Long-term effect of cover crop on rainwater balance components and use efficiency in the no-tilled and rainfed corn and soybean rotation system

Authors: YANG, WEI - China Agricultural University; Feng, Gary; Adeli, Ardeshir; KERSEBAUM, K - Institute Of Landscape Systems Analysis, Leibniz Centre For Agricultural Landscape Research; Jenkins, Johnie; LI, PINFANG - China Agricultural University

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2019
Publication Date: 6/20/2019
Citation: Yang, W., Feng, G.G., Adeli, A., Kersebaum, K.C., Jenkins, J.N., Li, P. 2019. Long-term effect of cover crop on rainwater balance components and use efficiency in the no-tilled and rainfed corn and soybean rotation system. Agricultural Water Management. 219:27-39. https://doi.org/10.1016/j.agwat.2019.03.022.
DOI: https://doi.org/10.1016/j.agwat.2019.03.022

Interpretive Summary: Cover crops (CCs) have been widely cultivated to bridge the winter period between two cropping seasons. They can provide multiple beneficial soil, agricultural production, and environmental benefits. Mississippi Blackland Prairie, located in the northeast Mississippi state, covers approximately 14% (25.4 × 104 ha) of the Mississippi total crop land. The area of soybean and corn individually accounts for 11% and 35% of the Mississippi's total crop arable land. Annual total precipitation during 1938-2017 in this region averaged 1,385 mm, and approximately 60% of annual total precipitation was in October through April. Most of the annual rain-water was either lost by surface runoff or deep percolation in the farmland during winter and early spring. Approximately 40% of annual rainfall is in main crop growth seasons from May to September. Main crop growth and yield are thus frequently limited by soil water availability in past several decade years. There is needed to take some favorable conversation agronomic practices to decrease water loss from runoff and subsurface drainage, and enhance soil water storage for high crop production and water use efficiency (WUE). It is generally difficult to measure runoff and drainage in farmland, mainly because these are substantially affected by uncertainties as soil type, climate, and rainfall availability. A one-dimensional, processed-based, and field-scale agricultural systems model, RZWQM2 (Root Zone Water Quality Model), was firstly released by USDA-Agricultural Research Service in the early 1990s. It was capable of simulating the effects of tillage, crop residue, irrigation, fertilization, and crop management on crop production, WUE, and soil water dynamics. In here, based on the field measurements of leaf area index, soil water content, crop above-ground biomass, and yield in continuous 4-yr (2014-2017) corn-soybean cropping system at the site, we have conducted a long-term (1938-2017) simulation study regarding winter wheat CC effects on deep percolation, runoff, soil water storage, and water use efficiency (WUE) under representative weather conditions. All experimental plots did not receive irrigation and tillage, but it was applied NH4NO3 at 190 kg ha-1 yr-1 in corn years in 2014 and 2016. The simulation results found that, planting CC did not change simulated runoff values but reduced annual deep percolation by 66 mm, compared no CC. Model-estimated corn yield and soybean yield were respectively increased by 5% (309 kg ha-1) and 4% (134 kg ha-1) in the CC system compared with no CC system. Compared to the plots with no CC, the simulation of WUE for corn and soybean were respectively improved by 12% (1.47 kg m-3 versus 1.31 kg m-3) and by 9% (0.64 kg m-3 versus 0.59 kg m-3) for the plots with CC, largely due to the decrease in surface evaporation without sacrificing crop growth. Soil water storage was increased especially within two months after terminating CC. Long-term use of winter wheat CC, if managed similarly, can increase soil water storage and improve precipitation use efficiency without sacrificing corn and soybean crop growth in subtropical agro-systems.

Technical Abstract: Incorporating cover crops into row crop production systems can affect soil water dynamics and crop production. However, the effect of this practice has not been well investigated under long-term representative weather conditions. We calibrated and tested the Root Zone Water Quality model (RZWQM2) using 4-yr (2014-2017) field data in the humid Mississippi Blackland Prairie, and also used this model to simulate the long-term (1938-2017) effects of a wheat cover crop on hydrological variables, crop yield, and water use efficiency (WUE) in a rainfed and no-tilled corn and soybean cropping system. The RZWQM2 simulation performance was considered as “satisfactory” in terms of crop yields, total above-ground biomass, leaf area index, and crop evapotranspiration with percent errors all were within ± 15% and Nash-Sutcliffe modeling efficiency > 0.75. The prediction in soil volumetric water content from 0 to 30 cm depth, 0-15 and 15-30 cm, was not good but was reasonable when compared with previous studies. Long-term simulation demonstrates that average annual percolation under the cover crop system was decreased by 8% (63 mm), 11% (90 mm), and 12% (46 mm) in wet, normal, and dry years. Simulated runoff for cover crop scenario was not different from values simulated for no cover crop scenario. Predicted actual evaporation during cash crop growth periods under cover crop plots was 25% less than under no cover crop plots (129 mm versus 172 mm) when averaged over the whole modeling period. Compared to no cover crop scenarios, the estimated crop evapotranspiration under cover crop scenario was reduced by 6.6% (31 mm) during corn growth period and by 3% (19 mm) during soybean growth period. Yearly predicted crop yields for corn and soybean were individually increased by 4.7% (309 kg ha-1) and 4.4% (134 kg ha-1) in the cover crop-based cropping system. Compared to the plots with no cover crop, the simulation of WUE for corn and soybean were respectively improved by 12.2% (1.47 kg m-3 versus 1.31 kg m-3) and by 8.5% (0.64 kg m-3 versus 0.59 kg m-3) for the plots with cover crop, largely due to the decrease in surface evaporation without sacrificing crop growth. These results suggest that long-term use of wheat cover crop to summer crops rotation is a promising practice to decrease deep percolation and restrict surface evaporation, and also improved crops WUE in the corn and soybean rotation in subtropical agro-system.