest, beds were subjectively rated on a 1 to 5 scale for vigor based on relative area of the bed filled with plants: 1= few total plants, and 5=complete or 100% of the bed filled.
Kent, Allstar, Cavendish, Idea, and Honeoye all exhibited yields of more than 20,000 lbs/acre (Table 1). The traditional favorite Earliglow yielded well, while the newer Delmarvel had only moderate yields. The varieties that we tested for the first time included Idea, Primetime, Winona, Latestar, and Mohawk. Of this group, only Idea and Primetime yielded well. The earliest varieties, with more than 70% of their yields in the first half of the season, included Delmarvel, Earliglow, Northeaster, Lester, Primetime, and Honeoye. The latest varieties included Idea, Kent, Winona, and Latestar. Bed fill was generally good, with Delmarvel showing exceptional runner plant production, while Latestar was a poor runner producer. Even though Idea and Primetime look good from the data, they were not without problems. Idea produced large berries that were very soft and difficult to harvest, probably a response to the wet harvest season. Primetime produced many moderate to small berries.
|Table 1. Strawberry variety performance in matted row production, 1998.|
|Variety||lbs/acre||1st Half Yield (%)||Bed fill|
|First 5 dates/10 total dates||1=low 5=high|
Interest by Kentucky growers in the strawberry production system developed in North Carolina has grown over the last few years. However, the feasibility of adapting this system to Kentucky’s colder climate and shorter fall planting and spring fruiting periods is unclear. In the last five years we have learned that the dominant variety used in the system in North Carolina, Chandler, will produce high quality, large fruit in this system in Kentucky. The optimum planting date is close to Labor Day in September. Earlier dates may be possible, but high August temperatures impose significant heat stress on transplants, inhibiting their growth and affecting plant establishment. Beds have been winter-protected with spun-bonded row covers and straw, initially placed on the beds when nighttime air temperatures have been (or have been predicted to be) below 25°F for extended periods in the fall. The row covers and straw were removed when plants showed visible growth in the spring. Although row covers were placed back on the beds when weather predictions indicated that a severe frost or freeze posed a danger to open flowers, this did not provide complete protection. Overhead sprinkling for frost protection was not used.
In prior years our yield per plant and estimated yield per acre have been below those obtained in North Carolina. Our yields have not exceeded 0.9 lbs per plant or 15,300 lbs/acre, while yields of at least 1.25 lbs per plant and more than 21,000 lbs/acre are expected. Since plant size at the end of the fall after transplant establishment may be closely related to spring yield, we established a plot in 1996 at three rates of nitrogen to stimulate post-planting growth.
Due to the high cost of establishing the system, some growers have asked if the beds can be carried into a second season to offset these costs. This is not recommended in North Carolina, due in part to the increased potential for disease (especially anthracnose, to which Chandler is very susceptible) and a decline in berry size. To address this question, we maintained the nitrogen-treatment plot of Chandler for a second cropping season to study yield, fruit size, and any problems which might arise. Further, growers have also asked if other strawberry varieties might be adapted to the system. Transplants of a few cultivars in addition to Chandler were made available to us to address this question.
A field plot of Chandler was established on September 5, 1996. Two rows of commercially produced transplants were set at a 1-by-1-ft spacing between plants and rows on methyl bromide-fumigated, raised, black plastic-covered beds. The beds were fertilized with ammonium nitrate at 0, 30, or 60 lbs N/acre broadcast in bed sections prior to laying plastic. The beds were covered with straw and spun-bonded row covers on November 11, 1997. On April 1, 1998, row covers and straw were removed and all beds were fertigated at 15 lbs N/acre weekly for 5 consecutive weeks until first harvest.
The plot was carried over into 1998 to determine the yield potential of Chandler plants in the second season. After harvest in 1997, the plants were mowed to remove foliage. They were not fertilized and were irrigated as needed until September 1997, when they received 15 lbs N/acre once. Runners were removed manually with a sharp knife in July and again in September. Straw and row covers were placed on the beds on October 20, 1997, and removed on April 7, 1998. The beds received 22 lbs N/acre twice at weekly intervals after removal of the row covers.
