584 



GARDE!\ERS' CHRONICLE 



of fruit or seed products ; hence plants often bear their maximum 

 amount of seed or fruit witnout attaining their maxnnum 

 dnnensions. in this connection some fruits are specially gialted 

 upon dwarfing stocks to prevent the undue growth of the plant 

 body at the expense of fruit production. Plants grown )or seed 

 or fruit are, therefore, less likely to be restricted in yield by 

 insufticicnt food than those grown for their leaves, stems, roots 

 or tubers. The cereals, for mstance, produce well upon land not 

 sufficiently fertile to yield equally good crops of beets, cabbage, 

 celery, lettuce or potatoes. At the same time, with sumcient 

 restriction of food, the seed or fruit product will suffer dimiau- 

 tion, or be wholly cut off. 



Obviously, crop-growing tends to reduce plant-food m the 

 soil in proportion as the fertilizing components are remove^ 

 from the land and, are not returned to it, directly or in equivalent. 

 At the same time, no amount of cropping will by itself render a 

 soil absolutely infertile, because a certain amount of plant food 

 is constantly being liberated by the disintegration of rock or 

 soil materials, this disintegration being increased liy good cultiva- 

 tion. But the largest returns are impossible without lestoring 

 to the soil certain materials that continual crop removal invarf- 

 ably reduces below the limits of satisfactory yield. 



Of the dozen or so materials necessary to the plant as food only 

 three are of direct importance, and are most likely to be deficient, 

 in considering a plant's food supply; these are nitrogen, phos- 

 phorus and potassium. One other, lime, is required but little as 

 actual food, but it is of great importance indirectly on account 

 of its mechanical action on the soil ; its chemical action on the 

 soil ingredients ; its action in correcting undue acidity, and its 

 favorable effect upon the beneficial soil bacteria to which it is 

 indispensable. The remaining food elements necessary for plant 

 life are only required in such minute quantities that there is 

 invariably sufficient of them in all soils, so that it is never neces- 

 sary to supply them. 



Nitrogen is the most important element of plant-food because 

 it is liberated scarcely at all by rock decay, and is the most expen- 

 sive to buy. Free nitrogen, while being a very abundant con- 

 stituent of the air, plays no direct part in plant nutrition. At 

 the same^ time we can make use of this atmospheric nitrogen and 

 supply it to the soil at comparatively little cost. Leguminous 

 plants, such as peas, beans and clover require a larger quantity 

 of nitrogen in their food than most other species, but even 

 when the entire crop of these is removed the soil is always left 

 richer in nitrogen than it was before; further, these leguminous 

 plants are benefited little or nothing by the direct application 

 of any form of nitro.genous fertilizer. Leguminous plants obtain 

 their nitrogen through the agency of bacteria, wdiich act upon the 

 free nitrogen of the air. These bacteria are practically para- 

 sitic, microscopic plants living in the tubercles, which can be 

 seen upon the roots of the host plants ; they change the atmos- 

 pheric nitrogen into nitric acid, which, combining with some 

 base such as lime, becomes a nitrate, and is available as plant- 

 food. It will be readily understood that if, when a crop oF 

 leguminous plants is removed from the ground it is left richer 

 in nitrogen than it was before, how very great must be the 

 enrichment in this element when we return the entire crop to 

 the soil, as can he done in several ways, one being to sow 

 crimson clover in .\ugust and turn it under before the ground 

 becomes frozen. 



The entire process of changing nitrogen into nitrates by these 

 bacteria, and by which means only nitrogen is rendered avail- 

 able as plant food, is known as nitrification. The conditionf 

 aft'ecting the growth and work of nitrifying bacteria are similar 

 to those affecting plant-life in general, since nitrification results 

 from plant life. As it takes place below the soil surface, iiitrifica- 

 tion is encouraged by the same conditions which favor the root 

 growth of land plants, namely, aeration, w'armth and moisture. 

 Conditions which make for the most active plant growth favor 

 nitrification. There is little doubt that the process also indirectly 

 releases other food ingredients contained in or.ganic matter. 

 Nitrification does not go on to any extent in an acid soil, there- 

 fore, soils should be kept sweet by periodical moderate dicssings 

 of lime. In addition to other benefits, lime also liberates phos- 

 phoric acid and potassium. 



There is never much available nitrogen present in the soil at 

 any one time, the greatest quantity being found at the end of 

 Summer, especially if it has been a comoaratively dry one. 

 Nitrates are easily washed out of the soil liy heavy rain, and 

 as they require warmth for their production, therefore, the sur- 

 face soil is invariably poor in nitrates in the Spring on account 

 of their being lost through .\utunin and Winter rains, and there 

 is great waste of available plant-food, as a whole, when cover 

 crops are not used. For this reason the direct annlicatioii of 

 available nitrogen in the form of nitrate of soda is esneciallv 

 useful for early sarden crops started when the soil is loo cool 

 for very active nitrification. 



