PLANT INDUSTRY 385 



is also directed towards accelerating the regeneration process while 

 the land is left fallow. Most of the methods employed fall under 

 the heading of forestry rather than of agriculture, and have been 

 mentioned in Chapter VII. 



Uganda provides an example where wild grasses can be em- 

 ployed with benefit to restore fertility. Experiments have been in 

 progress since 1932 at Bukalasa with planting grasses, particularly 

 the larger kinds such as elephant grass {Pennisetum purpureum) , as soon 

 as cultivated land is vacated. The results to date show that the 

 rest period, which is usually about ten years, can be reduced to 

 four years by this means. Similar studies have been started at 

 Serere and Ngetta and are also favourable. The introduction of 

 green manures and other methods foreign to native practice has 

 met with little success, but the use of grasses is regarded as a most 

 promising improvement to a system which already exists and which 

 has stood the test of time under the local conditions of soil and 

 climate. The Director has pointed out with some justice that the 

 natural regenerators of soil throughout the world are either grass 

 or forest, and that nature herself does not employ legumes for the 

 purpose, except in a minority compared with other plants. He 

 considers that the attention attracted to legumes as a result of 

 scientific work on their nitrogenous properties has led to neglect 

 of the possibilities of utilizing the ordinary processes of nature. 



MIXED CROPPING 



Mixed cropping, which consists of growing more than one crop 

 on the same soil at the same time, is practised by natives in many 

 places, and has received attention from agriculturalists in several 

 territories. One advantage of the system is that it may enable an 

 export crop to be grown without unduly extending the area of 

 cultivation or increasing the amount of labour involved in tilling. 

 The Nigerian agricultural department has found that the native 

 methods of growing Ishan cotton and other cottons of this type 

 as a mixed crop are more profitable than growing it as a pure crop. 



In the yam-growing districts in the Northern Territories of the 

 Gold Coast, particularly around Tamale, a similar practice is 

 almost universal. Definite combinations of crops grown in the 

 same year have been evolved to suit the particular types of soil. 



