REDUCING COMMERCIAL NITROGEN FERTILIZER BY GROWING LEGUMES
Sustainable Agriculture
James Hoorman
Assistant Professor
Ohio State University Extension
Ottawa
Abstract
Legumes are being used in Ohio to produce home grown nitrogen to reduce the use of commercial fertilizer. Cowpeas and winter peas consistently produced 135 to 150 pounds of nitrogen for corn. Cover crop biomass production times the nitrogen content of the biomass results in total nitrogen contribution. Cowpeas (7800 #/A), Mung bean (7500#/A), and winter peas (6500#/A) had higher biomass production (LSD=.05) than hairy vetch, red clover, and crimson clover. The nitrogen content of the legume biomass ranged from 2 to 4 percent with Mung bean (4%), red clover (2.7%), winter peas (2.50) and cowpeas (2.4%). Total nitrogen from the legumes ranged from 60 to 275 pounds per acre with Mung bean (275 #N/A), Cowpeas (190#N/A), and winter peas (160#N/A) having the highest total nitrogen. The nitrogen contribution to corn is dependant on the carbon to nitrogen (C:N) ratio of the legume residue and how quickly the residue decomposes. The C:N ratio of the legume residues ranged from 10 (Mung bean) to 22 (crimson clover). The total nitrogen for corn was approximately 135#/A for cowpeas and 125 #/A for wintrer peas. Over seven years, cowpeas supplied 138 to 152 #N/A to corn resulting in no significant corn yield difference compared to equal amounts of commercial fertilizer (150#N/A). Proper cover crop inoculation is critical to promote nitrogen accumulation. Cowpeas and winter peas were consistently used to reduce commercial nitrogen in corn.
Authors: Hoorman, J.
-
Hoorman, J. Extension Educator, Cover Crops & Water Quality, Ohio State University Extension, Ohio, 45841