Effects of tillage system and nitrogen supply on sugarbeet production

The sugarbeet industry in the Pacific Northwest is interested in strip tillage (ST) primarily due to the potential savings in tillage costs. This study was conducted to evaluate the use of ST in the Pacific Northwest compared to conventional tillage (CT) practices and to evaluate N requirements of sugarbeet under ST and CT. The effect of tillage method (ST, moldboard plow [MP] system, and chisel plow [CP] system) and N supply (5 levels) on sugarbeet production factors were investigated in Kimberly, ID from 2008 to 2010 on a Portneuf silt loam soil with barley as the previous crop. Root and estimated recoverable sucrose (ERS) yields were the same under all three tillage practices across N supply. There were no differences in N response across tillage systems. However, estimated tillage costs for ST were from 53% to 76% lower than other tillage systems tested. The CP treatment had a significantly lower harvest plant population compared to ST and MP, likely because residue inhibited seed-soil contact. Averaged across tillage practices, in 2008 and 2010, a significant quadratic relationship was observed between N supply and root and ERS yield. During 2008 and 2010, yields at the economically optimum N supply (EONS) ranged from 73.6 to 79.9 Mg roots ha -1 and 11,054 to 11,415 kg ERS ha -1 across tillage practice and N prices ranging from $0.44 to $2.20 kg -1 N. During 2008 and 2010, nitrogen use efficiency (NUE) at the EONS ranged from 50.1 to 67.9 kg sucrose kg -1 N supply over