Amber D. Moore1, Don Morishita1, Oliver Neher1 and David Tarkalson2, (1)Plant, Soils, and Entomological Sciences, University of Idaho, Twin Falls, ID (2)USDA-ARS, Kimberly, ID
Idaho sugar beet growers are interested in applying strip-till technologies to their fields, but are concerned about inconsistencies in growth related to small grain chaff trails left behind the combine. There is also interest in how residue cover and the strip-till system affect plant nitrogen use from broadcasted N fertilizer and banded N fertilizer. The objective of this two-year study was to determine how small grain residue level, nitrogen application method, and nitrogen fertilizer rate affect beet yield, beet quality, plant available soil N, N uptake, soil temperature, and soil moisture. The two nitrogen application methods were broadcast and shank. For the broadcast treatment, dry urea fertilizer was applied to plots using hand-crank fertilizer spreaders several days after planting, and then irrigated within 2 to 4 days to prevent volatilization losses. For the shank treatment, liquid urea ammonium nitrate was shanked into the soil to a depth of approximately 6 – 8 inches along with a strip-till implement on the same day as planting, using a CapStan fertilizer application system. Nitrogen application rates were established at 4 and 6 lbs N/beet ton, using 32 ton/acre as the realistic yield goal. Residue cover lowered yields and beet weight at high residue rates (greater than 6.9 ton/acre) and when there appeared to be eitehr too much or too little N fertilizer. Broadcast applications of N significantly reduced stand in both years of the study, and decreased beet yield in one year of the study, suggesting that shanking in N instead of broadcasting may be helpful to prevent stand and even yield losses. Based on our findings, growers should also be cautious of shanking or broadcasting N at high rates (140 lb N/acre or greater) on areas with residue cover of 5 ton/acre or greater, as we saw dramatic yield losses in these scenarios.