62 MANURING 



In old cocoa plantations it is generally found that 

 the roots have taken possession of the soil to such a 

 degree that it is impossible to bury the plants grown 

 for green-manuring without injuring the roots of the 

 cocoa trees. In such cases it would be advisable to pile 

 the plants in heaps until they decayed, and then to apply 

 the decomposed matter as a top dressing. 



With regard to the cultivation of leguminous plants 

 with the primary object of increasing the quantity of 

 nitrogen in the soil, it is well to point out that plants, 

 growing in a soil which does not contain nitrogen-fixing 

 bacteria, are not enriched by atmospheric nitrogen. 

 There are numerous kinds of these bacteria, and it does 

 not necessarily follow because, say, cow-peas produced 

 abundant nitrogenous nodules on their roots in a par- 

 ticular soil, that an Albizzia would be equally effective 

 in this respect. This particular soil, however, could 

 be inoculated with the form of bacteria associated with, 

 say, the Albizzia root nodules by broad-casting soil 

 brought from land in which Albizzias produced numerous 

 nitrogenous nodules on their roots. 



It sometimes happens that where a particular species 

 of LeguminoscE has not been previously cultivated com- 

 paratively few nodules are found on its roots the first 

 time it is cultivated, but the next time it is planted it 

 is generally found that the nodules wiU be produced in 

 much greater abundance, provided that the hygienic 

 condition of the soil is satisfactory. 



In 1900 the writer introduced the American cow-pea 

 as a green-cover crop in the cocoa plantation at the 

 Botanic Gardens, Gold Coast. When it was first sown 

 comparatively few nitrogenous nodules were produced 

 on the roots of the plants, but succeeding sowings gave 

 excellent results. After the cow-pea had been planted 

 for two or three years, by which time it had become 

 thoroughly acclimatised, it was found possible to grow 

 it aU through the year, and from three to four crops 

 were annually turned into the ground. Trenches were 

 dug between the rows of trees, and the cow-pea plants 

 were buried in these after being sprinkled with lime 

 or wood-ashes. Ptthecolobium trees were planted as 

 shade for the cocoa trees, and the prunings from these 

 were also biu-ied in the trenches. 



