The Birmingham age-herald., 1917-10-04
PRINCIPLES OF PLANT FOOD
By CHARLES A. WHITTLE Farm Service Bureau, Atlanta


 To keep plants properly fed is to dea! with problem lying at the very founda- tion of human welfare.
 With the purpose of setting forth in a direct manner the essentials of profit able plant feeding the following ques- tions and answers are presented;
 Of what does plant food consist?
 Plant food consists of 10 essential chem ieal elements, two or three others being of slight benefit under certain conditions These 10 are nitrogen, phosphoric acid, potash, lime, iron, sulphur, magnesium carbon, hydrogen, oxygen. Only four have to be supplied, as rule, to meet plant requirements. These are phosphorus (contained in acid phosphate), nitrogen, potassium, usually spoken of as potash, and lime, which is not so much required as plant food to improve the feed- ing conditions of the plant.
 How do plants feed?
 When a seed sprouts the young plant feeds on the contents or the nseed until roots, stem and leaves are formed. Through these they then get their food. Root hairs which are attached to the main roots and made up of porous cells take in water at rapid rate. The water holds the mineral plant food in solution, or dissolved. It passes up through the plant to the leaves, just as readily as 1t passes up through dry sponge, and all the water that is not needed to make Gp the body of the plant, passes off into the air through the leaves by transpiration or sweating"
 In the water is the dissolved phos- phoric acid, nitrogen, potash, etc, all must be there in just the right propor- tions to meet all of the plants require ments. The plant can't even be fooled a part of the time.
 What does the plant get from the air and sunlight?
 Plants breathe, by taking in during the day through their leaves, carbonic acid gas some of which gas they breathe out, or throw off at night. This gas, to- gether with the mineral elements that came up in the water through the roo ts, is elaborated or manufactured, in the leaves into substances that build up the plant and form it's fruit or grain.
 How did soils get their natural plant food?
 Soil is made up from broken down rock and decayed animal and vegetable matter. It has been in process of accommodating for ages. Much of the land was once the bed of the sea, and the bodies of all sorts of fish and their smells helped to form the original soil. To this has been added the accumulation of vegetable growth season after season for many thousands of years.
 Can the chemist tell how much plant food there is in the soil?
 Yes, the chemists can tell absolutely how much there is, but he cannot tell how much of the natural plant food in the soil will dissolve in water or serve for the plants "soup." That depends upon the condition of the soil, the kind of plant, the moisture conditions and tem- perature.
 What is available plant food?
 It is that which the plant can get at once It is that which is dissolved in the soil water or that which is readily dissolved by the acid action of the roots. Such food is a natural soup for the plant
 Unavailable plant food is that which is so locked up in the soil that the plant cannot get at enough of it to make nor mal growth. It is a good thing, of course, that providence locked up much of the plant food If it had all been turned loose and made water soluble at the beginning, the rains would have washed much of it away and there would be little held in reserve.
 Can one element of plant food take the place of another?
 One kind of plant food cannot take the place of another in the sense that any one can be left out of the diet and made up for by the others.
 The element in the soil that is chiefly deficient is called the limiting factor''- sort of last hole in the belt It limits the ability of the plant to feed on those other elements of food that are more abundant. If it is phosphoric acid that is short, the plant virtually says, Enough refuse to eat any more nj trogen and potash until I get some phos- phoric acid" And that settles it.
 For illustration: A wooden bucket with one stave broken in half determines how much water the bucket will hold. does 1t not? Make the short stave as long as the others and you will then get full bucket of water. So 1t Is with plant food. Let the food me complete and you will get the biggest possible crops in good seasons
 Can the amount of plant food removed