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Title: Report on the Agriculture Experiment Stations of the University of California (PH 4-16)(1890) Collection Type: Directories and Documents Collection Name: Pamphlets Catalog #: PH 4-16 Author: E.W. Hillgard Published: 1890 # of Pages: 211 Download PDF: User Login Required Download OCR Text: User Login Required

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Original Held At: Searls Historical Library Location: 161 Nevada City Hwy, Nevada City, CA 95959

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380 UNIVERSITY OF CALIFORNIA. as in truck gardens, orchards, flower gardens, lawns, etc. The sample analyzed probably represents pretty fairly the black adobe of the foothill slope, from San Pablo to within two miles of Oakland. The differences in the mechanical and chemical composition of the ridge adobe from that of the valley is sufficiently striking. It contains less than two thirds the amount of clay, yet it is much heavier in working, owing to the small quantities of the finer sediments, which chiefly serve to break up the extreme tenacity of pure clay, that is but little disturbed by the large sized grains. Then the soil contains less than half as much lime as the lowland adobe; less than half, also, of the primarily important ingredients, potash and phosphoric acid; and, finally, very much less humus, as is shown by its tint. The unproductiveness of this soil is clearly owing to two causes combined—it is naturally poor in plant food, and its mechanical composition makes it so refractory that it is only in exceptionally favorable seasons that what it does contain of plant food can remain available to plants, since, in drying, it becomes of stony hardness, with only cracks to aid the circulation or penetration of air and roots. This is one of the cases in which improvement by merely supplying the plant food would be a waste of money, unless the physical condition be corrected at the same time. Underdrainage would probably do this most effectually; green manuring would also be avery important aid. But the unusually small amount of clay for so heavy a soil promises excellent results from the use of a moderate quantity of quicklime, or marl. To test this conclusion, based upon the known effect of lime in rendering clays less cohesive, the following experiment was made: One hundred grammes (about three ounces) of the soil were kneaded into a paste, and allowed to dry at steam heat. Two other similar portions were similarly treated, after being mixed intimately with, respectively, one per cent and one half per cent, by welghl of quicklime, freshly slacked. The lumps of soil dried without addition were, as might be expected, of stony hardness. Those of the portion dried with one per cent of lime, on the contrary, were so crumbly as to make it difficult to handle them without breaking them all into powder. Those of the portion containing one half per cent of lime were not quite so loose, but still resembled a very sandy soil, and were readily crumbled to a loose powder between the fingers. Of course no such extreme change as that noted in the above experiments need be brought about in the soil ofa field. This would require an extravagant outlay for lime, even at the rate of one half per cent. But even a very small fraction of the effect produced by the quantity mentioned would suffice to effect a very material improvement in the tillability of these adobe ridge soils; and in the case of truck gardens, orchards, and vineyards, the saving of labor in tillage, together with the increased thriftiness of the soil, would probably very soon pay for the outlay in the purchase of lime. The quantities needed per acre to produce a profitable result will form the subject of experiment. As regards other fertilizers, the use of phosphates and of nitrogenous fertilizers (ammonia salts or Chili saltpeter) 1s indicated by the analysis, for the present; for the future, potash will also be required. This kind of “ridge adobe” the foothills of the Coast Ran question of wide importance. seems to be of very extended occurrence in ge, and its improvement forms a practica