Understanding Long-Term Cropping Systems Effects On Water Stable Aggregates.

Soil aggregation, measured as % water-stable aggregates (WSA) is an important indicator of soil quality that can be changed by soil and crop management practices, and influenced by several soil characteristics. Understanding the management practices that influence WSA most can help identify strategies to promote WSA. The objective of this study was to understand what factors explained the most variability in WSA of soils collected from four different long-term cropping systems during three different seasons in Pennsylvania. Soils were sampled from 10 crop entry points of four cropping systems that had been in place for 36-years, including: two annual systems: continuous corn (Zea mays L.), corn-soybean [Glycine max (L) Merr.]; a perennial system: 4yr corn-4yr alfalfa (Medicago sativa L.); and a diverse system: corn-oats (Avena sativa L.)/wheat (Triticum aestivum L.)-2yr red clover (Trifolium pratense L.)+ timothy (Phleum pratense L.) in spring, summer and autumn, 2005. Percent WSA were measured by wet-sieving the air-dried and slaked 1-2 mm aggregates in water. Other measured soil characteristics included soil organic C, soil microbial biomass C, soil moisture content, and soil matric potential. The proportion of time with presence of live roots and soil disturbance due to tillage were also estimated for each cropping system. Soil characteristics were statistically analyzed to examine the influence of cropping systems; results will be presented.