Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Most fresh market vegetable crops are either grown under conventional tillage or plasticulture systems requiring significant tillage. From a soil health perspective organic matter is the driver for healthy soils and the more the soil is worked, the faster that organic matter is decomposed and lost from soils.
One solution for this dilemma is using no-till, where organic matter can be conserved or increased. The best success story with no-till vegetables has been with pumpkins, which are commonly direct seeded through a killed cover crop mulch (often hairy vetch or rye) or through crop residue (most commonly barley or wheat small grain stubble). The mulch provided keeps pumpkins off the ground and has greatly reduced fruit diseases and improved quality. Other seeded crops such as sweet corn and snap beans have been successfully no-tilled in the region.
No-till also has been shown to work with transplanted crops. Systems were developed and tested for tomatoes on hairy vetch and for numerous crops transplanted through small grain cover from peppers to cantaloupes. There were several no-till transplanters developed and we tested one at UD back in the 1990s.
Incorporating leguminous cover crops into these systems can reduce nitrogen needs for the vegetable crop being grown. In the pumpkin no-till into hairy vetch system, typically no additional N will be needed.
There are several reasons why no-till has not been more widely adopted for vegetable crops. No-till vegetables cannot be grown for early crops which are often the most profitable, due to soil temperatures remaining cooler, longer. Establishment can be an issue, especially through thick cover crop mulches. Weeds are controlled partially by the mulches and herbicides can be used for residual control; however, weed escapes can be problematic because cultivation is not available as a tool. Certain pests such as slugs, mites, and several insects can be an issue in no-till. Drip irrigation is also more difficult to use in no-till.
An alternative that combines some of the benefits of no-till with conventional tillage is strip-till, where cover is maintained between rows and a 6-12 inch tilled strip is where vegetables are seeded or transplanted. Strips can be formed with narrow rotary cultivators or with strip till coulters. This allows for earlier crops and for better establishment. A subsoiler can be run in the strips to improve root development. Management of the strip area needs to be planned ahead of time so that cover crops do not get too large – strips are formed when cover crops are small. There is also potential to install drip irrigation in the strips. In a strip-till system weed management is critical and residual herbicides will be critical.
Research has shown that for many vegetables, yields in strip till and no-till are comparable or higher than similar season conventional or plasticulture production.
The following are some of the keys to success with no-till fresh market vegetables:
- Well drained soils are best for no-till and strip-till.
- Fields to be no-tilled or strip-tilled should have minimal weed seed banks and little or no perennial weed problems.
- An effective cover crop is required for no-till and strip-till systems to work. The cover crop should produce enough biomass to cover the soil and provide mulch that limits light and weed germination. Winter cover crops that have worked well for vegetable no-till in our area are hairy vetch, crimson clover, rye, vetch-rye combination, ryegrass, and subterrenean clover. For late summer no-till vegetable crops, several of the millets have provided good cover.
- The cover crop should be easy to kill by chemical or mechanical means and have little or no-regrowth potential. Proper timing of cover crop kill is necessary to avoid reseeding in no-till systems. For strip-till systems, strips need to be formed early in the growth stage of the cover.
- Attention needs to be paid at planting in no-till systems to provide good soil-seed contact for direct seeding or root placement and firming for transplants.
- Provision should be made for moving residual herbicides into the soil through the mulch cover. This may require overhead irrigation.
- Provision should be made to manage weed escapes. This may require spot spraying or hand weeding.
A thick stand of rolled rye with windbreaks left in place that can be used for no-till planting of many different vegetables.
Note the thick rye mat that totally covers the soil effectively controlling annual weeds.
Chevron bladed roller crimper for rolling cover crop prior to transplanting.