|Fehmi, Jeffrey - ERDC/CERL, US ARMY|
|Ries, Ronald - RETIRED USDA-ARS|
Submitted to: National Sunflower Research Forum Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 7, 2002
Publication Date: March 15, 2002
Citation: Merrill, S.D., Tanaka, D.L., Krupinsky, J.M., Liebig, M.A., Hendrickson, J.R., Hanson, J.D., Fehmi, J.S., Ries, R.E. 2002. Soil water use and soil residue coverage by sunflower compared to other crops. National Sunflower Research Forum Proceedings of the 24th Sunflower Research Workshop, p. 88-96. January 17-18, 2002, Bismarck, ND. 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. Crops planted the following year could be affected because measurements taken the following spring indicated that differences in soil water depletion persisted. 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. Although there were differences in the amounts of snow captured by crop residues, we found that differences in soil water use persisted the next spring. Measurements in April 2001 showed that soil profiles in sunflower residue held 8.9 cm less water than soil in dry pea residue. 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.