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Articles by W. W. Wilhelm
Total Records ( 2 ) for W. W. Wilhelm
  G. E. Varvel and W. W. Wilhelm
  Proposals promoting the use of massive amounts of crop residues and other lignocellulosic biomass for biofuel production have increased the need for evaluation of the sustainability of cropping practices and their effect on environment quality. Our objective was to evaluate the effects of crop rotation and N fertilizer management and their stover production characteristics on soil organic carbon (SOC) levels in a long-term high-yielding irrigated study in the western Corn Belt. An irrigated monoculture corn (Zea mays L.), monoculture soybean [Glycine max (L.) Merr.], and soybean–corn cropping systems study was initiated in 1991 on a uniform site in the Platte Valley near Shelton, NE. Soil samples were collected in 1991 before initiation of the study and in the spring of 2005 and analyzed for SOC. Significant differences in total SOC values were obtained between rotations and N rates at the 0- to 7.5- and 0- to 15-cm depths in 2005 and all total SOC values were equal to or greater than SOC values obtained in 1991. Residue production was greater than 6 Mg ha–1, a level that appears to be sufficient to maintain SOC levels, in all systems. Can residue amounts above this level be harvested sustainably for biofuel production in cropping systems similar to these? Though these results suggest that a portion of corn stover could be harvested without reducing SOC under the conditions of this investigation, the direct impact of stover removal remains to be evaluated.
  Y. Liang , H. T. Gollany , R. W. Rickman , S. L. Albrecht , R. F. Follett , W. W. Wilhelm , J. M. Novak and C. L. Douglas
  Management of soil organic matter (SOM) is important for soil productivity and responsible utilization of crop residues for additional uses. CQESTR, pronounced "sequester," a contraction of "C sequestration" (meaning C storage), is a C balance model that relates organic residue additions, crop management, and soil tillage to SOM accretion or loss. Our objective was to simulate SOM changes in agricultural soils under a range of climate and management systems using the CQESTR model. Four long-term experiments (Champaign, IL, >100 yr; Columbia, MO, >100 yr; Lincoln, NE, 20 yr; Sidney, NE, 20 yr) in the United States under various crop rotations, tillage practices, organic amendments, and crop residue removal treatments were selected for their documented history of the long-term effects of management practice on SOM dynamics. CQESTR successfully simulated a substantial decline in SOM with 50 yr of crop residue removal under various rotations at Columbia and Champaign. The increase in SOM following addition of manure was simulated well; however, the model underestimated SOM for a fertilized treatment at Columbia. Predicted and observed values from the four sites were significantly related (r2 = 0.94, n = 113, P < 0.001), with slope not significantly different from 1. Given the high correlation of simulated and observed SOM changes, CQESTR can be used as a reliable tool to predict SOM changes from management practices and offers the potential for estimating soil C storage required for C credits. It can also be an important tool to estimate the impacts of crop residue removal for bioenergy production on SOM level and soil production capacity.
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