Reducing tillage in organic vegetables

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STATE COLLEGE, Pa. — “Is there a way to try something different to move to less tillage?”
That’s the question Anu Rangarajan, the director of Cornell’s Small Farm Program, asked an overflowing crowd at the latest Pennsylvania Association for Sustainable Agriculture (PASA) conference.

Rangarajan urged the growers at this PASA annual Farming for the Future event to manipulate various ways to reduce tillage in their own operations.

She noted that cool, wet falls and springs in New York and other regions in the Northeast can make some of the options more difficult.

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Goal: Soil health

Nevertheless, growers should try to achieve reduced tillage goals to optimize soil health. Enhancing soil quality by conserving organic matter and soil moisture and reducing erosion, minimizing soil disturbance and weed germination, improving labor use, and importantly, reducing compaction will optimize soil health.

Improved soil will lead to greater productivity and farm sustainability.

Consider other practices

Since reduced tillage is one of a number of tools for improving soil quality and health, growers need to plan an overall strategy.

Several factors must be considered with another tool — cover crops. Seeding rates and timing, and the methods of the seeding and killing must be determined. Weed management may need to change.

Cover crop residue can interfere with some practices. Also, in-row challenges and late season clean-up may have to be altered. Rotation will need to be re-examined. The timing of the crop, for example, can dictate the choice of a cover crop.

Some tillage necessary

Rangarajan noted that all organic reduced tillage methods at some point in the rotation will require intensive or inversion tillage. However, the intensity and frequency, plus the energy demanded can be lessened.

Using a chisel plow instead of a moldboard plow lessens the destruction of soil structure and causes less crusting and erosion. Also the type of implement used, as well as, the rotation can minimize tillage frequency.

Minimizes soil disturbance

Rangarajan pointed out that soils in New York are too cool for permanent no-till systems. Consequently, the Small Farm Program focuses on developing profitable reduced tillage systems for vegetable production.

Therefore, the program’s research has concentrated on zone tillage, with particular emphasis on deep zone tillage systems. In zone tillage, soil only 4 to 6 inches wide and of similar depth is disturbed using three offset wavy Rawson coulters. In some cases, narrow rototillers with some of the tines removed are used.

Disturbing only enough soil for a good seed bed is the objective. And, the field is prepared in one pass. To break clods, a grower may occasionally run a cultimulcher type unit over the zone tilled field.

With large seeded crops such as pumpkins and sweet corn, this type of zone tillage works well in healthy soils with good tilth and low compaction. But in poor quality fields that have been extensively tilled in the past, shallow zone tillage may result in yield reductions.

Deep zone tillage achieves vertical tillage under the disturbed zones. This modification uses a straight shank that operates between 6 and 18 inches deep, under the planting zone.

The depth is set to operate just below any compacted areas. In this system, the shank breaks the compaction. This allows better drainage and improves deeper root penetration into the soil for water and nutrients.

Cabbage, peppers tested

In cabbage trials in the deep zone tillage system, no difference in yields resulted in the first two years. But the yield was lower in the third year. Pepper yields were also slightly lower in the reduced tillage system.

Rangarajan suspects that the primary challenge, and that which affected yield, is with nutrient management. With inversion of the soil to aerate and activate microbes, nitrogen mineralization could be lower. However, she points out that yields will at least equalize eventually.

Sidedressing could be an option. The trials used oats and field peas which were then killed, and cereal rye-hairy vetch or triticale-Austrian winter peas, which were over-wintered.

Weed comparisons

Rangarajan concluded that conventional tillage followed by hand weeding had higher weed pressure in two of the three years of trials. Rye vetch residue did not reduce weed pressure, but mechanical cultivation reduced weeds effectively in both systems.

Other systems studied

Fertility may be limiting yields after three years in the deep zone tillage system. Accordingly, trials are under way of modifications, such as permanent crop beds and long rotations which incorporate fallow periods.

Some approaches could require equipment changes. Also, changes in crop rotations may be needed. However, Rangarajan noted there are numerous opportunities for reducing tillage in organic systems.

Get more

Cornell’s assessment manual on soil health, which details soil management, including how to handle constraints, can be accessed at www.hort.cornell.edu/soilhealth.

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