Abstract
Much is not yet clearly understood about the interactive effect of nitrogen (N) fertilizer application rates, irrigation amounts, and tillage level in sugar beet. A 2-year study was conducted near Kimberly, ID to determine the effects of tillage type, irrigation amount, and nitrogen fertilizer rate on sugar beet yield and quality. Three tillage treatments were compared: conventional tillage (CT), strip tillage (ST), and direct seed (DS). Irrigation treatments were established as 50, 100, and 150% of sugar beet evapotranspiration (ET) model CT sugar beet. Four N fertility rates were applied: 60, 80, 100, and 120% of recommended rate for CT sugar beets. By late spray season common lambsquaters and green foxtail densities were the same between CT, ST, and DS at optimum irrigation and N rate. In 2013 leafminer egg and juvenile densities were greatest in CT compared with DS and ST. Averaged over 2 years, root yield was 8.7 and 6.7 Mg ha-1 higher in CT and ST, respectively, than DS, but estimated recoverable sucrose was equal between CT, ST, and DS. Combined results over the 2 years indicated no significant interactions between tillage, irrigation, and N rates suggesting N recommendations do not need to be adjusted for tillage.