Risk Assessment and Exposure Analysis On The Agricultural Landscape 

The NRCS National Soil Survey Center (NSSC) joined the University of Nebraska at Lincoln (UNL) and the USDA Risk Management Agency (RMA) to develop a "Risk Assessment and Exposure Analysis on the Agricultural Landscape.” A 2002 agreement tasked the National Soil Survey Center (NSSC) to develop the soils component of the project sponsored by RMA. Working with the UNL Department of Computer Science and Engineering, scientists at the NSSC developed criteria for a computer program that would generate soil productivity indices for dryland commodity crops, such as corn, wheat, soybeans, and cotton. RMA will evaluate the results for use as a risk assessment tool in its crop insurance program.

Productivity indices rate soils according to their inherent capacity to produce seed, fiber, and biomass. Inherent productivity is nearly invariant over long periods of time. Temporary fluctuations in productivity resulting from above average or below average management do not affect productivity indices. On the other hand, long-term changes in soil properties that cause significant changes in productivity do affect the indices. Erosion, land leveling, and salinization are examples of long-term changes that cause such changes.

The inherent capacity of the soil to produce cultivated crops is only one factor that determines the overall productivity. Crop varieties and management practices also cause yields to vary from place to place and partially mask the inherent quality of the soil. Except in extreme circumstances, such as prolonged drought, inherent soil capacity varies little throughout the geographic extent of a given soil identified in the Soil Survey Program.

The National Geospatial Development Center in Morgantown, West Virginia, created soil productivity index maps for a limited number of Nebraska counties using digitized soil survey data acquired from the Soil Data Mart. The maps show the geographic distribution of soils that range from nonarable (index <30) to very highly productive (index >70). These maps are useful not only for testing productivity indices, but also for displaying the distribution of agriculturally important soils.

Scientists at the NSSC developed soil productivity indices to avoid inequities that are possible when soils are arrayed by use of traditional yield data alone. These indices use soil data that are accessible in every county where commodity crops are grown. Although the immediate focus was on commodity crops in selected counties in Nebraska, productivity indices can be made available for commodity crops in other areas of the U.S.
Your contacts are Raymond Sinclair, NRCS soil scientist, at 402-437-5699, or Sharon W. Waltman , NRCS soil scientist, at 304-293-8232 ext. 6105.