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 3-yr orchardgrass (Dactylis glomerata L.) and red clover (Trifolium pratense L.) sod was examined in an existing 7-yr organic rotation with four row crop years: corn (Zea mays L.), soybean (Glycine max L. Merr.), wheat (Triticum aestivum L.), and kale with cowpea (Brassica oleracea and Vigna unguiculata). The study objectives were to determine changes in soil physical health indicators, nutrient stratification, and grass and/or legume biomass during the 3-yr 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 and cowpea going to grass-legume sod; 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 geometric mean diameter (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 × 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.