4^ THE FERTILITY OF SOILS IN THE TROPICS 



for bananas to contain : K = 160 Ib. of potash, P = 80 Ib, 

 of phosphoric acid, N = 40 Ib. of nitrogen, applied per 

 acre twice a year to normal crops, and in double quanti- 

 ties 2(KPN) to crops on exhausted lands. 



For the experiments, two blocks of land at the two 

 ends of the small fertile table-land on Buderim Mountain, 

 where the land has been under cultivation for over twenty 

 years, were chosen. The results of both series are prac- 

 tically identical, so that we need study only the results 

 of one. 



The soil is a porous, red volcanic loam of good depth r 

 but at the time of preparing it for cultivation, so worn 

 out that even weeds and grass would barely grow on it. 

 The soil still contained, however, a good amount of 

 humus (in all cases determined by Rather's modification 

 of the Grandeau method [12]), arid a good amount of 

 total phosphoric acid and nitrogen, but was low in total 

 potash and lime, and very deficient in " available " phos- 

 phoric acid and potash (see analyses Table III). 



Each block was divided into two plots of one acre 

 each, the first being planted in 1909, and the second in 

 1910, after being kept under a green-manure crop for 

 the year. 



The land was ploughed shallow at first, with narrow, 

 furrows, and harrowed and cross-harrowed several times, 

 until all the couch grass and other weeds were removed. 

 One month before planting the ground was ploughed 

 deeply, followed by a sub-soiler working to a depth of 

 18 to 24 in. The ground was again harrowed and cross- 

 harrowed, to get the soil into a good mulch, before 

 making the plant holes in October. The bananas planted 

 were of the Cavendish variety, the most profitable and 

 also the hardiest of the dwarf varieties. The plant holes 

 W'ere made 12 ft. apart, giving 302 plants per acre, and 

 twenty-eight stools to each experiment. The first lot 

 of manure was applied in the plant holes, well mixed 

 with the soil, before planting the suckers, and the sub- 

 sequent applications were made as top-dressings, and 

 were slightly hoed under. 



I must here state that I believe it is better, in the case 

 of old plantations, to apply part of the artificial fertilizers 



