Lisa Fultz and Brenda Tubaña

Soil health, first mentioned as early as 1910, focuses on the capacity of soil to act as an essential living ecosystem — sustaining plants, animals and humans. Improving soil health has been linked to decreased soil erosion as well as improved water infiltration, nutrient cycling and soil stability, which all contribute to improved water quality. Essentially, these all refer to the ecosystem services of soil in a given landscape. Keeping soil health in check is achieved by implementing best field management practices that maximize living roots, soil cover and biodiversity and reduce soil disturbance. Cover cropping is among the most commonly implemented best management practices along with reduced and no-tillage farming and no-burn post-harvest residue management. These all provide an added benefit of improving water quality.

Cover crops, which are crops intended to cover the soil without being harvested, have a long history of use. By providing a living root system (Figure 1) and surface cover during typically fallow periods, cover crops aid in reducing erosion and nutrient runoff by breaking and lessening the force of rainfall drops and wind. Cover crops also provide a host of secondary benefits, including increasing soil fertility and soil organic matter, improving conditions for water infiltration and retention, suppressing weed populations, reducing populations of pests and diseases and providing habitat for wildlife. The success of cover crops to meet these needs is dependent on cover crop selection and cultural management practices. For example, in a five-year study, conversion to no-till practices increased soil organic matter by 20%, but when paired with cover crops soil organic matter, it increased by 35%. Additionally, when compared to fallow and grass cover crops, only legume species contributed nitrogen to the subsequent corn crop, providing 30 to 35 pounds of nitrogen per acre. While grass cover crops may not have contributed significantly to soil nitrogen concentrations, they did aid in the suppression of weed populations, reducing stands of henbit at the Macon Ridge Research Station and annual ryegrass at the Dean Lee Research and Extension Center. Planting date is also important on stand establishment and biomass accumulation of cover crops. September-planted cover crops produced 1.5 times more dry biomass yield than November-planted cover crops (Figure 2).

In 2019, the Patrick F. Taylor Foundation awarded $1.4 million to research and extension faculty at the LSU AgCenter to implement best management practices on two model farms in Louisiana, one focused on cotton and grain production and one focused on sugarcane production. Over the last three years researchers have worked with Dugas Farms Inc. and Hardwick Planting Co. to demonstrate the benefits of best management practices on soil health, crop production and water quality. Specific best management practices were recommended based on many factors, including existing production practices, equipment availability and the needs for each producer. In the case of the Cotton and Grain Model Farm, best management practices include plant need-based application of fertilizer using variable rate technology and nutrient rich strips, reduced tillage and cover cropping. Similar sets of best management practices are implemented on the Sugarcane Model Farm but include sweeping off post-harvest cane residue as opposed to burning and intercropping of cover crops on newly planted cane.

From this work the team has demonstrated that reduced tillage coupled with cover crops resulted in decreased sediment in runoff samples compared to no-tillage with cover crop stale seedbed management (Figure 3). Other fields showed cover cropping increased plant-essential nutrient content of soils such as phosphorus and sulfur. Cover crops take up nutrients from the soil and stored them in their biomass. Biomass decomposition after cover crop termination in late winter or early spring releases these nutrients back to the soil.

With optimal management, cover cropping can bring a myriad of benefits to soil health and crop productivity while reducing agricultural footprint in the environment.

Lisa Fultz is an Associate Professor in the School of Plant, Environmental and Soil Sciences. Brenda Tubaña holds the Jack E. and Henrietta Jones Professorship in the School of Plant, Environmental and Soil Sciences.

This article appears in the winter 2023 edition of Louisiana Agriculture.

Figure 1. Hector Fajardo, a graduate student at the School of Plant, Environmental and Soil Sciences, shows the soil loosening root system of rapeseed, one of the cover crop species being evaluated in sugarcane field.

Figure 2. Average dry biomass yield of cover crops planted in September, October and November from 2017 to 2019 at the LSU AgCenter Central Research Station. Included in the graph is the native weeds dry biomass yield from the unplanted plots.

Figure 3. Water quality samples collected in July 2020 from cotton fields with best management practices implemented (top) and under stale seedbed management. Photos provided by Lisa Fultz and Brenda Tubaña.