Sensor-Based Nitrogen for Spring Wheat

O. S. Walsh, D. M. Jayawardena
University of Idaho
Introduction and objectives
Objective 1. To assess response of spring wheat varieties to different nitrogen (N) levels
Objective 2. To quantify their N uptake and N use efficiency (NUE) using ground- and aerial-based data
Objective 3. To conduct grower education
One of the most common questions asked by wheat producers is how to manage nitrogen (N) fertilizer depending on what variety they chose to grow. Previous work has shown that wheat cultivars may vary in N requirements, N uptake, and N use efficiency. Increasing the knowledge about newly released varieties will help to improve the adaption of these varieties by growers. One of the main reasons why many producers like to plant older varieties is the fact that they are very familiar with them, even though they may be substantially lower yielding, may not have the best grain quality and may not perform as well under various biotic and abiotic stresses associated with disease, water or nutrient limitations or pest or weed pressure. In a project previously funded by the Idaho Wheat Commission, we have initiated development of Unmanned Aerial Vehicle (UAV)-based methodology for in-season prediction of wheat yield potential, focusing on spring wheat using one variety at four eastern Idaho locations and another – at southwest Idaho site.
 
Nitrogen response by wheat class and variety
Evaluated wheat varieties by class
Hard red spring wheat - flour is ideal for baking breads and is what consumers know as whole wheat flour. Spring hard red wheat has the highest protein content of all wheat types and is also used for making bread, while winter hard red wheat is made into breads and all-purpose flours. SY Basalt – released by Syngenta Seeds in 2001; excellent yield potential in high input irrigated production, tolerance to stripe rust, good protein content and end-use quality. Jefferson – released by Idaho AES, USDA-ARS in 1998; intended for dry land, can be used as an irrigated variety; higher protein, excellent milling and baking qualities.
Jefferson outperformed SY Basalt in grain yield; could yield even more at greater N rates, when SY Basalt’s yield has leveled off.
Hard white spring wheat – used in baking of pan loaves, rolls, and other soft breads, high protein no bran color, sweeter and less bitter than hard red. UI Platinum -  released by Idaho AES in 2014; has average yielding wheat with average test weight, most desirable milling quality; susceptible to stripe rust and head blight. Dayn - released by the WSU in 2017; test weight, grain protein content, straw strength, and maturity are very good, excellent stripe rust resistance, very desirable end-use quality for domestic and export markets.
Dayn had substantially greater grain yield; much more efficient at N utilization; UI Platinum may outyield Dayn at even greater N rates.
Soft white spring wheat - is an important wheat class for domestic and international markets that is widely grown in the PNW. SWW - used mainly for bakery products other than bread. Examples include pastries, cakes, and cookies. It is also used for cereals, flat breads and crackers. It has a lower protein content and weak gluten. Seahawk – released by the WSU in 2017; very high yield potential, excellent quality, resistant to stripe rust, head blight tolerance. UI Stone - released by Idaho AES in 2012; high yield potential, reduced head blight susceptibility, has tolerance to Cereal Cyst Nematode, good end use quality; susceptible to stripe rust.
Seahawk had higher grain yield; Yield optimized at 179 lb N/a for both, but can increase yield for Seahawk with higher N application.
 
Materials and methods
In-season data collection:
The following data from 0.2 m2 section within each plot, at tillering and flowering:
  • plant height (by measuring height of 10 randomly selected plants per plot)
  • chlorophyll content estimate (using SPAD meter)
  • biomass production estimate- GreenSeeker NDVI
  • biomass weight and N content (lab and multispectral UAV camera)
At maturity, the following data will be obtained:
  • crop yield (by harvesting the rest of the crop within the strips and extrapolating the yield to kg per ha basis
  • yield components will be determined (test weight, number of spikes per plant, number of seeds per spike, weight of the seeds per plant)
  • grain nutrient content (grain will be analyzed for N content)
In-season wheat grain yield prediction

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