No. 7. DEPARTMENT OF AGRICULTURE. 249 



our control, and it is only by the admixture of an amount of clay 

 to the porous material, or by the formation of a dense subsoil that 

 we can prevent their escape with all the soluble contents which they 

 have extracted from the rock. It is, therefore, with the waters' 

 which are to be retained in the soil, and those v.hich should be ar- 

 rested on the surface, that we have any concern. 



Every ton of dry organic matter produced upon the farm requires 

 from 250 to 500 times its weight of moisture in the soil. An acre 

 of potatoes requires 1,300 tons of water to circulate during the 

 growing season; an acre of oats requires 1,000 tons to supply the 

 evaporation from its foliage and to carry the nutriment from the 

 soil to the plant. To retain such an amount out of the 4,500 tons 

 which fall, requires skilful husbandry and the most careful prepara- 

 tion of the soil. This calls for such a state of fineness that the 

 texture of the soil will hold and circulate the amount required. Cul- 

 tivation accomplishes this to a great degree, and yet not as vigor- 

 ously as the natural agencies which are engaged in aiding the farmer. 

 The mechanical movement of the solutions, their freezing and their 

 expansion, opens the pores to the water in the rainy season and to 

 air in the dry season. The air with its oxygen furnishes the final 

 element of the decay and sets free the plant foods, mineral and or- 

 ganic. That process of cultivation, which will retain this nutritive 

 element and prevents its extraction and removal by the surface 

 waters, will prove the best means of prolonging the fertility of the 

 soil and of ensuring frequent harvest. If, in addition, the land be 

 enriched by returning to it all organic wastes, the process of restora- 

 tion is more rapid than the process of exhaustion, and our system of 

 farming ceases to one of spoliation. A generous soil properly cared 

 for will continue to furnish all mineral nutritive elements; and, 

 with the organic elements provided for, the conservation of the 

 moisture within the soil and the torrents upon its surface becomes 

 our sole aim. A soil which has the highest degree of capillarity will 

 not only circulate through its mass the ground waters, but will also 

 carry them to the surface, where, during periods of drought, they 

 will accumulate to be evaporated and lost. If the surface is not 

 cultivated so that its clods are broken the evaporation from the soil 

 is more rapid than the exhalation from the foliage on the .plants, 

 and if the drought is protracted the crops are burned. The object, 

 then, of tillage is to retain the moisture by preventing loss at the 

 surface, and this loss alone is not insignificant, for untilled soil evap- 

 orates ait least 100 barrels more per acre in a given season than 

 does a properly cultivated soil. This evaporation is also at the 

 expense of heat and becomes cold. A light colored clay is exces- 

 sively so. Its wheat is winter killed. But this evaporation of the 

 water from the surface has still another effect. It deposits in the 

 17 



