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Wisconsin’s New Commodity Crop Productivity Index for Corn Added to the National Web Soil Survey

By cptp | 10:42 PM, 12/07/2016

Madison, Wis. ‒ The U.S. Department of Agriculture, Natural Resources Conservation Service (NRCS) has added a new web interpretation for Wisconsin to the National Web Soil Survey (WSS). The Wisconsin Commodity Crop Productivity Index (WCCPI) for Corn Interpretation provides soil survey users with an inherent soil property based ranking of Wisconsin soils and map units for common crop productivity. It replaces stored crop yields, produces a consistent statewide crop production index, better reflects local conditions, and improves statewide planning. Productivity indices have the advantage of being less vulnerable to changes in technology than expressions of productivity based on yield. This interpretation is currently for corn crop; separate crop interpretations may be completed in the future.

The interpretation is shown in WSS as a report and thematic map. The report and thematic map are found in two locations within the WSS. The thematic map is located under the “Stabilities and Limitations for Use” tab, then under the “Vegetative Productivity” folder. The report is located under the “Soils Reports” tab, then under the “Vegetative Productivity” folder.

NRCS partnered with many Universities, Extensions, Resource Soil Scientists, NRCS State Soil Scientists, Soil Science Regions, and the National Soil Survey Center to complete this project. Read the new, detailed soil interpretation report here or view the condensed poster here.

Soil survey data currently available via the WSS, include only crop yield estimates from original soil surveys indicating the performance of different areas of soils for certain crops. Many of these crop yield estimates are very outdated, inconsistent, and highly subjective to variable management inputs. Using the new interpretive index gives farmers, landowners, partners, and other WSS users the capacity to relate directly to the ability of soils, landscapes, and climates to foster crop productivity. Fluctuations in productivity caused by good or bad management and year-to-year variations in weather are not addressed. Productivity indices have the advantage of being less vulnerable to changes in technology than expressions of productivity based on yield.

A mechanism that determines soil productivity in Wisconsin consistently across political boundaries, over time, is needed for many uses. Crop varieties, management scenarios, and yields vary by location, over time, reflecting choices made by farmers. These factors partially mask inherent soil quality. Except for extreme circumstances, inherent soil quality or inherent soil productivity varies little by location, over time for a specific soil (map unit component) identified by NRCS soil surveys. The interpretation reflects a relative comparison on soils for crop yields. It does not forecast actual crop yields because values are based on weather conditions, soil health, tillage, management conditions, etc.

Depths for data entry for many of these properties are based on typical rooting depths for corn. For example, over 90% of corn roots are found in the upper meter of the soil. Over the growing season, about 70% of water used by corn will come from the first 60 cm of soil. Extraction is most rapid in the zone of greatest root concentration and where the most favorable conditions of aeration, biological activity, and nutrient availability occur. Therefore, properties are weighted heavily for conditions found in the upper meter of the soil.

Properties also quantify the capability of the soil, climate, and landscape to supply water for crop growth. Soil moisture availability is determined by the interaction of four factors (1) amount of moisture present in the soil, (2) characteristics of the soil profile, (3) moisture capacity of the crop, and (4) demand for water by the atmosphere. The WCCPI uses the properties of slope gradient; depth to a water table during the growing season; and the occurrence, timing, and duration of ponding and flooding during part of the growing season in calculating crop productivity index.

Climate conditions in June, July, and August are good indicators of a soil’s productivity for corn and soybeans. Rainfall and temperature during this timeframe greatly affect crop productivity. The impact of rainfall for a given area is decreased because of the effects of temperature, day length and latitude, and crop use. For example, consider two soils, both receiving the same amount of rainfall. One soil is hot, thermic, while the other is cool, mesic. A larger amount of rainfall on the cooler site is more readily available for crop growth due to lower evapotranspiration rate, and so the cool, mesic site receives a higher water balance value. The ratings are both verbal and numerical. Rating class terms indicate the estimated productivity which is determined by all of the soil, site, and climatic features that affect crop productivity.

Individuals interested in knowing when surveys in a particular state are updated should visit the WSS and click on the “Download Soils Data” tab, then choose the State they are interested in. WSS will display a list of all soil survey areas. Individuals interested in soil related issues may subscribe to topics of interest using a free subscription service through GovDelivery offsite link image. Individuals can e-mail inquiries to soilshotline@lin.usda.gov for assistance with GovDelivery and WSS.

This article was originally published at USDA.gov.