Phosphorus Fertilizer Management in Sugarbeets in the Bighorn Basin of Wyoming.

Root elongation in sugarbeets is reported to increase sugar yield. Phosphorus (P) is a nutrient that increases root growth, and sugar production. The objectives of this study were to determine the effect of P fertilizer placement and rates on sugarbeet root and sugar yield, and also to determine the optimum rate for banded and broadcast applications of P in the Bighorn Basin of Wyoming. The study was established under furrow irrigation in 2012 and 2013 at the University of Wyoming Research and Extension Center located in Powell, Wyoming. The experimental design was a RCBD split-plot array with four replications. Fertilizer product was the main plot, and fertilizer rates were the subplot. Treatments consisted of five fertilizer products, and seven fertilizer rates. Dry monoammonium phosphate (MAP, formulation 11-52-0) was broadcast in spring on tilled plots at 0, 34, 67, 135, 202, 269, and 336 kg P₂O₅ ha^-1. Liquid ammonium polyphosphate (APP, formulation 11-37-0, density 1438 kg m^-3) was banded at a depth of 7 cm directly below seeds at planting, at the same rates as the broadcast fertilizer applications. Syngenta HM 9120 sugarbeet seeds were planted April 18 - 19. Plants were sampled in mid-June and mid-July to determine early season response to P, and harvested on September 24. Pre-planting soil tests showed sugarbeets would respond to P fertilizer applications. Harvest results showed sugarbeet yields increased linearly from 62 t ha^-1 at the 0 kg rate to 67 t ha^-1 at the 336 kg rate.  Higher P₂O₅ rates corresponded to slightly higher yields. Mean Fertilizer product yields ranged from 66 t ha^-1 to 85 t ha^-1. Mean sugar yields was about 13% of root yield for all rates and fertilizer products. Sugar loss to molasses (SLM) was about 1 % of sucrose content. The optimum P₂O₅ rate was 220 kg ha^-1.