In purchasing a nitrogenous fertilizer, the special purpose for 



which it is required should always be considered. Under some 

 conditions, such as that above mentioned, and for foicing a 

 crop on an impoverished soil, nitrate of soda is the most satis- 

 factory. W hen a plant-food is desired which will give up its 

 nitrogen by degrees throughout the season, something that has 

 the nitrogen in a less available form will be preferable, such as 

 cottonseed meal, tankage, bones and blood. There is annually 

 expended in purchasing nitrcgenous fertilizers a large amount of 

 money which could be saved if a larger share of the nitrogen for 

 crop purposes were obtained indirectly from the air through the 

 agency of legumes. 



Phosphorus is used by plants in the form of soluble phos- 

 phoric acid, which exists in the soil in combination with lime, 

 alumina, or other base, as phosphates of these substances. It is 

 purchasable in the form of acid phosphate, which is mineral 

 phosphate rock treated with acid, ground bones and basic slag. 

 The best form is that of bones, and the finer the bones are ground 

 the quicker their action. Bones are a very safe fertilizer, wdiich 

 acid phosphate is not. Any excess of available phosphate in 

 the soil is retained by it as phosphoric acid, and is not readily 

 washed out. 



Potassium is used by plants in the form of potash or car- 

 bonate of potassium (K.CO3), and is found in Nature largely 

 in combination with sihcon and other elements, forming silicates, 

 which undergo slow but continuous disintegration with libera- 

 tion of potassium salts which become food for plants. The direct 

 application of potash is rarely necessary and never in any large 

 quantity, especially on soils containing any appreciable amount 

 of clay, as the average soil contains sufficient for many thousands 

 of plant generations. Potassium in the soil is brought into an 

 available condition by the action of lime. Wood ashes are an 

 important source of potash, although very variable in compo- 

 sition, the range being from i\ve to ten per cent, provided the 

 ashes are unleached ; the ashes of soft woods, like pine, contain 

 only about one-tenth of the quantity found in the ashes of 

 hard W'oods, like oak. Potash is found in all vegetable matter 

 and stable manures, being liberated upon their decomposition. 

 Wood ashes are an excellent dressing for sandy soils, these 

 being generally poorest in potassium. Wood ashes may also be 

 used as a source of lime, but, measured by itself, it is more 

 expensive to buy lirne in this way. An application of wood 

 ashes should not exceed three hundred pounds per acre, and 

 should never come into contact with seeds ; it is best worked 

 into the surface a few days before seeding. 



To some extent, plants suggest their own needs in the way 

 of food, so long as they are not suffering from drought. .\s a 

 rule, a lack of available nitrogen is indicated by a pale green 

 or yellow foliage, or small growth of leaf or stalk. E.xcess of 

 nitrogen is indicated by a very large growth of leaf or stalk, with 

 imperfect bud-, flower- or fruit-development. A deficiency in the 

 supply of phosphoric acid is generally the cause of scanty crops 

 of light or shrunken seed on plants of normal size. Lack of 

 potash is invariably the reason for small crops of inferior fruit 

 when this is accompanied by satisfactory growth. 



As previously mentioned, endeavor should be made to place a 

 balanced ration at the disposal of the plant, and undoubtedly the 

 best means of attaining this end is by the use of stable manure. 

 .\s it leaves the stable it is a perfectly balanced food, although 

 it varies somewhat ; also its composition and value may become 

 .greatly deteriorated by subsequent bad treatment, either by over- 

 fermentation, or by having much of its most valuable constituents 

 washed out by rain. Plant-food to the value of many millions 

 of dollars is yearly allowed to go to waste by want of care in 

 treating stable manure. 



Stable manure benefits the plant and the soil — both being 

 practically the same thin.g — beyond what it supplies in the way 

 of food. It is not exactly known why such benefit results, but 

 the fact remains that a given quantity of plant-food in the form 

 of stable maiuire will fall other things bein.g equal) produce far 

 greater results than the same quantity of food supplied in any 

 ether form. We have previously suggested in these columns that 

 stable manure may contain something which acts in connection 

 with plants in the same way that vitamines act in connection 

 wilh animals. Not only is this likely in regard to stable manure, 

 bill it is more or less equally so in connection with all manures 

 of an animal or vegetable origin. Be this as it mav, firactical 

 men have for long been aware that a given amount of plant-food 

 supplied by organic is of far .greater value than the same 

 amount in the form of inorganic fertilizers. The pulverized 

 stock-yard manures obtainable in bags are a useful and con- 

 venient substitute for stable manure when the latter is unobtain- 

 able ; they should, however, be worked into the surface of the 

 ground rather than spaded under. 



To obtain the maximum amount of return from the food suo- 

 nlied to plants we must see that as far as possible all the 

 hygienic conditions suitable for plant life are present. 



