Ha Darklight wrote from Hanoi with this question:
Could you tell me, in late autumm, how to apply fertilizer for seashore paspalum grass to prepare for early winter?
In general, for northern Vietnam, I would expect seashore paspalum to use N and K in approximately the amounts shown in this chart.
The expected amounts in the chart are based on the growth potential (GP) for warm-season grass in Hanoi temperatures, with a maximum N for seashore paspalum set at 3 g N/m2/month when the GP is 1, and recognizing that seashore paspalum uses nitrogen and potassium in a 1:1 ratio.
Our conversation continued:
If I take up high levels of K, ex rates of 3
Whether he means 3 g K/m2/month or 3 times more K than N, I don't see how that would be helpful. My exact reply was "Seashore paspalum uses the same amount of K as it does N. You can add more K if you want to, but it won't provide a benefit to the grass."
Then came another good question from Ha:
How does K affects to diseases?
My answer: "Not much effect. If you are severely deficient in K, or apply way too much K, you may increase disease susceptibility. Application of N and K in a 1:1 ratio to paspalum ensures the grass has enough. Also, you should do a soil test to be sure."
Why should one do a soil test? Because if the soil contains a high amount of K, the grass can use that K, using the soil like a nutrient bank, and the amount of K applied as fertilizer can be reduced. Without a soil test, one doesn't know if all the K the grass will use must be applied as fertilizer, or if some portion of the K used by grass will be supplied by the soil.