Chloride is a micronutrient that is needed in small amounts to grow a good crop.
Generally, chloride deficiencies are not common in Western Canada, but recent soil testing statistics suggest that most soils tested for chloride are either marginal or deficient. Are these results accurate, and if so, is chloride limiting crop production in Saskatchewan?
Soil test results in that province for the 2005 crop year suggested 35 percent of the soils tested had marginal chloride levels, and 40 percent were deficient.
It’s important to consider that these levels are based on research from North Dakota with winter wheat, said Trish Meyers, an agronomic specialist with Agricore United in Saskatoon. Critical levels for soils and the crops grown in Western Canada have not been developed.
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According to the North Dakota criteria for winter wheat, marginal results occur when chloride is between 30 and 60 pounds per acre in the top 60 centimetres of soil, and deficient when there is less than 30 lb. Laboratories applied the North Dakota guidelines to western Canadian soils, and simply divided by two to calculate marginal and critical levels for a zero to 25 cm sample.
So in Western Canada, a soil is marginal in chloride if the soil tested between 15 and 30 lb. of chloride per acre and deficient under 15 lb.
Another important consideration is that chloride moves with soil moisture. What if there’s chloride below 25 cm that the soil sample isn’t detecting?
Chloride deficiencies are not common in Western Canada. In fact, there hasn’t been a scientifically substantiated response to chloride fertilizer yet. That’s not to say a chloride deficiency can’t occur, or that a response to potash fertilizer can’t occur, even on soils testing high in chloride and potassium. Growers should work with their agronomists to determine the real risk of chloride deficiencies.
First, if chloride is a concern to the grower, taking a zero to 60 cm soil sample makes sense. Second, if the chloride level is only slightly below 30 lb. per acre, it is unlikely to limit crop production. If the number is significantly less than 30 lb. per acre, fertilizing with 30 to 40 lb. per acre of potash is good insurance.
In addition to potassium, potash consists of about 47 percent chloride. Growers need to abide by the safe rates of seed row applied fertilizer guidelines for potash.
