Long-Term Effects of Crop Management in Wheat-Fallow: II. CENTURY Model Simulations
1994
Parton, William J. | Rasmussen, P. E.
There is increasing need to develop models to assess the long-term effects of management practices on soil and environmental quality, and to test these models across a wide range of environments. The CENTURY model was used to simulated long-term management practices for wheat (Triticum aestivum L.)-fallow agriculture. The objectives were to compare the accuracy of predicted vs. observed data and use the model to help interpret observed data and to determine the long-term impact of crop management on C and N stabilization in soil. The model simulated grain and straw yield and grain N uptake within ±10% of the observed data, and 0- to 30-cm soil C and N within ±5%. Improvement in performance requires addition of a dynamic plant growth submodel to represent the effect of soil N on C and N allocation to roots, straw, and grain. Soil C changes were a linear function of aboveground C inputs; an input of 200 g C m⁻² yr⁻¹ (4650 kg straw ha⁻¹) was required to stabilize soil C at its present level. Estimates of soil C stabilization efficiency ranged from 12 to 27% and was highest for the high N fertilizer treatment. Soil N stabilization efficiency was higher for organic N additions (37–46%) than for inorganic additions (18–26%). Inorganic N treatments had similar N removal in grain, higher other nonidentifiable N losses, but lower N stabilization in soil than organic N treatments. Soil N data suggest that mineralization of N from the 30- to 60-cm layer needs to be considered in the N budget, as nearly 39 g m² were mineralized between 1931 and 1986.
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