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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Livestock Nutrient Management Research » Research » Publications at this Location » Publication #81459
Title: AGGREGATION OF SOIL CROPPED TO DRYLAND WHEAT AND GRAIN SORGHUM

Author
item Unger, Paul
item Jones, Ordie
item MCCLENAGAN, J - INDEPENDENT
item STEWART, B - WEST TEXAS A&M UNIVERSITY

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Effective soil water storage and erosion control are necessary to grow dryland crops successfully in semiarid regions and to assure that the land will be productive at future times. Water-stable and dry soil aggregates or crumbs are important with regard to storing water in soil for later crop use and for controlling erosion. A tillage method-cropping system study was sconducted on a Pullman soil from 1982 to 1994. For the study, no-tillage and stubble mulch tillage and continuous and rotation cropping systems were used for producing dryland winter wheat and grain sorghum. In 1994, we studied water-stable and dry aggregation of soil from the field plots. Water-stable aggregation was determined to a 20 cm soil depth. Dry aggregation was determined only to the 2 cm depth. Soil at 0-2 cm often contained more >4.0 and <0.25 mm water-stable aggregates where no-tillage rather than stubble mulch tillage was used. Small aggregates can clog soil lpores. The presence of more small aggregates helps explain why more water runoff often occurs with no-tillage under field conditions. It also points to the need to keep crop residues on the soil surface to reduce runoff, thereby possibly increasing water storage and reducing erosion. Some differences in soil aggregation due to cropping systems, rotation phases, land conditions (level or nonlevel), and crops grown were significant also, but the differences generally were small. Because neither no-tillage nor stubble mulch tillage caused the development of adverse soil conditions in this field study, we believe both methods are equally suitable for producing dryland wheat and sorghum at the present time and that their long-term use will not hinder crop production in the future.

Technical Abstract: Effective soil water storage and erosion control are essential for successful dryland (rainfed) crop production and for sustaining crop productivity in semiarid regions. Water-stable and dry aggregation of surface or near-surface soil are important regarding soil water storage and erosion control. A tillage method-cropping system study was conducted on a aTorrertic Paleustoll from 1982 to 1994. For the study, no-tillage (NT) an stubble mulch tillage (SMT) and continuous and rotation cropping systems were used for dryland winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] production. In 1994, we evaluated water-stable and dry aggregation of soil from the field plots. Water-stable aggregate size distribution and aggregate water-stability were determined at 0-2, 2-4, 4-7, 7-10, 10-15, and 15-20 cm depths. Dry aggregation was determined only at the 0-2 cm depth. Soil at 0-2 cm often contained more >4.0 and <0.25 mm water-stable aggregates where NT rather than SMT was used. The greater amount of small aggregates helps explain why runoff often is greater with NT under field conditions. It also points to the importance of retaining surface residues for reducing runoff, thereby potentially increasing water storage and reducing erosion. Some water-stable aggregate size differences due to cropping systems, rotation phases, land conditions (level or nonlevel), and crops grown were significant also, but aggregate water-stability and dry aggregation differences often were small and nonsignificant. Our results indicate NT and SMT are equally suitable for dryland crop production because neither tillage method resulted in the development of adverse soil conditions.