Cover Crop Management and Nutrient Type Effects on Collard and Cotton Growth

Abstract

Producing fresh vegetables and fiber, such as collards (Brassica oleracea L. var. viridis) and cotton (Gossypium herbaceum L.), in cover crop residue while minimizing soil disturbance can be helpful in lowering environmental impacts. Furthermore, using different types of fertilization, including poultry litter, for cotton can also promote soil health and manage input costs. Two experiments were performed to investigate 3 different residue management methods including rolled/crimped (Roll), mowed (Mow), and mowed + incorporated by tillage (MowIncorp) and their effects on a collard and cotton production system. Collards were grown in both an iron clay pea (Vigna unguiculata L.) and pearl millet (Pennisetum glaucum L.) cover crop and results showed that cover crop type influenced collard productivity in the 2015, 2016, and 2017 seasons. Pearl millet produced more biomass (P=0.0013) with a three-year average of 8461 kg ha−1 compared to 6465 kg ha−1 for iron clay pea. Carbon sequestration was evident in both cropping systems with 10.5% (from 5.04 to 5.57 g C kg-1) and 8.1% (from 5.08 to 5.49 g C kg-1) increases in total soil carbon for pearl millet and iron clay pea, respectively, in the top 15 cm of soil over three seasons. Overall, collard yield in the iron clay pea cover crop produced more (P<0.0001) with a 3-year average of 7268 kg ha-1 compared to 4724 kg ha-1 for the pearl millet. The cotton experiment investigated the residue management methods for a single rye cover crop and four different nutrient treatments for the 2022-2023 seasons. All nutrient treatments included the same amount of nitrogen (100.9 kg N ha-1) and consisted of: 100% poultry litter at preplant (PL), 67% poultry litter at preplant + 33% liquid urea ammonium nitrate (UAN) at sidedress (PLUAN), 33% granular fertilizer pre-plant + 67% liquid urea ammonium nitrate at sidedress (FERT), and a no nutrient applied control (NONE). Sidedress applications were performed prior to flowering using a coulter with knife spaced 10 cm from cotton row. Results show that nutrient treatments were the main influence on cotton growth with 11% taller plants, 31.8% greater dry weight, and 13.4% more cotton bolls, respectively, for the inorganic fertilizer treatments (FERT) compared to the poultry litter (PL) treatment in 2022. The FERT treatment had 10.7% taller plants, 16.9% greater dry weight, and 9.3% more cotton bolls compared to the PL treatment in 2023. The Mow method hindered emergence for the 2022 and 2024 seasons where rye dry biomass was 6464 and 5982 kg ha-1, respectively, but no differences in emergence were evident across methods in 2023 with rye biomass production of 3723 kg ha-1. For both seasons, no significant differences were realized between any of the nutrient treatments for seed cotton yield, but the yield was lower for MowIncorp in 2023 compared to the Roll and Mow. In conclusion, poultry litter was successful in sustaining cotton yield similar to inorganic fertilizers under cover crop residue management without tillage.