Soil Management

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1. Minimize mechanical and/or chemical damage of farmlands through phasing out the use of toxic pesticides, toxic fertilizers and toxic fungicides.

2. Better protect soil by increasing soil organic matter (which will promote better drainage), reducing tillage, promoting cover cropping, the use of windbreaks, using composts and other organic matter like manure.

3. Promote diversity by using new cultivars (like sugar belle oranges to combat greening) that are more robust and flood/drought tolerant and new species that seem to match a particular region’s changing climate.

4. Precision growing that promotes farms in regions where they will prosper. As practiced in ancient times, grow desert crops in the desert. IE California could become the date capital instead of the water consuming almond capital, water crops should be grown in wetlands.

5. Intelligent planting ie phase out growing alfalfa as feed for livestock because it uses 4 times as much water than wheat. Some crop varieties have greater tolerance for moisture stress than current dominant crops (ie switching from spring to winter wheat will help alleviate moisture stress).

Managing Soil Tips from Penn State

1. Reduce Inversion Tillage and Soil Traffic

Excessive tillage is harmful to soil health in a number of ways. Tillage increases oxygen in the soil, stimulating microbial activity, and results in the decomposition of organic matter. Tillage also disrupts soil aggregates, exposing particles of organic matter that had been physically protected within aggregates to microbial consumption. If additions of organic matter are not sufficient to counteract the losses from decomposition, organic matter levels will decline over time, reducing soil health. Inversion tillage also reduces the soil coverage provided by crop residues, leaving soil more exposed to erosion.

Common Primary Tillage Implements

Moldboard Plow

  • Inverts the soil to bury residues, terminate cover crops and perennial sod, and kill weeds

Disk Plow

  • Concave disks mounted in a gang cut residue and invert soil laterally, loosening soil and mixing residue into the soil
  • Soil disturbance and residue incorporation depends on the size, shape, and tilt angle of the disks

Chisel Plow

  • Curved shanks with chisel points are dragged through the soil without inversion
  • Loosens surface soil, mixes some residue into the soil
  • Soil disturbance and residue incorporation depends on the width and twist of chisel points

Tillage with a moldboard plow (left side of the photo) inverts the soil, burying weeds, sod, and surface residue. Chisel plowing (right side of the photo) loosens the soil without inversion, retaining residue on the soil surface.

Tillage can also disrupt the hyphal network of mycorrhizal fungi, which can lead to their decline over time. When not managed carefully, most inversion and noninversion tillage methods compact the subsoil, creating a plow pan, which restricts root growth and access to water and nutrients in the subsoil. Excessive wheel and foot traffic can compact the surface soil, reducing macroporosity and impeding root growth.

Soil Compaction

Soil compaction occurs when soil is exposed to excessive foot and equipment traffic while the soil is wet and plastic. This traffic compresses the soil, reducing pore space and increasing bulk density. Macropores are compressed more so than micropores, leading to poor water infiltration and drainage and increased runoff. Soil compaction increases soil hardness, making it more difficult for plant roots to grow through the soil. The reduction in pore space also affects habitat for many soil organisms that are very small, cannot move soil particles, and are restricted to existing pore space and channels in the soil.

Physical disturbances such as inversion tillage can also have profound effects on the biological properties of soil. Compaction and removal of surface residue may contribute to reduction in soil moisture and living space for soil-dwelling organisms. Diversity and abundance of arthropod predators associated with the soil surface can be greater under conservation tillage management in comparison to conventional inversion tillage, and natural control of pest insects in soil may be enhanced in conservation tillage systems. Beneficial insects associated with the soil are more likely to survive in fields where noninversion (e.g., chisel plowed) tillage is used. In comparison with inversion tillage practices (e.g., moldboard plow), noninversion tillage causes less soil disturbance and thus less direct mortality of beneficial soil organisms.

Some tillage is still a necessary practice in certain production systems, especially organic systems that do not use herbicides for weed control. When tillage is used, it is important to offset the increased rate of organic matter decomposition with increased inputs of organic matter through crop residues, manure, and compost. Integrating several years of a perennial forage crop into a rotation with annual crops that require tillage is one way to reduce tillage intensity over time.

2. Increase Organic Matter Inputs

To maintain or increase soil organic matter levels, inputs of organic matter must meet or exceed the losses of organic matter due to decomposition. Healthy crops can be a valuable source of organic matter, and crop residues should be returned to the soil to the extent possible. Incorporation of cover crops or perennial crops and judicious additions of animal and green manure and compost can also be used to increase or maintain soil organic matter. Soil organic matter content can be monitored over time if you request an organic matter analysis when submitting soil fertility samples to your soil testing laboratory. Be sure that your organic matter comparisons over time are based on data from the same lab or from labs that use the same procedure for organic matter analysis, as results can differ significantly between analysis methods.

