Best Nitrogen Rates for Oat Crops Explained

By Scout Nelson

A research conducted by South Dakota State University Extension, choosing the right nitrogen fertilizer rate is key to successful oat production. Nitrogen helps boost yield, but too little can reduce profits while too much can harm the environment. This study reviewed two common nitrogen recommendation methods to see which better matches oat crop needs in South Dakota.

The two approaches compared are the yield goal method and the maximum return to nitrogen, or MRTN, method. The yield goal method has been used for decades and bases nitrogen rates on expected yield, soil test nitrogen, and legume credits.

Its main strength is simplicity, but it can be difficult to estimate yield and nitrogen efficiency before the season begins. The MRTN method uses data from field trials to find the nitrogen rate that gives the best economic return. It also considers fertilizer and grain prices but does not automatically adjust for soil nitrogen unless added by the user.

Researchers conducted 28 oat nitrogen rate trials across central and eastern South Dakota from 2017 to 2022. These sites varied in soil type, tillage system, and crop rotation. Nitrogen rates ranged from 0 to 150 pounds per acre. Soil samples were taken before planting, and oat yields were measured at harvest.

Results show that oat yields ranged from 65 to 162 bushels per acre. The average optimal fertilizer nitrogen rate was 27 pounds per acre, though soil nitrogen levels played a major role. When using the yield goal method, nitrogen recommendations were generally close to the true economic optimum. On average, the method slightly underapplied nitrogen by one pound per acre.

The MRTN method alone tended to recommend too much nitrogen. However, accuracy improved greatly when soil tested nitrogen from the top 2 feet of soil was subtracted. When full soil nitrogen was included, the MRTN method matched the optimal rate very closely.

“We think it’s some pretty significant news, and we’re excited about getting it in front of our Cattlemen’s Education Day audience,” the research team noted. “What we’re always working toward is trying to find solutions for the citizens of South Dakota, things that solve real problems and help cattle producers.”

Overall, the study shows that both nitrogen recommendation methods work well when soil test nitrogen is included. This allows oat producers to manage fertilizers more accurately, improve returns, and protect soil and water resources.

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