Organic Crop Rotations: Effect of Temporary Grass Component on Corn Productivity.

In organic crop rotations, a temporary grass component may improve soil quality and consequently benefit crop performance. The objective of this research was to evaluate corn biomass/yield affected by changes in soil quality in two different rotations: with and without grass and at two rates of manure application. Variables measured were corn biomass/yield, bulk density (BD), wet/dry aggregation(WA&DA GMD), and soil nutrients(SOM, N, P, K, Ca, Mg, and Zn).

The research was conducted on a rotation experiment at the WVU Organic Farm in Morgantown, WV. Two rotations were studied: four and seven year durations, with the same crop sequence (corn, soy, wheat, kale), and three years of orchard-grass/red clover added to the 7-year rotation. Two bi-annual manure rates (Low (L):0 and High (H):22.5Mg/ha) were applied. Analysis of variance (ANOVA) was performed on the data.

For the year 2014 results indicated that there was no significant effect of manure rate on corn productivity, although manured plots exhibited higher productivity (1.08kg/ha biomass, 4335kg/ha yield) than unmanured plots (0.78kg/ha biomass, 3885kg/ha yield). Several soil properties were significantly improved by manure addition in the 7-yr rotation (e.g. BD=H 1.22g/cm³, L 1.33g/cm³; SOM=H 68.1g/kg, L 40.9g/kg) while not in the 4-yr rotation. Manured plots had significantly higher surface (0-5cm) fertility (e.g. P =43.9ppm, K=143.6ppm, pH =5.65) than unmanured plots (e.g. P= 15.2ppm, K=107.4ppm, pH=5.08).

A significant effect of rotation was observed on several soil properties. In the 7-yr rotation, BD was significantly lower (1.15g/cm³) and OM was significantly higher (54.5g/kg) than that of plots in the 4-yr rotation (BD (1.28g/cm³) and SOM (39.5g/kg)). Wet aggregate stability in the 7-yr rotation was significantly higher (5.62mm) than that of plots in the 4-yr rotation (2.32mm).

This research may increase the understanding of the effect of a grass component within organic rotations on soil quality and corn productivity.