Posts Tagged ‘no-till’

Soil Health and Vegetable Production

Friday, April 3rd, 2009

Gordon Johnson, Extension Ag Agent, Kent Co.; gcjohn@udel.edu

Experienced growers and crop advisors know that one of the keys to vegetable productivity is a healthy soil. According to the Cornell Soil Health Group, “Soil health describes the capacity of a soil to be used productively without adversely affecting its future productivity, the ecosystem or the environment.” “Soil health emphasizes the integration of biological with chemical and physical measures of soil quality that affect farmers’ profits and the environment.”

From a biological standpoint, soil health relates directly to the root environment and organisms that inhabit the soil. A healthy soil for vegetables will be one that has few limits to root growth; supports high numbers of beneficial soil organisms, such as earthworms; supports a diverse microbial community with high levels of beneficial bacteria, fungi, Actinomycetes, protozoa, and nematodes and low levels of plant pathogens (such as root rot fungi, bacterial and fungal wilt organisms, soft rot bacteria, and plant parasitic nematodes). In a healthy soil, vegetable crop root systems explore a large portion of the soil volume, crops are under reduced stress, and pest problems are minimal. A healthy soil will also support mineralization of organic matter by soil microorganisms at levels appropriate to the climate.

From a chemical standpoint, healthy vegetable soils will be at a proper pH (6.0-6.8 in most soils); have a high cation exchange capacity; have optimal levels of calcium, magnesium, and potassium held on exchange sites; contain optimal but not excessive levels of other mineral nutrients needed by crops, have high levels of organic matter in various levels of decomposition and high levels of stable humus; support aerobic mineralization processes; and be free of toxic minerals from natural sources (such as high free aluminum levels) or from toxic chemical contaminants.

From a physical standpoint, healthy soils will have high levels of stable aggregates in the topsoil (creating a stable granular structure); an optimal mix of pore sizes (macropores and micropores) so that it is well aerated in the root zone, well drained, but also has a high available water holding capacity; and a low bulk density relative to the soil texture. They will be free of compaction, which limits root growth. Healthy soils are highly permeable to water and not prone to crusting.

From a management standpoint, vegetable growers have several tools at their disposal to maintain and improve soil quality including:

Crop Rotations
It is critical to choose crop rotations that minimize soil born diseases and at the same time can help to improve or maintain good soil physical and chemical characteristics. Mixing in deep rooted crops, crops with extensive root systems, and crops with high residue in the rotation will add organic matter, leave root channels which benefit future crops, break up compaction, and recycle nutrients from deeper in the soil. Crops that have similar pest profiles should not being planted consecutively, especially those vegetable and field crops that are susceptible to the same soil born diseases. Crop diversity in rotations is a key to maintaining or improving soil quality health.

Cover Crops and Green Manures
These are crops that are specifically used to recycle nutrients and to add organic matter to the soil. They occupy land and time periods in the rotation when grain and feed crops are not being grown. It is important to always have something growing on the land, even when not in production, to maintain soil health. Including cover crops and green manures in rotations increases crop diversity and provides the benefits associated with that diversity. For example, certain cover crops and green manure crops have been found to have benefits in reducing soil born diseases.

Reduced Tillage
It is important to reduce the levels of tillage in soils to maintain soil health. The more that soils are tilled the more soil aggregates are broken down and the more quickly soil organic matter is oxidized (decomposed). Soils that are excessively tilled generally have lower organic matter levels and often have poor physical characteristics. While some vegetables and vegetable cropping systems are not well adapted to no-till planting, there have been some great successes with vegetable no-till, such as pumpkins. Reduced tillage tools may be appropriate for other vegetable cropping systems. Zone tillage, vertical tillage (such as turbo till), and soil aeration are all examples of approaches that may be used successfully in vegetables. Other field crops in the rotation should be planted using no-till or reduced tillage tools as much as possible and attempts should be made to conserve crop residue (as long as it does not interfere with the vegetable portion of the rotation).

Compost, Manures, and Other Organic Matter Additions
Compost, manures, and other organic matter sources can be added to vegetable soils to improve soil quality. This approach is most appropriate where heavy tillage must be used, such as in plasticulture. By adding these organic matter sources you can counteract the effect of the heavy tillage and maintain soil health. These materials offer all of the benefits associated with increased organic matter in the soil: increased microbial diversity, reduced disease pressure, increased nutrient holding capacity, slow release of mineral nutrients, increased water holding capacity, improved aeration, and reduced bulk density.

Traffic Management
Managing traffic in vegetable crops is another soil health key. By reducing trips across a field with heavy equipment and trucks, soil compaction is reduced and soil health is maintained. Limiting traffic to designated areas, driveways, drive lines, or tram lines is another way to achieve this because areas in between are conserved and remain uncompacted. These heavy traffic areas can then be targeted with a subsoiler or other tillage equipment to break up compaction. While it is not always possible, reducing trips across vegetable fields when wet is also important. One pass by heavy equipment over wet soils can destroy the productivity of that area for a long period of time.

In 2009, the University of Delaware Cooperative Extension is launching a soil health education initiative specifically aimed at vegetable growers. In this initiative we will provide vegetable growers with information on soil health and vegetable production, soil health testing methods, how to evaluate soil health on farms, and how soil health testing can fit into an integrated pest management plan. We will be working with growers on how to create healthy rotations for vegetable crops specific to their farms. We will be doing demonstrations and field trainings on the use of different cover crops and green manure crops in vegetable rotations and demonstrations on the use of different types of composted materials and their the effects on soil health and subsequent vegetable production. For more information on this initiative, contact Gordon Johnson or Joanne Whalen.

Fall Herbicide Treatments for Next Year’s No-Till

Friday, September 19th, 2008

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Fall herbicide treatments have been discussed as options for no-till crops. The idea is to apply an herbicide this fall that will control existing weeds and possibly provide residual weed control so that fields do not have lots of vegetation next spring. Less vegetation in the spring allows the soil to warm up faster and conserve moisture. This practice has worked in many of the Midwest states, but their winters are colder and often with more snow cover. We have looked at various herbicides the past few years for no-till soybeans. Products tested include Valor, Canopy EX, and Express. In our trials the fall treatments were applied with 2,4-D plus Gramoxone or glyphosate. Applications were made in late October to mid-November, after weeds have emerged. Most of the products provided some control when evaluated in March. The remaining weeds were small and less vigorous. However, as the spring progressed Valor and Express became much less effective, as well as allowed for spring germination of many species. Those plants that were present were large by early May. As a result, non-selective herbicide was needed before soybean planting. However, fall treatments helped to conserve spring moisture and provided for a better soybean stand when rainfall was limited. In 2006 and 2007, Canopy EX applied in the fall with Gramoxone or glyphosate provided excellent weed control up to the time of soybean planting (including horseweed). Canopy EX restricts your rotation to allow only soybeans the following spring.

Fall treatments should be applied while the plants are still actively growing. If you are considering a fall herbicide program, be sure to consider all pros and cons, including resistance management.