and Magazine of the Ceylon Agricultural Society.— April, 1910. 



371 



CLEAN WEEDING FOR RUBBER. 



An experienced practical planter, with a strong 

 bent towards botanical sciences, asked by us 

 the other day if he believed in permitting the 

 growth of weeds on rubber estates, replied em- 

 phatically : "Theoretically it is all right: in 

 practice it is hopelessly wrong," and he went 

 on to relate how he had allowed an area of 

 rubber so to be covered with weeds with most 

 disastrous results. The growth of the trees was 

 retarded; and in the covering fotmed by the 

 weeds, all things that creep or fly, injurious 

 to the rubber tree, found refuge — bandicoots 

 and porcupine being particularly destructive. 

 We chink, whatever scientists may say, the 

 best practical planting experience in Ceylon 

 will be found to support clean weeding as 

 against unweeded estates. On the former the 

 growth of the rubber is unquestionably more 

 rapid, while the danger of damage from pests 

 is reduced to a minimum. Weeding is expensive 

 and this is a drawback to the system ; but weed- 

 ing is not going to be a permanent charge, for, 

 when the rubber grows up and covers the land 

 like a forest, the necessity for weeding on the 

 same scale as is required on a young plan- 

 tation will disappear. In any case the plautor 

 at present feels the money spent on weeding 

 brings a handsome return in very much quicker 

 growth and practical immunity from pests ; and 

 the returns from rubber will stand it. There is, 

 of course, a great deal to be said in favour of the 

 growing of cover plants instead of clean weed- 

 ing, and on sloping land especially, an im- 

 mense amount of top soil containing a large 

 proportion of humus can be saved by this 

 method. Able and experienced Ceylon planters, 

 however, have come to the conclusion that 

 growing such plants adds to the difficulty of 

 supervision on large areas of rubber. In short 

 the conclusion arrived at appears to be that 

 "the game is not worth the candle," aud 

 that clean weeding, well done, is the ' cheap- 

 est and most profitable system in the long 

 run. One rarely comes across a Ceylon rub- 

 ber estate now, which is not clean weeded. 

 A glimpse at the other side of the shield is 

 given by Mr. H.N. Ridley, Director of the Bota- 

 nic Gardens, Straits Settlements, in the March 

 issue of the Agricultural Bulletin of the Straits 

 and F. M. S. in an article on the Tillage of Soil 

 in the course of which he deals with " Denuda- 

 tion." The rainfall in the Malay Peninsula, he 

 says, is very heavy, and in exposed situations and 

 on slopes the loss of soil in a heavy shower is 

 very large. Where the rain runs over these 

 slopes, in a very few minutes it is seen to be 

 quite opaque from the soil washed off. With 

 this soil goes all exposed humus, decayed leaves 



and sticks When grass grows over the stiff 



clay soil it prevents denudation to a very much 

 larger extent, and in a fewyears produces a layer 

 of humus which fact itself shows that denuda- 

 tion has been stopped ; the roots also break up 

 the fctiff clay soil for some depth, and render it 

 possible for other roots to penetrate." Mr. 

 Ridley quotes the following observations made 

 in the Botanic Garden to support his theory :— 

 " In examining, the rubber plantations in 

 the Botanic Garden a very strong contrast 

 is to be noticed where a path through the 



trees has been opened and kept free of grass. 

 The ground is covered with roots of Para 

 rubber trees, the tope of which are an inch 

 and-a-half or more above the soil. Exam- 

 ining the ground on the other side of the tree, 

 which is not weeded, I find the correspon- 

 ding roots as much or more below ground, so 

 that the opened path (not opened many years, 

 and well shaded so that the rainfall is broken up 

 by the foliage above and does not fall so heavily 

 on the ground) has lost four or five inches of 6oil 

 since it was opened. In the case of another lot 

 of trees seen in Perak, where the ground was 

 bare, sloping and of stiff clay, roots as thick as 

 the wrist were completely exposed and dead, the 

 ends being gone. These roots must have been 

 originally some distance underground. The roots 

 of the Para rubber lie usually very high, but this 

 doubtless depends to a large extent on the depth 

 of the water, in the soil. In the damper parts 

 of the Botanic Gardens the rootlets of the Para 

 rubber come quite to the surface wherover there 

 are any decayed leaves and even sometimes rise 

 up between scraps of detached bark on the trunk 

 of the tree itself. Dead wood, old stumps are 

 quickly invested and permeated by them. This, 

 1 think, shows that Para rubber demands good 

 humus and is ready to utilise all it can find. The 

 fallen leaves are kept on the ground in all estates 

 to decay, but a vary large portion of the resulting 

 humus must be swept away by the heavy storms 

 of rain as there is nothing to prevent this in a 

 clean weeded estate especially on the slopes." 



Dealing with the question of "the Action of 

 Sun Heat," Mr. Ridley says : — 



" The action of the heat of the sun in cleared 

 ground is another factor which has to be con- 

 sidered. It is not at all uncommon to seethe 

 ground beneath the rubber trees deeply cracked 

 after hot weather. As Para Rubber roots high, 

 and frequently the rootlets come very near the 

 surface, under such circumstances a consider- 

 able number of the small growing roots must 

 be broken across by the cracking of the soil, and 

 further the great heat on the exposed earth will 

 probably injure the roots lying near the surface 

 even if the soil is not cracked. Injuries caused 

 by excessive heat, however, should only affect 

 young trees, where the ground is insufficiently 

 shaded by the trees themselves. A grass cover- 

 ing of the soil prevents cracking and also the 

 excessive heating of the soil. More experi- 

 ments are required to decide how far sun heat 

 on the bare soil is injurious to the young roots. 

 It has been the custom in the Botanic Gardens 

 to clear the soil round the palms of herbaceous 

 plants, grass, and other weeds, leaving a circle 

 of bare soil round each plant. This was done 

 for convenience in manuring. On one occasion, 

 however, the ground round the palms was 

 turfed up to the stem with the result that they 

 made quite a surprising growth, now the greater 

 part of the roots of the palms were really under 

 the grass, and the only ones affected were those 

 close to the base of the trees. The only conceiv- 

 able cause of improvement from turfing up the 

 circles is that these roots were protected from 

 sun heat, and consequent excessive drying. 

 Palms do not give much shade with their leaves, 

 aud the roots close to the stem are practically 

 exposed to the full sun all day." 



