October, 1909.] 



291 



Saps and Exudations. 



differently treated from a manurial 

 point of view. At the end of two years 

 the circumferences of the trees on the 

 different plots were measured, at one 

 yard above the ground, and the average 

 for each plot was calculated. The results 

 are shown as follows : — 



Plots. 



Manuring 

 per tree 



Average 

 Circum- 

 ference 

 of Stems 



I. 



No 

 Mannre. 



9 incbet 



II. 



Completely 

 Manured. 



2 lb. Pea-nut cake 

 meal 



L2 oz. Double super- 

 phosphate 



8 oz. muriate of 

 Potash. 



14 inches 



111. 



Manured without 

 Potash. 



2 lb. Pea-nut Cake 

 Meal 



12 oz. Double Super- 

 phosphate 



12 inches 



From the results of these and other 

 experiments it is clear that potash may 

 be made to play a very important 

 part in the manuring of rubber. While 

 this ingredient may be applied fairly 

 abundantly with advantage, nitrogen 

 may be used with a little more caution, 

 in order to prevent a too luxuriant 

 growth of foliage. Phosphoric acid is 

 also, of course, indispensable, and 

 although it may not benefit the wood to 

 the same extent as potash, it serves like 

 it to counteract the stimulating effect of 

 nitrogen on the development of the 

 foliage. 



Bearing the foregoing facts in mind, 

 we may lay down manurial mixtures of 

 the following compositions, as being 

 suitable for application under different 

 conditions. 



I. 



The mixture is suitable for land rich 

 in nitrogen and where there is a good 

 leaf growth. 



Phos- Nitro . 

 potash, phorio ^i' 

 acid. fien - 



28 per cent, muriate of potash 14 — — 

 Vb ,, superphosphate (18) — 4 - 50 — 



20 ,, „ bonemeal (28) (1) — 5'60 0-2 

 17 „ „ oilcake (6) — — \'" 



10 ,, ,, sulphate of ammonia — — 1 "6 



100 ,, contains 14 101 3'1 



400 to 300 lb. per acre to be applied. 



II. 



The second mixture is recommended 

 for land which is in a poor condition 

 with regard to its nitrogen content. 



Pbos- Nitro . 

 Potash, phone 



acid. gen - 



20 per cent, muriate of potash. 10 — — 



30 ,, „ sulphate (18) — 5-4 — 



10 „ „ bonemeal (181) — 2 8 01 

 24 ,, sulphate of ammonia — — 1'3 

 15 ., ,, oilcake (6) — — 1*0 



100 



contains 



10 8-2 6-0 



400 to 700 lb. per acre to be applied. 



As to the form in which the different 

 plant foods should be supplied, no hard 

 and fast rule can be laid down. This 

 will depend on the climate, condition of 

 the soil and also the kinds of artificial 

 manures at one's disposal. In cases 

 where the soil is deficient in organic 

 matter, it will pay to employ as a source 

 of nitrogen organic manures like fish 

 guano, blood meal, oilcake, or as in the 

 above case, for the purpose of producing 

 a more rapid effect, a mixture of one or 

 more of these substances with the 

 inorganic manure, sulphate of am- 

 monia. 



Phosphoric acid can also be employed 

 in various forms such as superphosphate, 

 basic slag or bonemeal. While super- 

 phosphate is the most active of these 

 manures, basic slag owing to its high 

 lime content will be found valuable for 

 soils deficient in this particular con- 

 stituent. For land, which is lacking in 

 organic matter, the use of bones is 

 specially recommended. 



Potash may be given in the form of 

 muriate or sulphate of potash, but in 

 many cases muriate seems to produce 

 the better results in the dry cli- 

 mates. 



These artificial manures can be sprin- 

 kled round the tree at a distance of 1 to 

 li feet from the stem for each year of 

 the plant's growth and then very lightly 

 forked into the soil. In order to preveut 

 the manure from being washed away by 

 the rain, however, a shallow trench may 

 be cut round the tree, the manure 

 forked therein and the surface soil then 

 replaced. 



Green-manuring or the system of grow- 

 ing and plough-into the land special 

 leguminous crops might also be practised 

 with advantage in the cultivation of 

 rubber. In this way it is possible not 

 only to add to the soil a large quantity 

 of nitrogen from the atmosphere, but 

 also to improve greatly the physical 

 condition of the soil by means of the 

 organic matter. An essential condition, 

 however, to the success of green-manur- 

 ing is that the leguminous crop in 

 question must be well manured with 

 potash and phosphates in order to 

 ensure a rich production of green plant 

 material. While green manuring will 

 be found an excelleut substitute for 

 farmyard manure in cases where the 

 latter is not available in sufficient 

 quantity, its adoption must be regarded 

 merely as supplementary to the use of 

 artificials. 



