Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/5/2017
Publication Date: 11/22/2017
Citation: Baumhardt, R.L., Johnson, G.L., Schwartz, R.C., Brauer, D.K. 2017. Grazing and tillage effects on soil properties, rain infiltration and sediment transport during fallow. Soil Science Society of America Journal. 81:1548–1556. doi:10.2136/sssaj2017.04.0133.
Interpretive Summary: Water availability for irrigation from the Ogallala Aquifer is declining on the Southern High Plains, and to maintain farm income with reduced water withdrawals, dryland row crop agriculture will need to intensify. The current three-year dryland wheat-sorghum-fallow rotation has stabilized crop production except under extended drought. Inclusion of grazing cattle at various stages of the rotation can increase income potential; however, the sustainable management protocols that preserved the infiltration of rain have not been adequately identified. Therefore, grazing and no-till (NT) or stubble-mulch (SM) tillage effects on rain infiltration and soil loss and stability were compared by ARS scientists from Bushland, Texas. Infiltration did not differ significantly with grazing. Soil loss from sorghum fallow increased with grazing and SM tillage. With good residue, SM tillage after grazed wheat increased infiltration > 100 % over NT. We recommend occasional SM tillage to disrupt trampled soil and increase rain infiltration in dryland cropping systems that combine grazing and NT. These results apply to commonly produced dual purpose wheat throughout the southern Great Plains.
Technical Abstract: On the semiarid Southern Great Plains, precipitation and soil water stored during fallow determine dryland production of wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] grown in the wheat-sorghum-fallow (WSF) rotation. In this three-year rotation, soil water storage is typically greater with no-tillage (NT) residue management than stubble-mulch (SM) tillage for improved yields. Intensifying this cropping sequence with cattle (Bos taurus) grazing provides an attractive sustainable alternative to irrigated production as groundwater resources decline, but biomass removal and soil trampling by cattle may reduce water conservation. Our objective was to quantify the effects of grazing and NT or SM tillage on rain infiltration, soil erosion, and aggregate stability. We measured the wet aggregate size distribution of a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) plus infiltration and sediment transport during simulated rain for fallow periods after wheat and sorghum. Residue reducing SM tillage and grazing management increased both sediment concentration and soil loss in runoff from sorghum fallow by up to 100% over NT, which had improved aggregate stability for a 42 % greater mean weight diameter (MWD). The mean final infiltration rate and amount did not vary significantly with grazing, but was usually 20% less than the ungrazed treatment. Because SM tillage after grazed wheat significantly increased infiltration greater than 100 % after disturbing the soil surface, we recommend occasional SM tillage to disrupt surface compaction and increase rain infiltration for dryland cropping systems that combine grazing and NT residue management.