Nitrogen, an essential nutrient for optimum corn production, can be supplied from soil organic matter, a previous legume crop, livestock manure and commercial fertilizers.

However, N management in soils is challenging. Improper use can cause environmental implications. Too often, when these events surface, farmers’ land use practices are questioned by the public and government officials. Non-farmers want to know more about what farmers do to raise crops and to understand why certain management practices are followed.

N MANAGEMENT: Many farmers follow best management practices when applying nitrogen. However, most consumers do not know what those are. The MAWRC is working to gather general information about N management so staff will be able to explain to non-farmers what is being done on the landscape.

To gain insight into farmers’ use of N to help educate consumers about nutrient management, staff with the Minnesota Ag Water Resource Center conducted a survey during Farmfest in early August. The response, though small and limited in geographic scope, offered the following information, according to Jerome Lensing, MAWRC nutrient specialist:

Who makes N rate decisions? Sixty-three percent of respondents said decisions were made by the farmer. Twenty-seven percent indicated that N decisions were made by both the farmer and the agronomist.

What are N rates are based on? Of the respondents, 73% said they considered their past experience, with 59% of them following university recommendations. Twenty-seven percent used their previous experience combined with university suggestions.

Do you use predictive models? Among respondents, 31% said they use a predictive model, such as Adapt N, Climate Corp. FieldView, Encirca N, Farmers Edge or another.

Do N rates vary across your farm? Twenty percent of the respondents said they used the same N rate across all their corn acres; 46% varied N rates by field, with 34% varying their N rates within fields.

What factors do you consider when making N rate decisions? Eighty-one percent of the respondents said they use soil tests. Sixty-three percent make adjustments to the N rate based on the previous crop. Fifty percent make adjustments for manure use and soil organic matter. Soil type was considered by 47% of the farmers, with 34% making adjustments for the nitrogen contained in fertilizers such as ammonium sulfate, ammonium phosphate, or monoammonium phosphate.

When is N applied? Respondents said 65% of their acres receive N in the spring, and 59% of acres receive N in the fall. Nitrogen application supplied via starter was being used by 27%. Twenty-nine percent of respondents were split-applying with a portion in the fall, with the remainder applied the following spring. Nine percent used an in-season application of nitrogen or nitrogen stabilizer.

What is your N source? Three-quarters of the respondents said they use commercial nitrogen sources, while 9% reported using a combination of manure and commercial N fertilizer. Manure was the total nitrogen source for 6% of the farmers surveyed.

Do you track and calculate nitrogen use efficiency (nitrogen applied per bushel produced)? Forty-six percent of the respondents said they calculated NUE by field, with 29% reported doing so on a whole-farm basis. A quarter of the respondents said they determined NUE by management zones.

Lensing said that overall, the number of farmers who have adopted a model to predict use of N is impressive.

“With time, the models will be improved,” he said. “As is the case with all new technologies, tools used to predict N use will improve with research.” He said the number of farmers making adjustments for manure and soil organic matter is encouraging, as is the number of farmers applying N in the spring.

However, the in-season application of nitrogen and the use of N stabilizer was lower than expected. “This may be an indication of the geographical differences that determine whether or not a retailer can recommend stabilizers,” he said. “For the in-season application, it also may be a time factor and/or lack of equipment.”

MAWRC staff would like to gather further data on N use and welcome future comments from farmers. To respond to the survey, email Lensing at [email protected]. 

Source: Minnesota Agricultural Water Resource Center