Gums, Resins, 510 



obtained by growing herbaceous legum- 

 inous crops : — 



(a) If properly done, there is a reduc- 

 tion in the cost of weeding, in fact this 

 cost becomes practically nil when the 

 green crop has become well established. 

 The seeds of the " green manure" should 

 be sown in regular rows, and when the 

 plants have grown to a height of one or 

 more feet varying with the species sown, 

 such a dense cover will be formed that 

 the weeds being deprived of the neces- 

 sary light and air, either die out 

 completely or have their growth con- 

 sideiably checked. At any rate seed 

 formation will not take place. 



(6) The partial prevention of wash. 

 The word partial is used here, because 

 on most rubber estates of a hilly nature 

 the rows of rubber trees run straight up 

 the hill, or in a slanting direction. The 

 green crop if sown iu rows between the 

 trees will leave small channels between 

 the rows of green crop for the soil to be 

 washed down. To prevent this, the crop 

 should be sown in rows across the slopes. 

 The roots and stems of the plants will 

 save a good deal of the soil. 



(c) Protection of the soil from the 

 direct rays of the sun. The bacteria 

 which bring about nitrification are 

 active within certain limits of temper- 

 ature, but cease to work when these 

 limits are exceeded. Hence the value 

 of the green cover which will keep the 

 soil at a more even temperature during 

 the twenty-four hours, keeping off the 

 direct hot sum's lays during the day, and 

 to some extent preventing radiation of 

 heat from the soil at night, allowing bac- 

 terial activity to be continued. 



Much remains to be learnt about green 

 manuring with herbaceous leguminous 

 crops in the tropics, as to which species 

 will give the best results in the different 

 districts and at the various elevations, 

 what amount of seed should be sown per 

 acre, when to sow, what distance apart 

 the rows should be, when to cut, etc. 

 The planter may find out a good deal for 

 himself, by looking carefully around his 

 neighbourhood for likely looking plants, 

 collecting the seeds, and sowing small 

 areas and comparing the results, a record 

 of which should be kept. In selecting a 

 plant remember that it is desirable to 



(1.) Rapidity of growth to allow the 

 crop to become established and to keep 

 ahead of weeds. 



(2 ) Some plants are of a climbing 

 nature which, though excellent as a 

 ''cover crop" or weed-smotherer, may 

 take to climbing up the tree and thus 

 incur labour in pulling it down. 



(3.) There should be a good yield of 

 green material per acre. 



[June, 1909. 



The following figures of experiments 

 with Green manure crops in Antigua, 

 West Indies, are quoted to show the 

 great variation in yield per acre of a 

 leguminous crop. These figures are. how- 

 ever, not applicable to Ceylon, as the 

 crops were grown under different condi- 

 tions : — 



lbs. per 

 acre. 



Barbuda Bean (8 months) ... 20,000 

 Woolly Pyrol (Phaseolus Mungo) 14,850 

 Cow peas Vigna sp. : 



White 10,570 



Black eye 9,440 



Clay 8,440 



Red 8,250 



Pigeon Pea (Cajanus indicus) 4,950 

 Polygonacese Buckwheat Pagro- 



pyrum 4,922 



Babricon Bean (Canavalia) sp. ... 3,520 

 The number of plants which might be 

 given a trial is very large, but when put 

 through a course of selection would be 

 greatly reduced, and perhaps only one 

 or two would fulfil all the requirements. 



As pointed out above, the same plant 

 may not answer the purpose in each 

 district A plant growing say at 700 

 feet elevation might not give the best 

 results at 1,500 feet, and even smaller 

 differences than this may affect any 

 particular plant. 



The Peradeniya Experiment Station 

 has a number of interesting plots of 

 different leguminous crops, the number 

 being added to as time goes on. One 

 plot of para rubber planted 15 feet each 

 way was marked out into 18" rows, a 

 string was stretched along each row 

 and coolies scratched a line in the 

 giound about 1"— 2" deep, and the seed 

 was sown on at the rate of 10 lbs. per 

 acre. Previous to the sowing no culti- 

 vation was given except the ordinary 

 weeding with mamoties as practised on 

 estates, and which cannot be strictly 

 termed cultivation. At the time of 

 sowing the surface soil was baked hard, 

 but in spite of this the crop has grown 

 splendidly, being at the present time 

 3£ feet high. It is very striking to 

 seethe luxuriant growth of the Crotola- 

 ria where the soil is loose, either from 

 an accumulation of wash or from old 

 cocoa pod holes. When the crop is 

 cut and mulched with the soil, the re- 

 sults, which will doubtless be published 

 will be of great interest. 



