Soil Health Indicators during Transition from ROW CROPS to Grass/Legume SOD.

Grass/legume sod inclusion in row crop rotations changes soil health. The transition to a three-year orchardgrass/red clover (Dactylis glomerata L./Trifolium pratense L.) sod was examined in an existing seven-year organic rotation with four row crop years: corn (Zea mays L.); soybean (Glycine max L. Merr.); wheat (Triticum aestivum L.); and kale/cowpea (Brassica oleracea/Vigna unguiculata). The study objectives were to determine changes in soil physical health indicators, nutrient stratification, and grass/legume biomass during the three-year sod growth period, at two composted beef manure rates applied twice in the rotation, prior to corn or wheat establishment. Soil properties were determined in 2013 and 2014 on a four (annual rotation components: TY0 –kale/cowpea going to grass/legume; TY1 –first sod year; TY2 –second sod year; TY3 –third sod year) by two (non-manured and manured) factorial treatment subset. Sod biomass was determined in 2013 and 2014 on the three (TY1, TY2, and TY3) by two (non-manured and manured) factorial treatment subset. Surface (0-5 cm) soil health parameters increased between TY0 and TY3, including bulk density (non-manured 1.21±0.08 to 1.29±0.06; manured 1.10±0.07 to 1.18±0.09 kg m^-3); wet aggregate GMD (non-manured 3.68±2.28 to 4.32±2.83; manured 3.99±1.39 to 5.27±0.45 mm); organic matter (non-manured 36.1±6.0 to 39.4±5.1; manured 49.3±9.1 to 60.7±9.9 g kg^-1). Nutrient (P, K, Ca, Mg and Zn) stratification was observed. There was a transition year by manure interaction where manure increased the rate of soil parameter change. Both manure addition and sod insertion improved aggregate stability, organic matter, total N and bioavailable nutrients.