46 



THE AGRICULTURAL NEWS 



Febeuary 10, 1911 



FUNGUS NOTES. 



SOIL FUNGI AND THEIR ACTIVITIES. 



Current research in the Leeward Islands on the amount 

 of lime required for partial sterilization of soils and on the 

 soil reaction, some results of which are being prepared for 

 publication, is providing data of fundamental importance. 

 "The information obtained regarding Dominica by Mr. G. A. 

 -Jones, Chemical Assistant, is remarkable for the high 

 -acidity shown for the soils of that island, especially those 

 oi the interior forest lands. A similar condition may be 

 -expected to be found in >St. Lucia and, to some extent, 

 <jlrenada and St. Vincent. 



The micro-liora of the soil, as it affects fertility and 

 especially nitrogen supply, is usually considered, owing to 

 ■the preponderance in the discussion of the subject of 

 xesults obtained from arable soils, entirely in terms of 

 Ijacteria. It has however long been known that in the heath 

 ;ind moorland soils of Europe, with their high humus content 

 ■and acid reaction, the growth of bacteria is largely inhibited, 

 and their place is taken by fungi, which as a general rule are 

 acid-tolerant 



It is highly probable that when the soils of Dominica 

 and other islands of similar character come to be examined 

 from this point of view that a similar relationship between 

 acidity and the soil flora will be found to prevail. 



In respect of the plants at present cultivated, namely 

 limes and cacao, high acidity is not prejudicial to growth. 

 When other conditions are favourable, the lime trees on some 

 ■of the most acid of the soils examined are exceedingly 

 luxuriant. Whether they are able, as has been suggested, 

 to directly utilize ammonia produced by fungus activity 

 requires investigation. Another line of enquiry suggested, 

 ■with regard to which preliminary steps are being taken, is 

 how far the action of roots in such soils is assisted by 

 mycorhizal associations. 



Pending a mycological examination of the Dominica 

 ^oils, which cannot at present be undertaken, there may be 



reproduced here, as illustrating the trend of research on this 

 matter, the summary given in conclusion of a most inter- 

 esting paper by Mr. S. A. Wakman in Soil Science, II, pp. 103- 



lijij. The investigations were made on representative 



United States soils. 



SUMMARY OF THE PHYSIOLOGICAL STUDIES. 



Five fungi isolated from the soil and representing distinct 

 groups of organisms were not found to fix any appreciable 

 quantities of atmospheric nitrogen, which would not lie 

 "within the analytical error. 



The fungi of the soil are vrry strong ammonifiers, most 

 of them liberating larger quantities of ammonia than thestrong 

 ammi.mifying bacteria, when tested under similar conditions. 



The Trn-Iuxhrnia Koningi proved to be, under the 

 conditions at hand, the strongest ammonifying organism; 

 the Penicillia differing with the different species, most of 

 them being comparatively weak ammonifiers: the Mucorales 

 •.ire fairly strong ammonifiers, the different species not differ- 

 ing so much from one another as the Penicillia. 



The gro\\ing of the organisms on artificial culture 

 media for six months affected the ammonifying powur of the 

 organisms differently: while that of the Mucorales was 

 hardly affected, or was even beneficial, that of the Penicilli* 

 and other organisms tested, was detrimental, their power 

 decreasing with almost' all organisms. 



Most of the fungi are very strong cellulose decomposers, 

 fifteen out of twenty two organisms tested prove to decomposft 

 the cellulose rather rapidly; most of the fungi have a rather 

 weak ability to secrete diastase, only six out of twenty-two- 

 organisms forming an enzymic ring in the starch medium. 



GENER.\L SUMMARY. 



The fungi of the soil represent a numerous group of 

 organisms found in all the soils studied in hunibers large 

 enough to warrant a conclusion that they probably play an 

 important pare in the fertility of the soil. 



There does not seem to be any distinct difference between 

 the species of fungi found in cultivated soils and those in 

 uncultivated soils, though each soil seems to have a more or 

 less characteristic fungus flora: for example, the cultivated 

 orchard soil has a great abundance of Mucorales, while the 

 forest, uncultivated soil, has an abundance of I'enicillia and 

 Trichodermae. This might be due rather to the soil reaction, 

 methods of manuring, and crop grown upon the soil, than 

 to the cultivation itself. 



The number of fungi decrease rapidly with deptli, so 

 that at 12 to 2(1 inches below the surface very few fungi 

 can be found, the largest numbers occurring within the upper 

 4 inches of soil. As to the species, no distinct differences 

 among the organisms were found with the different soil 

 depths, except that in the subsoils of most of the soils studied, 

 Zygorhynchua Vuilleminii was found to be present, often as 

 the only organism, when soil was inoculated directly upon 

 sterile medium. 



Over 100 distinct species of fungi were isolated from" 

 the soil, belonging to thirty-one genera, many of the species 

 being isolated from several of the different soils. 



Many pathogenic fungi, such as different I'usaria, 

 Alternaria, Aspergiili, Coniothyrium, and others, have been 

 isolated from the soil, a fact which leads one to think that they 

 pa.ss certain stages of their life-history in the soil, or are able 

 to live sapropliytically in the soil, and perhaps play a pait in 

 its fertility. 



The study of the physiological activities of the fungi 

 pointed out the fact that they do not play a very' great, if 

 any, part in the fixation of atmospheric nitrogen, but they 

 do prove to be able to decompose organic matter rapidh- and 

 liberate ammonia, under laboratory conditions. 11 any of 

 them prove to be strong decomposers of cellulost, though 

 fewer of them hydrolize starch. 



The question, 'Is there any so-called fungus tloia of the 

 soil;' cannot as yet be answered in the affirmative till mo;-c work 

 has been done with soils collected from different parts of the 

 world. But it is seen from the data at hand that there is 

 a rather distinct fungus flora of the .soils studied, and this 

 holds particularly true with regard to certain organisms. 

 The importance of tin fungi in the soil seems to lie in the 

 formation of humus and in the liberation of amtnonia, wkkh 

 can then be utilized by the higher plants, either diitctly or 

 after it is changed by other orj-anisms into nitrates. The 

 numerous species of soil fungi i.solated and tlie large nupibers 

 of them supply an impetus to a further ttudy i.f these 

 organisms, which will help to solve the probien. of their 

 importance in tlie soil. 



