Alfalfa in rotation with annual crops reduced nitrate leaching potential

Authors

• Arshdeep Singh, University of Nebraska-LincolnFollow
• Tahseen Afzal, University of Nebraska-Lincoln
• Bryan Woodbury, USDA-ARS
• Charles Wortmann, University of Nebraska-Lincoln
• Javed Iqbal, University of Nebraska- LincolnFollow

Document Type

Article

Date of this Version

2-23-2023

Citation

Singh, A., Afzal, T., Woodbury, B., Wortmann, C., & Iqbal, J. (2023). Alfalfa in rotation with annual crops reduced nitrate leaching potential. Journal of Environmental Quality, 1–10. https://doi.org/10.1002/jeq2.20473.

Comments

Open access.

Abstract

Rotation of perennial alfalfa (Medicago sativa L.) with annual crops has the potential to reduce nitrate-nitrogen (NO₃-N) in the vadose zone and increase soil organic carbon (SOC) sequestration. The objective of this study was to determine the long-term effects on SOC, NO₃-N, ammonium-N (NH₄-N), and soil water in the 7.2 m depth with an alfalfa rotation compared with continuous corn (Zea mays L.). Soils from six pairs of alfalfa rotation versus continuous corn observation points were sampled to 7.2 m depth in 0.3 m increments. The uppermost 0.3 m was divided into 0–0.15 and 0.15–0.30 m. For the 0–7.2 m depth, the alfalfa rotation compared with continuous corn had 26% less soil water (0.29 vs. 0.39 g cm⁻³) and 55% less NO₃-N (368 vs. 824 kg ha⁻¹). The cropping system and NO₃-N concentration did not affect NH₄-N in the vadose zone. The alfalfa rotation compared with continuous corn had 47% higher SOC (105.96 Mg ha⁻¹ vs. 72.12 Mg ha⁻¹) and 23% higher total soil nitrogen (TSN) (11.99 Mg ha⁻¹ vs. 9.73 Mg ha⁻¹) in the 0–1.2 m depth. The greater depletion of soil water and NO₃-N with alfalfa rotation was primarily below the rooting zone of corn, suggesting no negative implications for corn following alfalfa but greatly reduced potential of NO₃-N leaching to the aquifer with the alfalfa rotation. Alfalfa rotation compared with continuous corn is a means to greatly reduce the leaching of NO₃-N to the aquifer and improve the surface soil with the potential to increase SOC sequestration.