Conservation tillage impacts and adaptations in irrigated corn production in a humid climate

Authors: Anapalli, Saseendran; Reddy, Krishna; JAGADAMMA, SINDHU - University Of Tennessee

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2018
Publication Date: 9/6/2018
Citation: Anapalli, S.S., Reddy, K.N., Jagadamma, S. 2018. Conservation tillage impacts and adaptations in irrigated corn production in a humid climate. Agronomy Journal. 110(6):1-14.

Interpretive Summary: Plowing the soil for growing crops leaves the soil prone to its organic matter and fertility losses to water and wind erosions. A system of land-management practices known as ‘no-tillage’ promote growing crops with minimum soil disturbance and leaving crop residues on the soil surface (NT) has often been promoted as a remedy for this problem. The NT can bring savings on soil-cultivation costs and better water use efficiency in irrigated cropping systems. However, the location-specific viability of the system, especially, in producing sustainable crop yields depend upon the growing season climate and soil properties. In this regard, in certain soil-climate combinations, significant grain yield losses under the NT were reported at various locations over the world. For the first time in the MS Delta, researchers with the USDA ARS Crop Production Systems Research Unit at Stoneville, MS, and the Department of Biosystems Engineering , University of Tennessee, Knoxville, conducted a nine-year (2009-2017) experiment to assess the impacts of NT system over a conventional-tillage system (CT) under irrigated corn production at Stoneville, MS. Crop management practices except tillage were maintained like those followed by the farmers in the area. In seven out of nine years, harvested grain yields in the NT were significantly lower than those harvested in the CT. Further investigations on the possible reasons for the yield declines in NT over CT were conducted by integrating the experiment with a cropping system model. The study concluded that the yield reduction under the NT was due to lower N availability in the soil for crop-uptake due to higher nitrogen losses to runoff and deep percolated water, and lower plant residue decomposition and release of plant nutrients from plant tissues for crop uptake. This study showed that an additional N application at 40 kg/ha at planting or a split application of 50 kg/ha at planting and the remaining 174 kg/ha in the second week of May could restore yield under NT comparable to CT.

Technical Abstract: A thorough evaluation of the location-specific impacts of conservation land management practices is critical for their acceptance in farming systems across climates and soils. We initiated a long-term experiment in 2008 on 1.25 ha farm-scale plots to assess the production impacts of a no-till with full residue retention (NT) system over a conventional-tillage (CT) under irrigated corn production on a Dundee silt loam soil in the humid climate of the lower Mississippi (MS) Delta. Crop management practices except tillage were maintained like those followed by the farmers in the area. In seven out of nine years (2009-17), harvested grain yields (GY) in the NT were significantly lower than those harvested in the CT, and in one year, they were not significantly different. To investigate the possible reasons for the yield declines in NT over CT, we integrated the experiment with a cropping system model (Root Zone Water Quality Model, RZWQM2) to synthesize information on the various components in the system. Data collected in the experiment from 2009-2015 were mainly confined to grain yield at harvest. In 2016 and 2017, additional data were collected including soil surface crop-residue mass (Rm) and -cover (Rc); corn leaf area index (LAI) and biomass (BM); soil water (SW), temperature (Ts), nitrogen (N), carbon (C), and bulk density (BD); and the corn phenology. Under the NT, corn BM, LAI, grain yield, Ts, C, and N were lower, and Rc, Rm, and SW were higher than those measured under CT. The RZWQM2 correctly simulated these measured trends and the corn phenology. Simulated runoff and deep percolation losses of water and N, and denitrification losses of N were higher in NT, and infiltration, evapotranspiration (ET), and N mineralization were higher in CT. Evidently, the lower N mineralization and higher N losses in NT lead to the measured low crop productivity under this system over the CT. Simulations showed that an additional N application at 40 kg ha-1 at planting or a split application of 50 kg ha-1 at planting and the remaining 174 kg ha-1 in the second week of May could bring back the yield return under NT comparable to CT.