How to Fertilize in a Dry Year

Faced with the consequences of consecutive drought years, producers are considering removing fertilizer from their shopping list in an attempt to reduce production costs and economic risk. However, several factors should be considered before making a decision.

Contrary to common wisdom, dry soils in spring are not a sure sign of crop failure. More than 30 years of fertilizer trials conducted under stubble cropping conditions in southwestern Saskatchewan have revealed that growing season rain was above average more often than not when spring soil moisture was below average. The opposite occurred more frequently when spring soil moisture was above average.

Results from these tests also indicated that 8.1 bu/ac would have been lost if no nitrogen fertilizer had been applied to wheat grown on cereal stubble when spring soil moisture was below average.

The bottom line: wheat responds to nitrogen fertilizer even in dry years. The exceptions are those years when there is enough residual nitrogen in the soil to carry the crop to maturity, or when the season starts with adequate soil moisture and then turns dry.

Fertilization of low nitrogen soils resulted in above average yields in more than half of field trials. This highlights the importance of soil testing when making fertilization decisions, and is especially important in drought areas where fields fertilized in 2002 may still have a high nitrogen residual. Given that the cost of testing for nitrogen is only about 10 cents per acre - far less than the cost of one pound of nitrogen - it's money well spent.

Crops need an adequate supply of nutrients early in the growing season to promote vigorous growth and to develop a strong root system. Fertilizing at seeding will start your crop off on the right foot, especially in soils with low residual nutrients.

Based on these considerations, a fertilization plan for 2003 should start with soil testing for nitrogen to determine the optimal amount to apply. This step alone may save you a bundle on your fertilizer bill. Apply a starter fertilizer at seeding that meets your nitrogen requirements, as well as phosphorus. If your crop demands high levels of sulphur, such as canola, apply this at seeding as well. The rest of the nitrogen, if required, can be applied by topdressing at a later date if moisture conditions improve, and if crop growth warrants it.

For more information, please contact Fernando Selles or Robert Zentner, Agriculture and Agri-Food Canada, Semi-Arid Prairie Agricultural Research Centre (SPARC) at (306) 778-7200.