The Effects of Legume and Nonlegume Green Manures on Soil Carbon and Nitrogen Dynamics and on Growth and Yield of Potato Crops

EPA Grant Number: U915352
Title: The Effects of Legume and Nonlegume Green Manures on Soil Carbon and Nitrogen Dynamics and on Growth and Yield of Potato Crops
Investigators: Plotkin, Jeremy M.
Institution: University of Maine
EPA Project Officer: Lee, Sonja
Project Period: August 31, 1998 through January 1, 2000
Project Amount: $38,846
RFA: STAR Graduate Fellowships (1998) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Engineering and Environmental Chemistry , Fellowship - Agricultural Engineering


The objective of this research project is to evaluate the effects of legume and nonlegume green manures (GMs) on soil carbon and nitrogen and on the growth and yield of potato crops.

GMs are crops that are grown to be directly incorporated for the purpose of enriching agricultural soil. It has been demonstrated that legume GMs can provide a significant source of nitrogen to the subsequent crop plant, replacing some portion of economically and environmentally costly chemical fertilizers. Some sources in the popular agricultural press also recommend GMs for increasing soil organic matter, which has associated benefits of improved soil physical properties and crop growth. However, the scientific literature has found that organic matter can be maintained, but not improved, by most GMs. One exception to this rule is grass GMs, which can cause slight increases in soil organic matter, but have the drawback of making less nitrogen available to the plant. This project seeks to evaluate the extent to which grass, legume, and grass-legume mixture GMs can be used to balance the objectives of supplying nitrogen to the crop plant, and affecting soil organic matter and/or physical properties.


This research project includes two experiments, both split-plot factorial randomized complete block design with rotation crop as mainplot, and N fertilizer level as subplot. Experiment 1 has four rotation crop treatments: lupin GM, pea-oat-vetch GM, pea-clover GM, and a control treatment of oats, as well as five fertilizer treatments evenly spaced from 0 to 240 lbs/acre nitrogen. Experiment 2 has seven rotation crop treatments: corn, sorghum-sudangrass, and annual ryegrass GMs, corn-soybean, sorghum-sundangrass-soybean, and ryegrass-clover GM mixtures, and a control treatment of oats. There are three nitrogen fertilizer treatments in Experiment 2, evenly spaced from 0 to 240 lbs/acre nitrogen. The same measurements are taken from both experiments; rotation crop measurements include total biomass production, and carbon, nitrogen, cellulose, hemicellulose, and lignin contents of the rotation crops. Nitrogen measurements include soil organic and inorganic nitrogen, total potato plant uptake of nitrogen, potato petiole nitrate concentration, readily mineralizable soil nitrogen, and inorganic nitrogen in microplot cylinders designed to simulate soil conditions but exclude nitrogen loss to leaching and to plant uptake. Soil organic matter and physical properties measurements include soil carbon, gravimetric soil moisture throughout the season, and water stable aggregates. Potato yield and quality also will be measured.

Supplemental Keywords:

fellowship, legume, green manure crops, GMs, nitrogen, N, potato crops, soil organic matter, randomized complete block design, RCBD., RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Environmental Chemistry, Ecosystem/Assessment/Indicators, Ecosystem Protection, Ecological Effects - Environmental Exposure & Risk, Ecology and Ecosystems, Agronomy, Ecological Indicators, Agricultural Engineering, green manure crops, soil nitrogen, grass manure crops, legume green manure crops, agriculture, soil organic matter, potato cropping system

Progress and Final Reports:

  • 1999
  • Final