Economic and yield benefits of using cover crops to reduce nitrogen fertilizer inputs in corn production on U.S. coastal plain soils

Authors: HAYMAKER, JOSEPH - Virginia Tech; REITER, MARK - Virginia Tech; MASON, JOHN - Virginia Tech; STEWART, RYAN - Virginia Tech; STEPHENSON, KURT - Virginia Tech; Balkcom, Kipling

Submitted to: International Soil Tillage Research Organization Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/31/2024
Publication Date: 9/1/2024
Citation: Haymaker, J., Reiter, M., Mason, J., Stewart, R., Stephenson, K., Balkcom, K.S. 2024. Economic and yield benefits of using cover crops to reduce nitrogen fertilizer inputs in corn production on U.S. coastal plain soils [abstract]. 22nd International Soil Tillage Research Organization Conference, Virginia Beach, VA. Sept. 23 - 27, 2024.

Interpretive Summary:

Technical Abstract: Sandy loam soils on the U.S. Coastal Plain are prone to nitrogen (N) leaching, and fluctuations in fertilizer prices have further affected corn (Zea mays) production profitability. In fall 2014, we initiated a long-term study to evaluate the impact of 12 different crop rotations on soil health and cash crop yields. Rotations included four no-cover crop (NCC) controls, seven cover crop (CC) treatments, and a perennial mix treatment where corn was planted every third year. In fall 2022, CCs were planted after corn harvest on October 12 (five treatments) and soybean harvest on November 9 (two treatments). Biomass and N accumulation from CCs and weeds were assessed before chemical termination on April 24, 2023. Corn was planted across all 12 treatments the following day, with 56 kg N ha-1 of starter fertilizer applied. At the V6 growth stage, each main plot was split into four 3.7m × 12.2m subplots and sidedressed at 0, 56, 112, and 168 kg N ha-1 rates. Corn yields were measured at harvest and adjusted to 155 g H2O kg-1. Total CC and weed biomass production ranged from 1,383 to 5,405 kg ha-1 (p < 0.001, LSD0.05 = 1208 kg ha-1), and N accumulation ranged from 24 to 186 kg N ha-1 (p < 0.001, LSD0.05 = 28 kg N ha-1). Among CC treatments, cereal rye (Secale cereale) had the lowest total biomass production (2,623 kg ha-1) and N accumulation (34 kg N ha-1), which were similar to NCC controls. Early-planted hairy vetch (Vicia villosa) accumulated significantly more biomass (4,578 vs. 3,440 kg ha-1) and N (186 vs. 134 kg ha-1) than late-planted vetch. However, late-planted vetch accumulated similar N as the early-planted CC mixes (121 to 160 kg N ha-1). At the zero N sidedress rate, N accumulation from total biomass positively correlated with corn yield (R2 = 0.68), while total biomass C:N ratio negatively correlated with corn yield (R2 = 0.60). Monoculture and hairy vetch-dominant mix treatments exhibited the lowest C:N ratio (=12:1) and highest N accumulation (>134 kg N ha-1), resulting in the highest corn yields and lowest yield response to increased N fertilizer. In contrast, NCC controls and cereal rye treatment had the lowest corn yields at each N-sidedressing rate. Although all treatments experienced yield increases with higher N rates, economic returns were minimal for hairy vetch treatments, with partial net profits ranging from US$1,733 to US$1,758 ha-1 for early-planted vetch and US$1,588 to US$1,740 ha-1 for late-planted vetch across N rates. However, cereal rye treatment yielded negative net returns, earning US$73 to US$174 less than the NCC control across N rates. This study highlights that legume CCs and mixes can improve corn yields, reduce N fertilizer inputs, and enhance profit potential.