August 17, 2012

This was a challenging year for irrigators, particularly in western Nebraska, where it was difficult to keep up with crop water needs. The reservoir system had enough water to get irrigators through this season, but what about for next year and beyond? Producers who are under pumping allocations may have already used up water they “banked” in previous years.

If western Nebraska receives the same amount of snowfall as last year, expect major problems with crop water management. Pathfinder Reservoir is about 50% of capacity, probably enough to supply irrigation needs for 2013; however, if snowpack is limited this year, there may be some rationing or allocations in 2013 to get irrigators through to 2014.

Staying Flexible for 2013

Many producers plant winter wheat as a cover crop after dry bean harvest to reduce wind erosion and trap snowfall for moisture. If irrigation water in reservoirs will be in short supply and pumping allocation reserves have been used up, growers may want to consider using this winter wheat cover crop for grain harvest. 

Winter wheat requires about 18 inches of moisture. Depending on soil moisture left from the dry bean crop, a pre-irrigation in the fall to provide good soil moisture to an 18-inch depth would be ideal. Research in the Panhandle shows that In “normal” years, about 7 to 8 inches of irrigation will produce maximum yield. In dry years, 11 to 12 inches of irrigation is required and in wetter years, 5 to 6 inches.

In comparison, corn requires 24 to 26 inches, fully irrigated alfalfa requires 28 to 32 inches, and dry beans require about 16 inches of irrigation.

Irrigated winter wheat offers a number of options. First, it spreads a grower’s risk. It would be harvested sooner and,compared to corn and dry beans, crop water use would be lower and earlier in the season.

Second, irrigated winter wheat can be harvested for grain and the straw baled for forage. (See Forage Following Winter Wheat:  What are the Options and Production Costs?)

Or the crop could be green-chopped or swathed and baled as forage. If the irrigated winter wheat is taken off early enough, there is the potential for planting another forage crop back in the stubble: sorghum sudan grass, foxtail millet, or an oat mixture for a second crop. Depending on rainfall, this second crop would probably require at least an additional 4 to 6 inches of irrigation.

Fertilizer management for the winter wheat crop should include soil testing after dry beans. Growers should apply adequate phosphorus in the fall to promote rooting. Nitrogen rates can be in the range of 25 to 30 lb N per acre with additional nitrogen being applied before boot stage the following spring, depending on stand, winter survival, and yield potential.

If the decision is not to take the irrigated winter wheat to grain yield, or to harvest it for forage or spray out, nutrient carryover can vary, depending on the stage of growth at cutting or spraying. Removing the crop as hay will remove most of the nutrients. Additional N and possibly some P will be required for the next crop. If it's used as a cover crop and sprayed, the nutrients won't be released until the residue decomposes and returns to the soil nutrient cycle.  

Producers planting winter wheat as a cover crop this fall will add flexibility to their cropping options.  Over the winter they can watch the reservoir water supply and the futures market for all crops before deciding what to do with the crop.

For more information on winter wheat production, see

• CropWatch Soils Nutrient Mangement, including fertilizer/nutrient management to optimize winter wheat production
• CropWatch Wheat Production Systems – Nebraska seeding rates and dates, tillage management, and more.

Gary Stone, Extension Educator
Gary Hergert, Soil and Nutrient Management Specialist
Both at the UNL Panhandle REC, Scottsbluff