Research suggests a new method to protect groundwater quality

Farmers can prioritize areas within fields to reduce nitrate contamination

Fine-tuning fertilizer and irrigation management requires farmers to carefully balance optimizing yield and protecting groundwater quality. Some states even require farmers to use crop production practices to minimize nitrate leaching to groundwater in environmentally sensitive areas.

One such practice is using a nitrification inhibitor when applying nitrogen fertilizer, which helps protect nitrogen from leaching below the root zone until the crop can use it. Farmers are often reluctant to use nitrification inhibitors since they add to the cost of production, and only increase yield or protect from nitrate loss with specific combinations of soil type and climate – such as a warm, wet spring and sandy soils.

Recent research in the central Platte river valley of Nebraska investigated a promising new option for producers growing irrigated corn in environmentally sensitive areas, according to Richard Ferguson, professor of agronomy, University of Nebraska.

The study, conducted from 1995-1998, explored ways to reduce nitrate leaching to groundwater. Results from the study are published in the May/June issue of the Soil Science Society of America Journal, published by the Soil Science Society of America. Co-authors are Murray Lark, Silsoe Research Institute, Great Britain; and Glen Slater, University of Nebraska.

Using information about soil properties obtained from grid soil sampling, along with maps of crop yield and soil electrical conductivity, these researchers developed management zones to direct the application of nitrification inhibitors.

In relatively dry-to-normal growing seasons, the use of a nitrification inhibitor had no effect on grain yield or nitrate leaching. However, in a growing season with a very wet spring, the use of a nitrification inhibitor increased yield. Patterns of higher and lower yield in the wet growing season corresponded closely to patterns of soil electrical conductivity.

According to Ferguson, producing soil electrical conductivity or yield maps is much easier and cheaper for producers than grid soil sampling.

“If we can develop an approach to allow farmers to prioritize areas within fields where nitrification inhibitors will be most beneficial, we believe that will encourage more farmers to use the practice. This approach could help protect groundwater quality while significantly reducing the cost and time required for the farmer,” he says.

While it’s premature to say that maps of soil electrical conductivity or grain yield can be used to predict where nitrification inhibitors should be used, the researchers have seen enough similar results in other studies to warrant continued study.

Soil Science Society of America Journal (SSSAJ), http://www.scijournals.org is a peer-reviewed, international journal of soil science published six times a year by the Soil Science Society of America. SSSA Journal contains soil research relating to physics; chemistry; biology and biochemistry; fertility and plant nutrition; genesis, morphology, and classification; water management and conservation; forest and range soils; nutrient management and soil and plant analysis; mineralogy; and wetland soils.

The American Society of Agronomy (ASA) www.agronomy.org, the Crop Science Society of America (CSSA) www.crops.org and the Soil Science Society of America (SSSA) www.soils.org are educational organizations helping their 10,000+ members advance the disciplines and practices of agronomy, crop and soil sciences by supporting professional growth and science policy initiatives, and by providing quality, research-based publications and a variety of member services.