For May, 1921 



583 



A Lesson on the Plant In Relation To Its Food I 



Being One of a Series of Lessons of a Home Study Course on Gardening. Appearing Regularly in The Gardeners' Chronicle | 



Under the Direction of ARTHUR SMITH I 



aiiiiiiiiniiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii I inn m i i , ,„„„„„ 



Ill I Ill iiiNiiiuiiinimiiiiiiniiiiiiiiiiiniiiii iiiiuiiiiiiii'uiiii iiiiiiiuiiniiiiiiiiiiiiiiiiininril 



THE great fuiKlamental in plant production is growth, there- 

 fore a proper conception of it is of the utmost importance, 

 and all matters connected with a plant's environment are 

 good or bad, as thej' facilitate or retard grow^th. 



Growth is the normal, permanent change in the form of a 

 living vegetable or animal body, and is usually accompanied by 

 increase m size. It may occur either through expansion of cells 

 already formed, or through cell multiplication. The latter may 

 take place either by division of older cells into two or more 

 smaller cells, or by the formation of new cells within older 

 ones — the young cells thus formed attaining full size by subse- 

 quent enlargement. No growth in a plant or in an animal can 

 take place except by the enlargement or multiplication of cells, or 

 a combination of both. 



Practically, the increase in growth is the yield the plant gives 

 whether by the mere increase in size of the plant itself, or in 

 the fruit or seed it produces. Necessarily, growth receives con- 

 sideration in all studies connected with every phase of plant life, 

 for it enters into any discussion of the relation of the plant to its 

 environment ; to the making, use, and accumulation of food 

 materials ; and also to reproduction. 



Obviously no growth can take place without the use of 

 material ; suitable material we class as food, while unsuitable 

 material becomes, if imbibed, sometimes absolute poison ; and 

 the want of matter agreeable to the plant, or the existence of 

 matter disagreeable to it, may not only decrease growth, but stop 

 it altogether, and, if long continued, death may result. 



There are many internal and external factors by wdiich growth 

 is conditioned. Amon.g the former must be assumed that inex- 

 plainable, invisible factor known as vitality, which is the attribute 

 of a living individual. The external factors are many, the most 

 essential being moisture, a suitable range of temperature, oxygen, 

 and the presence of several nutrients and crude food materials. 

 Taken as a whole, there are many important relations between 

 continuous growth and certain external factors: and most plants 

 exhibit such complex relations as to render the problem extremely 

 difficult, and which call attention in a very emphatic manner to 

 the many intricate points connected with the art of plant grow- 

 ing. For instance, conditions causing extreme luxuriance of 

 growth are more or less inimical to a large production of flowers, 

 fruit or seed. Again, when potatoes, for example, grow an 

 excessive amount of haulm, tubers are generally sparingly pro- 

 duced. 



Of course, growth can only go on as the result of the intake 

 and assimilation of food, which growth in the case of the embryo 

 starting into life when seed germinates, is brought about by the 

 use of the highly concentrated food stored in the seed by the 

 parent plant. Taking all the plant-food constituents as a whole. 

 excessive food supply is not the extreme we have most to fear, 

 since soils are rarely excessively fertile, and in the ordinary 

 sense over-manuring is not a fault very prevalent in gardening, 

 and indeed in any case practically all of the plant-food con- 

 stituents mav be present in excess without doing material harm. 

 Harm, however, may result if any one constitutent is present in 

 an available form greatly in excess of the others, and this is 

 especially the case with respect to nitrogen. \n excessive quantity 

 of any form of available nitrogen, such as nitrate of soda, or 

 easily available, such as sulphate or ammonia, stimulate growth 

 at the expense of flowers, seed and fruit. In crops grown for the 

 latter parts, available nitrogen must be used with caution. 

 .Apple, pear and quince trees liberally manured with such fer- 

 tilizer produce an excessive, over-succulent growth of wood, 

 which is subject to blight and Winter injury, and forms few, if 

 any, fruit-lnids. Grain imder similar conditions forms long, weak 

 straw, with poorly filled heads. Grapes grown upon over- 

 manured ground produce excessive amount of vine, with few 

 and late ripening bunches. For plants occupying tl;c ground per- 

 manently, such as fruit trees, grape vines, roses and the like, it 

 is necessary to add nitrogen to the soil in a direct form because, 

 unlike ground devoted to annual crops, there are no other means 

 of supplying it. To this end ground bones are an excellent and 

 safe plant-foodj as the nitrogen becomes available by degrees. 

