Emma Kurth Doctoral Exit Seminar
A Doctoral Exit Seminar by Emma Kurth will be presented Thursday, November 21st, 2017 at 1:30pm in 370 Kottman Hall. Her presentation will be Three Field Studies To Examine Cropping Management Effects On: Runoff Quantity And Quality; Soil Water Content And Temperature; And Selected Soil Quality Indicators.
Agriculture today is faced with the challenge of feeding 9.7 billion by 2050 and to achieve this goal sustainably, best management practices that improve soil and water quality, and mitigate environmental impacts, will need to be implemented. Long-term food security is further threatened by the declining growth in yield for major cereal crops, extreme weather events, and changes in growing seasons for these major cereal crops. Literature has demonstrated that conservation practices, including no-till and cover cropping enhance soil physical, biological, and hydrological properties, but the effects on the overall agricultural system are less definitive. The studies presented herein separately examined the impacts of recommended practices including winter cover cropping and no-till management on surface runoff quantity and quality, temporal behavior of soil water content and temperature, four soil quality indicators, and crop yield.
The first study, presented in chapter 2, evaluated the effects of a no-till corn (Zea mays L.)-soybean [Glycine max (L.) Merr]-wheat (Triticum aestivum L.) rotation with an annual cover crop on event-based runoff quantity and quality through quantification of the quantity of water lost and concentrations of nutrients lost in that runoff. Results showed that seasonal precipitation patterns and spring time nutrient applications were major factors that contributed to nutrient concentrations in the runoff. Runoff quantity was greatest in the summer, despite having lower average seasonal precipitation, suggesting that runoff was generated from less frequent, but more intense, precipitation events. Ammonium concentration in the runoff was greater for the wheat phase compared with the corn and soybeans phases, while phosphate and total P concentrations in runoff were greater for the soybean phase.
The second study (chapter 3) characterized the soil moisture and temperature regimes under the no-till corn-soybean-wheat rotation with an annual cover crop presented in chapter 2. The results showed that residue cover and growing season water use patterns had the greatest impact on soil moisture. Findings of greater soil moisture during the winter following corn suggest that corn residue provides greater percent cover due to a high carbon to nitrogen (C:N) ratio and less post-harvest microbial decomposition. During the fall, soil temperature was higher for the soybean phase than the wheat or corn phases and may be due to having a lower albedo, a lower C:N ratio, faster decomposition of residue cover, and greater light transmittance
The final study (chapter 4) assessed the effects of nine cover crop treatments on subsequent corn yield and four soil quality indicators: mineralizable carbon, permanganate oxidizable carbon (POXC), soil protein, and water stable aggregates (WSA). Results showed that of the soil quality indicators, only the mineralizable carbon content was greater with a cover crop than no cover crop, suggesting that cover crops can provide short-term nutrient availability, but are less associated with processes that accumulate and sequester carbon. Corn yields were not significantly greater for cover crop treatments, but following red clover (Trifolium pratense L.), corn had the highest mean yield of all treatments.
The findings of these studies are encouraging as they demonstrate that cover crops are a conservation practice that can have the potential for improving soil quality without decreasing yields compared with conventional bare fallow systems. Seasonal precipitation patterns demonstrate an overwhelming influence on generating runoff and subsequent nutrient loss, but cover crops and residue cover show potential for mitigating these losses through improved water retention and hydrological properties, and protection of the soil surface. The information in these chapters can help develop guidelines for producers on how to best implement practices that mitigate environmental impacts while maintaining sustainable yields.