Nitrogen and Phosphorus Fertilizer in Sugarbeet-Bean-Barley Rotations Under Conservation Tillage and Limited Irrigation.

As producers in Big Horn Basin Wyoming convert from furrow irrigation systems to overhead irrigation systems and from conventional tillage practice to conservation tillage methods, new approaches to soil fertility management are needed. As a result, an investigation to develop an optimal rates of nitrogen (N) and phosphorus fertilizers under different tillage systems and limited irrigation that enhances yield and quality of sugarbeet, beans and barley under rotation in the great Big Horn basin was established. The first year study was conducted from April to October 2014 at University of Wyoming Research and Extension Center in Powell (PREC).The experimental design was a split-split plot embedded in a randomized complete block design replicated four times. The treatment on the main plot was irrigation levels (100% and 75%), the sub plot factor were conventional tillage (CT) and strip tillage (ST) while nitrogen and phosphorus rates are the sub-sub plot factors. Root yields, sugar yields, sugar content, sugar loss to molasses, grain yields, dry biomass, were recorded. The 75% irrigation level significantly influenced sugarbeet root yield and total sugar (t/ha) by 11.5% compared with 100% irrigation level in nitrogen fertilized plots. The CT was statistically higher than ST by 2% in influencing sugar content. Highest levels of nitrogen fertilizers (211.1 and 281.4 kg/ha) resulted in greatest total root yield of about 22% and 28% respective compared to control. Bean and barley grain yield and dry biomass were similar with irrigation levels, tillage systems, N and P rates. The reduced root and sugar yield on full (100%) irrigation can be attributed to excessive leaching of nutrients compared to limited irrigation (75%). It was concluded that nitrogen rate beyond 140 kg/ha does not increase sugarbeet root yield.