Evaluating Alfalfa Mulch As a Nitrogen Source for Corn Production.

Organic systems without livestock are common throughout much of the Corn Belt, requiring organic corn and grain producers to find ways to supply nitrogen to their crops without manure.  While alfalfa and other forage legumes grown in rotation with organic corn can meet crop needs, it is difficult for farmers without livestock to justify maintaining the necessary acreage of perennial forage for this practice.  When organic alfalfa is grown the hay may be sold, with much of the fixed nitrogen exported off-farm.  Although alfalfa mulch has been investigated as a nitrogen source for vegetables and small grains, little work has been done to confirm its capacity to supply N to organic corn, a high N‐demanding crop.  The objective of this research was to test effects of varying rates of spring surface-applied alfalfa mulch on corn crop yields and nitrogen, weed biomass, and soil nutrient status.  Replicated field research was conducted at two research stations in 2010 and 2011.  Alfalfa was applied at rates containing 50, 100, 150 and 200% of the recommended N rate. Other treatments included a 0 N control and the recommended rate of  N fertilizer.  Alfalfa applied at the 150 and 200% rates resulted in corn yields, plant and grain nitrogen uptake, and soil N status equal to those with fertilizer N application.  Weed biomass levels were significantly lower in the two higher alfalfa application treatments, while the 50 and 100% rates of surface mulch applied had equal or greater  weed biomass, than the N fertilizer treatment.