Primary Tillage for Clay

Lowrey A. Smith


Current tillage recommendations for clay and clay loam soils say that, in general, subsoiling is not beneficial. Previous research on crop response to subsoiling clay also indicates that subsoiling does not provide significant crop responses, but recent research at Stoneville, MS, has demonstrated that subsoiling clay is of great benefit if it is performed when the soil has a low moisture content. Therefore, the validity of the current recommendation is questioned. Tillage recommendations for clay soil should include qualifiers with respect to soil moisture content at the time of tillage. Subsoiling dry clay tends to disrupt the soil structure and expose large blocks of soil, but the structure of wet clay experiences very little disruption as the subsoiler cuts a slit through it. Tillage in most of the previous studies was performed in the spring; therefore, the subsoil was probably at a high moisture level. A more accurate recommendation than the one currently being used might by that 'subsoiling is generally not beneficial on clay soils which contain high levels of moisture but may be beneficial if performed when clay soils are cracked.' Based on recent research results from Stoneville, the recommendation might also state that 'subsoiling clay soils with low moisture contents (when the soil is cracked) disrupts the soil structure and seems to improve the infiltration, storage, and drainage of water in the soil profile.' This technology offers an economical way to improve the reliability of dryland crop production on clay through increased yield.

Reprinted from Proceedings of the 1994 Beltwide Cotton Conferences pp. 532 - 534
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998