REPORT OF COMMITTEE ON CLASSIFICATION OF ORGANIC SOILS

The principal field work thus far done in connection with the attemptbegun last year to work out a system of classifying organic soils is re-presented by the collection of 61 type and locality samples of peat andmuck. These were taken in 127 horizon samples, along with 3 overlyingsamples of inorganic soil material and 38 underlying samples* These comefrom representative areas in Florida, Georgia, South Carolina, NorthCarolina, Virginia and Mississippi. A few small samples also were takenfrom insignificant patches of organic soils in Arkansas and east Texas.On an extensive trip in Central America and South America, covering muchterritory in eight countries, only an approximation- of peat was found,and that as a buried layer in a small drained area of reclaimed allumiumin Costa Rica. Mr. Baldwin reports extensive occurrence of peat in theEast Indies.

The samples were collected by horizons in such a way as to avoid orpretty well avoid mixing. The method used was a process of mining witha long handled spade and post hole digger, the soil auger being used tobring up material from some of the lower depths after the deep excavationshad been made. In most of the samples the auger was not used at all, andas many of the areas were covered with water, considerable labor wasnecessary to get down through the layers, the collector operating in analmost submerged state in some instances. The bottom of the peat formationwas not reached in several places; but some samples were taken down tofifteen feet. After going down as far as practical with the spade andpost hole digger, it was found possible to use the soil auger effectivelyand without or with but very little mixing in taking small subsamples.

Some form of tube sampler should be included in the peat samplingoutfit for working in the deeper beds.

Many of the samples were taken in 2-bushel amounts, includinglarge chunk* which held intact so that it was possible to saw out blocksfrom these showing the material in its natural state. This, of course,could not be done in case of the wet, finely disintegrated material,owing to its pasty to semi-liquid condition.

Most of the samples were from virgin areas; a few were from fieldswhere some interesting crop results have been obtained, such as a re-duction of corn yields, in one case, from 75 to 10 bushels within aperiod of about 8 years.

The vegetation was carefully noted, and in most cases the originof the bulk of the surficial layers was obvious. Studies of the plantmake-up of the sublayers have not yet been made; something further, per-haps, should be done along this line.

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Some of the samples are composed almost wholly of grass; others ofleaves and decaying wood of the trees from which the leaves have accumulated,Sphagnum moss is the parent material of some of the samples, and pineneedles, leaves and grass of others. In one sample from the outer edgeof the Savannah River bottom charcoal was found in a 2-inch layer between36 and 38 inches*

The pH values of the material were determined on the ground by theWherry method, Dr. Wherry himself making some of them. This method'worksvery satisfactorily on the organic soils. Where the peat was saturatedby water from alkaline springs, as at Wekiva Springs, Florida, the pHvalue found was 8.5; the marly peat o* the marl beds south of Miami,Florida, went up to the limit of alkaline measurement with this method.The organic deposits of the Everglades, underlain by limestone werefound to be alkaline in all cases, except in some of the higher lyingmuck rimming Lake Okeechobee, where the pH value was as low as 6*5 to 7.In the Everglades hammocks of the southern or marl plain portion of theEverglades, an interesting example of sudden change from acid to alkalinepeat was found. These hammocks are mound-shaped accumulations of peatbuilt upon the flat white marl of the region through the agency ofclumps of subtropical plants. These mounds often are 4 or 5 feet higherthan the surrounding marl plain. (Such mounds found in the prairie por-tion of Okefenokee Swamp are known as "houses"). The top layer consistsof coffee-brown, fibrous leaf peat, while the sublayer, that in contactwith marl, .consists of very dark brown nonfibrous peat. This changeapparently takes place at the line of saturation in time of flood. Thetop layer, which has relatively good aeration has a pH value of 4*5,while the dark sublayer has an alkalinity of 7 or higher, the changebeing very sharp*

Peat was found with an acidity as high as pH 3.5 to 4, as in eas-tern North Carolina where there has been so much trouble with reducedcorn yields. In the swamps at Wekiva Springs, Florida, peat taken fromhammocks standing above the permanently saturated material was decidedlyacid, although composed of the same material as the alkaline peat below.

