Computer models may be useful tools to design management practices for green manures, to maximize N uptake by the following crop while minimizing N losses to teaching. A previous paper tested CERES models predictions of soil processes in the absence of a crop, but did not consider effects of the crop, such as water and N uptake or shading of the soil surface. In this paper, we evaluated the ability of the CERES models to predict N dynamics during wheat and maize growth following legume cover crop (LCC) incorporation. Soil and crop data were collected in 2-year wheat and maize rotations from 1994 to 1998 at the Long Term Research on Agricultural Systems facility at the University of California, Davis. In unfertilized fallow/wheat and LCC/wheat rotations, soil inorganic N content and crop N uptake were mostly within 20% of predicted values, but the greater N uptake by wheat predicted after LCC incorporation (relative to no LCC) did not actually occur. Midwinter N uptake rate of unfertilized wheat was three times that predicted by the model, even though the soil inorganic N was only half that predicted. In maize, following earlier LCC incorporation, inorganic soil N was underestimated throughout growth in 1996 and 1997 (by 25-150 kg N ha-1 in 1996 and 25-55 kg N ha-1 in 1997), due to the underestimates of rapid N mineralization shortly before active maize N uptake. Maize N uptake was predicted within 20% in 1997, but was underestimated by 25-70 kg N ha-1 in 1996. Overpredictions in soil temperature were sometimes of the order of 10°C, which could cause doubling of metabolic rates, e.g. soil N mineralization. This could explain slight but consistent overpredictions in inorganic soil N in the wheat system, but makes underprediction of soil N in the maize system even more surprising. The CERES models could give a rough estimate of N budget in a wheat rotation following a fallow or late-incorporated LCC. Further improvements of the CERES models should address predictions of winter-grown LCC decomposition after early incorporation (e.g. prior to maize), midwinter wheat N uptake, and soil temperature. (C) 2000 Elsevier Science B.V.
|Original language||English (US)|
|Number of pages||17|
|Journal||Field Crops Research|
|State||Published - Aug 10 2000|
Bibliographical noteFunding Information:
We thank Gerrit Hoogenboom, Department of Biological and Agricultural Engineering, University of Georgia, for additional information about the CERES models. Supported by the Japan International Cooperation Agency (JICA), UC Davis College of Agricultural and Environmental Sciences, and USDA (Grant no. 95-37108-2411).
- N dynamics
- Soil temperature
- Soil water