Tillage and cover crops in processing vegetables (The Vegetable Grower)
(Editor’s note: Gordon C. Johnson is an Extension Vegetable and Fruit Specialist at the University of Delaware.)
(Nov. 14, 2017) There has recently been increased interest in cover crops and reduced tillage in the production of processing vegetables.
Research has been conducted at the University of Delaware on cover crops and tillage practices for major processing crops including lima beans, sweet corn, peas, and snap beans.
Cover crop research
In 2012, a small plot trial with eight fall planted winter killed cover crop species (mustards, oats, radishes) was established and peas were no-tilled into the plots the following March.
Results showed that forage radish, oilseed radish, and Kodiak mustard treatments provided the best yields.
In addition, a large plot pea study was conducted in a field where winter killed forage has been planted the previous fall.
The trial had three treatments: Conventional tillage, vertical tillage, and no-till.
These studies showed that no-till peas following winter killed forage radish may be a viable option for growers and had better yields than conventional treatments.
In 2013 and 2014 the trials were repeated.
These small plot studies also showed that peas were successfully no-till planted after radishes or mustards.
However, in large plot studies, pea stand counts were lower in both no-till and vertical tillage plots and compaction was lower in conventional plots.
Forage radish did not reduce compaction in large plot studies and there was no yield advantage with no-till peas following winter killed radishes.
Studies were initiated in 2012 looking at tillage practices in processing vegetables.
This included a pea study planted into winter killed forage radish under three tillage practices, a processing sweet corn study planted after winter cover crops under three tillage practices, and a lima bean study planted after small grain under three tillage practices.
Results indicated that peas are successfully no-tilled, early processing sweet corn performed best under conventional tillage and lima beans performed best under conventional tillage.
Studies were conducted in 2013-14 and included pea, sweet corn and snap bean planted into winter killed forage radish under three tillage practices and lima bean, snap bean, and sweet corn planted after wheat under four tillage practices — no-till, strip till, vertical tillage, and conventional tillage.
In 2013 there was no yield reduction with no-till in peas, sweet corn or snap beans in spring studies planted after forage radish.
Summer studies planted after wheat showed no difference between tillage treatments in any crop.
In 2014 there was no yield reduction with no-till in peas or snap beans in spring studies planted after forage radish.
Summer studies planted after wheat showed reduced yields in lima beans in no-till and vertical tillage treatments.
In both spring and fall studies, no-till plots had significantly lower sweet corn yields, whereas vertical tillage and strip tillage performed similarly to conventional tillage.
Overall, studies showed that peas can be successfully no-tilled into winter killed forage radish, oilseed radish and mustard cover crops without a yield decrease or change in maturity.
However, there was not a consistant advantage in yields.
Compaction was not reduced in no-till plots when compared to no-till into forage radish with the exception of wheel tracks.
An advantage to the no-till pea/forage radish winter killed forage crop has been illustrated by the reduced trips across the field and reduced field tracking.
This work gave enough evidence to recommend the practice to growers on a trial basis.
Studies showed that both no-till and vertical tillage are viable systems for producing peas after radish or mustard cover crops.
Spring-planted sweet corn and snap bean are more variable following forage radish due to the potential for stand losses when using no-till.
Vertical tillage performed equal to the conventional tillage in these trials and can be recommended.
For no-till after small grain, results were also more variable.
Sweet corn performed equally well in row cleaner and vertical tillage methods but not consistently in no-till.
Lima beans cannot be recommended to be no-tilled at this time due to potential yield losses when compared to conventional tillage as shown in two of three years of the studies.
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