In addition to this the run-off from both the mountain and the genya lands is largely used upon the rice fields, more than sixteen inches of water being applied annually to them in some prefectures.  If such waters have the composition of river waters in North America, twelve inches of water applied to the rice fields of the three main islands would contribute no less than 1200 tons of phosphorus and 19,000 tons of potassium annually.

Dr. Kawaguchi, of the National Department of Agriculture and Commerce, informed us that in 1908 Japanese farmers prepared and applied to their fields 22,812,787 tons of compost manufactured from the wastes of cattle, horses, swine and poultry, combined with herbage, straw and other similar wastes and with soil, sod or mud from ditches and canals.  The amount of this compost is sufficient to apply 1.78 tons per acre of cultivated land of the southern three main islands.

From data obtained at the Nara Experiment Station, the composition of compost as there prepared shows it to contain, in each 2000 pounds, 550 pounds of organic matter; 15.6 pounds of nitrogen; 8.3 pounds of potassium, and 5.24 pounds of phosphorus.  On this basis 22,800,000 tons of compost will carry 59,700 tons of phosphorus and 94,600 tons of potassium.  The construction of compost houses is illustrated in Fig. 116, reproduced from a large circular sent to farmers from the Nara Experiment Station, and an exterior of one at the Nara Station is given in Fig. 117.

This compost house is designed to serve two and a half acres.  Its floor is twelve by eighteen feet, rendered watertight by a mixture of clay, lime and sand.  The walls are of earth, one foot thick, and the roof is thatched with straw.  Its capacity is sixteen to twenty tons, having a cash value of 60 yen, or $30.  In preparing the stack, materials are brought daily and, spread over one side of the compost floor until the pile has attained a height of five feet.  After one foot in depth has been laid and firmed, 1.2 inches of soil or mud is spread over the surface and the process repeated until full height has been attained.  Water is added sufficient to keep the whole saturated and to maintain the temperature below that of the body.  After the compost stacks have been completed they are permitted to stand five weeks in summer, seven weeks in winter, when they are forked over and transferred to the opposite side of the house.

If we state in round numbers the total nitrogen, phosphorus and potassium thus far enumerated which Japanese farmers apply or return annually to their twenty or twenty-one thousand square miles of cultivated fields, the case stands 385,214 tons of nitrogen, 91,656 tons of phosphorus and 255,778 tons of potassium.  These values are only approximations and do not include the large volume and variety of fertilizers prepared from fish, which have long been used.  Neither do they include the very large amount of nitrogen derived directly