Effect of nitrogen supply by soil depth on sugarbeet production and quality.
Determining the effect of N supply by soil depth on sugarbeet production is important to continue fine-tuning management practices. To accomplish this objective, a greenhouse column study was conducted at USDA-ARS in Kimberly, ID. The study was conducted using 30 1 m x 0.3 m columns filled with 0.9 m of soil. The treatments consisted of adding N fertilizer at a rate of 132 kg N ha-1 differently to three 0.3 m soil depths. Although all treatments had a total N supply of 222 kg N ha-1 in the 0.9 m soil depth, the distribution of the N in the soil profile affected the yields and N uptake. Sugarbeet root mass, root sucrose mass, leaf mass, root N mass, and leaf N mass were higher for treatments where N fertilizer was added to depths 1 (0-0.3 m) and 2 (0.3-0.6 m) compared to when N fertilizer was added to depth 3 (0.6-0.9 m). The sugarbeets were not able to utilize N from depth 3 as efficiently as from depth 1 and depth 2. There were no treatment effects on sugarbeet quality factors. The findings of this study highlight the need to question the value of a depth 3 soil sample for determining N fertilizer requirements.