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ARS Home » Plains Area » Las Cruces, New Mexico » Range Management Research » Research » Research Project #444210

Research Project: Identifying Drivers of Soil Carbon and Nitrogen Cycling in Semi-arid Agroecosystems

Location: Range Management Research

Project Number: 3050-12610-001-043-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Jul 1, 2023
End Date: Jun 30, 2025

Background and Objectives: Agricultural management influences soil health and nutrient cycling in agroecosystems. Climate variability and change adds pressure to land managers seeking to balance economic and ecological sustainability in arid and semi-arid regions, including major crop production areas of New Mexico. Improved knowledge of how land and water management can enhance soil health and sustain crop production could support the resilience of communities and agroecosystems. In recent years, conservation and regenerative farming practices (e.g., no-tillage, cover cropping, perennial cropping, etc.) have been increasingly adopted to improve soil health and resilience. We aim to monitor soil organic carbon (SOC) and nitrogen (N) fractions and dynamics under diverse cropping systems as an index of agroecosystem resilience in the semi-arid southwest. The specific objective of this project is to: • Quantify SOC and N fractions under diverse cropping practices. • Study the long-term SOC dynamics by using a DAYCENT Ecosystem model.

Study Approach Site characteristics: The study will be conducted at the New Mexico State University Agricultural Science Center, Clovis, NM (34°35´ N, 103°12´ W, elev. 1348 m). The study site has a semi-arid climate with a long-term (110-yr) mean annual temperature of 15°C and mean annual precipitation of 470 mm, 70% of which occurs between May and September. According to USDA soil classification, the soil at the site is Olton clay loam (fine, mixed, superactive, thermic, Aridic Paleustoll). Task 1, Quantifying soil organic carbon and nitrogen fractions: Soil samples will be collected from 0-15 cm and 15-30 cm depths of existing cover crops, tillage, and perennial cropping fields. The SOC and total N concentrations will be determined using a high-induction furnace C and N analyzer (LECO Inc.). Soil inorganic C (SIC) will be removed using a 6M HCl. Soil mineralizable C and N, inorganic N, microbial biomass C, and Mineral Associated Organic Carbon (MAOC) and Mineral Associated Organic Nitrogen (MAON) concentrations will also be determined using standard laboratory procedure. Similarly, soil inorganic and labile organic N content and other basic properties will also be estimated using a standard protocol. Task 2, Study the long-term SOC dynamics by using a DAYCENT Ecosystem model: Observations in task 1 will serve as data input for DayCent model simulations. Following parameter optimization and validation of the model against field data, we will run simulation experiments to understand thresholds and tipping points of GHG flux and SOC accumulation under diverse management practices. DayCent simulation can be useful to challenge assumptions about management practices that increase SOM and reduce GHG in hot, dry agroecosystems. These simulations can then inform near-term future research directions to test whether reduced tillage and increased crop rotation improve system resistance to expected climate. Expected Outcomes Soil C and N fractions and long-term SOC dynamics under diverse cropping will be estimated and simulated using the DayCent model. At least one publication and one conference presentation is expected from this work.