The effects of in-row subsoil tillage and soil water on corn yields in the southeastern coastal plain of the United States

Abstract

Soil erosion is a problem in the Southeastern Coastal Plain of the U.S.A. where clean tillage row cropping exists without adequate soil conserving practices. Conservation tillage practices in the region have frequently incorporated in-row subsoiling to overcome root restricting soil layers 0.20 to 0.35 m below the surface. A number of studies have been conducted to determine the benefits of in-row subsoiling and results have been contradictory. The objective of this study was to evaluate the relationships between in-row subsoil and non-subsoil tillage treatments, soil water, and corn grain yields. The study was conducted for two years on an Orangeburg sandy loam (Typic Paleudult). The study contained irrigated and non-irrigated treatments. The four tillage treatments used were (T 1) in-row subsoiler followed by a double disk bedder, (T 2) double disk bedder, (T 3) fluted coulter followed by in-row subsoiler and slot filler tines, and (T 4) fluted coulter. Tillage and planting were accomplished simultaneously. Each corn ( Zea Mays L. ‘Dekalb XL72B’) crop was preceded by fall-planted wheat and the wheat ( Triticum aestivium L. “Coker 747”) was killed with herbicides in the spring before corn planting. Wheat mulch was disked in prior to the bedding treatments and left undisturbed for the two fluted coulter treatments. Corn was planted 0.04 m deep with double disk openers. Soil water potential was maintained above 0.05 MPa in the irrigated corn plots. Forty kg/ha of N was applied at planting and followed 42 days later with eight weekly applications of 50 kg/ha N. In-row subsoiling and irrigation treatments significantly increased grain yields. Irrigated corn grain yields were 12333 and 7872 kg/ha in 1978 and 1979, respectively. Non-irrigated corn yields were 7697 and 4892 kg/ha in 1978 and 1979, respectively. In-row subsoiled to a depth of 0.36 m and non-subsoiled grain yields were 8577 and 7820 kg/ha, respectively. There was no significant difference between bedding and fluted coulter treatments.