LONG-TERM BENEFITS OF DEEP TILLAGE ON SOIL PHYSICAL PROPERTIES AND CROP YIELD

Authors: Baumhardt, Roland; JONES, O - TAES

Submitted to: Southern Conservation Tillage for Sustainable Agriculture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/30/2005
Publication Date: 6/27/2005
Citation: Baumhardt, R.L., Jones, O.R. 2005. Long-term benefits of deep tillage on soil physical properties and crop yield. In: The 27th Annual Southern Conservation Tillage Systems Conference, The Science of Conservation Tillage: Continuing the Discoveries, June 27-29, 2005, Florence, South Carolina. p. 95-101. 2005 CDROM.

Interpretive Summary: Plant available water limits dryland crop yields, but deep tillage used to disrupt dense subsoil layers may increase infiltration and root distribution for more soil water. Our objectives were to quantify long-term effects of deep tilling a clay loam soil on a few important soil properties and crop yield at the USDA-ARS, Conservation and Production Research Laboratory, Bushland, TX (35 deg 11’ N, 102 deg 5’ W). In 1971, paired 80 x 1500 ft. level conservation bench terrace plots were stubblemulch tilled or moldboard plowed to 27 in. and cropped with grain sorghum (milo) through 2004 for yield comparisons. Ponded infiltration, bulk density, and penetration resistance were measured during the summer of 2002. Deep tillage decreased soil profile density and penetrometer resistance initially, but they were no longer different after 30 years. Ponded infiltration increased with deep tillage after 30 years. The mean annual grain yield increased approximately 10% in deep tilled plots compared with stubblemulch tillage because of increased infiltration and, possibly, rooting. Increased yields with deep tillage for three of 14 crops accounted for 75% of the total yield benefit, which was attributed to better drainage of rain that flooded untilled plots. Deep tillage effects measured after > 30 years show that dense subsoil layers did not redevelop, which provides an extended period to recoup the 1971 installation costs of $65 per acre. For a Pullman soil, deep plowing may be an economical soil profile modification treatment to use with conservation systems.

Technical Abstract: Plant available water limits dryland crop yields, but deep tillage used to disrupt dense subsoil layers may increase infiltration and root distribution for more soil water. Our objectives were to quantify long-term effects of deep tilling a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) on select soil properties and crop yield at the USDA-ARS, Conservation and Production Research Laboratory, Bushland, TX (35 deg 11’ N, 102 deg 5’ W). In 1971, paired 80 x 1500 ft. level conservation bench terrace plots were stubblemulch tilled or moldboard plowed to 27 in. and cropped with grain sorghum [Sorghum bicolor (L.) Moench] through 2004 for yield comparisons. Ponded infiltration, bulk density, and penetration resistance were measured during the summer of 2002. Deep tillage decreased initial soil profile bulk density and penetrometer resistance, but they were no longer different after 30 years. Ponded infiltration increased with deep tillage after 30 years. The mean annual grain yield increased approximately 10% in deep tilled plots compared with stubblemulch tillage because of increased infiltration and, possibly, rooting. Increased yields with deep tillage for three of 14 crops accounted for 75% of the cumulative yield benefit, which was attributed to improved drainage of rain that flooded untilled plots. Deep tillage effects measured after > 30 years show that dense subsoil layers did not redevelop, which provides an extended period to recoup the 1971 installation costs of $65 per acre. For a Pullman soil, deep plowing may be an economical soil profile modification treatment to use with conservation systems.