7 



soil which he has thus prepared coarser substances to serve as a free conduit for the water which, if 

 retained around his plant, would mar all his efforts. 



Loam is composed generally and chiefly of siliceous sand, clay, and carbonate of lime. Other sub- 

 stances, too, are present in smaller quantities, 3uch as iron, in the form of peroxide magnesia, and 

 various other substances ; seldom, however, in such proportions as to affect its nature in any material 

 degree. Decayed vegetable matter, too, is present in most loams, and although no less a person than 

 the great chemist, Baron von Liebig, has declared that humus exercises a comparatively small in- 

 fluence upon the life and growth of plants, every cultivator knows perfectly well how materially its 

 presence enhances the fertility of his soil. A. great advantage of the presence of humus in soils, inde- 

 pendeutly of its directly fertilising qualities, arises from the fact that in the chemical changes which 

 it continually undergoes gases are being evolved which act mechanically in loosening the soil and 

 bringing it under the influence of the air and sun. Of course there are various varieties of loams, 

 varying from a hungry loam, lurgely composed of sand and deficient in organic matter through all 

 degrees of fertility, to a stiff clay loam containing a proportionally small quantity of sand, most diffi- 

 cult to work, and requiring expensive cultivation and often drainage. For purposes of irrigation, a 

 light loam, containing a fair proportion of organic matter and resting on a gravel subsoil, cannot be 

 surpassed. It is on this variety of land that I have seen the very best results achieved from irrigation, 

 in India. The native of that country — those, at least, of them who are engaged in tillage — have 

 learned from centuries of experience that in a warm climate the soil must retain its porosity to pro- 

 duce good results, and they will not apply water to the surface of a variety of soil which will solidify 

 after the water has drained off, or if they do, it will be only over such an area as can be quickly gone 

 over with the hoe after the water has been drawn off. Where unsuitable soils have been irrigated in 

 India with disastrous results, the fault lies not with the cultivators so much as with those who thought 

 that the art of irrigation consisted in the erection of engineering works for the distribution of water, 

 without any reflection as to the nature of the soil to which the water was to be applied. The propor- 

 tion in which the different earths are present in loams varies considerably, often without any corres- 

 ponding variatio 1 in their fertility. A good loam, and one which we may take as a standard, consists 

 of three parts clay, two parts sand, and one part chalk. A mixture of humus will add to its fertility, 

 or this can be supplied by manure. Such a soil, given a good sand subsoil, can be freely cultivated 

 at all seasons ; the constituent of which it is deprived by plants can be restored by the aid of manures, 

 natural and artificial. It will have its fertility increased by irrigation, always bearing in mind that 

 irrigation, thorough cultivation, and systematic manuring must go hand in hand, or the results will be 

 deterioration and ultimate sterility. The aim of the cultivator who would seek to improve the charac- 

 ter of his soil should be to bring it as nearly as possible to the condition of loam, by adding to it those 

 substances which it lacks. Thus, if it is a stiff clay, caking on the surface after rain and retaining 

 moisture, the natural remedy is the admixture of a sufficient quantity of sand and chalk t > get it as 

 nearly as possible to the condition above described. Soil in this condition may be improved to a vary 

 great extent by burning a portion of the clay. This process of c.ilcining destroys the affinity for . 

 water, and it becomes converted into a substance like burnt brick, which acts mechanically the part of 

 sand, if mixed with the remaining soil, in keeping it porous, and in fact in forming it into a loam. 

 Any admixture of a gravel containing quantities of calcareous or living matter is more useful in this 

 respect, since it has not only the mechanical effect here referred to, but has also a chemical action 

 upon the organic matter in the soil, reducing it to soluble forms, readily assimilable by the delicate 

 rootlets of plants. Should the soil be good, containing too great a proportion of sand, allowing the 

 water to run through too rapidly, then the remedy is to endeavour to bring it to a state of loam by 

 the addition of marl. This is a word used in a general sense to indicate a very valuable factor in the 

 improvement of certain varieties of soils. I have met in several parts of the world very different sub- 

 stances locally called by this generic title. Marl was formed by the collection together of vast quan- 

 tities of shells, either in fresh water lakes or in torrents, and these were mixed with quauaUes ui clay 

 or sand. As either of these substances predominate, it is called clay marl, sand marl or shell marl, 

 and when it has been subjected to such pressure as to solidify it, it is known as slate marl — in which 

 form it must be burned to be of use to the agriculturalist. In many parts of England, clay marl is 

 largely used on light soils with the most beneficial results, while shell marl, and very frequently chalk, 

 is largely applied to heavy soils for the double purpose of rendering them mechanically lighter, and 

 for the more speedy solution of the organic matter contained in them. Besides the chief constituents 

 to which I have here referred, it will be at once seen that since all soils were formed in the first in- 

 stance by the erosion of rocks under atmospheric and aqueous influences, they must contain certain 

 proportions of the minerals which originally formed part of those rocks, and it only needs a moment's 

 reflection to assure us that in the chemical changes which are constantly taking place in the soil these 

 tame minerals are being converted into soluble substances, which plants, by that process of endosmosis 

 with which you are no doubt all familiar, can take up, and by means of those wonderful natural labo- 

 ratories, the leaves, convert into a part of its own substance. Of these mineral substances I will spaak 

 presently. Let us take a case of two soils called A and B. A may be rich ia all the chemical consti- 

 tuents required for the growth of, say, the orange plant, and found in the ash of that plant, whilst B 

 may show some deficiency in some of those particular constituents, and yet an orange grove ou A 

 might be a most lamentable failure, whilst B might produce a tolerably fair crop. The physical con- 

 dition of the soil A may be such that the process of solution cannot take place, as is often the case 

 with humus imprisoned in a stiff clay. Hants cannot live on the crude material. Their food must 

 be. so to speak, cooked for them, and this is what is at the head of the system of rotation of cropping, 

 and the practice of allowing land to lie fallow. The expression ** giving the soil a rest," applied to 

 the latter system, is a misnomer. What is really done is to give the soil tima to work, time to resolve 

 under the influence of sun and air the crude substances contained in it, into soluble and, so to spaak, 