3. Use Cover Crops

Cover crops contribute numerous benefits to soil health. They keep the soil covered during the winter and other periods of time when crops are not growing, reducing the risk of erosion. The biomass produced by cover crops is usually returned to the soil, enhancing organic matter levels. Cover crops with taproots can create macropores and alleviate compaction. Fibrous-rooted cover crops can promote aggregation and stabilize the soil. Species of cover crops that host mycorrhizal fungi can sustain and increase the population of these beneficial fungi. Legume cover crops can add nitrogen to the soil through nitrogen fixation. Cover crops can retain nitrate and other nutrients that are susceptible to leaching losses.

Forage radish, a taprooted cover crop (left), and cereal rye, a fibrous-rooted cover crop (right).

4. Reduce Pesticide Use and Provide Habitat for Beneficial Organisms

Beneficial insects that contribute to biological control or pest organisms can be harmed by the application of broad-spectrum insecticides. Farmscaping is a whole-farm, ecological approach to increase and manage biodiversity with the goal of increasing the presence of beneficial organisms. Farmscaping methods include the use of insectary plants, hedgerows, cover crops, and water reservoirs to attract and support populations of beneficial organisms such as insects, spiders, amphibians, reptiles, bats, and birds that parasitize or prey on insect pests. Farmscapes placed in contours between fields, steep ditches, or places that are easily eroded give stability to the soil. Farmscaping can also be used as a filter strip to prevent water runoff and soil erosion. Plants used in farmscapes contribute to healthy soil by adding organic matter, the base of the soil food web.

5. Rotate Crops

Diverse crop rotations will help break up soilborne pest and disease life cycles, improving crop health. Rotations can also assist in managing weeds. By growing diverse crops in time and space, pests that thrive within a certain crop are not given a chance to build their populations over time. Rotating crops can also help reduce nutrient excesses.

6. Manage Nutrients

Carefully planning the timing, application method, and quantity of manure, compost, and other fertilizers like manure will allow you to meet crop nutrient demands and minimize nutrient excesses. Healthy, vigorous plants that grow quickly are better able to withstand pest damage. However, overfertilizing crops can increase pest problems. Increasing soluble nitrogen levels in plants can decrease their resistance to pests, resulting in higher pest density and crop damage.

Maintaining a soil pH appropriate for the crop to be grown will improve nutrient availability and reduce toxicity. Maintaining adequate calcium levels will help earthworms thrive and improve soil aggregation.

Using diverse nutrient sources can help maintain soil health. Manure and compost add organic matter as well as an array of nutrients, but using just compost or manure to meet the nitrogen needs of the crop every year can result in excessive phosphorus levels in the soil. Combining modest manure or compost additions to meet phosphorus needs with additional nitrogen inputs from legume cover or forage crops in a crop rotation can help balance both nitrogen and phosphorus inputs.

Maintaining residue on the soil surface helps to suppress weeds, conserve moisture, and provide habitat for insect predators.

Managing Nutrients in Soil

Nitrogen (N) Management

  • Nitrate nitrogen is susceptible to leaching losses because the negative charge of the molecule is not held by cation exchange sites of soil particles. Leaching occurs mainly in the fall, winter, and early spring.
  • Nitrogen in urea-containing fertilizers and manure is susceptible to volatilization losses as ammonia gas when not incorporated into the soil.
  • Nitrate nitrogen can be lost to the atmosphere through conversion into nitrous oxide and nitric oxide gases by microorganisms in warm, poorly aerated soil.
  • Nitrogen losses can be minimized with appropriate timing and application of fertilizers and manures and by using cover crops to limit leaching losses in the winter.

Phosphorus (P) Management

  • Phosphorus is tightly bound to soil particles and does not easily diffuse through the soil.
  • Mycorrhizal fungi can assist plant roots in P acquisition in low-P soils.
  • Adding organic matter can mask the P binding sites on soil particles, increasing P availability.
  • Phosphorus can accumulate to excessively high levels when P inputs in manure and fertilizer exceed P removal by crops; this can occur in soil that receives annual manure applications at rates to supply crop nitrogen needs.
  • Erosion can transport soil particles with high levels of P into waterways where P can become a pollutant.
  • Environmental P pollution can be limited by reducing erosion and maintaining soil P levels in the optimum range of 30–50 ppm Mehlich 3 P.
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