Author
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Merrill, Stephen |
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Tanaka, Donald |
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Krupinsky, Joseph |
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RIES, RONALD - RETIRED USDA-ARS |
Submitted to: National Sunflower Research Forum Proceedings
Publication Type: Proceedings Publication Acceptance Date: 2/10/2003 Publication Date: 3/10/2003 Citation: MERRILL, S.D., TANAKA, D.L., KRUPINSKY, J.M., RIES, R.E. SOIL WATER DEPLETION AND COVERAGE BY RESIDUE UNDER SUNFLOWER COMPARED TO OTHER CROPS. National Sunflower Research Forum Proceedings. 2003. Interpretive Summary: Conservation tillage and greater control of nutrition through more efficient fertilization has allowed producers in the semiarid and subhumid Northern Great Plains to move away from small grain ¿ fallow rotations to more continuous cropping. Continuous crop rotations with a diversity of species are essential for improving soil health and decreasing the impact of disease, weeds and insects. Soil water content and soil surface coverage by crop residues were studied in a crop sequence study carried out using no-till management. The experiment was set up in replicated blocks so that all combinations of ten crops grown in strips one year were created by growing the same ten crops in strips perpendicular to the first year¿s crops the following year. We found that the oilseed crops sunflower and safflower extracted significantly more water from the soil than some of the other crops, while dry pea used the least amount of water. We found that dry pea would leave 3 to 4 more inches in the soil than sunflower by seeding time the next spring. Given the rule that every additional inch of water, when it is limiting, will yield 5 bu/acre spring wheat, there is a considerable economic implication for producers. Under no-till management, soil coverage by residues was good for most sequences of crops. However, our results showed that back-to-back sequences consisting of combinations of sunflower and pulse legumes (soybean, dry pea, and dry bean) could potentially produce marginally protective levels of soil coverage under drought conditions. Technical Abstract: Continuous crop rotations with a diversity of species are essential for improving soil health and decreasing the impact of disease, weeds and insects. Soil water content and soil surface coverage by crop residues were studied in a crop sequence study carried out using no-till management. The experiment was set up in replicated matrices so that all combinations of ten crop species (sunflower, safflower, spring wheat, barley, flax, crambe, canola, soybean, dry pea, and dry bean) grown in strips one year were created by planting the same ten crops in strips perpendicular to the first year¿s crops the following year. We found that sunflower depleted the most soil water, dry pea depleted the least, and barley and crambe were the next lowest depleters of water on average. During a year of higher than average seasonal precipitation, the depth distribution of soil water depletion did not vary greatly among four crops. But in a year of average and a year of below average precipitation, both sunflower and canola depleted proportionally less water from above 60 cm depth, and proportionally more water from greater than 60 cm depth compared to spring wheat and canola. Root growth measurements made in a prior study indicated that the most deeply rooted crops (sunflower, safflower) depleted the most soil water. As a result of no-till management, soil coverage by residues was above 50% for most sequences of crops. However, dry pea-sunflower and sunflower-sunflower sequences yielded somewhat marginal levels of soil coverage in the range of 30% to 40%. Drought conditions coupled with sequences of lower residue-producing crops (sunflower and all three pulse legumes) have the potential for generating unacceptably low levels of soil protection. |