Vol. VIII. No. 195. 



THE AGRICULTURAL NEWS. 



331 



FUNGUS NOTES. 



MINUTE FORMS OP LIFE IN THE 

 SOIL. 



A.-i the knowledge of the minute orgaaiisms whii li li\e in 

 the soil increases, the tendency grows -u'hich places them in 

 a position of greater importance every day. The recognition 

 of this importance i.s enhanced all the more as the fact is 

 grasped that the higher plants are mainly' aflfected favourably 

 or adversely by soil conditions in an indirect manner. Such 

 plants depend chieHy upon the changes that are caused by 

 the life-proce.'ises of the microscopic organisms in the soil fur 

 the origin and continuation of a state of that medium which 

 will enable them to flourish. The herbivorous animal is 

 dependent upon the existence of suitable conditions in the 

 soil before it can feed indirectly upon the substances which 

 it eventualjy gains from it, and from the air, through the 

 medium of the plants which it takes |into its system. 

 Similarly, those plants themselves are largely dependent 

 upon favourable conditions for the exist4nce of still lower 

 organisms for the unlocking of the stor| of food, which is 

 present, but not available for them, in the soil. 



The chief forms of minute life that work beneath the 

 .surface of the ground are the bacteria, true fungi, moulds 

 and yeasts. The magnitude of this work, both beneficial 

 and clestructive as far as the higher plants are concerned, is 

 hardly realized This is, perhaps, because the minuteness of 

 the individuals is well recognized, the limitations as to effect 

 being gauged, in the case of bacteria for instance, by the 

 fact that the measure of their diameter is only about 

 one- twenty -five thousandth of an inch. ;When it is re- 

 flected, however, that a cubic inch of soil can contain 

 about 10 billions of these before there is undue competi- 

 tion in the matter of food supply, .the capacity of 

 such organisms for effecting rapid and deep-seated changes 

 can be more fairly a[)preciated. Bacteria are most abundant 

 to a depth of 1 foot beneath the surface. Below this, they 

 decrease cjui'-kly in number.^, though it was found by 

 Fraenckel in Berlin that that they were still present in 

 considerable numbers at a depth of .9 feet below the pave- 

 ments. 



It is ■\\ell known that the effects of various bacteria on 

 the media in which they live are very different. Some 

 decrease the amount of nitrogen ; others, when supplied 

 with air, increase it. Some reduce compounds of sul[)hur, 

 such as bydrated sulphate of calcium (gypsum) and set free 

 hydrogen sulphide ; others make use of this hydrogen sul- 

 phide, emi)loyi:ig the sulphur which they liberate from it as 

 part of their food. Some re(iuire organic matter in oixk-r 

 that they may continue an active existence, while oihers 

 can live on an inorganic medium, and so on._ The favourable 

 or unfavourable conditions of the soil in regard to each will 

 determine whether or not that kind will "flourish. This i-; 

 partly why the same soil, under dilferentj conditions, will 

 exhibit such varying properties in regard to, its capacity for 

 supporting crops. Again, if such a soil is sabjected to treat- 

 ment such as draining, ploughing, or cultivation for the 

 purpose of ameliorating its state, it is not long before the 

 evidences of response are at hand. As bacteria biing about 

 in a large degree the causes of the changes that supply those 

 evidence.s, and as each kind of bacterium has its own definite 

 effeer, it must be a fact that these organisms have the power 

 of changing the balance of numbers of the different species 

 irk a comparatively .short time. It ia easy to account for this 

 fact when it is remeanbcred that each individual lives about ■ 



thu-ty-five minutes, and at the end of that time, if conditions 

 are favourable, forms two new individuals by division, so 

 that, at the end of twelve hour.s, in the event of the survival 

 of the whole of its offspring, its descendants would number 

 four mdhons For every state of the soil there is a bacterial 

 balance, as each kind will reflect the favourableness of its 

 environment in the magnitude ..of its numbers, the chief 

 factors iDeing temperature, amount of moisture, supply cjf 

 food, presence or absence of air, effect of the excretory 

 products of other bacteria, and the rate at which removal 

 of Its own waste products takes place. In a change of 

 environment, that is in the soil, those forms which are 

 not suited to the new conditions suffer a check which 

 IS sufficient to reduce their rate of propagation, and therefore 

 to lessen their numbers. At the same time, such as are 

 favoured by the new state of attairs will, as has been seen, 

 increase at a sufticient rate to produce an entirely new bac- 

 terial balance, with most of the new phenomena due to its 

 influence, in a very .short space of time. 



The soil, then, is not the^rigidly constituted, slowly 

 changeable medium that was pictured so long in the minds 

 of the earlier investigators. It is not a collection of matter 

 which is merely undergoing comparatively slow chemical and 

 physical changes. It is alive, in the truest sense of the word. 



A GREEN MANURE AND FIBRE PLANT. 



On page 271 of the present volume of the Ar,r/r„/fand 

 A'ews, a description is given of a plant, Sesbani'u acu/eata, 

 which IS attracting attention in India as a green manure and 

 fibre plant. In Progress Report, No. XLV, of the Ceylon 

 Agricultural Society, an analysis, 'tof the material obtained, 

 when a crop of this plant is cut and allowed to dry naturally' 

 is detailed. This is given below, and for the purposes of 

 comparison, similar information, in regard to naturally dried 

 weeds and leaves, from the Botanic Station, Dominica, which 

 is taken from the West Indian Bulletin, Vol. ^TI^, p. 49 

 is also tabulated : — ' ' 



Sesbania aculeatd. Weeds, leaves etc. 

 Per cent. Per cent.' 



Water 13'5 12 -6 



Organic matter 803 • 77-9 



Ash 6-2 9-.^ 



Nitrogen 

 Potash 

 Phosphoric acid 



2-80' 

 97 

 13 



212 

 0-64 

 0-lG 



In making comparisons by means of the dat.i which 

 ap[)ear in the above table, it must be rememb'jred that the 

 grass, _ leaves, etc., which were obtained from the Dominica 

 Botanic Station, contained pods and 9ther debris of leguininous 

 plants. This accounts for the fact that this material has 

 a nitrogen content which is not ve,ry far below that of the 

 leguminous plant Sex/ianin <iruleata., 



The amounts of water and organic matter that are present 

 are very similar in the two cases. It must be taken into 

 account, however, that the grass, leaves, etc , probably lost 

 more water in drying than the SesbcUiia, which is an under- 

 shrub, .so that the organic matter in the former before drying 

 will, as would be expected, bear a 'lower proportion to the 

 weight of the undried plants than is the case with the latter. 

 A similar explanation would api>ear to account for the 

 apparently high ash content of tiie weeds, etc. It is notice- 

 able that the ash of the leguminous plant is richer in potash 

 and phosphoric acid than that of the vegetable debris. 



