SOME THOUGHTS TO CONSIDER: Single applications • Convenient, low application costs • Can produce high yields if lodging risk and Nitrogen (N) losses are minimal However, split nitrogen applications • Enables an early N and Sulphur (S) application to stimulate or maintain tillers in late-planted wheat, while minimizing loss of N • Potential to increase N use efficiency, especially with high fertilizer prices • Reduce lodging risk while using higher rates of N to maximize yield potential • Potential to increase protein in hard red wheat varieties In some years, split N applications may provide little or no benefit to yield compared toa singleapplication (Figure 1). Various factors including crop development stage, variety and field-specific characteristics need to be considered to maximize returns. DEVELOPMENTAL STAGE Fields with minimal tillering early in the spring tend to benefit from an application of nitrogen and sulphur at green-up (Figure 2). This early application helps to maintain and encourage additional tillering. A second application in these fields can be made between GS 32-39. A single application strategy with all N applied upfront at green-up may not be advisable because of N loss potential. In contrast, fields with early planting dates, high seeding rates, a variety susceptible to lodging or toomany tillers, have a greater risk of lodging (Figure 3). In these fields, delaying an N application until GS 30, and applying only a portion of total N, may reduce the risk for lodging. The second application can be made between GS 32-39. FIELD SPECIFIC CHARACTERISTICS Soil type is also an important factor to consider. N losses through leaching and/or denitrification are more likely to occur with earlyapplied N on wheat before the onset of rapid N uptake (GS30). The potential of these losses tends to be the highest on sand and clay soils. However, N losses are insignificant if rainfall after application is not excessive. Early N applications also enables an early application of S which is particularly important on sandy soils or soils with low organic matter levels and no history of manure. l Split apply nitrogen? CROP SIDE WITH... Crop side ONTARIO GRAIN FARMER 13 MARCH 2022 FIGURE 3: EARLY PLANTED WINTER WHEAT FIELD WITH 8+ TILLERS AND HISTORY OF MANURE WOULD BENEFIT FROM A DELAY IN N APPLICATION UNTIL CLOSER TO GS 30 TO REDUCE LODGING RISK. A GOOD SPLIT-N STRATEGY IN THIS SCENARIO IS 40% OF N + 10 LBS OF S IN THE FIRST APPLICATION AND 60% OF N IN THE SECOND APPLICATION. FIGURE 2: LATE PLANTED WINTER WHEAT BENEFITS FROM AN EARLY N APPLICATION TO ENCOURAGE TILLERING AS THE CROP BEGINS TO GREENUP. A GOOD SPLIT-N STRATEGY IN THIS SCENARIO IS 60% OF N + 10 LBS OF S IN THE FIRST APPLICATION AND 40% OF N IN THE SECOND APPLICATION. PHOTOS COURTESY OF JOANNA FOLLINGS. FIGURE 1: YIELD RESPONSE TO SPLIT N APPLICATIONS VARIES YEAR OVER YEAR. TRIALS CONDUCTED BY DR. DAVE HOOKER, UNIVERSITY OF GUELPH, RIDGETOWN CAMPUS. Joanna Follings, Cereals Specialist, Ontario Ministry of Agriculture, Food and Rural Affairs
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