. Improving crop yields by the use of dynamite . soil underlaid by an imper-vious or partly impervious subsoil, sometimes known as * hardpan,will not produce crops at all, or else only produce them in a verylimited degree, or for a short time only, unless the subsoil be thor-oughly broken up. Where the fertile surface soil is fairly deep,attempts have been made to farm this land by means of drainageand irrigation, the surplus water of the wet season being drainedoff, and the lack of water in the dry season being overcome by irri-gation. This system is expensive, and at best gives only temporar
. Improving crop yields by the use of dynamite . soil underlaid by an imper-vious or partly impervious subsoil, sometimes known as * hardpan,will not produce crops at all, or else only produce them in a verylimited degree, or for a short time only, unless the subsoil be thor-oughly broken up. Where the fertile surface soil is fairly deep,attempts have been made to farm this land by means of drainageand irrigation, the surplus water of the wet season being drainedoff, and the lack of water in the dry season being overcome by irri-gation. This system is expensive, and at best gives only temporaryrelief, for in the end it tends to increase the thickness of the hardpan,and in some localities may be responsible for alkali soil. The heavyrains of the wet season often cannot penetrate this subsoil, so thewater rushes to the low ground, carrying much of the valuable sur-face soil with it. There, still unable to sink through the hardpan,it prevents plowing until the water evaporates or causes the seed torot if it is already in the ground. 63. SUBSOIL BLASTING—THE RESULT—CORN RAISED ON THE BLASTED GROUND PREPARING THE LAND FOR CROPS In places where irrigating is carried on extensively, the groundsometimes becomes so saturated that the water level rises close tothe surface. This makes the land practically worthless for vegeta-tion of any kind other than pasturage. If alkali exists in the soil,or is deposited by irrigation, no crops can be raised when the groundwater reaches the level of the plants roots. In some parts of the country, ridges or dikes are run at regu-lar intervals over all of the higher ground, to keep the thin surfacesoil from being washed away. Considerable time and labor is re-quired to make these dikes, as well as to keep them in shape, andthey take up ground that should be bearing crops. On land of thiskind, drainage, irrigation, dikes, late plowing and rotting seed couldall be done away with if the subsoil or hardpan were properlybroken up. There is on
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