Dry spring weather is great for seeding but may play havoc with some fertilizer applications and losses.
1.Seedplaced fertilizer – Where seedbed moisture is low or when weather is hot and windy, reduce the rates of seedplaced nitrogen by approximately 50 per cent. Table 7 of the Manitoba Soil Fertility Guide http://www.gov.mb.ca/agriculture/crops/soil-fertility/soil-fertility-guide/nitrogen.html indicates safe rates of seedplaced urea under different soil texture, moisture and seedbed utilization conditions. But as conditions dry, these rates should be reduced accordingly.
2.Surface applied urea or urea-forms (like UAN solution 28-0-0) – are vulnerable to volatilization losses. The soil and environmental factors increasing risk of loss are well known and include:moist soil conditions, followed by rapid drying
- high wind velocity
- warm soil temperatures
- high soil pH (> pH 7.5)
- high lime content in surface soil
- coarse soil texture (sandy)
- low organic matter content
- high amount of surface residue (Zero Till)
Volatilization losses can be reduced with dribble placement of UAN versus broadcast applications and the use of an urease inhibitor. The active ingredient NBPT used in Agrotain Ultra is now marketed by a number of companies. To expect the same level of protection as Agrotain Ultra, ensure the application rate is similar, since formulation strength and recommended rates differ among suppliers. Agrotain Ultra contains 27% NBPT with an application rate of 3.1 l/tonne urea or 1.6 l/tonne UAN.
3. Last year the lack of rainfall through much of May left surface applied nitrogen stranded at the surface. If possible, a portion of the crops nitrogen for cereals and canola should be in-soil placed. In season applications should be targeted prior to stem elongation of cereals and bolting of canola.