AGRICULTURE 4 i 3 



Another series of investigations that may have considerable outcome in practice deal 

 with the results of the partial sterilisation of soil. Various observers had noticed from 

 time to time that a soil which had been heated to the temperature of boiling 

 water was thereby markedly more productive than before. A similar in- 

 crease of fertility follows treatment with volatile antiseptics such as chloro- 

 form, toluene, etc. Russell & Hutchinson, working in the Rothamsted Laboratory, 

 arrived at an unexpected solution of the problem. They found that the increased 

 productivity was due to the rapid rate at which the soil developed ammonia after the 

 treatment; the ammonia did not change further to nitrates because the nitrifying or- 

 ganisms had been destroyed, but the plants utilised the ammonia directly. The treat- 

 ment moreover did not completely sterilise the soil; a small number of organisms, capable 

 of decomposing the nitrogenous residues in the soil into ammonia, are left and multiply 

 with great rapidity, until within a few weeks the numbers of bacteria within the soil are 

 far in excess of those prevailing in the untreated soil. These bacteria account for the 

 increased production of ammonia and therefore fertility of the treated soil. Further 

 investigation led to the conclusion that normal soil contains agencies restricting the 

 development of bacteria and therefore the rate of ammonia production and consequent 

 fertility, which negative agencies are wholly removed by the heating and treatment with 

 antiseptics, and these agencies were identified as. protozoa, amoebae, etc., living in the 

 soil, large organisms which feed upon living bacteria. They are killed off by the partial 

 sterilisation, and on the removal of this check the bacteria are enabled to increase their 

 numbers to an extent previously impossible, thus raising the rate of production of plant 

 food from the otherwise unavailable nitrogenous material in the soil. It has been found 

 practicable to apply these principles with commercial success to the treatment of green- 

 house soils, which rapidly degenerate and have to be replaced because the conditions of 

 warmth and moisture are especially favourable to the development of protozoa. Again 

 the soil of sewage farms rapidly deteriorates and becomes ineffective towards the puri- 

 fication of sewage from the same causes, but can be restored to its proper character. by 

 partially burning the soil or treatment with antiseptics. Much progress has not been 

 made with the treatment of ordinary farm land, as heating is out of the question; the 

 desideratum is a cheap antiseptic of the right degree of volatility. 



The rediscovery and extension of the Mendelian theories of inheritance have placed 

 the question of breeding new varieties of domesticated animals and plants upon a new 

 basis, insomuch as they offer a method by which the attainment of a particu- 

 a nd cereals ^ ar desired result can be foreseen. While animals present certain special diffi- 

 culties because of the complexity of the factors involved in such characters 

 as meat, milk or wool, plants are simpler, and considerable progress has been made in the 

 application of breeding on Mendelian lines to the production of new varieties of cereals, 

 which afford particularly easy material for work because they are naturally self fertilised. 

 The English and West European varieties of wheat for example are distinguished by 

 their capacity for heavy cropping, but they do not command the higher range of prices 

 because flour made from them is not " strong," i.e. it does not make large loaves and is 

 starchy rather than nitrogenous in comparison with the wheats grown in the east of 

 Europe, Manitoba, Kansas, etc. Some of the latter wheats preserve a considerable 

 measure of their strength and high nitrogen content on English soils, but the yield is too 

 low to enable them to be profitable even at the higher price per bushel. Biffen at Cam- 

 bri Ige has shown that this high nitrogen content and strength is a Mendelian character 

 that segregates in the offspring of cross-bred parents, and has succeeded in breeding one 

 or two varieties which combine to a marked degree the cropping powers of the English 

 wheats and the strength of other varieties, and one at least of these new cross-breds is 

 now being grown commercially in England. Other experiments that promise success on 

 a working scale deal with the breeding of wheats proof against rust, a disease which 

 seriously affects the yield of wheat in many of the warmer countries and may indeed 

 prohibit their growth, as over much of S. Africa. A rust-proof species had been found, 

 and though its miserable yield deprives it of all commercial value it transmits its 



