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In the January 27, 2012 issue of the Agronomy e-Update (No. 334), we had an article an article on predicted irrigated corn and sorghum yields for 2012 based on available soil water at planting time, in-season precipitation, and irrigation levels. This is important this year because irrigators will need to tailor their water management to have the expectation of producing at least their irrigated proven yield to qualify for crop insurance as an irrigated practice. If they do not have enough water to produce their proven yield on the whole field, they may need to reduce irrigated acreage to fully irrigate the planted area. They need to know how much water it will take to produce their proven yield.

Predicted soybean yields for 2012 (see tables below) were based on a crop simulation model developed by K–State Research and Extension (Crop Yield Predictor available at http://www.mobileirrigationlab.com/). The stored soil water that is available for plant use at the beginning of the growing season is one of the sources of water to produce the crop. The other sources are growing season precipitation and irrigation. 

In the tables, the change in available soil water (ASW) from October 1, 2011 through April 1, 2012 is based on the average annual precipitation expected during the dormant season. Water accumulation depends on the storage capacity of the soil, how much evaporation occurs at the soil surface, and how much water drains below the expected root zone.

These tables are provided by K–State Research and Extension for producers as information for determining possible strategies for 2012. They were not derived by the USDA-Risk Management Agency. Crop insurance underwriters should be contacted for additional information.

Example: Crop = soybeans

               Annual Precipitation = 17 inches

               Available water on April 1= 20%

               Proven Yield = 56 bu/acre

               Then Irrigation needed = 14 inches

               Irrigation volume available = 1200 ac-inches (example 12 inches for 100 acres)

               Irrigated acres to produce proven yield = (1200 ac-inches)/14 inches) = 88 acres