Vol. IX. No. 207. 



THE AGRICULTURAL NEWS. 



107 



spcnf/leri, also a .serious pest. The shot borer of the cane 

 {Xi/ieboms perforanfi) also belongs to this group. 



In the I'nited States, the Me.xican cotton boll weevil 

 occurs as the greatest enemy of cotton that is known, and it 

 may perh^ips rank as the most serious pest ever known to 

 Agriculture. 



A sufficient number of e.xani[iles has been given to show 

 tliat all weevils are undesirable insects. It is hoped that 

 readers of the yly)*V"//Hi'a/ A'Vw.'! will realize the importance 

 of distingui.shing between the injurious and the beneficial 

 insects mentioned. 



THE FERTILIZING INFLUENCE OF 



SUNLIGHT. 



The following e.xtracts are taken from a letter in 

 Nature, of February 17, 1910, signed by A. Howard 

 (Imperial Economic Botanist, India: sometime Mycolo- 

 gist to the Imperial Department of Agriculture for the 

 West Indies). They are of special interest in relation 

 to the articles that apfieared recently in the Af/ri- 

 eidtural News, Vol. IX, Nos. 202 and 203, entitled 

 ' The Balance of Life in the Soil': — 



The past history of agricultural science furnishes several 

 examples of belated explanations of the utility of practices, 

 the value of which has long become a tradition among practi- 

 cal men. The explanation of the value of leguminous crops 

 in agriculture is a good example. While the recognition of 

 the role of these crops iTi increasing the nitrogen-supply in 

 the soil has done much to improve agriculture in new 

 countries, it has only served to provide a scientific approval 

 of the cultural practices of ancient civilizations, such as that 

 of India, where from time immemorial it has been the custom 

 to grow leguminous crops in the rotation, and also as ('ue of 

 the constituents of the mixed crojts cultivated in many parts 

 of the country. 



Agricultural science has recently provided another 

 explanation of an ancient Indian practice. In the Journnl 

 of A;/n'cultiirnl Science of October last, Drs. Rus.sell and 

 Hutchinson have found that partial sterilization of the soil 

 by heating, or by poisons, leads to an increase in the supply 

 of nitrogenous compounds and to increased fertility. These 

 investigators state that partial sterilization of the soil kills fitf 

 the phagocytes which live on bacteria, and also large organ- 

 isms inimical in other ways to bacteria. At the same time 

 the soil bacteria are killed off, but the spores remain, which 

 germinate, and rapidly multiply when the soil is moistened. 

 The new bacterial cultures increase at an enormous rate, and 

 the resulting nitrogenous plant food becomes so great that 

 [ilant growth is greatly stimulated. The authors then go on 

 to state (p. 120): 'There is reason to suppose, therefore, that 

 the large destructive and competing organisms will be found 

 of common occurrence in ordinary soils, checking the benefi- 

 cial bacteriii and limiting fertility. An important jiractical 

 problem arises : Is it possible to supi>ress them in ordiruiry 

 field soils by any economical and practical process?' 



The practice among many of the best cultivators in the 

 IndoGangetic plain furnishes a most emphatic affirmative 

 to the above iiuestion. It has been the practice of the 

 ryots for centuries past to expose the alluvial soils of the 

 plains of India to the intense heat and light of the Indian 

 liot weather in April and Maj-. The beneficial result on the 



succeeding crop is extraordinary, and has all the eflFect of 

 a nitrogenous manin-ing. It is much more than probable that 

 the result of this weathering is a partial sterilization nf the 

 .soil, and that Russell and Hutchinson's explanation is the 

 correct one. Except in market-garden crops near the cities, 

 and in crops like sugar-cane and tobacco, manures are but 

 little used in India. The growih of leguminous crops and 

 the weathering of the soil during the hot season appear to 

 be sufficient to keep up the fertility. More nitrogenous 

 manure would, no doubt, be an advantage, but a great deal 

 could be done by the cultivators themselves in weathering 

 the soil during the hot weather in a more efficient manner 

 than at present. . . . 



...In collaboration with Jlr. H. M. Leake, Economic 

 liotanist to the Government of the United Provinces, we have 

 in progress a series of experiments in which the practical 

 effect of weathering during thejiot months, on both the yield 

 and ([uality of wheat is being ascertained. 



YIELD OF LATEX FROM YOUNG CEARA 



RUBBER TREES. 



Some investigations that were made in connexion with 

 this subject are described in Rulletin 19 of the Hawaii Agri- 

 cultural Experiment Station, entitled £.rpi'i-!iiie>>is in Tap2n7i(/ 

 Ceara liiMer Trees. The first trial was made with eighty trees, 

 which averaged 1.3] inches in circumference at 3 feet from 

 the ground, and were 2.3 feet in height; the first branches 

 were at 10 feet from the ground. The trees were tapped by 

 means of one vertical cut each day,and nearly thirty-seven hours 

 of labour were required for tap]iing them, collecting the latex, 

 and obtaining, by coagulation, lA lb. of dry rubber. It was 

 found that four ordinary .lapanese labourers, who had had no 

 previous experience of the work, could tap eighty trees in 

 a period which varied between seventeen and forty minutes. 



In a .second lot of trees, which numbered 160 in this 

 case, two vertical cuts were made instead of one, and it only 

 required forty hours of labour to tap the trees, collect the latex, 

 and obtain 7i lb. of rubber, of which 2 J ft), was scrap. The 

 experiment showed that, with the prices which obtained for 

 rubber at the end of 1909, when two vertical cuts were made 

 daily, jirofitable returns were obtained from two-year-old 

 trees. It has to be considered that the labour of tapping 

 small trees is greater than that of dealing in the same way 

 with large ones, and that the yield of latex is much lower, so 

 that, with the same amount of labour, more rubber would 

 have been obtained from older trees. 



It was found, during the experiments, that one labourer 

 can tap about fifty trees in an hour, while the latex produced 

 by the work of two such labourers can be collected by one. 

 Subsequent experiments with mature C'eara rubber trees 

 have shown that about J-oz. of dry rubber may be obtained 

 as a daily yield from each tree. This leads to the conclusion 

 that three men should be able to obtain rubber from mature 

 trees at the rate of about lib. per hour. 



In the matter of the relation between the -size of the tree 

 and the amount of tapping that can be effected, it was found 

 that the area of bark on plants 4 inches in diameter will 

 permit of tapping, with one vertical cut daily, for two suc- 

 cessful weeks, or with two vertical cuts, every day, for one 

 week. Larger trees would, of course, permit of the collection 

 of latex for a much longer period. 



