Plants fed liberally with potash suffer less in drought. Potash stiffens cereal straws, increases oil content of oil-bearing seeds and has an important role in plant protein formation. Plants which store starches and sugars in tubers or corms, such as dahlias and potatoes, quickly show injury or decline when they are suffering potash deficiency. Later, the keeping qualities of the tuber, bulb or conn will be seriously affected if potash is too low for normal growth.
Other types of plants do not readily show signs of potash shortages. If soil is only slightly deficient in potash, plants tend to remain smaller in all parts, yet they flower, fruit and reach full maturity. It is only when potash-deficient plants are compared directly with those fed liberally with potash that the difference can be seen.
Some crops do use rather large amounts of potash. A single acre of celery may use up as much as much as 200 pounds. On the other hand, grain may remove very little if the straw is plowed under. An excellent way to maintain potash reserves is to return all plant residues to the soil.
In the home garden a well-managed compost pile can produce organic matter that will help to sustain potash in the soil, particularly if extra table wastes are added to the refuse gathered from the garden. A lawn on which clippings are allowed to remain will need to be fed only half as much potash as needed by an always cleanly raked lawn.
CLAY SOILS RICH IN POTASH
Clay soils may not always show a response following addition of potash fertilizers. Clay particles hang onto this element tenaciously,
yet release it readily to plant roots. When fertilized regularly, clay soils tend to accumulate potash, since rates recommended for most crops are usually made with sandy soils in mind.
In home gardens, regular use of a good mixed fertilizer plus additions of compost should insure all the potash needed. Sandy soils, particularly if strongly acid, are another matter. Sandy soils, mucks and peats have little or no reserves of potash on which plants can draw, and little capacity to hold what is applied. For this reason, fertilizer applications in such soils should be split, so that about one-fourth of the potash goes on in early spring, half in mid-summer and the final one fourth as crops are nearing maturity. While potash is vital for early growth, not much is used at this stage. Toward maturity the demand is much greater. Thus, if all of it is applied in spring, a shortage may develop by fall on sandy soils.