Crop rotation considerations to control annual grass weeds |

Crop rotation considerations to control annual grass weeds

Mark Watson
Panhandle No-Till Educator

I would like to start by extending a big thank you to Drew Lyon and Karla Jenkins, researchers with UNL Panhandle Research and Extension Center for their time and effort in making our Crop Rotation Workshops a success. I would also like to thank Dipak Santra and Paul Burgner, also with UNL Panhandle Research and Extension Center for the information they provided for the workshops.

Dipak Santra provided a presentation on the alternative crops he is looking at for our region. He is working on forages, oil seed and grain crops which may have a fit in our cropping rotations in the future. Paul Burgner provided extensive economic analysis of crop production budgets for dry land winter wheat, corn, sunflower, proso millet and field peas along with budgets for irrigated winter wheat, corn, and edible beans.

Drew Lyon presented information on research he has conducted at the High Plains Ag Lab near Sidney, Neb. Drew has done extensive research looking at crop rotations that fit our growing region. When Drew first came to the Panhandle Research Center a common problem with the winter wheat/ summer fallow crop rotation used by most producers was the prevalence of winter annual grasses which hurt winter wheat yields with this monoculture system.

Downy brome, jointed goatgrass, and rye consistently proved detrimental to winter wheat production in the region. These winters annual grass weeds continue to be problematic in winter wheat/summer fallow production systems today. Drew’s research showed adding a summer crop to the rotation helped immensely in controlling these weeds in winter wheat production. The type of summer crop doesn’t matter as long as these winter annual grasses are controlled and aren’t allowed to produce seed during the growing of the summer crop and the fallow period following the summer crop.

Drew also looked at some possible replacements for the fallow period following the summer crop. He conducted research during the 1999-2001 growing seasons in which he followed a sunflower crop with summer fallow, spring canola, an oat-pea forage, edible beans, proso millet and corn. He then looked at these rotations as far as how they affected the yields of the following winter wheat crop and the economic return of the rotation.

Drew also looked at the soil moisture available at winter wheat planting as a gauge to determine winter wheat yields the following year. As you would expect, the winter wheat following the fallow had the most soil moisture available and produced the highest yield. The winter wheat behind the oat-pea produced the second highest yields, followed by winter wheat behind the proso millet. The longer the previous crop used moisture into the growing season prior to winter wheat planting, the lower the soil moisture at planting resulting in lower winter wheat yields. The wheat behind the corn had the lowest yield due to late planting and low soil moisture.

The economic analysis of the rotations showed a slightly different picture. The most profitable rotation was the winter wheat following the oat-pea forage crop. The yields were lower for the winter wheat, but the oat-pea forage made enough economic impact on the rotation that the loss of winter wheat yield was made up for with the economic benefit of the oat-pea forage crop. The economic returns for the proso millet and summer fallow rotations were the next most profitable, with no significant difference in the two rotations.

The research conducted by Drew shows the potential for eliminating extended periods of fallow prior to winter wheat production and increasing the economic returns of the entire crop rotation system. The key component is selecting a summer crop which is profitable and adding a short term crop such as oat-pea for hay, field peas, or early season forage for grazing to replace the long fallow period prior to winter wheat planting. The choice of a short term early season crop needs to provide economic profitability which offsets any potential reduction in winter wheat yield.

Ideally the short term crop should provide an extended fallow period of 2-3 months to allow for the capture of some moisture prior to winter wheat planting. Although proso millet provided similar returns to summer fallow in Drew’s study, there is little time between proso millet harvest and wheat seeding, which makes it a riskier choice than an earlier planted and harvested crop such as field peas as a summer fallow replacement.

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