 In addition to nitrogen, bones supply phosphoric acid, and by 

 using a little lime with them, soil potash is liberated. For grapes, 

 bones from the family tabic may be saved, roughly broken with 

 a hammer and buried near the roots of the vines. 



There is less danger of over-feeding crops growm for parts 

 other than flowers, fruits, or seed, especiallv if decomposed stable 

 manure is used, and with crops like lettuce, cabbage and cauli- 

 flower, available nitrogen is useful if used with discretion, but 

 this and all other high grade, concentrated and compound 

 mineral fertilizers will kill plants if used to excess. The more 

 easily any fertilizer becomes available the more likely will harm 

 result from a large application at one time. In the case of 

 nitrate of soda, for example, this is readilv dissolved by soil- 

 moisture, IS at once available as plant-food and the plant takes 

 It up immediately m the water absorbed by its roots; therefore 

 the plant would, as the result of a large qu'antitv of nitrate being 

 supplied, be unable to prevent an excess of nitrogen being carried 

 nito its system. Exactly how harm or death results from this 

 is not definitely known. There are several possible reasons, but 

 probably the most important factor is that the necessary balance 

 between the various food ingredients is upset to a degree which 

 disorganizes entirely the assimilating powers of the plant, and its 

 cells being unable to effectively handle such a large quantity 

 of one in the face of an obvious deficiency of all others. Prob- 

 alily. therefore, toxic conditions are brought about similar in 

 effect to the state of things produced in the animal stomach by 

 the same means. 



We have several times discussed, the question of the nitrogen 

 element in plant-food, and have pointed out means of supplying 

 ground under crops with nitrogen from the air at comparatively 

 no cost, by means of turning under a growth of crimson clover 

 and other legumes; this to be followed, as well as preceded, by 

 the creation of soil conditions, with the application of lime', so 

 that the soil-bacteria by which, only, nitrogen can be turned into 

 nitrate, may be increased and enabled to carry on their work, 

 and along these lines soils may undoubtedly have their nitrogen 

 content greatly increased, and thus the direct purchase of the 

 very expensive nitrogen be avoided. Circumstances may, how- 

 ever, arise so as to cause the application of nitrate of soda, 

 sulphate of ammonia, blood, and other highly nitrogenous and 

 easily available plant-foods to be a profitable procedure. Such 

 circumstances may be : previous neglect, a period of cold rain, or 

 some other exceptional state of things which may retard plant 

 growth._ The important point is to use as little as possible of these 

 at one time. A small application several times during the growing 

 season being preferable and more economical. With nitrate of 

 soda an application should not exceed two hundred pounds per 

 acre at any one time, and even this quantity is better divided in 

 two and used at three-week intervals. The quantitv for a small 

 area may be gathered from the fact that three hundred pounds 

 to an acre equals one ounce to the square yard. 



As mentioned above, the harmful effects of large doses of 

 one element of plant-food in an available condition is intensified 

 when there is a paucity of other elements in a similar condition. 

 Like animals, plants must have properly balanced rations; excess 

 of one does net make up for deficiency in others, but. further, 

 deficiency in any mav render excess of one actually liarmful. 

 In the case of ourselves, we know- that the consumption of a 

 large quantity of a food rich in proteid eaten alone is harmful, 

 but if we consume carbohydrates or starchy food at the same 

 time, the effects of the excess of proteid are counteracted; 

 further, the use of starchy food really decreases the amount of 

 proteid consumed. Practically the same thing occurs with plants. 

 .\ given quantity of soil-water can only hold a certain nuantity 

 of material in solution, and the water will naturallv take up the 

 largest amount of that ingredient which exists in a soluble or 

 available condition in the greatest quantity. When there is a 

 sufficiency of all the necessary plant-food ingredients in a con- 

 dition to be absorbed by water, the latter will naturally not 

 contain an excess of either. It is. therefore,^ of fundamental 

 importance to place a properly balanced ration at the plant's 

 disposal. 



It is difiicult to separate the effects of a lack of food from 

 those of a lack of water, since plant-food is mainly conveyed to 

 the plant in the soil water. Rut even with a proper 'water 

 supply, jf one or more of the required food materials are absent, 

 a normal plant structure cannot be built up. Insufficient food 

 dwarfs the plant in all its parts. .A dwarfing in the size of the 

 plant IkkK ni;iy occur, bo\' ever, without a corresponding (hvarfin.g 



