Previous Research

Developing organic no-till systems to improve soil health, nutrient management, and productivity
Organic agriculture has demonstrated benefits in building soil health, including increasing soil organic matter, nutrient supply, and water holding capacity. However, intensive tillage, that is often required for weed control in organic agriculture can also lead to soil degradation. I am assessing the benefits of adopting innovative organic no-till practices such as using the Roller Crimper to terminate cover crops on soil health and the  productivity of organic agricultural systems. 



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Microbial regulation of soil organic matter turnover in dairy-forage cropping systems in the Midwest
Intensive agricultural activities often deplete soil organic matter (SOM), the largest terrestrial C pool, leading to land degradation, declining soil fertility, and increased CO2 emissions. Agricultural strategies to increase SOM typically rely on enhancing C inputs to soil but the effectiveness of this strategy has been controversial because inconsistent results have been observed. This is largely because the role of soil microbial communities in SOM turnover is still not well known. Therefore, understanding the interactions of soil microbes and agricultural management practices on microbial SOM turnover is critical for the adoption of proper management practices to maintain or improve soil organic C level and key ecosystem services to promote more sustainable and resilient agriculture.
Soil fertility and nutrient management in North Central USA
​​Economic and environmental issues have increased the need for improved nutrient management in crop production systems. In the North Central USA agriculture continues to grow, with trends towards enterprise specialization where producers either grow grain crops or raise livestock for meat or dairy. This has resulted in a landscape-scale nutrient imbalance. However, increased variability in precipitation under climate change presents a challenge for nutrient management. Improved nutrient management practices were essential to avoid excessive N and P losses and yield reductions in this region. I am investigating the potential of alternative N sources (e.g. enhanced-efficiency fertilizers, and liquid manure applications) and timings on crop yield, soil properties and nutrient use efficiency. ​
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Warming and grazing effects on soil C and N cycling and microbial communities in alpine grasslands of the Tibet Plateau
Uncertainty about the effects of warming and grazing on soil C, N, and P dynamics, microbial communities species composition, and aboveground net primary production limits our ability to predict how global carbon sequestration will vary under future warming with grazing in alpine regions. Through a controlled asymmetrical warming (1.2/1.7°C during daytime/nighttime) with a grazing experiment in an alpine meadow on the Tibet Plateau, I investigated how combined warming and grazing affected soil C, N, and P pools, microbial abundance, net N mineralization. Findings suggest that soil N availability does not determine ANPP under simulated warming and that heavy grazing rather than warming causes degradation of the alpine meadows.
Soil organic matter turnover and microbial activity in dryland agricultural systems in Western Australia
Spatial and temporal patterns of water availability are the fundamental drivers of biological processes in arid and semi-arid ecosystems. Microorganisms determine if fresh C input is converted into stable soil organic matter or lost as CO2. I investigated the response of microbial biomass and respiration to organic matter amendments and how wetting patterns (frequency and intensity) and nutrient additions altered microbial biomass and CO2-C loss from a semi-arid soil. Findings suggest increasing plant residues are not able to build microbial biomass while smaller more frequent summer rainfall may decrease CO2 emissions compared to infrequent larger events; and enhance microbial C use efficiency where sufficient background SOM and nutrients are available.
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