Soil Health


9457236711_c6f0bf3c67_kThe term soil health is often used interchangeably with soil quality. Both refer to the capacity of soil to sustain plant and animal productivity, maintain or enhance water and air quality and support human health and habitation. Soil health integrates biological, chemical and physical qualities of soil that affect agricultural productivity and the environment. Soil is generally not considered healthy if it is managed for short term productivity at the expense of future degradation.

Soil health deals with both inherent and dynamic properties of soil quality. Inherent soil quality refers to the natural characteristics of the soil, such as its texture. These qualities are the result of soil forming factors and cannot be changed easily.

Dynamic soil quality can be affected by management practices. Management choices can affect soil organic matter levels, soil structure, water and nutrient holding capacity, erosion, water quality, microbial biomass and microbial diversity.

How organic production interacts with soil health

soil-2Organic management aims to improve soil health through addition of organic matter and total reduction of chemical fertilizer. Additions of compost and manure are important in building soil organic matter and providing nutrients for crop growth. At Bradford, we produce our own compost from food wastes and we purchase turkey litter compost.

The use of cover crops is also an important factor of both soil health and organic production. Cover crops add organic matter, increase water holding capacity and water infiltration, and enhance nutrient cycling.

Tillage

Tillage for weed control is very common in organic production and can be detrimental to soil health. Negative effects of tillage include:

  • Compaction of soil below the depth of tillage
  • Increased susceptibility to water and wind erosion
  • Accelerated decomposition of soil organic matter
  • Destruction of soil structure
  • Loss of mycorrhizal fungi, earthworms and other advantageous soil macro and microorganisms.

One way to improve soil health and build organic matter is to reduce tillage as much as possible. Because tillage is often used for weed control in organic production, we are searching for ways to reduce weeds and reduce the soils weed seedbank without using tillage.

Organic Transition Study

We are comparing seven different organic cropping systems to see which do the best job of reducing weeds and building soil quality during the three years of transition from conventional to organic production. This project is funded by the Ceres Trust.

Rotational System
Year Cover Crop Only (CCO) Modified Cover Crop (MCC) No-Till Corn-Soybean (NTCS) No-Till Sorghum-Soybean (NTSS) Conventional Corn-Soybean (CONVCS) Conventional Sorghum-Soybean (CONVSS) Modified Conventional (MC)
2012 winter crop mix of hairy vetch, winter rye, Austrian pea, oats, tillage radish, crimson clover
tillage minimal till minimal till none none as needed as needed minimal till
summer crop sorghum-sudangrass sorghum-sudangrass hay soybean soybean soybean soybean sorghum-sudangrass
2013 winter crop mix of hairy vetch, winter rye, Austrian pea, oats, tillage radish, crimson clover wheat
tillage minimal till minimal till none none as needed as needed as needed
summer crop buckwheat sorghum-sudangrass hay corn grain sorghum corn grain sorghum soybean
2014 winter crop mix of hairy vetch, winter rye, Austrian pea, oats, tillage radish, crimson clover wheat cover crop mix
tillage minimal till minimal till none none as needed as needed as needed
summer crop sunn hemp corn soybean soybean soybean soybean corn

Rationale for each rotation:

Cover crop only: Uses the transition years as a time for intense soil building and weed control. Sorghum/sudangrass increases organic matter build-up, and along with buckwheat, is an excellent weed smother crop. The terminal rotation crop is high nitrogen-fixing Sunn hemp, providing N for the next year’s cash crop. The other six treatments will be compared to this system as a strategy for maximum soil building and weed control vs. practices that provide a cash crop during the transition years.

Cover crop modified: Based on two years of good soil building and weed control before a cash corn crop. The sorghum/sudangrass will be mowed once during the season to force greater root development, which produces more soil organic matter than aboveground vegetation. Residue will be removed from one cutting to simulate a hay crop. A corn cash crop is grown the third year.

No-till: Uses covers crops with a soybean/corn/wheat rotation, which is a typical grain crop rotation once organic certification is achieved. A no-till strategy is included because many Missouri farmers want to see the feasibility of organic no-till demonstrated before adopting it. No-till reduces the carbon footprint of organic farmers by using cover crops flattened and killed by a roller/crimper as a weed blocking mulch instead of relying on multiple tillages for weed control.

Conventional tillage: This is the most widely used organic grain crop system in Missouri and includes a soybean/corn/wheat rotation with cover crops exploited for nitrogen, weed control and soil building. Tillage prior to planting and during the growing season will follow conventional practices and be used as needed to control weeds.

Sorghum-soybean rotations: Both no-till and conventional rotations will be replicated using grain sorghum as the 2nd year cash crop rather than corn. Grain sorghum has a history of success in Missouri, has better weed control and yields more organic matter than corn.

Modified conventional: The transition begins with one year of soil building and weed suppression, using a winter cover crop mix and sorghum-sudangrass in the summer. This is followed by winter wheat and soybeans in year two and the cover crop mix and corn in year three, with tillage as needed to control weeds.

Soil Health Testing

soil-4On organic research plots, we test changes in soil health from management practices by testing for microbial diversity and activity, active and total soil organic carbon, and aggregate stability. We also test soil pH, cation exchange capacity, and levels of available nutrients.

The University of Missouri has two soil testing laboratories. The Soil and Plant Testing Lab tests for CEC, nutrients, pH and soil organic matter. The Soil Health Lab tests active carbon, aggregate stability and microbial activity and diversity.

It is extremely important to soil test to understand how your management practices are affecting the health of your soil.

At Bradford, like much of Missouri, our topsoil is very thin and must be protected to maintain sustainable soil health.