It appears that neither acidity nor alkalinity in the organic soilsof this region is due to the origin of the vegetative material, but thatacidity is the normal state of things and alkalinity the result ofsaturation, or constant bathing of the material by water made alkalineby contact with lime deposits or by sea water. This will not be statedas a final conclusion just yet; but it is certainly the prevailing orderof things for that region. It is known that some of the northern peatshave marly beds beneath them in which the lime appears to have come fromcertain plants growing in the bogs. As yet, neither these nor any ofthe other northern peats have been studied in detail in connection withthe work now being reported on.

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LABORATORY WORK1

A large number of chemical analyses have been made of the samplescollected. Results of -the analysis of only 53 samples were available foruse at the time this report was written; other analyses have been com-pleted since then. It is not deemed necessary at this time to report onthese analyses in detail, and accordingly some of the more outstandingresults only will be referred to.

Of the soils which run high in lime, all of which are alkaline,the amount of .organic matter soluble in 4 per cent ammonia solution ismuch lower than of those low in lime , ail of which are acid. The averageamount of organic matter which want into solution from 13 high limepeats whose analyses were available for this report vras 19.17 per centof the air-dried samples; as against an average of 38.16 per cent orpractically twice as much, for 20 samples of low lime content. Therange of organic matter in both of these groups is from 62»58 to 97.78per cent. The range of CaO in the high lime group is from 3.62 to 23,87per cent and the average 6.61 per cent; while the range of CaO in thelow lime group is from 0.02 to 1*01 per cent, and the average 0,29 percent. Magnesia is five times higher in the high lime than in the lowlime peats, or 0.47 against 0.09 per cent. Nitrogen in the samples ofhigh lime content amounts to an average of 2.32 per cent as against1,97 per cent in those of low lime.

Silica is the most plentiful of the constituents present other thanorganic matter, although lime almost equals silica in some samples. Thecontent of silica, therefore, varies inversely with the content of or-ganic matter. Iron is low in all the samples. Alumina is considerablyhigher than iron, but does not often run over 2.5 per cent, averagingless than 2 per cent, Neither iron nor alumina thus far has shown anyespecially interesting correlations, nor has the phosphorus content.

In the determination of the ammonia soluble organic matter, thematerial was first treated with a 1 per cent solution of HCl> filteredand then treated with a 4 per cent ammonia solution. Less organicmatter went into solution when the material was not acidulated in allthe samples tested except one, which was a fibrous peat includingmuch undecomposed material. Solubility following acidulation was in-creased about three times in the samples high in lime, and from nothingto about 30 per cent in the low line

This soluble material may correspond in part or closely with thatpart of the organic matter which has been referred to by some investiga-tors as unsaturated humus, and the insoluble to that designated assaturated humus (absorptively satisfied) with respect to lute.

samples.

^ Analyses by'Holmes, R. S,, in laboratory, Bureau of Soils.

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Usually the fibrous peats of low lime content are much lees solublethan those of fine disintegration. Five samples of the former averaged29.31 per cent soluble in ammonia solution as against 48.41 per cent forthe average of nine samples of the latter. This does not hold true, how-ever, for all of the fibrous samples, as some containing an abundance ofplant roots show a higher per cent of solubility than some of those ofvery fine disintegration. In these rooty samples, however, it was ob-served that a large proportion of the material was well decomposed andsoft, but not yet in the disintegrated state.

The fibrous peats of high lime content also are less soluble thanthose of fine disintegration; but the difference appears to be not nearlyso pronounced as with the samples of low lime content.

No satisfactory method for measuring the undecomposed part of peatsamples has been found thus far. Some work was done with the destructionof the organic matter by H2O2 of varying strength with the idea that thismight lead to such measurement, but the results were not encouraging.Just what relation the crude fibre of food analysis may have to the un-decomposed organic matter of peat will be looked into'.

The amount of organic matter dissolved by ammonia and precipitatedby hydrochloric acid, which is soluble in alcohol, has not led to any-thing particularly interesting thus far.

Hugh H. Bennett, Chairman,Committee on Organic Soils.

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