Nitrogen and irrigation effects on sugar beet emergence.

Abstract

Every year a portion of Alberta growers apply urea nitrogen fertilizer in spring prior to seeding sugar beets. Twenty-two separate trials over a 5-year period between 2015 and 2020 were conducted to assess the potential for sugar beet stand loss when urea is soil incorporated prior to planting and irrigated prior to sugar beet emergence. In addition, nine separate trials were conducted between 2015 and 2021 to assess the potential for sugar beet stand loss when urea is surface applied and irrigated after planting but prior to emergence. Urea rates up to 200 lbs N/acre were applied in all trials, with the 200 lb rate being used to accentuate and differentiate treatment effects. When urea was soil incorporated, highly significant (p<0.01) sugar beet stand reductions averaging 28% were observed with applications of 200 lbs N/acre urea in 6 tests where a single irrigation ≤0.5 inch was applied. Where a single irrigation ≥0.6 inch was applied, sugar beet stand reductions with 200 lbs N/acre averaged 11% and were only significant (p<0.05) in 2 of 6 trials. Stand reductions with 100 lb N/acre soil incorporated urea averaged 12% and were significant (p<0.05 and p<0.01) in 4 of 6 trials where a single irrigation of ≤0.5 inch was applied. When a single irrigation ≥0.6 inch was applied, sugar beet stand reductions with 100 lbs N/acre averaged 2% and were not significant in any trials. Results were similar for single and multiple irrigations with 100 and 200 lbs N/acre soil incorporated applications. When urea was surface applied and irrigated prior to sugar beet emergence, sugar beet stand reduction ranged from 2 to 98% with applications of 200 lbs N/acre, with higher stand reductions observed for lower irrigation plus rainfall volumes. Results from these trials show that greater amounts of applied water can mitigate the toxic effects of spring urea applications. Many Alberta growers use lower irrigation volumes when watering for sugar beet emergence. When spring urea is incorporated at 100 lbs N/acre with current watering practices, a sugar beet stand loss in the order of 12% could be expected.