July i, 1886.] 



THE TROPICAL AGRICULTURIST. 



47 



PLANT CULTIVATION AND MANUEES. 



The roots of plants will only absorb from the soil 

 such materials for food as are in a liquid or gaseous 

 form. No matter how richly plants may be supplied 

 with food-substance, they cannot avail themselves of 

 it, or assimilate it into their structure while in a 

 solid condition. Bearing these facts in mind, it is 

 not difficult to understand the great su'icess which 

 has attended the application of Liquid Manure for 

 garden purposes in Flanders, Jersey, and in various 

 parts of our own country, soils that previously 

 were proverbially barren being by this treatment 

 rendered enormously productive. 



The late Dr. Voeleker said, " Any one who has 

 passed through Belgium, and examined the nature 

 of the soil, must have been struck with the wonder- 

 ful change which liquid manure has produced there." 

 The gardener in his practice must, however, alway 

 remember that soils containing a fair proportion of 

 clay, and more especially stiff clay soils, are diametric- 

 ally opposed in their chemical and physical character 

 to those which are porous and sandy. Generally 

 speaking the retentive and stiff soils contain not 

 only the more common mineral elements which we 

 find in the ashes of plants, such as' lime, magnesia, 

 .soluble silica, sulphuric acid, kc, in sufficient abundance, 

 but also the more valuable mineral substances, such 

 as phosphoric acid and potash. They, moreover possess 

 in a high degree the power or absorbing nitric acid, 

 ;ind retaining it for future use; and in addition, 

 under good garden cultivation, the vegetable remains 

 lett lu such soils, in the shape of roots and ftaves 

 from former crops, yield much nitrogenised organic 

 food for succeeding plants. The decided benefit which 

 IS usually found by the gardener to result from a 

 liberal dressing of stable-dung is owing to the fact 

 that by the very bulk of the manure the physical 

 and chemical characters of the soil are so altered 

 tliat in reality the plants feed upon a new and 

 artificially formed soil. 



Particular cultures may demand particular manures, 

 but the standard man-ire, such as well made farm- 

 dung, affords all the ingredients necessary to the 

 development of plants. Such manure contains all the 

 usual elements which enter into the composition of 

 plants, and all the mineral substances which are 

 distributed throughout their tissues; in fact, carbon, 

 hydrogen, nitrogen and oxygen are found therein united 

 with the phosphates, sulphates, and chlorides, &c. 



In order to be directly efficacious, every manure 

 must present this mixed composition. 



The nitrogen of nitrogenised organic substances 

 only benefits plants when converted into nitric acid, 

 hence no Di.acerial can act as a powerful fertiliser 

 untd it passes into a state of oxidation or decom- 

 position, and the presence of any ingredient which 

 hastens the material applied as manure into that 

 condition, although in itself probably comparatively 

 unnecessary to the plant in that particular soil, yet 

 furms a useful manure. It is in this way we often 

 may explain the great benefits derived from an 

 application of lime, marl or gypsum. Straw, Bracken- 

 Fern, Potato haulms, turf and vegetable refuse, are 

 sometimes mixed with quicklime and earth, to form 

 a compost, in order to facilitate their disintegration 

 and decomposition. The utility of this practice cannot 

 be disputed while confined within reasonable limits, 

 but It is sometimes abused ; fur it is beyond question 

 that alkaline salts, such as that supplied by lime 

 mingled indiscriminately with manure, become in 

 reality very mischievous on certain classes of very 

 light soil, where the business is rather to preserve 

 than to destroy the substances that are used as manure. 

 Such soils part too easily with the stores of fertility 

 committed to them ; consequently we find soluble 

 plant-food is washed away by the rain, or even eva- 

 porated into the air. Mechi aptly remarked that 

 "the best portion of manure is always attempting 

 either to run away, or to fly away ;" and time tends 

 to increase this action. 



The most suitable manure for the looser and more 

 friable classes of soil, is some substance which wil, 



combine intimately with the fertilising materials, and 

 thus husband them securely for future plant use. 

 Thus hungry loose sands are rendered fertile by the 

 application of c^ayf^y composts or materials for con- 

 solidating the mass, so as to impart a greater resisting 

 power to atmospheric action. 



One great objection to the extensive employment 

 of composts, however, is the amount of labour they 

 require in the repeated turnings which are ht;ld ne- 

 cessary in their preparation, and in the large quantity 

 of matter which has to be transported. 



In order to show why potash, lime, phosphoric acid 

 and nitrogen are the most important elements of 

 plant food, it is necessary to consider the chemical 

 composition of our of various garden productions, and 

 the amount of each constituent they remove from 

 the soil in order to build up their vegetable fabnc. 



The following table, compiled from various sources' 

 brings before us at a glance the amount of these 

 constituents removed from the land in 1 ton of each 

 crop in a fresh condition as taken from the garden, 

 which of course includes a very large quantity of water.' 



Amount of Selected Chemical CmiMituenU in Prodnce 

 Removed from the Land, in Pounds. 



The true economy of manure can be understood 

 only when we become aquainted, as by the statistics 

 given above, with the special characters of the crops 

 we cultivate ; but we not only have to con.sider the 

 materials required to form a crop, but the power the 

 particular plant we are cultivating has of assimilating 

 the higredients applied in manure. 



For this reason farmyard dung, purchased or home- 

 made, which supplies all the essential elements of 

 plant food, and particularly the constituents shown to 

 be required to such a large extent by the vegetables 

 we cultivate, is so largely used by growers- But on the 

 other hand the immediate return from an application of 

 farmyard manure is muck less than from the same 

 aniount of plant food applied in well selected arti- 

 ficial manures. We shall hope to continue the sabject 

 on a future occasion.— Gfmleneis' Chronic/ 1. 



Olli Aiii-UKAN Exchanges say that golden millet 

 {setaria yermanica) is the best of annual grasses for 

 hay, as it yields largely can be cut in six or eight 

 weeks after planting. This is borne out by Queens- 

 land Q\\)Qnence.— Planter and Farmer. 



