10 BULLETIN 1419, U. S. DEPARTMENT OF AGRICULTURE 
peat. This can be practically solved through the protection afforded 
to crops by shrubs or trees planted as windbreaks and shelter belts, 
by crop rotations, by irrigation, or by proper cultural treatment of 
the wind-swept muck soil. 
Layers of woody peat (pl. 6 and digit 3 in the series of profiles in 
pl. 1) consist partly of granular, well-disintegrated organic material 
and partly of irregular-shaped woody fragments which have resisted 
the decomposing action of air and microorganisms. Plate 6, A, shows 
a profile section of an area of woody peat derived from a coniferous 
swamp forest. The layer represents dark-brown, moderately well- 
disintegrated granular material, as well as coarse woody fragments 
from the stumps and roots of trees. The moisture content of the 
underlying mineral soil was sufficiently low during the period of for- 
mation to favor the growth of trees and a fair degree of decomposi- 
tion of the plant remains. The ground-water level became elevated 
in time, with the gradual accumulation of the peat material. Plate 
6, B, shows a sample more or less typical of brown, laminated, poorly 
decomposed, woody peat derived from shrubs. The lamination, 
perhaps, is annual. Plate 6, C, represents a dark-brown, largely 
disintegrated woody peat derived from a swamp forest. This air- 
dry sample reveals a varying proportion of granular material and 
woody fragments. 
The growth of forest trees causes a greater humification of the peat 
material containing the living roots, whieh in turn gives rise to the 
formation of soluble organic and mineral substances. Because of 
this varying rate of decay, a layer of woody peat may show a banded 
or bedded appearance and a critical water content differing ac- 
cordingly. 
In the raw state all types of peat of whatever stage of previous 
disintegration have a low value as nutritive constituents. When 
surface peat soils are removed from a cultivated area, as in the case 
of certain industries which dispose of peat for fertilizer purposes, the 
exposed underlying brown and yellow-brown peat material is detri- 
mental to crops, at least for a period. - Dwarfing of root systems and 
cessation of plant growth appear to be partly due to the lack of sol- 
uble nitrogen in the large supply of carbonaceous matter. Investi- 
gations bearing on the nitrogen supply in peat materials have proved 
that the content of organic nitrogen is not available for crops. In 
the absence of any adequate balance between carbonaceous materials 
and soluble nitrogen, deficiencies must be made up by manuring or 
fertilizing. When properly aerated, cultivated, and mineralized, the 
change from the peat stage to a material resembling humus mav take 
place rapidly (pl. 5, A and D). oo 
The fixation of atmospheric nitrogen by bacteria might be one of 
several methods to measure the nutritive value of different types 
of peat or of different stages of decomposition. It is doubtful, how- 
ever, whether a layer of peat which has reached a mature stage of 
disintegration in the field 1s in consequence more productive. Atten- 
tion should be focused not so much upon the stage of decay but rather 
upon the conditions, including the character of the layers below the 
surface, which are antagonistic or associative in the continuance 
of the soil-forming process. Field observations on the size and abun- 
lance of trees present in undrained swamp forests may he cited here