Date of Graduation

12-2025

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Roberts, Trenton

Committee Member

Nicolli, Camila

Second Committee Member

Hardke, Jarrod

Third Committee Member

Brye, Kristofor

Keywords

Cover Crops; No-till; Nutrient Uptake; Rice; Soil Health

Abstract

In an effort to build and maintain soil health and sequester soil C, many producers and researchers are turning towards regenerative management practices in agricultural systems, such as reduced tillage or no-tillage (NT), the implementation of winter cover crops (CC), and the use of organic or green manures, such as biochar. However, little research is being conducted on the long-term soil health and agronomic benefits of these practices in a flood-irrigated rice (Oryza sativa L.) production system. Three replications of seven treatment combinations were applied to 6.1 x 30.5 m rice plots. Baseline soil health properties were quantified at six depths (0-10, 10-20, 20-40, 40-60, 60-80, and 80-100 cm) to establish a soil health baseline. Many soil health parameters, such as soil organic matter (SOM), total C, respiration, permanganate-oxidizable C, and water-extractable C were greatest at the 0-10 cm depth and significantly decreased with depth. In contrast, water-extractable organic C:N, salinity, CEC, and base saturation of Mg and Na were lowest at the soil surface and increased with depth. For two rice crop years (2023 and 2024), a one-way ANOVA and planned comparisons were performed on nutrient uptake at two sample times and rice yield with a P < 0.05 considered significant. The second year (2024) of treatment implementation revealed a significantly greater yield in the conventional treatment when compared to the NT, legume/grass CC mixture treatment, averaging 6,700 and 4,960 kg ha-1, respectively. In contrast, rice grain and tissue uptake of N, C, K, S, and Zn were greatest for the NT/legume CC treatment and lowest for the NT/burned residue treatment in the second crop year, indicating nutrients both leaving the system via the grain and returning to the system via the residue are significantly greater when CCs are implemented and the residue remains on the soil surface. While these results suggest an initial yield drag by implementing CC and NT, the results of previous studies follow a similar trend with an initial yield decrease, and a subsequent increase in rice yield can be expected amongst CC and NT treatments in the next two to four years.

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