Restoring the Soil - Canadian Foodgrains Bank

74Green Manure/Cover Crop SystemsS81. Rice/azolla. Azolla is an algae thatgrows in rice paddy water and fixes up to30 kg of nitrogen per hectare. It can bespread from paddy to paddy to fertilizethe rice virtually for free.44. Indonesia. Cowpeas and other edible gm/cc species often grow well on paddy fields duringseasons when there is not enough water in therivers to irrigate paddy rice.S82. Various crops/tephrosia. Tephrosiavogelii is planted as a contour barrier inmountainous areas to recuperate wastelands.This is done in various provinces ofnorthern Vietnam, especially Son La andThai Nguyen Provinces. Hundreds orthousands of farmers use this introducedsystem.S83. Various crops/yam bean. Yam bean (Pachyrhizus erosus) is used in southernVietnam, both as a gm/cc in rotation with other crops, and as a home-made insecticide.This traditional system is practiced widely by an unknown number of farmers.S84. Various crops/soybeans. Throughout Vietnam, soybeans (Glycine max) arerotated with other crops to improve soil fertility and to produce a valued food.Hundreds of thousands (if not millions) of farmers use this traditional system.S85. Maize/mungbeans. Mungbeans are intercropped in maize fields in northernVietnam. Both crops are planted at the same time. Thousands of farmers use thistraditional system.S86. Several crops/jackbean. The jackbean is occasionally grown on wastelands inYen Bai Province to recuperate the areas for the cultivation of many other crops.Jackbean seeds are broadcast on the land a week or so before the beginning of therainy season, at about two or three seeds/square metre. Where weeds are particularlyaggressive, you may need to cut the weeds back once, in order to allow the jackbean togrow vigorously. In such cases, planting the seeds (placing them about two cm underthe soil surface) might also solve the problem, because planted seeds will germinateabout two weeks sooner than if they are broadcast. The number of farmers who usethis traditional technology is probably well into the thousands.S87. Several crops/Indigophera spp. Indigophera trees are used like the jackbeanin S86, except the tree is usually used where farmers expect to spend several yearsrecuperating the wasteland. Again, the number of farmers who use this traditionaltechnology is probably in the thousands.S88. Cassava/rice bean. Bushy-type varieties of rice bean are intercropped with cassava.When the rice bean starts to compete with the cassava, the rice bean plants arepruned down to between 1 and 1.5 m in height, forcing the plant to grow laterallyrather than vertically. Hundreds, if not thousands, of farmers use this traditional system.