Potash for oilseeds

[shamus]

Recently read an article on benefitsof potash on cereals in dry conditions. Knowing how it builds cell structure it makes sense. Does it work as well for canola and flax?

[emiled]

These crops utilize potash (or potassium) for many of the same reasons although their requirements may differ somewhat...
Looking at Canadian Industry Guidelines a 40 bushel wheat crop consumes about 90 lbs of potassium (K20), a 35 bushel canola crop consumes similar levels while a 25 bushel flax crop consumes about 55-60 lbs of potassium (K20).

I would take a close look at soil test levels to determine need. Generally, we would consider soil test levels of 300 lbs per acre (or more) to be the breaking point between deficient and adequate.

[mhartman]

I have recently reviewed canola response to K fertilizer as part of the Canola Grower's Manual revision.
The numerous K research studies on the prairies have rarely found a canola response to added K, even at sites where cereals normally respond to K. The K soil test is a weak indicator of plant availability, but critical levels are usually stated to be around 250 lb K/acre (112 ppm) in the top 6 inches. The past research with canola response to K indicates that there will not be a consistent, economical response to fertilizer K unless the soil test is very low (70-100 lb K/acre). Very sandy or peaty soils are the most likely soil types to have such low K test values. Other factors that increase the likelihood of K deficiency are: free lime in the root zone, acid soil, poor drainage, cold soil, or compacted soil. Unlike cereals, potash has not been show to help with canola disease resistance, lodging or seed quality (oil or meal protein content).

[winston]

Dont waste your money. As was allready stated no one has been able to show a response to postash in canola. Use the money for something else that will provide you with a payback. And dont fall for the old "it only costs 3.00 per acre" line either.

[tman]

The problem about finding information about fertility is that the so-called "experts" out here in western Canada don't help farmers out. Whether the problem stems from their research or from the testing labs that give the test results, or a combination. Everyone out here focuses on lbs/ac or ppm levels in the soil. No one looks at the "fancy numbers", the cation exchange capacity (CEC) of the soil and the percent base saturations of the cations (K, Mg, Ca, H, Na), which are a thousand times more important than the ppm levels. I know that research (University and government) has shown many times the lack of yield response to K(potassium), but this stems from not being able to read a good soil test with all the numbers. I know of other research and actual farmers' fields where K (plus other nutrients) made a huge difference. But you must soil test and test it right. Unfortunately, there is only one lab that does the job right in Canada, and that one is in Ontario. Nutrients must be in a specific balance in the soil. Just because a soil tests high or medium in a nutrient, doesn't mean anything until you look at everything else. For instance, if magnesium gets too high, potassium becomes deficient, and vice versa. If aluminum (which isn't a nutrient) gets too high, phosphorous availabity drops. Boron also affects the plant's abilty to uptake K. I could go on. Research in the States has shown how green foxtail is associated with high magnesium soils, which are common in western Canada, as I know since I've done the sampling and read the soil tests.

People in western Canada have their soil nutrient levels set too low and not in balance when recommendations are made. Research in the U.S. has shown that when soil copper levels are 8 ppm, rust is eliminated. This level is about 20 times greater than research done here in western Canada.

I know of crops' yields in AB, SK, and MB that have been dramatically and economically increased due to good fertilty. Yields that you wouldn't believe.

This shows that agriculture still has great potential. You just have to know where to look.