more than 46,800 tons of rock phosphate having a purity of 75 per cent, or in the neighborhood of seven pounds per acre. If this amount, even with the potash and limestone added, appears like a trifling addition of fertility it is important for Americans to remember that even if this is so, these people have felt compelled to make the saving.
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Fig. 114.—Japanese farmer tramping green herbage for fertilizer into the water and mud between rows of rice.
In the matter of returning soluble potassium to the cultivated
fields Japan would be applying with her ashes the
equivalent of no less than 156,600 tons of pure potassium
sulphate, equal to 23 pounds per acre; while the lime
carbonate so applied annually would be some 62 pounds per
acre.
In addition to the forest lands, which have long been made to contribute plant food to the cultivated fields through fuel ashes, there are large areas which contribute green manure and compost material. These are chiefly hill lands, aggregating some twenty per cent of the cultivated
