Soil Biodiversity and Grass Cropping Systems

Grass cropping in the rotation and the use of no-till seeding appear to be important components for developing sustainable cropping systems. Grass cropping and no-till seeding improve soil organic matter content, increase the soil microbial biomass, increase earthworm numbers, likely cause a buildup of fungivorous microarthropods and nematodes, and greatly increases the resistance of soil to erodibility. Grasses in the rotation usually result in a large rotational effect. All of these factors point to beneficial effects on soil biodiversity. It is unlikely that soil biodiversity is increased but more likely that the beneficial portions of the diverse population are encouraged. Methods for measuring many components of soil biodiversity on a temporal basis are unavailable. Combinations of microbial biomass, enzyme activity, genetic probes and markers, measurement of mRNA and more precise methods for separating individual micro and mesofaunal groups are potential approaches. In this manner procedures may be developed to follow key groups as indicators of healthy biodiversity. Counts of bacteria and fungi have not been particularly useful. Earthworm counts appear to be a sensitive indicator to the biodiversity of an agricultural system. More studies are needed regarding tillage and cropping interactions as they affect the microflora, microfauna, mesofauna, and macrofauna. Tillage reduces the soil organic matter content, the microbial biomass content, earthworm numbers, and generally greatly increases soil susceptibility to erosion. Tillage can be very damaging to soil structure. Tillage disrupts micro and mesofaunal relationships but results are not clear at this time. It appears that protecting soil from the negative impacts of tillage is essential for preserving soil biodiversity. Grasses in the rotation appear to protect soil biodiversity and are an important component of sustainable cropping systems. Being able to define components of soil biodiversity that promote soil health and sustainable cropping systems are very important to users and policymakers. This knowledge will provide a basis for appropriate decisions based on fact.