Sugarbeet Response to Incremental Application of Nitrogen with High Frequency Sprinkler Irrigation
1981
Roberts, S. | Weaver, W. H. | Richards, A. W.
Applying N in sprinkler H₂O during June and July was compared with topdressing earlier at thinning for sugarbeets (Beta vulgaris L.) grown in a split-plot experiment with high-frequency irrigation treatments of 50, 75, and 100% replacement of evapotranspiration (ET). Nitrogen was applied preplant at a rate of 70 kg/ha in all treatments. Sprinkling N too late in July significantly decreased sucrose content, averaged over N rates of 112, 224, and 336 kg/ha and moisture regimes, to 17.2% compared with 17.7% for topdressed N. Sugarbeet yield and percent sucrose at each combination of N rate and irrigation regime were similar with both methods of supplemental N application. Deficit irrigation (50 or 75% ET replacement) gave significantly higher sucrose percentages than full (100%) replacement, but the 50% ET-replacement regime decreased beet yields by 10 metric tons/ha for a net loss of sugar yield. The optimum N rate was 224 kg/ha, with petiole NO₃-N averaging just under 1% at the end of July and approaching 0.1% by the end of August. Results show that sugarbeet yields were only slightly lower, with two thirds of the total N at the optimum N rate applied in sprinkler H₂O than by topdressing at thinning in early June. However, percent sucrose was significantly lower with N applications in sprinkler H₂O, which resulted in much lower sugar yields with delayed N applications.
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