Short-Term Impact of Monocultured and Mixed Cover Crops on Soil Properties, Weed Suppression, and Lettuce Yield

Abstract

ABSTRACT The objective of this project was to investigate if integrating cover crops into the lettuce (Lactuca sativa L.) production can control weeds and improve various components of soil health. A two-year field study was conducted at the research farm of the University of Mohaghegh Ardabili, Ardabil, Iran, during the 2017 and 2018 growing seasons. In this study, we used monoculture, two-way, and a three-way mixture of barley, chickling pea, and buckwheat cover crops and no cover crop (local weeds). Sole barley cover crop produced the highest biomass in both growing seasons. The barley and buckwheat mixture in 2017 and barley and chickling pea in 2018 were most efficient in suppressing weeds. The dominant weeds included lambsquarters, redwood pigweed, and charlock mustard. Although the number of earthworms was more in the sole barley plots, the microbial population was highest in the three-way cover crop mixture. Soil carbon improved in the three-way cover crops by 12%; however, the differences amongst cover crop treatments were not statistically significant. Bulk density was reduced by 13% and water infiltration rate reduced by half averaged across cover crop treatments compared to no cover crop. Lettuce fresh weight increased in all cover crop treatments; however, a mixture of chickling pea and buckwheat cover crop improved the yield of lettuce by 17.8%, compared with the no cover crop.