4 R’s of nutrient stewardship
USDA’s Natural Resources Conservation Service is encouraging Iowa farmers to adopt the 4R nutrient stewardship concept to help define the right source, rate, time and place for plant nutrient application.
John Myers, state resource conservationist with NRCS in Iowa, says the 4R concept considers productivity, profitability, cropping system durability and a healthy environment. “The approach is simple and universally applicable,” says Myers. “Apply the correct nutrient in the amount needed, time and place to meet crop demand.”
• NRCS management standards endorse 4R nutrient stewardship concept.
• Focus is on the right source, rate, time and place for crop nutrient application.
• Goal is to produce economic, social and environmental outcomes beneficial to all.
The four R’s will change and improve with new gains in knowledge and technology development, says Iowa NRCS nutrient management specialist Eric Hurley. “The four R’s provide flexibility to nutrient management,” he adds, “depending on soils, climate, crops, cropping history, management style and farm size.”
Learning the 4 R’s
Here’s the lowdown on the 4R concept:
• Right source. The right source means matching the right fertilizer product with soil properties and crop needs. Hurley says it’s important to balance applications of nitrogen, phosphorus, potassium and other nutrients according to crop needs and available soil nutrients. “Take care to address all nutrient needs in your fertilizer plan,” he says. “Nitrogen is wasted if inadequate P or K is stunting your crop.”
Hurley also suggests reviewing the forms and formulations that best fit your management and needs of your crops.
• Right rate. This means matching application rates with crop requirements. Hurley says soil testing, crop history, in-season testing and crop nutrient budgets will impact application rates. “Time and money can be saved by applying only the nutrients needed to optimize your production,” he says. Iowa NRCS state agronomist Barb Stewart says to test soil for P, K and micronutrient availability. “Use the Iowa State University N-Rate Calculator’s MRTN [Maximum Return to N] rate to determine your nitrogen needs,” she advises.
• Right time. This means synchronizing nutrient availability with crop demand. Hurley suggests applying N fertilizer in the spring, and encourages producers to look at split applications of N.
Controlled-release fertilizers, and urease and nitrification inhibitors are designed to manipulate the timing of nutrient availability. “As research demonstrates the effectiveness of these products, they may become important tools in improving fertilizer efficiency,” says Hurley.
• Right place. This means placing and keeping nutrients where the crop can get to them and where nutrient use efficiency will be maximized. Crops, cropping systems and soil properties will dictate the most appropriate method of placement. “Injection or incorporation is usually preferred to keep nutrients in place and to increase their use efficiency,” says Hurley, “though this soil disturbance needs to be balanced with your soil erosion control goals.”
Stewart says cropping systems such as strip till place nutrients close to the developing plant to ensure nutrient availability. “Less fertilizer is lost to the environment this way compared to broadcasting fertilizer across the field,” she says.
The best application, placement and nutrient source is specific for each site. Stakeholders such as farmers, fertilizer dealers, natural resource specialists and crop advisers must help decide what is the right nutrient management practice.
The system will be officially endorsed by NRCS in the new 590 Nutrient Management Standard. “The 4R concept is gaining acceptance, but continued education and dialogue between all stakeholders is needed,” says Myers.
Johnson writes for NRCS in Iowa.
This article published in the April, 2011 edition of WALLACES FARMER.