On silt Ioam and sandy loam soils, except on Baca series, 1 and 3 per cent of ..... Bull. 71. (3) CHEPIL, W. S. 1952 Improved rotary sieve for measuring state and ...
Reprinted from Son. SCIENCE Vol. 77, No. 6, June, 1954 Printed in U.S.A.
FACTORS THAT INFLUENCE CLOD STRUCTURE AND ERODIBILITY OF SOIL BY WIND: 111. CALCIUM CARBONATE AND DECOMPOSED ORGANIC MATTER W. S. CHEPIL
U.S. Department of Agricultu~el Received for publication December 14, 1953
Hopkins (8) observed in Canada that soils high in organic matter and CaC03, or lime, have been eroded severely by wind and suggested that these factors may be responsible for the development of a loose, fine soil structure susceptible to erosion by wind. Initial laboratory studies (2) on some soils of Canada substantiated, in general, the observations of Hopkins. Hardt (7) concluded from his investigations of muck soils in Bavaria, however, that organic matter or humus has little influence on erosion of soil by wind but that the high content of lime, particularly in the clay fraction, increases erodibility appreciably. This paper presents information on the influence of CaC03 and decomposed organic matter on structure and erodibility of some soils of the High Plains area of the United States. Lime, where mentioned in this paper, refers to CaCOa contained naturally in soil. MATERIALS AND METHODS
Precipitated CaC03 was applied in October 1948 to 6-pound samples of five different soil types of the chernozem, chestnut, reddish chestnut, and brown soil zones of Kansas. After being shaken in water the CaC03 particles settled out readily. Only 0.4 per cent of the particles in water were smaller than 0.002 mm. in diameter (table 1). The treated soils were kept for 2 years in a moist condition in glazed earthenware pots in the greenhouse. They were then transferred into porous-bottom trays and kept in the field until the end of the experiment in 1953. The trays were covered with a %-inch mesh screen to prevent erosion. In another experiment, initiated in the greenhouse in 1950 and later transferred to the field, precipitated CaC03 with and without ground wheat straw was applied. One soil from the brown soil zone, one from the reddish chestnut, and one from the chernozem were used (table 2). Two groups of high- and low-lime soils of the reddish chestnut soil zone, one group from near Portales, New Mexico, and the other from near Lubbock, Texas, were chosen for study. The high- and low-lime soils were similar in texture but differed in CaC03 content. The soils treated with differed amounts of CaC03were analyzed for structural characteristics and erodibility by wind at approximately 1-year intervals throughout the experiments. The high- and low-lime soils from Texas and New 1 Contribution 494, department of agronomy, Kansas Agricultural Experiment Station, Manhattan, and the Bureau of Plant Industry, Soils, and Agricultural Engineering, U. S. Department of Agriculture. Cooperative investigations in the mechanics of wind erosion. 473
TABLE 1
Size distribution of particles of precipitated calcium carbonate* PARTICLE SIZE DISTRIBUTION DISPERSION M D N M
> 0.05 nun. 10.05-0.01 Water alone. . . . . . . . . . . . . . . . . . . . . . . . . Water and dispersing agent. . . . . . . . . .
mm.~O.OZ-O.O~ m.1 0 . 0 g F 2
1
6.4
mm. mm. -
mm.
- -
Hastings silt loam
DRY AGGREGATES
--
CaCO1 ADDED >0.8~ 1.8440
DP
ERODI3ILITY BY WIND
%
%
%
%
%
%
#./A.
0 1 3 10 0 1 3 10 0 1 3 10 0 1 3 10 0 1 3 10
2.0 2.1 2.2 2.1 1.6 1.5 1.3 1.4 1.6 2.2 1.8 2.1 0.9 1.2 1.0 0.9 1.2 0.8 1.6 0.9
72.1 72.2 72.7 67.9 73.1 71.8 72.5 68.1 76.3 77.9 76.8 71.7 85.7 87.0 85.4 80.5 94.9 95.7 92.7 88.6
25.9 25.7 25.1 30.0 25.3 26.7 26.2 30.5 22.1 19.9 21.4 26.2 13.4 11.8 13.6 18.6 3.9 3.5 5.7 10.5
57.8 42.0 42.7 45.3 50.3 41.2 40.0 50.5 49.5 49.3 46.7 47.4 45.1 42.1 41 .O 44.9 8.6 10.4 16.9 31 .O
90.6 82.1 84.9 89.5 84.4 75.5 77.8 85.8 87.7 86.7 89.3 89.4 83.5 82.2 80.4 83.2 31.2 31.4 49.7 68.1
0.11 0.61 0.62 0.38 0.42 0.64 0.80 0.29 0.27 0.24 0.30 0.29 0.62 0.86 1.oo 0.63 16.4 14.0 7.0 2.1
- - -* Experiment started October 1948. Data represent averages for determinations made in October 1949, September 1950, April 1952, and February 1953. Properties of soils at start of experiment: I
I
I
MECHANICAL COMPOSITION SOIL TYPE AND ZONE
ORGANIC MATTER
CaCOa
Sand >0.05 mm.
Hastings silt loam (chernozem) .... Keith silt loam (chesnut). . . . . . . . . . Baca silt loam (brown). . . . . . . . . . . . Dalhart fine sandy loam (brown) . . Pratt loamy fine sand (reddish chesnut) . . . . . . . . . . . . . . . . . . . . . . . .
Silt 0.050.002 mm.
Clay 0.84 mm. were small compared with the decreases in the proportion of fraction < 0.02 mm. Consequently, the net effect from decomposed wheat straw, as may be expected, was to increase substantially the erodibility by wind (table 3). The decomposed wheat straw, as indicated by the amount of organic matter in soil 2% years after the straw was applied, increased soil erodibility much more than did like amounts of CaC03 (table 3). Moreover, it increased the erodibility of soils containing a high proportion of CaC03 more than of soils containing a low proportion. The highest erodibility was recorded for soils receiving the highest quantity of both straw and CaC03.
Field studies on the inJluence of calcium carbonate The percentage of erodible soil fraction < 0.84 mm. in diameter was substantially higher in the high-lime than in the low-lime soils of similar texture and similar content of organic matter (tables 5 and 6). Mechanical stability of clods was considerably lower in the high-lime soils than in the low-lime soils. TABLE 5 Some structural conditions and erodibility of low- and high-lime soils near Portales, New Mexico Data based on surface to 1-inch depth, April 1952 NWKBER OF FIELDS
SOIL CLASS
Loam and clay loam Sandy loam
I :
I
DRY PXACTION
CaCOa
',
