Variable Rate Nitrogen and Reduced Irrigation for Potato Production in Minnesota.

The expansion of fertilizer intensive and irrigated agriculture in Minnesota has led to concerns over the potential cost of these activities to groundwater resources. New regulations from the state government are being developed to address these issues with the goal to improve drinking water quality, which is commonly impaired by nitrate-nitrogen, and to manage future groundwater withdrawals in a sustainable manner. Renewed interest has been place on nitrogen [N] and irrigation [IRR] best management practice to meet these environmental goals, as well as improve input use efficiency and producer profitability. Variable-rate N applications based on multi-spectral remote sensing and reduced IRR rates are two promising management strategy to meet both of these goals. This study was carried out on Russet Burbank variety potatoes grown on an irrigated, coarse-textured soil in central Minnesota. A total of six N-treatments were imposed including (N1) a 45 kg N/ha control treatment, (N2) a split-applied urea treatments of 180 kg N/ha, (N4) and of 270 kg N/ha, (N3) a controlled-release polymer coated urea [PCU] treatments of 180 kg N/ha, (N5) and of 270 kg N/ha, and (N6) a variable-rate split-applied urea treatment based on remote sensing observations using the MERIS Terrestrial Chlorophyll Index paired with the Nitrogen Sufficiency Index. IRR treatments included (I1) conventional irrigation rate and (I2) irrigation rate reduced by 15% relative to the conventional treatment. Reduced IRR had a non-significant difference in tuber yield compared to conventional practice, while reducing percolation losses by 9 and 15% in 2016 and 2017 respectively. The variable-rate treatment (N6) received 248 and 226 kg N/ha in 2016 and 2017 respectively, which is 22 and 44 kg N/ha less than the conventional best management practices (N4, N5), and there were no significant differences in yield between these treatments. This study demonstrates that these IRR and N management practices have the potential to improve producer profitability and reduce impacts on water resources.