March, 1909,] 



211 



GUMS, RESINS, SAPS AND EXUDATIONS, 



IS CLEAN WEEDING ADVISABLE ? 



(Extract from the Report of the Director 

 of Agriculture, P.M.S., for the year 1907). 



The remarks iu my last report as to 

 the value of a green manure plant, of 

 which I gave examples, in the place of 

 the general habit of regularly scraping 

 off weeds and allowing the sun and rain 

 free access to the soil, had little or no 

 effect at that time, but the desire to cut 

 down expenses has caused the sugges- 

 tion to be reconsidered. 



Weeding on most of the rubber estates 

 in the Federated Malay States is the 

 item costing most annually. This sum 

 is spent on labour, and represents in 

 many cases 70 per cent, or more of the 

 total labour of the estate. 



The object of the rubber planter is to 

 obtain as quickly as he can vigorous 

 trees of as large a girth as possible, at 

 the smallest cost, and in order to effect 

 this he keeps his fields as clear of weeds 

 as possible and so allows the rubber tree 

 to have all the moisture and plant-food 

 available in the soil. 



That clean weeding will show a better 

 result in the growth of the rubber trees 

 than allowing all and any weeds to grow 

 continuously, can no doubt be proved. 

 In Perak, however, some of the estates, 

 from want of money or shortness of 

 labour, have not been able to keep their 

 plantations clear of weeds and have 

 abandoned weeding. In some cases the 

 weeds are checked by being regularly 

 cut, but in others nothing at all has been 

 done to eradicate or discourage the 

 weeds. 



The growth of trees on such places is 

 somewhat poorer than trees in similar 

 conditions which have been kept free 

 from weeds, but the vigour and girth of 

 trees where the weeds have been allowed 

 to grow is not so markedly different as 

 the disciples of clean weeding would 

 expect to see. 



The belief in clean weeding is a tradi- 

 tion handed down from English farming 

 to tea and coffee planting in the East ; 

 good farming is associated with absence 

 of weeds. In Europe, the farmer of 

 cereals and other crops does not practise 

 the method of using certain plants as a 

 substitute for weeds. There are various 

 reasons why clean weeding in such crops 

 is a good policy in Europe, but annual 

 crops have to be treated differently 

 from permanent cultivations, and the 



conditions of laboui% cultivation, plant 

 growth and especially climate are 

 entirely different in the tropics from 

 those in temperate climates and conse- 

 quently methods have to be modified. 



The objections to clean weeding in 

 rubber cultivation in the Federated 

 Malay States and removal of all protec- 

 tion from the surface of the soil, are 

 that it allows a large amount of percola- 

 tion, of heat radiation and of evapor- 

 ation of moisture, also that heavy rainfall 

 on all but flat surfaces always results in 

 the constant removal of very large quan- 

 tities of top soil, which are either carried 

 away in streams or transferred to the 

 drains. It is not easy to estimate the 

 loss that takes place in tropical climates 

 where soils are allowed to remain ex- 

 posed and frequently scraped. An im- 

 mense amount of plant-food is continu- 

 ally also lost through percolation and 

 drainage ; the greater part of this is 

 absorbed by the roots of any plants 

 growing on the surface, and when the 

 leaves and stems of these plants are cut 

 this is to a great extent returned to 

 the soil. 



With the soil protected from the rays 

 of the sun the conditions of moisture 

 and temperature are most favourable to 

 the development of bacteria which are 

 responsible for the liberation of plant 

 food. Injclean-weeded land the top two 

 inches or more of soil are, because of 

 admission of heat and light, made impos- 

 sible for feeding roots and the prepar- 

 ation of food for them. When the ground 

 is covered this surface layer is kept 

 moist and useful for the feeding roots. 

 A considerable area is thus added to the 

 area of soil available for rubber roots 

 and the growth of the trees is improved. 



In addition to arguments for clean 

 weeding there is a local one, the danger 

 of the ground being taken possession of 

 by "lalang" {Imperata arundinacea), a 

 pestilent weed, which once allowed to 

 invade a plantation can only be eradi- 

 cated at enormous expense. This plant 

 is ubiquitous, is always one of the first 

 to cover newly-opened land„ and by far 

 the most difficult weed to eradicate. 



The experience gained in the use of 

 tapioca as a catch crop in rubber, which 

 obtains on some thousands of acres of 

 rubber showing excellent growth, is 

 another argument in favour of keeping 

 the soil covered up. Few, if any, crops 

 take more from the soil than tapioca, 

 but this loss of valuable plant-food in 

 the soil is to a great extent compensated, 



