title: Prediction of nitrogen responses of corn by soil nitrogen mineralization indicators.
abstract: Soil nitrogen mineralization potential (N min) has to be spatially quantified to enable farmers to vary N fertilizer rates, optimize crop yields, and minimize N transfer from soils to the environment. The study objectives were to assess the spatial variability in soil N min potential based on clay and organic matter (OM) contents and the impact of grouping soils using these criteria on corn grain (Zea mays L.) yield, N uptake response curves to N fertilizer, and soil residual N. Four indicators were used: OM content and three equations involving OM and clay content. The study was conducted on a 15-ha field near Montreal, Quebec, Canada. In the spring 2000, soil samples (n = 150) were collected on a 30- x 30-m grid and six rates of N fertilizer (0 to 250 kg N ha(-1)) were applied. Kriged maps of particle size showed areas of clay, clay loam, and fine sandy loam soils. The N min indicators were spatially structured but soil nitrate (NO3-) was not. The N fertilizer rate to reach maximum grain yield (N max), as estimated by a quadratic model, varied among textural classes and Nmin indicators, and ranged from 159 to 250 kg N ha(-1). The proportion of variability (R2) and the standard error of the estimate (SE) varied among textural groups and N min indicators. The R2 ranged from 0.53 to 0.91 and the SE from 0.13 to 1.62. Corn grain N uptake was significantly affected by N fertilizer and the pattern of response differed with soil texture. For the 50 kg N ha(-1) rate, the apparent N min potential (ANM) was significantly larger in the clay loam (122 kg ha(-1)) than in the fine sandy loam (80 kg ha(-1)) or clay (64 kg ha(-1)) soils. The fall soil residual N was not affected by N fertlizer inputs. Textural classes can be used to predict N max. The N min indicators may also assist the variable rate N fertilizer inputs for corn production.
authors.affiliation: Soil Science Department, University of Manitoba, Winnipeg, Canada. Regis_Simard@umanitoba.ca
authors.forename: R R
authors.initials: RR
authors.lastname: Simard
authors.forename: N
authors.initials: N
authors.lastname: Ziadi
authors.forename: M C
authors.initials: MC
authors.lastname: Nolin
authors.forename: A N
authors.initials: AN
authors.lastname: Cambouris
mesh_terms: D000383:Agriculture; D000538:Aluminum Silicates / Q000032:analysis; D018533:Biomass; D000077215:Clay; D005308:Fertilizers; D009584:Nitrogen / Q000378:metabolism*; D010316:Particle Size; D011792:Quebec; D012987:Soil / Q000032:analysis*; D003313:Zea mays / Q000254:growth & development / Q000378:metabolism*
chemical_list: D000538:Aluminum Silicates; D005308:Fertilizers; D012987:Soil; D009584:Nitrogen; D000077215:Clay