Gordon Johnson, Extension Ag Agent, Kent Co.; gcjohn@udel.edu
Pea harvest will begin at the end of May; the first pickles have been planted; early plantings of sweet corn and snap beans are in the ground; lima bean planting will begin at the end of the month. A key to profitability in these processing vegetables is having a high percent of the crop at peak when harvest begins. Wide variability in crop maturity will lead to significant quality discounts. To achieve maximum returns and highest quality, the crop should be as uniform as possible. The following are considerations in achieving uniform crops:
1. Choose your most uniform fields to plant processing vegetables. Wide variations in soil conditions will lead to differences in crop growth, development, and maturation. Early plantings should be in fields that warm up evenly, with few, if any, low spots and wet areas. Avoid planting in fields that are prone to crusting. Avoid fields with shading from woods or hedgerows.
2. Tillage operations should be performed as to produce a seedbed that will allow for good seed to soil contact and rapid seed emergence. If soils are dry, irrigate to raise moisture levels prior to seedbed preparation. Make an effort to deal with compaction prior to planting. Variability in field compaction is one of the primary causes for non-uniformity in processing vegetables. Manage field traffic prior to and after planting to avoid additional compaction.
3. Planting operations are critical. Use planters that will deliver seed precisely with uniform spacing and depth. The goal is to have the crop all emerge at once. Late emerging plants will be much less productive and will be behind in maturity. This is particularly important for processing sweet corn. Change planting depth to account for soil conditions (moisture and temperature).
4. Plant entire field sections that are to be harvested together on the same day. Large differences in maturity have been seen in delays of just one day. In spring plantings, plant when a warming trend is predicted. Avoid planting if heavy rains are forecast. Avoid planting in wet soils and in conditions unfavorable to germination and emergence. Do not plant when soil temperatures are below critical values for that crop.
5. Use high quality seed. Seed should be of high vigor and high germination percentage. Handle seed gently so as to preserve quality. This is particularly important with beans.
6. Pay attention to seed protectant chemical choices and adjust seed or furrow/banded applied fungicides and insecticides to match fields and planting dates.
7. Work with processors to match varieties for the planting date as much as possible. Early plantings should be made with cold tolerant varieties. Late plantings should be planted with varieties that can tolerate heat during maturation. Split sets are a particular problem in crops exposed to stress conditions, especially heat and/or water stress.
8. Plant at recommended populations. The interaction of plant density with emergence and germination rate can have a significant effect on uniformity at harvest.
9. Manage irrigation so that water is applied as uniformly as possible. Center pivots and linear move systems are preferred over traveling guns. Have irrigation systems checked for uniformity. Money spent on replacing bad nozzles will be rewarded with more uniform crops. Use irrigation as tool to achieve even emergence in dry conditions and to “soften” crusted soils.
10. Pay attention to soil fertility variations. Processing vegetables will benefit from fields that have been grid sampled, particularly to manage soil pH. Many fields have wide variations in pH and variable rate liming can help to achieve a more uniform crop.
11. Apply all inputs as evenly as possible. This includes fertilizers, fungicides, insecticides, and herbicides. Check fertilizer application equipment, especially starter fertilizer applicators and sidedressing equipment for uniformity.
12. Avoid the use of pesticides that may cause damage to the crop. In particular, herbicides should be used with care. Non-uniform application or incorporation of preemergence herbicides will lead to variable crop emergence; damage by post-emergence herbicides will lead to more variable crops.
13. Weed control is an important part of achieving uniform crops. Map weed populations in fields and target controls to take into account higher weed density areas, or areas with particularly troublesome weeds (spot spraying, hand work or extra cultivation may be necessary in these areas).
14. Cultivation practices should be done at a uniform depth and distance from the row. It is best to use one operator for a given field. Train operators on how to cultivate in a proper manner. Adjust cultivators for differences in soil conditions. Excessive root pruning during cultivation can lead to delays in maturity, additional stress on the crops, and increase the risk of split sets.