Nitrogen and Water Use Efficiencies in Drip-Irrigated Sugarbeets.

Traditionally, sugarbeets in California have been cultivated with flood irrigation. However, because of diminishing high quality water supplies in the State, there is need to assess the effect of transitioning to low volume irrigation practices to optimize yield and quality of sugarbeets. Hence, the goal of this research was to evaluate Nitrogen and Water Use Efficiency (NUE and WUE) for sugarbeets grown under different irrigation regimes and N fertilizer application rates. The experimental design was a split plot arrangement with 3 replicate of Irrigation as the main treatment (100% ET surface-drip, 70% ET surface-drip, and 100% ET furrow) and N rate as the secondary factor (0, 100, 150, and 200 lbs of N/ac). Sugarbeets were grown in Central California in sandy loam and clay loam soil. Preliminary results from the first season show that Irrigation had a significant effect (P < 0.05) on the total sucrose yield per acre in the sandy loam soil, with the 100% ET surface-drip treatment resulting in 43% greater yield. However, the irrigation regimes did not significantly affect the sucrose yield of the crop grown in the clay loam. For WUE, determined as sucrose yield as a function of the amount of total applied water, the 70% ET drip irrigated plots exceeded the 100% ET furrow irrigated plots by 25% and 39% for the sandy loam and clay loam, respectively. No sucrose yield responses to N application rates was observed in the sandy loam soil. However, there was a strong positive correlation (r2 = 0.81) between sucrose yield and N fertilizer rates in clay loam. In addition, the greatest NUE measured as tons of sucrose yield per lbs of N applied per acre, were observed for plots receiving 100 lbs of N/acre, with values of 0.25 and 0.33 for sandy loam and clay loam, respectively.