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Title: Crop Residue in North Dakota: Measured and Simulated by the Wind Erosion Prediction System

Author
item Van Donk, Simon
item Merrill, Stephen
item Tanaka, Donald
item Krupinsky, Joseph

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2008
Publication Date: 8/4/2008
Citation: Van Donk, S.J., Merrill, S.D., Tanaka, D.L., Krupinsky, J.M. 2008. Crop Residue in North Dakota: Measured and Simulated by the Wind Erosion Prediction System. Transactions of the ASABE. 51(5): 1623-1632.

Interpretive Summary: The Wind Erosion Prediction System (WEPS) includes a model for the decomposition of crop residue, because residue cover is very important for controlling soil erosion by wind. WEPS will be implemented throughout the USA, but most of the data used to develop the decomposition model have been collected in the southern USA. We compared the WEPS simulated residue cover with that measured in south-central North Dakota for 50 two-year cropping sequences for nine crops that were grown under no-tillage conditions. Simulated residue cover underestimated measured cover for 33 out of the 50 simulated cropping sequences and overestimated measured cover for five cropping sequences. This study will help improve the WEPS residue decomposition model and the capability of WEPS to evaluate the effect of management alternatives on wind erosion, which is a problem that is estimated to cost the US economy over $20 billion per year.

Technical Abstract: Residue cover is very important for controlling soil erosion by water and wind. Thus, the Wind Erosion Prediction System (WEPS) includes a model for the decomposition of crop residue. It simulates the fall rate of standing residue and the decomposition of standing and flat residue as a function of temperature and moisture. It also calculates residue cover from flat residue mass. Most of the data used to develop and parameterize this model have been collected in the southern USA. We compared the WEPS simulated residue cover with that measured in south-central North Dakota for 50 two-year cropping sequences for nine crops that were grown under no-till conditions. Measured data included residue mass at the time of harvest and residue cover just after planting the next spring. Simulated residue cover significantly (P < 0.05) underestimated measured cover for 33 out of the 50 simulated cropping sequences and overestimated measured cover for five cropping sequences. Some of the differences may be explained by the fact that, for many WEPS crops, the residue decomposition parameters are not based on measured field data, but on expert judgment. WEPS did not predict any stem fall for most of the crops during winter, which contradicts observations that, in the northern USA, snow storms flatten many residue stalks of crops such as sunflower. In addition to stem fall and residue decay by biological means, driven by temperature and moisture, the model needs to explicitly simulate stem fall by mechanical forces, such as snowstorms, that are important in northern climates. WEPS does not model the process of unanchored residue migration caused by rain or windstorms either, although this does affect residue mass-to-cover ratios and susceptibility to erosion. This study will help improve the WEPS decomposition model and its parameterization, but more data on residue decay and stem fall are needed for different climates and crops to ensure the applicability of the model over a wide range of conditions.