salt in kelp meal
I bought a sack of feed kelp meal. The tag on it said 7-8 percent salt. Then i emailed a reputable online garden center that sells kelp meal for the garden and they said theirs was 6 percent salt. Have used this in the past with good results.The vegetable garden is ten inch raised beds of non native soil with compost and peat based store bought soils.The underlying soil is alkaline anaerobic clay,some of which is wet a lot of the year.Is the salt in the kelp high enough to harm the growth of vegetables next year if it is applied this fall.Thanks.
The confusion about "salt" is that there are many different forms of salt. We often think of sodium chloride (table salt), but potassium nitrate (a common fertilizer), and magnesium sulfate (epsom salts) are other types of salts. With the exception of sodium, all of these ions are also essential plant nutrients. One of our challenges in arid climates is the accumulation of excess salts in the rooting zone - this means that you have too much of a good thing. When the label says 7-8 percent salt, I don't know if that means only NaCl (table salt) or all of the salts combined.
Sandy or well drained soils rarely have issues with accumulated salts, unless the irrigation water is also saline. However, poorly drained clay soils are very prone to salt problems. Since you have a well drained raised bed you may be able to use this product with no issues. It sounds like you have used it successfully in the past. I would read the label carefully and keep track of what/when you apply.
Here is a bulletin that you may find helpful.