. The first principles of agriculture [microform]. Agriculture; Agriculture. 28 FIRST PRINCIPLES OP plant food amounts to a large number of pounds per acre* According to Warington, the surface of an acre of clay loam, to a depth of 9 inches, when perfectly dry, weighs from three to three and a half million pounds (3,000,000 to 3,500,000 lbs.). Taking this as a correct estimate, we find that ^ per cent, of nitrogen, ^ per cent, of phosphoric acid, and ^ per cent, of potash, yield as follows : Nitrogen 4,286 to 5,000 lbs. per acre. Phosphoric acid 12,000 to 14,000 " " Pot
. The first principles of agriculture [microform]. Agriculture; Agriculture. 28 FIRST PRINCIPLES OP plant food amounts to a large number of pounds per acre* According to Warington, the surface of an acre of clay loam, to a depth of 9 inches, when perfectly dry, weighs from three to three and a half million pounds (3,000,000 to 3,500,000 lbs.). Taking this as a correct estimate, we find that ^ per cent, of nitrogen, ^ per cent, of phosphoric acid, and ^ per cent, of potash, yield as follows : Nitrogen 4,286 to 5,000 lbs. per acre. Phosphoric acid 12,000 to 14,000 " " Potash 15,000 to 17,500 " *' 44. Active and Dormant Constituents of Soil.—Not more than perhaps one per cent, of the substance of soil, even the most fertile soil, is at any time in such a condition that plants can make use of it. The greater part of the plant food in soil is quite insoluble, and cannot be used by plants till it undergoes some chemical change. Hence a soil may contain several thousand pounds per acre of nitrogen, phosphoric acid, and potash, and all the while be unproductive. For that reason chemical analysis alone is not generally sufficient to decide whether a soil will produce good crops or not; because it merely tells how much of each substance is present, without making known what proportion of it is in a fit condition to nourish plants. Those portions of plant food which are (at any given time) available for the use of plants are sometimes called the active constituents of soil; and those compounds which (at that time) are insoluble in water or dilute acids, and therefore incapable of being taken up by plants, are often spoken of as the dormant constituents^ that is, the sleeping or inactive portions which serve only as stores of food for future use. Most of the soils in this Province contain plant food enough to produce crops for generations: to come, if we only treat them in such a way as to change from year to year a sufficient amount of the insolu
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectagriculture, bookyear
