Green Manuring

plowing the green parts of plants into the soil in order to enrich the soil with organic substances and nitrogen. The term was introduced by the French scientist G. Ville (1824–97). Green manuring requires the cultivation of green-manure plants, basically such legumes as lupin, seradella, sweet clover, lotus, lathyrus, clover, vetch, and crotalaria. The plants are usually plowed under in the same plot of land on which they are grown, but infrequently they are cut and used as fertilizer in other fields or for making compost.

The use of green manuring improves the soil’s physical and physicochemical properties, lowers the soil’s acidity, and increases the soil’s buffering, absorption, and moisture-retaining capacities. It also promotes the activity of beneficial microflora and enriches the organic substances of the plowed layer of soil. The mineralization of the green parts of the plants is followed by an accumulation of nitrogen assimilated by nodule bacteria and of other nutritive elements drawn by the roots from the deep layers of the soil. Fertility is thereby increased, especially in low-humus sandy and sandy loam soils, and yield is also increased. Green manure has approximately the same effectiveness as animal manure. In the nonchernozem zone of the USSR the average additional yield obtained by green manuring is 8–10 quintals per hectare of grain and 40–50 quintals per hectare of potatoes. Green-manure crops are planted after the harvesting of the basic crops, thereby intensifying the use of plowed lands.

Green manuring has been used since ancient times. It has been known for more than three millennia in the irrigated agriculture of China, India, Indonesia, and the states of Middle Asia. The system has been used in the Mediterranean countries since the fourth or third century B.C. In Central Europe, for example, in Germany and Poland, green-manure crops were first cultivated in the 19th century. In European Russia the first green-manure crops were raised in 1903 in Chernigov Province. Green manure is used in Asia, Europe, Africa, and, on a smaller scale, the Americas and Australia.

In the USSR green manure is used in the nonchernozem zone (Byelorussia, the Ukrainian Poles’e, Briansk Oblast). The plants are often sown in the spring on winter rye fields and are plowed under the same summer. Sometimes they are sown immediately after the harvest of the main crop, or they are sown in fallow fields (green-manure fallow). In the irrigated lands of Middle Asia, the Volga region, and other regions there is an intermediate crop of green-manure plants. In the second half of the summer Persian clover is sown between rows of cotton, and peas or winter vetch are sown among rice fields before the water is taken from the fields. Green-manure crops are plowed under in the fall or spring. In the humid subtropics of Transcaucasia, annual lupine, seradella, and lathyrus are grown in midsummer between rows of tea, citrus fruits, tung, geranium, and tobacco. The green parts of the plants are usually plowed under in early spring. It is also possible to sow green-manure crops immediately after harvesting the main crop. In all zones it is best to combine green manure with inorganic phosphorus and potassium fertilizers.