Vol. XI. No. 273. 



THE AGRICULTURAL NEWS. 



335 



The disease does considerable damage in the district in 

 which it occurs, but it has been proved by experiments 

 conducted at the Botanic Gardens in Georgetown that it can 

 be successfully controlled by collecting and burying with 

 lime all diseased fruits lying under the trees, and by spraying 

 the fruits of infected trees with a 4 per cent, solution of 

 copper sulphate or with Bordeaux mixture. The first 

 application of the fungicide should be made when the fruits 

 are very young. 



It is interesting to note that all three of the diseases 

 dealt with in this article are probably due to species of the 

 genus Gloeosporium. ilembers of this genus and of its near 

 relative Colletotrichum are extremely common in the tropica 

 and cause damage to a number of fruits of various kinds; 

 examples are cotton boll anthracnose, ripe rot of bananas and 

 plantains, and cacao anthracnose, to mention only very few. 

 Often they are confined to the fruit and leaves, or 

 more generally all the soft green parts including the tips of 

 young twigs. Often too, the spots resulting from an individual 

 infection are limited in extent, especially on leaves, while on 

 fruits they may not spread or cover any considerable area until 

 the fruit commences to ripen. Practically all cases of this 

 kind of fruit rot can be dealt with by spraying the leaves 

 and young fruits, or in some cases the flowers before the 

 fruits set, and by collecting and burying with lime all 

 diseased and rotting fruit on the ground. 



THE DURATION OF SOIL FERTILITY. 



The following extract is taken from an account 

 of a discourse entitled Recent Advances in Agricultural 

 Science — the Fertility of the Soil, delivered at the 

 Royal Institution on Friday, May 24, by A. D. Hall. 

 The account appeared in Nature for August 22, 1912. 



The question of the duration of the fertility of the land 

 under continual cropping has excited much attention of late, 

 chiefly because the United States has begun to take alarm 

 about the reduced production of some of its most fertile 

 lands, as, for instance, the old prairie lands of the middle 

 West — a reduced production which, amongst other causes, 

 has helped to set in motion a stream of migrants from the 

 United States to the newer lands (if the Canadian North- 

 West. In the development of agriculture three distinct 

 stages may be observed. In the first place, we may have 

 a process of pure exploitation of the initial resources of the 

 soil, when the farmer is to all intents and purposes mining 

 in its fertility. This is the process which, in the main, has 

 been going on in America, and, indeed, in all the newer coun- 

 tries which have been opened up to agriculture during the last 

 two centuries. Not all virgin soils are rich, and the system 

 of cropping alternately with wheat or maize which prevails 

 over so much of North America has reduced great areas of 

 the land in the eastern States to such a poverty-stricken 

 condition that it has been allowed to go derelict. In the 

 great plains, however, where the first settler found 4 or 5 feet 

 of black soil, containing nearly I per cent, of nitrogen, 

 the land has kept up its productivity almost unimpaired for 

 nearly a century. If we suppose the black soil only 

 extended to a depth of 3 feet, and contained ^ per cent, 

 of nitrogen, both limited estimates, there would still be 

 30,000 lb. of nitrogen per acre — that is to say, nitrogen 

 enough for -500 crops larger than the American farmer has 

 been accustomed to win from that land — and yet in less 

 than a century such soils are beginning to show signs 

 of exhaustion. The farming of the kind just described 



is destructive; but in the older lands of the west of 

 Europe, which have been under cultivation for something 

 like a century, a conservative system has been devised 

 which is capable of keeping up the productive power 

 of the soil, though not, perhaps, to a very high pitch. 

 Perhaps the best example of this may be seen in the Norfolk 

 four-course rotation prior to the introduction of artificial 

 fertilizers. In this system a turnip crop, which was either 

 consumed on the ground or converted into manure, and so 

 returned to the soil, was followed by barley in which clover 

 was sown, and the clover, which also got back to the soil, 

 was followed by wheat. The farming covenants prevented 

 the sale of anything more than barley and wheat grain, 

 and the meat that was produced by the consumption of the 

 turnips and hay. Thus but a small proportion of the nitro- 

 gen taken out of the soil by the crop left the farm; the rest 

 was returned and used over again, although considerable 

 losses of gaseous nitrogen occurred during the making of the 

 dung. Both losses, however, were more than replaced by 

 the nitrogen which the clover crop gathered from the atmos- 

 phere during its growth. At any rate, we find that under 

 such a conservative system of farming the productivity of 

 the land remained pretty constant at about a level of 20 

 bushels to the acre from the time of Queen Elizabeth down 

 to the beginning of the nineteenth century. This conserva- 

 tive farming about 1840 began to give place to the third 

 stage in the development — intensive farming, rendered 

 possible by the discovery of artificial fertilizers and the cheap 

 freights which brought foreign fertility in the shape of cheap 

 feeding stuffs to the soil of this countr}'. By these means 

 the average production of the land of the British Isles has 

 been raised from the twenty-bushel level to something 

 over 30 bushels, and the most intensive farmers reach an 

 average level at least 25 per cent, higher. In their case the 

 soil has become practically a manufacturing medium trans- 

 forming the nitrogen and other fertilizing materials added to 

 it into crops, giving nothing to those crops from its original 

 stock, and indeed up to a certain point gaining rather than 

 losing fertility with each year's cultivation. 



Dominica and the Canadian National Exhi- 

 bition. — The Secretary of the Dominica Permanent Exhibi- 

 tion Committee reports on the exhibit of limes sent from 

 Dominica to this exhibition as follows (Dominica OfRcial 

 Gazette, September 6, 1912): — 



'I beg to report the despatch of twenty-seven barrels of 

 limes to the Canadian National Exhibition to be held in 

 Toronto at the end of this month, and of one box containing 

 Roseau plumes to assist in decorating the West Indian 

 section . 



'A large number of leaflets of the "Lancet's" article on 

 Dominica limes were also forwarded for distribution to 

 visitors at the Exhibition. 



'The exhibit of limes was contributed by the follow- 

 ing gentlemen to whom the thanks of the committee a»e 

 due; Dr. Nicholls, C.M.G ; J. F. Johnson, Esq.; A. D. 

 Riviere, Esq.; F. A. Gordon, Esq.; F. Potter, Esq , A. R. C. 

 Lockhart, Esq.; J. T. CJreg, Esq ; A. Emanuel, Esq,; 

 S. Didier, Esq., and the Dominica Fruit Growers' Association. 



'Owing to the action of the above it has been possible to 

 send on a good exhibit of Dominica limes, which, it is hoped 

 will prove of considerable assistance in advertising the fruit 

 in Canada. 



'The Superintendent of the Quebec Steamship Company 

 kindly allowed the exhibit to be conveyed to New York on 

 board the S.S. "Guiana" free of charge.' 



