230 GARDENS AND THEIR MEANING 
65 pounds of nitrogen, 21 pounds of phosphoric acid, and iii 
pounds of potash. (United States Department of Agriculture, 
Farmers' Bulletin No. 16.) 
VI. Commercial Fertilizers furnish Nitrogen, Phosphoric 
Acid, Potash, and Lime 
Nitroge?! is to be obtained from nitrate of soda, sulphate of am- 
monia, dry fish, cottonseed meal, etc. 
Phosphoric acid is to be obtained from phosphate rocks, bones, 
fish scraps, etc. 
Potash is to be obtained from potash mines. Wood ashes con- 
tain potash. 
Lime is supplied to the soil in the shape of quicklime. It is 
valued chiefly for its effect on texture, making clay soils mealy and 
sandy soils more adhesive. 
General Conclusions 
Small grains — wheat, oats, and barley — can easily obtain 
phosphoric acid and potash, but they are weak in obtaining nitro- 
gen and are benefited, therefore, by the addition of nitrates. 
Legumes collect nitrogen from the air, but take from the soil 
lime, phosphoric acid, and potash. Hence these last must be 
supplied by manures. 
Root crops are unable to use the insoluble mineral elements in 
the soil. Hence all the chief elements may be advantageously ap- 
plied in a state ready for use. 
Stem and leaf crops in particular require nitrogenous food. A 
healthy green foliage indicates good nourishment ; pale yellowish 
green indicates lack of nitrogen. 
Fruit trees are slow-growing plants and do not need quick- 
acting fertilizers. Small fruits are rapid-growing plants and are 
benefited by readily soluble fertilizers, 
