[August, 1912. 



Baron or Kelly was the earlier, their 

 systems being on similar lines. 



Space does not permit of drawing 

 attention to the numerous modern ex- 

 pedients for 



POT- WASHING, WEED KILLING, VERMIN 

 EXTERMINATION, 



and other necessary operations. All 

 these have been placed at the disposal 

 of the gardener within a comparatively 

 short period, and have wonderfully 

 lightened his labour and shortened his 

 hours.— B. in Gardeners' Chronicle. 



NITRATES IN THE SOIL. 



Plant Nutrition and Nitrogen. 



We give below a summary of a paper 

 by Dr. F. L. Stevens, of the Porto Rico 

 Agricultural College, originally read 

 before the Society of American Batei io- 

 logists at Washington, and reproduced 

 in Science of June 28th :— 



In spite of the close study of the re- 

 lation of nitrogen to plant life, during 

 the last two centuries, there still remains 

 some of the most fundamental questions 

 for solution. 



It has been clearly demonstrated that 

 Nitrogen is Essential to Plant Life, 

 and certain of its functions in plant 

 economy have been definitely ascertain- 

 ed ; but it is rather puzzling to find 

 that though a soil contains an abundance 

 of available nitrogen sufficient for a 

 number of crops, it is benefitted by the 

 addition of still more nitrogen. It has 

 been suggested that nitrogen compounds 

 may serve other uses than by being 

 absorbed or even assimilated. But what 

 uses ? 



As an element of nutrition, however, 

 the importance of nitrogen cannot be 

 questioned ; and this raises the question 

 "In what forms is Nitrogen avail- 

 able to the Plants"? 



The answer to this has been emphatic, 

 and has been accepted for many years, 

 but it is thought that it has been found- 

 ed on insufficient evidence and therefore 

 likely to be modified as the result of 

 further research. 



The generally accepted view is that 

 the nitrogenous food of plants takes the 

 form of nitrates. 



Nitrification is the result of two pro- 

 cesses — the conversion of Ammonia into 

 Nitrites and the latter into Nitrates — 

 each process depending upon the activity 

 of specific groups of bacteria. Ammonia 

 is thus essential to nitrification, and 

 ammonification of organic matter may 

 be said to go on in all soils. Only in 

 exceptional cases is ammonification re- 

 tarded by the action of predatory pro 

 tozoa. But 



there has been a misconception 

 in supposing that nitrifying organisms 

 are practically present every where— an 

 assumption which a bacterial soil survey 

 by Dr. Stevens shows to be unwarrant- 

 ed ; so that while there is no deficiency 

 in ammonification, the degree of nitri- 

 fication may fall below the requirements 

 of a good crop. 



The reason for nitrification being less 

 vigorous in some crops than in others 

 is not known. 



It may be due, in some cases, to ex- 

 cessive acidity, moisture, etc., but in 

 others no reason is assignable. Abund- 

 ance of organic matter cannot be said 

 to check it, since it proceeds in pure 

 cattle manure. 



" Denitrification," 



or the destruction of nitrates by bac- 

 teria is detrimental it it proceeds below 

 the Ammonia stage, i.e., if it results in 

 oxides or free nitrogen; The mixing 

 of nitrates with blood, cotton seed, &c, 

 should afford ideal conditions for deni- 

 trification, but no definite experiments 

 have been made to ascertain what con- 

 ditions favour or retard the process. 

 Dr. Stevens thinks it absolutely neces- 

 sary in bacteriological work to make 

 tests in soils and not solutions, pointing 

 out that organic matter inhibited nitri- 

 fication in solutions but not in soils. 



Is Nitrification of Superlative 

 Value 



as we have been led to believe by scienti- 

 fic workers ? 



