Link between wheat protein levels, fertilizer to be studied by UNL

A multi-disciplinary team of University of Nebraska-Lincoln researchers will conduct a two-year study to see how soil nitrogen levels affect protein levels in the grain that comes from Nebraska wheat fields.

The team hopes to evaluate how grain quality, yield and field stands are affected by nitrogen fertilizer rates and application timing. The trials will be conducted across the state and with variations in the amount of precipitation the plots receive.

The project also will test the effectiveness of crop sensors in monitoring wheat crop conditions and whether inputs are needed during the growing season.

Lead principal investigator is Bijesh Maharjan, soil and nutrient management specialist at the UNL Panhandle Research and Extension Center in Scottsbluff. Co-investigators are several of Maharjan’s colleagues at the Panhandle Center: Dryland Cropping Systems Specialist Cody Creech and Alternative Crops Breeding Specialist Dipak Santra. Investigators based in Lincoln or elsewhere in eastern Nebraska include Wheat Breeding Specialist Stephen Baenziger; Research Assistant Professor Teshome Regassa; Devin Rose, associate professor in Food Science and Technology in the UNL Food Innovation Center; Yeyin Shi, assistant professor in Biological Systems Engineering and Agricultural Information Systems Specialist; and Extension Educator Nathan Mueller.

Research plots will be located at Scottsbluff, Sidney, Grant and Mead.

The project is funded by grants from the Nebraska Wheat Board (for the coming year) and the University of Nebraska Agricultural Research Division Innovation Fund for Wheat/Cereal Crops (for the next two years).

One reason for the study is Nebraska wheat crop yield data from 2016 and 2017, which revealed low protein levels in both years.

Wheat growers receive lower prices when grain protein levels fall below certain levels. According to the project proposal, low protein levels cost Nebraska producers somewhere between $2.3 million and $9.6 million dollars in 2016 alone, despite high yields, based on reports from elevator personnel and Wheat Board members.

Among many potential factors, soil nitrogen is probably the most important factor that affects protein levels in wheat, Maharjan said. With low grain prices, farmers are under pressure to lower input costs, including nitrogen fertilizer.

“Reducing or eliminating nitrogen applications to winter wheat will typically result in low protein when yields are high and/or residual soil nitrogen is low.”

In addition, abundant fall and spring precipitation during both growing seasons increased the plants’ tillering and grain yields, but may have moved soil nitrogen deeper into the soil profile, where the crop’s roots cannot reach it.

“In order to increase protein levels in wheat, N must be properly managed in the soil and be available for plant uptake during grain development,” the project proposal stated. “The interacting effect of N with available soil moisture becomes a contingent issue for a profitable winter wheat production.”

Predicting how much nitrogen a wheat crop will need requires an extensive data set, and UNL’s formula for predicting wheat’s nitrogen requirement was developed in the 1970s. The formula is due to be updated, based on changes in wheat variety traits and management, as well as changing climatic conditions, Maharjan said.

At the same time, crop-sensing technology has been used with success in predicting nitrogen requirements for another of the state’s important crops, corn. Research established a strong relationship between total chlorophyll content in a corn canopy and the crop’s nitrogen status. This project will explore whether crop sensing technology can potentially benefit wheat management.

The research project will also look at other nutrients, specifically links between nitrogen and sulfur rates. Sulfur deficiency can adversely affect wheat.

Maharjan said the researchers hope the two-year project will not only answer questions about how factors such as fertilizer timing and precipitation affect grain protein levels, but also will show whether crop sensing can be used as a management tool for fertilizer management in wheat.

“Provided all goes well and we get good data, in two years we will understand a lot about management for optimum yield and protein,” he said, adding that precipitation variation also will be tracked at one of the sites, hopefully providing insight into how fertilizer management is related and can be adjusted to weather.

The grants will provide funding for a graduate student whose time will be dedicated completely to the protein project, Maharjan said. The student will start in the spring of 2019. The plots will be planted in September this year.

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