B. Rogers Leonard
Louisiana’s abundant natural resources have offered tremendous economic opportunities for farmers, ranchers and forest managers. In many situations, sustainable production systems require intensive management practices that incorporate supplemental fertilizers to promote optimum growth and plant development. These requirements are similar for the commercial and homeowner horticultural industries in Louisiana. Runoff from agricultural and urban landscapes caused by excessive rainfall or irrigation discharges creates a means for soil, fertilizers, pesticides, fecal materials or other organic materials to move into lakes, streams and rivers. These sources of discharge into the environment are considered nonpoint sources of pollution.
Production of food and fiber at sufficient levels to feed a growing population typically requires supplemental amendments to the soil to optimize plant development. Plants need essential nutrients such as nitrogen and phosphorus in fertilizers to maintain nutrient availability in soils. Without the application of fertilizer, the soil would quickly become depleted of these reservoirs; plant development would slow, and crop yields would decline rapidly. The use of chemical fertilizers and animal manures in crops and horticultural environments makes agriculture a contributor to nitrogen and phosphorus contamination in water bodies through rainfall, flooding or irrigation.
Movement of soil and nutrients is a natural process in the environment. The average annual rainfall in Louisiana exceeds 60 inches and in some locations this level occurs over 100 days or more. Tropical and inland storms can intensify that amount within a few hours or days, as experienced during 2016. Four independent events caused flooding across every region of Louisiana in 2016, affecting rural cropland and urban communities.
Many Louisianians have beautiful lawns and landscapes, which usually require the use of fertilizers and pesticides. Sports fields for schools and communities, as well as golf courses, are examples of areas that also require soil and plant amendments to maintain their performance and aesthetic value. Many of these fertilizer products include nitrogen and phosphorus. As urban infrastructure continues to expand, the amount of hard surfaces and nonporous landscaping also increases, reducing water infiltration throughout the soil profile and contributing to the runoff of nutrients during normal rainfall and storm events.
In addition, there are a variety of procedures used in sewer treatment plants and septic systems to treat waste generated by municipalities, industry and rural residences. Unless these systems are adequately monitored and maintained to efficiently manage nutrients, this is another source of nitrogen and phosphorus being discharged into waterways. In many instances, this source is combined with the storm water runoff from lawns and landscapes. For rural agricultural areas, it can be even more important because the treatment systems are maintained by individual households and not monitored as frequently as those for municipalities.
According to data from the Louisiana Department of Environmental Quality, more than 200 bayous, lakes or rivers have been designated as impaired waterways due to nutrient pollution. One outcome that some scientists have associated with nutrient pollution is the designated area of a “dead” zone in the Gulf of Mexico at the mouth of the Mississippi and Atchafalaya rivers. It is important to note that estimates suggest Louisiana contributes less than 7 percent of the total nutrient load associated with river pollution. The vast majority of this nitrogen and phosphorus runoff into waterways originates in the Midwestern agricultural regions.
Inland water bodies can be impacted by nutrient pollution as well. Many bayous, rivers and lakes have been contaminated for the past several decades, resulting in environmental and human health issues. Nutrient pollution also can reach the underground aquifers used to supply drinking water. One form of nitrogen (nitrates) found in groundwater can be harmful, even at low levels.
All of these examples contribute to nonpoint sources of nutrient pollution in Louisiana waterways. The problem is far more complex and comprehensive than simply regulating the use of fertilizers or water available for agricultural and urban irrigation. State and federal regulations exist to protect water quality and offer guidance for nutrient management, but these policies frequently are difficult to enact in many situations due to the nonpoint-source nature of the problem.
There is not a single solution capable of eliminating all nonpoint-source movement of nutrients. Therein lies the challenge for scientists and those interested in environmental management. Research conducted to find science-based recommendations and implementation strategies serves as a foundation for nutrient management in Louisiana. The LSU AgCenter with state and federal agency partners and collaboration from nonprofit groups expressing environmental concerns is well-positioned to address nonpoint nutrient pollution from agriculture and associated sources.
The LSU AgCenter’s environmental research and outreach programs to maintain water quality have been ongoing for decades. In fact, the 2004 winter Issue of Louisiana Agriculture described the initiation of numerous AgCenter programs focused on water quality projects and public education. That issue highlighted the ongoing problems and potential solutions to soil erosion, water pollution and environmental contamination. One specific outcome of that work was the development of a series of manuals for crop and animal production to help farmers protect natural resources, especially water. Another outcome was the initiation of the Louisiana Master Farmer Program. This education and certification program is based on the voluntary compliance of farmers and ranchers to modify production practices and reduce nutrient pollution in the water that leaves their fields and pastures.
Many LSU AgCenter projects involve cooperation with state agencies such as the Department of Environmental Quality, Department of Natural Resources, Department of Agriculture and Forestry, and the Department of Wildlife and Fisheries. At the federal level, collaboration with the U.S. Environmental Protection Agency, the U.S. Department of Agriculture’s Natural Resources Conservation Service, and USDA‘s Agricultural Research Service is supporting AgCenter research and outreach efforts.
This issue of Louisiana Agriculture highlights LSU AgCenter research and extension programs that focus on efforts to manage one of Louisiana’s most important natural resources, water. The articles illustrate diverse approaches to improve and maintain a fragile environment, cutting across several disciplines, numerous commodities and a range of ecosystems. AgCenter scientists continue developing novel approaches to refine methods based upon new technologies with the goal of protecting Louisiana’s water resources. Watershed-level studies are using new models to predict sediment and nutrient movement across large acreages, as well as documenting the value of freshwater swamps in assimilating nutrients. Research is underway to refine nutrient availability to crops in conservation-till systems, develop prescriptions for fertilizer rate and application timing, manage nitrogen losses in saturated soils, as well as evaluate optimum grasses as filter strips. Animal and waste management projects have examined precision feeding in dairy cattle, management of poultry litter, and the use of floating vegetation to remove nutrients from retention ponds. A report is included on the progress of AgCenter-developed best management practices, known as BMPs, in managing sediment and nutrient loads in the environmentally sensitive Lake Pontchartrain drainage basin. The impact of the Master Farmer program was documented with survey data. Forestry BMPs are prescribed for long-term sustainable production systems. The value of a fisheries resource in reducing nitrogen concentrations in the Gulf was quantified. These studies and educational efforts have a similar goal: to better understand nonpoint-source pollution and offer science-based solutions to mitigate nutrient pollution in all of Louisiana’s waterways, while maintaining the productivity of Louisiana agriculture.
The AgCenter BMP publications are available online in PDF form. Click the titles to access the publications:
(This article appears in the fall 2017 issue of Louisiana Agriculture.)
B. Rogers Leonard is the associate vice president for plants, soils and water resources and the G&H Seed Company Endowed Professor at the LSU AgCenter. Photo by Olivia McClure