A field plot was established on September 15, 1997, by the methods described above with the varieties Chandler, Camarosa, Sweet Charlie, Jewel, and Northeaster. The beds received 15 lbs N/acre once after planting and were irrigated as needed. Straw and row covers were placed on the beds on October 20, 1997 and removed on April 7, 1998. The beds received 22 lbs N/acre twice at weekly intervals after removal of the row covers.
Fall nitrogen rate had no effect on yield or fruit size in 1997, so the overall means are shown (Table 1). This may be because the plots all had adequate N in the fall, or the spring N application made up for any differences resulting from the fall applications. Regardless, on most sites with adequate fertility, N should be applied, but the rate will not affect spring yield. Yield per plant and per acre the first year was comparable to previous years.
In the second cropping season, yield per plant and per acre were higher than in the first season, although berry size was smaller. Fruit quality (color, shape, sugar content, flavor) was comparable both years. In 1998, fruit disease, primarily gray mold, was somewhat higher, although foliar disease was no worse than in 1997. The major problems with maintaining the plot into the second year were weed control between the beds and runner removal. Weeds were controlled with a combination of cultivation and herbicide applications using chemicals approved for use in strawberry fields. Manual runner removal was especially labor intensive.
Yield of Camarosa exceeded that of Chandler, while Jewel yield was slightly lower than Chandler (Table 2). Berry size of both Camarosa and Jewel was greater than Chandler. Our subjective field evaluations indicated that Jewel quality was at least as good as Chandler if not better, but that Camarosa looked as good but had less flavor. Nonetheless they both deserve more study. Neither Northeaster nor Sweet Charlie performed well in the study. It should be noted that Sweet Charlie was developed in Florida for their industry and grows in response to even a short warm period during the winter. In our plots, it was in bloom at least 2 weeks before the other cultivars, before the row covers could be safely removed, and many of the first blooms were not pollinated or suffered cold injury, which led to the low yields.
|Table 1. Chandler Fall-planted Plasticulture Plots Years 1 and 2.|
|Year||lbs/acre||lbs/plant||Mean berry wt (oz)|
|1 - 1997||12700||0.84||0.58|
|2 - 1998||18040||1.10||0.52|
|Table 2. Alternative Variety Trial.|
|Variety||lbs/acre||lbs/plant||Mean berry wt (oz)|
The blueberry is a fruit crop that is native to North America. At present, Kentucky has a small established commercial blueberry market and an excellent potential for local sales, U-pick, and home use.
A blueberry cultivar trial was established in 1993 with 8 cultivars in a randomized block design with 5 replications (rows). Plant spacing is 14 feet between rows and 4 feet between bushes. The pH was reduced from above 6 to 5.4 with elemental sulfur prior to planting. The planting is mulched yearly with sawdust mulch, is trickle-irrigated with 1 gph vortex emitters, and receives 6 monthly applications per year (beginning in April) of 17-7-10 Sierra Blend Nursery Mix at the rate of 5 oz per bush per application (about 240 lbs/acre/application of this fertilizer at this plant spacing, which is 777 bushes/acre). The planting is netted during the last week of May, and fruit is harvested from mid-June through the first week of July.
Cumulative yield, the 1998 yield, and average percent fruit ripe by June 12 are shown in Table 1. Duke and Sierra have produced the most fruit to date. Duke has also been the earliest-ripening cultivar in our planting, while Nelson has been the latest to ripen.
These results may be useful to growers in selecting a blueberry cultivar. Avoiding labor peaks and harvest times coinciding with other crops may have to be weighed against choosing the highest-yielding cultivar. Other factors important to cultivar selection are discussed in other UK publications (1,2).
|1993 Blueberry Cultivar Trial.1|
|Cultivar2||Yield (lbs/bush)||Average Percent Fruit Ripe by June 12|
|1The planting was established in April, 1993. Plant spacing is 4 feet between bushes in rows 14 feet apart. There are three bushes per cultivar/rep combination.|
2In descending order of cumulative yield (1995-1998). Cultivars ranked from easiest to hardest to pick: Toro, Duke, Sierra, Sunrise, Bluecrop, Bluegold, Nelson, and Patriot.