etiver grass(Vetiveria zizanioides)planted in line with contour furrows in slopingciturs groves of red soil grew and developed quickly and strongly,with an annual yield offresh herb plant of about 15t/hm￣2.The plants were cut down to cover the surface soil underthe citrus trees so that the air temperature and soil temperature in the citrus groves wereboth decreased effectively,and on the contrary,the air relative humidity and water content ofsoil were both increased during the period of high temperature and...