Agronomy and Horticulture Department
First Advisor
Humberto Blanco
Date of this Version
4-2018
Abstract
Large-scale crop residue removal for livestock or biofuel production may negatively affect soil and water resources. A combination of management practices could be the key to manage such resources under increasingly variable climate. For instance, use of cover crops (CCs) could offset the negative impacts that corn (Zea mays L.) residue removal may have on soil water and energy balance. We studied: 1) the effect of corn residue removal (56%) with and without winter rye (Secale cereale L.) CC on soil hydraulic and thermal properties including water infiltration, water retention, pores-size distribution, thermal conductivity, specific heat capacity, and thermal diffusivity, 2) whether CCs offset any negative impacts of residue removal effects on the above properties, and 3) relationships of hydraulic and thermal properties with soil organic C and other properties. An experiment of corn residue removal and CCs in an irrigated no-till continuous corn located in south central Nebraska was used. All soil properties were measured 5 and 6 years after experiment onset except water infiltration and soil thermal properties, which were measured only after 6 years. Cover crops generally had no effect on soil hydraulic and thermal properties but increased soil organic C concentration (p = 0.10) in the 0 to 5 cm depth. However, corn residue removal consistently affected soil properties in the 0 to 10 cm soil depth. Residue removal reduced cumulative infiltration by 22 to 58% compared with no removal. It also reduced available water by 21 to 31%, thermal conductivity by 19 to 28%, specific heat capacity by 23 to 28%, soil wet aggregate stability by 17 to 30%, and soil organic C concentration by 25% in the 0 to 5 cm depth. The reduction in available water with residue removal was strongly correlated with a decrease in soil organic C concentration and wet aggregate stability. Thermal conductivity decreased with a decrease in soil water content, soil organic C, and bulk density due to residue removal. In conclusion, corn residue removal negatively impacted soil hydraulic and thermal properties and CCs were unable to completely offset but partially mitigated the negative impacts of residue removal.
Advisor: Humberto Blanco
Comments
A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agronomy, Under the Supervision of Professor Humberto Blanco. Lincoln, Nebraska: April, 2018.
Copyright (c) 2018 Michael Sindelar