November, 1912.] 



355 



GIRTH MEASUREMENTS OF HEVEA. 



The following short account of the experiments made by Mr. P. G. 

 Spring in three small plots of rubber at Kuala Lumpur on girth mea- 

 surements is from the Agricultural Bulletin of the Federated Malay- 

 States. 



The jungle was felled and burned during February and March of 1907 

 and all timber removed from the land. Each plot was planted with six 

 months old stumps at distances of 12^ x 25 feet ; the stumps being more 

 or less of similar size. Plot (1) referred to in the table given below was 

 changkolled every month to a depth of 2 to 3 inches ; plot (2) once every 

 three months to a depth of 6 to 7 inches. In plot (3) seed of Terphrosia pur- 

 purea was drilled in rows 3 feet apart in the beginning of January, 1910. 

 The tephrosia was pruned on an average twice in a year and the land 

 surface weeded when the lalang grew to a height of 12 to 16 inches. In 

 August, 1912, the girths of all the trees were taken at a distance of 1 foot 

 from the base of the tree. 



The results obtained are as follows :— 



No. of 

 Plot. 



Treatment. 



No. of Trees 

 in Flot. 



Date of Planting. 



Date of Girth 

 Measurement. 



Total Girth of 

 Trees. 



Average 

 Girth of 

 Trees. 



1 



Weeded once each 





December 



August 



inches 



inches 





month 



107 



1909 



1912 



985 



9'2 



2 



Weeded once every 















three mouths 



107 



1909 



do 



do 



6 '5 



3 



Tephrosia pur- 









do 







purea 



107 



1909 



do 



5 8 



It will be seen by referring to the table that the trees in the land 

 weeded every month have an average girth of 9"2 inches while the 

 girth of the trees in the plot weeded every three months have an 

 average girth of 6*5 inches. Comparing those two plots, there are prob- 

 ably two factors which affected the growth of the trees: — (1) extent of 

 cultivation and (2) the amount of weeds present in the respective plots. 

 I am rather of opinion that the greater girth obtained in plot (1) is chiefly 

 a question of cultivation. 



The objects of cultivating a soil are :— to allow the air to enter the 

 soil and thus promote oxidation ; to allow vegetable and mineral matter 

 to decompose more rapidly and supply plant food ; to loosen the particles 

 of a soil and mix them ; to allow air and water easy access to roots and 

 the soil; to promote absorption of moisture and gases from the atmos- 

 phere ; to encourage the growth of bacteria which help in the formation 

 of nitrates ; to check the growth of anaerobic bacteria which promote the 

 liberation of free nitrogen from nitrates ; to allow the roots to penetrate 

 easily into the soil. 



The climate may aff ect the soil to a small depth rendering it hard 

 and inert, a state which I am rather of opinion does exist, in which 

 case merely turning over the surface layer is promoting fertility, 



