SOIL MICROARTHROPODS IN LONG-TERM NO-TILLAGE AND CONVENTIONAL TILLAGE CORN PRODUCTION

Cultivation is known to reduce the number and diversity of microarthropod (Acarina and Collembola) populations from levels observed under natural forest or grassland vegetation. Under no-tillage crop production, the soil remains relatively undisturbed and plant litter decomposes at the soil surface, much like in natural soil ecosystems. The objective of this study was to investigate whether microarthropod populations under long-term (19 yr) continous corn (Zea mays L.) production were increased by no-tillage (NT) vs. conventional tillage (CT; moldboard plow and harrowing) managment. Numbers of microarthropods were also obtained from a soil managed as the CT treatment for 15 yr until seedling to bromegrass (Bromus inermus L.) hay for the last 4 yr. During the growing seasons over 2 yr, soil cores were taken every 2-3 wk and extracted for microarthropods using a high gradient extractor. The surface 5 cm of soil was sampled during the first year. All three treatments were different (P < 0.05), with bromegrass, NT and CT soils containing respectively, 15.9, 12.4, and 5.8 microarthropods x 1000 m-2 of which 84, 69, and 70% were Acarina. In the second year, the surface 15 cm was sampled and the number of microathropods in the corn soils was similar (P < 0.05), containing 33.6 microarthropods x 1000 m-2, 92-98% of which were Acarina. However, microarthropods and soil organic-C were more concentrated in the surface 5 cm of soil in NT than CT. The soil under bromegrass contained 1.3 times more microarthropods (99% were Acarina) than under continuous NT and CT corn. Thus, when examined to a depth of 15 cm, 19 yr of NT corn did not increase the size of the microarthropod populations compared to CT, whereas production of bromegrass hay for 3-4 yr following long-term continuous CT corn did increased microarthropod numbers.