80 



THE IRRIGATION AGE. 



to long action, they retain too much of it. In the arid 

 regions deep cultivation is essential to admit moisture 

 from the atmosphere, as for example, the dews of night. 

 In irrigated sections deep and thorough cultivation 

 checks evaporation and reduces the accumulation of 

 alkali salts to a minimum, besides saving water. 



Heat is tempered by deep cultivation, which is a 

 great desideratum in the arid and semi-arid regions, the 

 layer of pulverized soil serving the purpose of shade 

 or mulch, and the evaporation retarded, the moisture 

 acquires a uniform temperature. This seems to be a 

 small matter in plant growth, but practical experience 

 has demonstrated that it is an important part of the 

 general combination of practices which result in suc- 

 cessful agriculture. 



Whenever the soil is opened, turned over and oth- 

 erwise prepared for planting, a portion of the atmos- 

 pheric air is buried in the soil and this air so confined, 

 is decomposed by the moisture retained in the earthy 

 matters. Ammonia is formed by the union of the 

 hydrogen of the water with the nitrogen of the atmos- 

 phere, and nitre by the union of oxygen and nitrogen. 

 So also, the oxygen of the air may unite with the car- 

 bon contained in the soil and from carbonic acid gas. 

 Heat is given out during all these chemical processes. 

 As a rule farmers do not pay much attention to these 

 simple facts, but the plants he is growing do, and they 

 are more or less benefited as they are permitted to take 

 advantage of these laws of nature, or prevented. 



The depth of cultivation must depend upon the 

 nature of the soil and the variety of plant grown in it. 

 The subsoil, also, is not to be disregarded. Rich clayey 

 soils can hardly be cultivated too deep, and even in 

 sands, unless the subsoil contains alkali in dangerous 

 quantities, or other plant poisons, deep cultivation 

 should be practiced. When the roots are deep they are 

 less liable to be injured by excessive water or drought; 

 the radicles are shot forth into every part of the soil, 

 the space from which nourishment is to be drawn be- 

 ing extended over a much greater extent than when the 

 seed is superficially inserted in the soil. 



In this respect cultivation should be attended with 

 a thorough mixture of the soil by turning it over and 

 over. Plowing, of course, accomplishes this result in 

 a great measure, but the difference of gravity between 

 the organic and the inorganic matters in the earth, 

 has a tendency to separate them, for which reason light 

 or shallow stirring of the soil is of little or no use 

 practically, because it leaves the surface of the soil too 

 light and spongy and the lower part too compact and 

 earthy. Even where the plant roots are near the sur- 

 face cultivation with a plow and a complete turning 

 over of the soil is much better than the mere scratching 

 of the surface, for there, as has been said, it is equiva- 

 lent to root pruning. 



In a former chapter reference is made to the fact 

 that plant roots consume all the food in their neigh- 

 borhood, and this furnishes another obvious reason for 

 deep cultivation, otherwise the roots of a new crop reach- 

 ing out for nourishment find an empty cupboard. 



Some soils, however, require the opposite of pul- 

 verization and demand mechanical consolidation. This 

 will be understood in the case of spongy peats and light, 

 dusty sands. A proper degree of adhesiveness is best 

 given loose soils by the addition of earthy matters in 

 which they are deficient, perhaps the bringing up of 

 a heavier and more consistent subsoil will accomplish 

 the purpose. Rolling and treading, however, are simple 



methods, but in that case the soil must be dry, and 

 the operation must not be carried too far, or so far 

 as to concrete the earth, which is its constant tendency, 

 as has been observed. 



A peat bog drained and rolled will sooner become 

 covered with grass than one equally well drained but 

 left to itself. Drifting sands, however, may well be 

 rolled when wet, and by repeating the process after rains 

 or floodings, they will in time acquire a surface of 

 grass or herbage. Light soils should always be rolled, 

 and the seeds should be "tread in" when planted, a 

 pat with the hoe not being sufficient, as in the case 

 of heavier soils, unless the seeds be very small. 



Exposure to the atmosphere, speaking with refer- 

 ence to soils, means "lying fallow," the only benefit of 

 which, and sometimes it is not a small one, is to ex- 

 pose insects and their eggs, weeds and their seeds, to 

 destruction. In climates where there are severe win- 

 ters and hard frosts, a hard, lumpy soil becomes pulver- 

 ized by the action of the frost, and soils that have be- 

 come soured, sodden and baked by the tread of cattle or 

 other cause in wet weather, are more rapidly sweetened 

 and restored to friability by exposure to the hot sun of 

 summer, than by the frosts of winter. Some maintain 

 that the only benefit of fallow, that is, turning up the 

 soil roughly to the atmosphere, is to free the soil from 

 the roots of weeds. There is nothing, indeed, in the 

 idea that the land "needs a rest," for if properly culti- 

 vated, soil will keep on producing as long as there are 

 any elements capable of feeding plants. The idea origi- 

 nated in ancient times when lack of help to till the 

 entire farm, or a deficient supply of manure, compelled 

 the suspension of cultivation on certain parcels or fields. 

 It is certain that what is called an "exhausted soil" ob- 

 tains no renewing material from the atmosphere. 



To alter a soil is to add or subtract the ingredients 

 which are lacking, or which exist in excess. The so- 

 called "alkali soils" are an illustration of excessive in- 

 gredients, and any sterile, sandy or gravelly soil may 

 be regarded as one representing a deficiency of food 

 producing elements. In case of sterility, the only rem- 

 edy is to add the ingredients lapking, or convert sterile 

 material into fertile ones by chemical means. Thus: 

 where in sterile soil, on washing it, there is found the 

 salts of iron or acid matters, the application of quick- 

 lime will ameliorate it, and in a soil of apparently good 

 texture, but sterile on account of the sulphate of iron, 

 a top dressing of lime will afford a remedy by converting 

 the sulphate into a manure. 



If there be an excess of calcareous matter in the 

 soil it may be remedied by the application of sand or 

 clay. Too much sand is improved by clay, marl, or veg- 

 etable matter, and light sands are benefited by a dress- 

 ing of peats, and peats improved by adding sand. The 

 labor of thus improving the texture or constitution of 

 the soil is more than repaid by the requirement of less 

 manure, in fact, accretions in the way of new soil are a 

 natural manuring and insure the fertility of the soil, 

 where manure might be doubtful on account of its adding 

 an excess of organic matter, which is equally as deleteri- 

 ous to plant growth as too much inorganic matter. An 

 equal number of tons of sand, clay, marl, or other natural 

 soil, as of manure, will often tend to greater productive- 

 ness than from the addition of manure. When there 

 is an excess or superabundance of soil material, the 

 problem of its removal is much more difficult and seri- 

 ous, the reclamation of alkali lands abundantly demon- 

 strating this. Ordinary sand and gravel may be plowed 



