Impact of compost, manure and inorganic fertilizer on nitrate leaching and yield for a 6-year maize-alfalfa rotation in Michigan

An accurate estimate of nitrate (NO3N) leaching from agricultural land is critical to environment impact studies. Although NO3N are almost always present in groundwater, their continued increase in managed agricultural land can lead to nitrate concentrations in groundwater above acceptable human health standards. The amount of NO3N leached during the growing season may be minimal compared to leaching losses that occur between the harvest of one crop and the planting of the next. In this study we compared the effect of inorganic N and raw and composted animal manure on crop productivity and N leaching under field conditions in a maize-alfalfa system using undisturbed drainage lysimeters in Michigan. The cropping system rotation consisted of 3 years of continuous maize (Zea mays L.) and 3 years of continuous alfalfa (Medicago sativa L.). One cropping system consisted of a maize crop grown in the 1994-1996 seasons and alfalfa in the 1997-1999 seasons. The other cropping system was alfalfa (1994-1996) then maize (1997-1999). Four N treatments were imposed on the cropping systems. Treatment 1 was a check, no N fertilizer; Treatment 2 was manure; Treatment 3 was compost; Treatment 4 was inorganic fertilizer. No significant differences in yields of maize and alfalfa were found between N treatments in the 6-year rotation, although the no N treatment in maize had consistently lower yields. The highest amount of NO3N leaching was measured in the manure treatment with a mean annual value of 55 kg NO3N ha−1 in maize-alfalfa rotation and 59 kg NO3N ha−1 in alfalfa-maize, followed by compost (35 kg NO3N ha−1 in alfalfa-maize and 30 kg NO3N ha−1 in maize-alfalfa), inorganic N (33 kg NO3N ha−1 in alfalfa-maize and 25 kg NO3N ha−1 in maize-alfalfa) and no N (27 kg NO3N ha−1 in alfalfa-maize and 25 kg NO3N ha−1 in maize-alfalfa). The highest rates of NO3N losses were also observed in the manure treatment with a mean value for the 6-year rotation of 0.14 kg NO3N mm−1 in alfalfa-maize and 0.35 kg NO3N mm−1 in maize-alfalfa.