SULFUR AND MICRONUTRIENT CHANGES AS A FUNCTION OF DRYLAND CROPPING INTENSITY

Authors: Bowman, Rudolph; Vigil, Merle

Submitted to: Proceedings Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/10/2000
Publication Date: 3/1/2000
Citation: N/A

Interpretive Summary: Because of a general lack of fertilizer application other than N and P in the Great Plains, a need exists to evaluate and monitor sulfur and micronutrients, and other changes that may be occurring because of greater cropping intensities than wheat-fallow, and subsequent nutrient uptake and removal. In general, our data for the surface 2 inches showed lower soil pHs, higher extractable soil Zn, Fe, Ca and K, lower Mn, and no difference in sulfate levels with continuous cropping systems versus systems with fallow. Present data seem to indicate that these nutrients exported in the grain are not yet limiting production because of current recycling through crop residues from 4-yr rotations, or continuous cropping, and because of the sufficiency of the cation-exchange capacity and nutrients in the original soil.

Technical Abstract: With low levels of soil organic matter in the central Great Plains, and a general lack of fertilizer application other than N and P, a need exists to evaluate and monitor sulfur and micronutrient (Zn, Fe, Cu, Mn) and other changes that may be occurring because of greater cropping intensities and subsequent nutrient uptake. We evaluated in a Weld loam at three different tdepths (0-2 , 0-6, 6-12 inches), the effects of increasing cropping intensity (wheat-fallow to continuous cropping) on extractable levels of soil sulfate-S, micronutrients, and exchangeable K and Ca. Soil reaction (pH), cation exchange capacity, and texture, along with grain yield, and nutrient concentration in the leaves of corn and sunflower were also evaluated. Data showed significant responses of cropping intensity to pH, exchangeable Ca and K, and extractable Zn, Fe and Mn at the 0-2 inch depth, to pH and extractable Mn at the 0-6 inch depth, and no differences at the 6-12 inch depth. Soil sulfate did not show any significant differences an leaf nutrient concentration differences were a function of plant species and not of cropping intensity. In general, differences were due to soil changes created by continuous cropping systems, which received greater fertilization and produced more biomass per unit time than fallowed systems.