Fate of legume and fertilizer nitrogen-15 in a long-term cropping systems experiment
Date
1994-09
Authors
Janke, Rhonda R., author
Peters, Steven E., author
Paul, Eldor A., author
Hesterman, Oran B., author
Harris, Glendon H., author
American Society of Agronomy, publisher
Journal Title
Journal ISSN
Volume Title
Abstract
Relying more on biological N2 fixation has been suggested as a way to meet one of the major challenges of agricultural sustainability. A 15N study was conducted to compare the fate of applied legume and fertilizer N in a long-term cropping systems experiment. Nitrogen-15-1abeled red clover (Trifolium pratense L.) and (NH4)2SO4 ere applied microplots within the low-input and conventional cropping systems of the Farming Systems Trial at the Rodale Institute Research Center in Pennsylvania. The 15SN was applied to soil and traced into corn (Zea mays L.) in 1987 and 1988. Residual 15SN was also traced into second-year spring barley (Hordeum vulgare L.). Legume and fertilizer 15SN remaining in soil was measured and loss of N was calculated by difference. More fertilizer than legume N was recovered by crops (40 vs. 17% of input), more legume than fertilizer N was retained in soil (47 vs. 17% of input), and similar amounts of N from both sources were lost from the cropping systems (39% of input) over the 2-yr period. More fertilizer than legume N was lost during the year of application (38 vs. 18% of input), but more legume than fertilizer N was lost the year after application (17 vs. 4% of input). Residual fertilizer and legume 15SN was distributed similarly among soil fractions. Soil microbial biomass was larger in the legume-based system. A larger, but not necessarily more active, soil microbial biomass was probably responsible for the greater soil N supplying capacity in the legume-based compared with fertilizer-based system.
Description
Rights Access
Subject
biological N2 fixation
N
15N
nitrogen input