Effect of Long-Term (35 years) No-till and Conventional Tillage Systems on Soil Quality.

A long-term tillage systems experiment was initiated in 1982 at Texas A&M University research farm near College Station, Texas (30⁰ 37’ 16.8” N, 96⁰ 32’47.2” W), to understand the long-term impact of tillage practices on soil quality (C mineralization and CO₂ emissions). Two tillage regimes were compared in continuous sorghum production: conventional tillage (CT) and no-tillage (NT). Results showed that C-mineralization was significantly greater (50 g kg^-1 of soil greater) in the soils of NT system compared to that of CT system at 0-5 cm soil depth. However, this trend was reversed at 10-20 cm depth (33 g kg^-1 of soil greater in the CT compared to NT). This might be due to the presence of small soil aggregates as well as the transport of soil carbon to the lower layers due to mechanical soil inversion in the CT system. Soil organic carbon (%) and organic matter (%) were significantly greater in NT system compared to CT system at 0-5, 5-10 and 10-20 cm soil depths. This might be due to the retention of crop residues and lack of soil inversion in NT system, resulting in improved soil organic carbon as well as organic matter content. Soil CO₂ flux was measured in the field after crop harvest. Preliminary results showed that tillage induced CO₂ emissions were greater in the CT system (5.69 g m^-2 CO₂ day^-1) than in the NT system (4.33 g m^-2 CO₂ day^-1). Results provide evidence that long-term conservation tillage practices improve soil health and sustainability.