DYNAMIC SOIL PROPERTIES IN THE LOWER RIO GRANDE VALLEY: CARBON AND NITROGEN RESPONSES TO DIFFERENT TILLAGE PRACTICES
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There has been increased attention in utilizing agriculture for carbon sequestration. Soil carbon and nitrogen are two dynamic soil properties (DSPs) that are indicators of soil health and function and have overlapping cycles. These soil properties change frequently as a result of environmental conditions and agricultural management practices. This study focuses on the impact of tillage practices in unirrigated agricultural fields in Hidalgo and Willacy counties located in South Texas on Hidalgo Sandy Clay Loam; With a particular focus on Soil Total Carbon (TC), Soil Inorganic Carbon (SIC), Permanganate Oxidizable Carbon (POXC), Carbon and Nitrogen ratio (C:N), Soil Organic Matter (SOM), and Total Nitrogen (TN). The tillage regimes are strip tillage (conservation tillage for 3 to 6 years), intermittent tillage (strip tillage for 2 to 3 years followed by conventional tillage), and conventional tillage. Two ecological sites (established tree lines that have been undisturbed for at least 50 years) are included as reference points. Results show ecological reference sites on average are significantly higher than those fields under conventional, intermittent, and strip-tilled for TC, TN, and SOM for the top 0 - 5cm. POXC on ecological reference sites was significantly higher from 0 - 5cm, 5 - 10cm, and 30 - 50cm. However, when comparing conventional tillage to intermittent and strip there was no statistically significant difference among TC, TN, SOM, POXC, and C:N at all depths. Finally, the most significant differences among the parameters measured could be observed on the top 0 - 10 cm with the exception of SIC due to the soil high content of calcium carbonates and POXC in which the ecological reference sites were significantly higher at 30 – 50cm than conventional sites.