Gums, Resins, 



390 



[November, 1909. 



and gradually becomes clearer when 

 many tons of water have passed tbrougb 

 tbe soil, will show tbat this same process 

 of exhaustion of the soil is sroing on 

 very rapidly on clean weeded flat lands 

 though not to the same extent as on 

 the hillsides. 



Most practical planters have observed 

 that the roots of plants in the tropics 

 grow more quickly and vigorously when 

 the earth where they are growing is 

 shaded from the sun, and for this reason 

 the .surface of nurseries is covered with 

 a thatch of grass or other convenient 

 covering. 



These arguments seem in themselves 

 sufficient to induce a trial of cover 

 plants ; but the additional argument 

 that the process of clean weeding is 

 continuous and the most costly of all 

 the work on a rubber estate before it 

 comes into bearing should be a further 

 reason for the adoption of the system 

 of cover plants. 



Various cover plants have been used 

 on acreages varying from 400 acres, and 

 practically in all cases with successful 

 results. 



It is unfortunate for the increase in 

 the belief in this method of rubber cul- 

 tivation that a large number of the 

 planters who tried cover plants did so 

 on the weediest and worst-drained 

 parts of their estates. It would be as 

 fair to test a food, which is recommend- 

 ed for supporting working men, on 

 emaciated and abnormally weak persons, 

 and when it did not produce the results 

 hoped for, deeming it a failure. 



Another reason for some planters not 

 finding the use of cover plants so perfect 

 a substitute for weeding as they hoped 

 was that cover plant (very often crota- 

 laria) was sown broadcast, and it has 

 been found by experience over large 

 areas tbat this method of planting 

 cover plants is wastef ul and very much 

 less effective than sowing the seed by 

 dibbling, plauting in furrows, or similar 

 methods. The loss may be due to the 

 exposure of the germinating seed to the 

 sun, or to its being washed along when 

 the tender rootlets are beginning to form, 

 or birds may eat the seed, but what- 

 ever is the cause it is always found that 

 the proportion of the seed-producing 

 plants is very small indeed. 



On the other hand, the planting in 

 lines, the seed being slightly covered, 

 results in 80-100 per cent, of the seed pro- 

 ducing healthy plants. 



In plantirg cover plant on steep land 

 it is imperative that the lines should 

 follow the contour of the land; when 

 they are made to run up and down the 



hillside the seed will be washed down 

 with the loosened earth. This results 

 in the seed being massed in one place, 

 and the young plants growing closely 

 together in clumps at the foot of the 

 lines. 



The use of cover plants in place of 

 clean weeding is now, after three years' 

 constant advocacy, very generally con- 

 sidered as an economical and practical 

 practice, which I have no doubt will 

 greatly increase when the benefit to the 

 rubber and the saving in expense have 

 been proved on a large number of estates. 



The relative advantages of various 

 plants as cover plants for rubber clear- 

 ings is an important question to decide 

 before proceeding to lay down fields 

 with one or other. Leguminous plants 

 possess the property of increasing the 

 amount of available nitrogen in the soil 

 by means of bacteria living in their roots 

 which obtain nitrogen from the air, and 

 in this respect should be preferred to 

 other plants. 



The chief thing to consider in laying 

 down a cover plant is rapidity and 

 cheapnesss in thoroughly establishing it, 

 and if a plant is found to quickly take 

 possession of the soil and cover it to the 

 exclusion of all others, the fact of its 

 not being leguminous should not weigh 

 against it. 



The ideal plant for the purpose of 

 protecting rubber land and eliminating 

 or reducing very considerably the weed- 

 ing bill, is a plant which grows not more 

 than a foot to 18 inches high, is perma- 

 nent or persistent for three or four 

 years, producing shade over the ground, 

 growing so luxuriantly as to exclude 

 weeds without forming a thick turf, is 

 leguminous, has no thorns or spikes to 

 interfere with coolies working, has no 

 leaves, fruit, or flower which will attract 

 vermin or other animals. 



None of the plants at present in use, 

 or being tried in the experimental plots 

 of the Agricultural Department, fulfil 

 absolutely all these requirements, and 

 it is probable that a plant will yet be 

 found better than any at present tried. 



The condition on differenc estates in 

 Malaya do not vary very greatly, but 

 the differences are sufficient to make 

 some places specially favourable to 

 one cover plant and other places to 

 other plants. 



In different districts on sloping and 

 flat land with different soils and some 

 estates it is found that in some passion 

 flower will thrive and rapidly cover the 

 land where the sensitive plant or crota- 

 laria do not grow vigorously. On other 



