Water and Fertilizer Nitrogen Management to Minimize Nitrate Pollution from a Cropped Soil in Southwestern Quebec,Canada

Nitrate-N (NO₃ ^--N) pollution of water resources is a widely recognized problem. Water and nitrogen fertilizer are the two most important factors affecting NO₃ ^--N movement to surface and groundwater. Field trials were conducted from 1998 to 2000 growing seasons to investigate the combined impacts of water table management (WTM) and N fertilization rate on NO₃ ^--N concentration in the soil profile and in drain discharge. There were two water table treatments: free drainage (FD) with open drains at a 1.0 m depth from the soil surface and subirrigation (SI) with a target water table depth of 0.6 m below the soil surface, and two N fertilizer rates: 120 kg N ha^-1 (N₁₂₀) and 200 kg N ha^-1 (N₂₀₀) in a split-plot design. Compared to FD, SI reducedNO₃ ^--N concentration in the soil by up to 50% averaged over the two N rates. Concentrations of NO₃ ^--N in drainage water fromSI plots were lower than those from FD by 55 to 73%. These findings suggest that SI can be used as a means of reducing soil NO₃ ^--N pollution and drainage water NO₃ ^--N concentrations.     

Predicting maize and soybean production in a sheltered field in the Cornbelt region of North Central USA

Shelterbelts (field windbreaks) are an important tool for farming in semi-arid areas but are not commonly used. An obstacle to the adoption of shelterbelts is the lack of site-specific information about the benefits and costs associated with establishing and maintaining them. A group of researchers has been developing a modeling system that will estimate site-specific effects, benefits, and costs for sheltered fields that produce maize or corn (Zea maize) and soybean (Glycine max) in the U.S. Corn Belt region. Akey component of the modeling system is the use of the CROPGRO-Soybean and CERES-Maize models to simulate yield response to microclimatic changes acrossa sheltered field. In this work, we tested the ability of both models to simulate yield in a sheltered field, evaluated the potential yield increase of shelterbelts based on long-term simulations, and compared the influence of shelter induced changes in temperature and windrun on yield. Both models simulated yield increases due to shelter. The soybean model was more responsive to microclimatic differences than the maize model. Long-term simulations generally showed a field level increase in yield due to shelter for maize and soybeans with an average increase of 4.1 and 3.3, respectively. Change in windrun due to shelter is more important in increasing yield than changes in temperature. The CERES-Maize model seems to be more sensitive to changes in windrun than the CROPGRO-Soybean model.