Lisa M. Fultz
With the growing global population and intense variability in climate, there is a mounting need for environmentally and economically sustainable production practices to support the increasing need for food and fibers. It has long been accepted that soil losses often occur when soils remain bare following harvest, during fallow years and following plowing. Soil losses can be reduced by in the incorporation of best management practices, like cover crops, that retain residue on the soil surface, acting as a buffer to the energy of raindrops hitting the soil surface.
While there is no silver bullet for agriculturally sustainable production, there are many tools available to assist producers. Louisiana’s unique environment and diversity of cropping systems offer an ideal opportunity to understand environmentally beneficial and economically sustainable soil and water conservation practices for southern field crops. Louisiana is a key state with a critical interest in nutrient management and soil stability to reduce contributions to the Mississippi River’s drainage basin and the Gulf of Mexico’s hypoxic zone. The chemical and physical properties of Louisiana’s soils are conducive to extensive leaching of applied agricultural chemicals, particularly when coupled with intense rainfall throughout the year.
Cover crops are one multipurpose tool that has been in use for thousands of years. The primary goal of a cover crop is to provide surface cover and protection for losses due to erosion. Cover crops also provide a host of secondary benefits, including nutrient cycling, improved water infiltration, pollinator food sources, weed suppression and a living root system for soil microbial populations. For example, in annual grain crops, monocultures or polycultures of grasses, brassicas and legumes will scavenge nutrients (particularly important for mobile nutrients) that would have been otherwise lost through leaching and runoff.
In sugarcane production, the early growth of newly planted sugarcane is slow and allows much of the soil surface to be exposed during the fall and winter months. The use of some cover crops, like soybeans, during the summer before planting sugarcane has the added benefit of providing an additional income source. Belowground activity is also important by providing a nutrient source for living organisms and can help to break up compacted layers in the case of some grasses and brassicas. But even with all the possible benefits, the complete environmental value has not been consistently captured, particularly in Louisiana. It is estimated that approximately 95% of croplands in Louisiana remain bare and thus susceptible to erosion. For these reasons, a diverse group of LSU AgCenter faculty and staff has worked together to answer many of the existing questions regarding the incorporation of cover crops into Louisiana’s cropping systems.
Over the past four years more than $2 million in funds have been awarded to further our understanding of how cover crops may work within Louisiana’s crop production systems. Researchers have examined cover crop impacts in both small-scale trials on research stations and in large-scale demonstrations on farmers’ fields across the state in corn, cotton, soybean, sugarcane, rice and pasture production systems. Studies have included how to manage cover crops, including seeding and termination timing, seeding rates, termination methods, and the use of monocultures versus polycultures. Studies have also expanded our knowledge of how cover crops impact soil fertility, crop yields, greenhouse gas emissions, weed suppression, economics and soil health. This information will aid producers in deciding whether to use cover crops and, if so, which cover crops are best suited to their needs.
Lisa M. Fultz is an associate professor in the School of Plant, Environmental and Soil Sciences and the lead scientist for this issue of Louisiana Agriculture.
(This article appears in the fall 2020 issue of Louisiana Agriculture.)
Lisa M. Fultz. Photo by John Wozniak