10 BULLETIN 502, U. S. DEPARTMENT OF AGRICULTURE. 
of combinations and soil and moisture conditions under which these 
injurious salts may occur, it is not possible to state definitely the 
highest percentage a soil can contain and still support ordinary vege- 
tation. However, in order to convey a general idea of what is 
meant by an alkali problem, the results of recent and very extended 
experiments by Frank S. Harris, professor of agronomy, Utah Ex- 
periment Station, are summarized in part as follows: 
*In this paper results of over 18,000 determinations of the effect of alkali 
salts on plant growth are reported. * * * Only about half as much alkali 
is required to prohibit the growth of crops in sand as in loam. * * * The 
toxicity of soluble salts in the soil was found to be in the following order : Sodium 
chlorid, calcium chlorid, potassium chlorid, sodium nitrate, magnesium chlorid, 
potassium nitrate, magnesium nitrate, sodium carbonate, potassium carbonate, 
sodium sulphate, potassium sulphate, and magnesium sulphate. Land con- 
taining more than about the following percentages of soluble salt are probably 
not suited without reclamation to produce ordinary crops. In loam, chlorids, 
0.3 per cent; nitrates, 0.4 per cent; carbonates, 0.5 per cent; sulphates, above 
1 per cent. In coarse sand, chlorids, 0.2 per cent; nitrates, 0.8 per cent; 
carbonates, 0.3 per cent; and sulphates, 0.6 per cent. 
Using the figures as given by Prof. Harris as a basis for com- 
parison, it is apparent that great danger to crops from alkali exists 
in those lands represented by the foregoing samples of drainage 
water, provided the water be allowed to rise above the root zone 
of any cultivated plant. If the rise be such as will permit of evap- 
oration from the ground surface, it also is obvious that the trouble 
will be aggravated rapidly. 
Illustrating this latter point, there follow the results of the soil 
analysis of a composite of two samples at each depth taken from 
near the center of about 4 acres that produced thrifty alfalfa previous 
to the season of 1913, but which became so wet the summer of 1913 
that water rose to the surface of the ground and ran off through the 
waste ditches. Needless to say the land became wholly unproductive. 
TasLe III.—Salt content of shale-land soil. 
Parts per 100,000 of soil by weight. 
Substance. ES ea a: © Ses pee | a ae eae | 
First | Second Third | Fourth Fifth Sixth Anaraee 
foot. Se foot. foot. | foot. foot. foot. ss 
Sodium chloride (NaCl) ....-.-.- 173 | 92 132 337 | 132 | 46 153 
Sodium sulphate (Na2SO;) -...- 44 231 141| 1,166 | 53 620 | 376 
Magnesium sulphate (MgSO,) -- 278 535 377 615 615 436 | 476 
Sodium bicarbonate (NaHCOs). 116 116 149 | 116 132 | 116 124 
Calcium sulphate (CaSQx).----- 680 1343 720 3, 425 8, 837 | 4, 337 3, 229 
| 1,296 2, 347 | 1,519| 5,659} 9,769 5,555 4,358 
INGtICTACIG (GN @3)) 22a se 89 600 | 500 556 353 188 381 
| 
Attention is called to the fact that these soil samples, as well as 
the water samples in Tables I and II, are unusually high in the 
nitrates and carry also considerable sodium chloride. As noted 
1 Journal of Agricultural Research, U. S. Department of Agriculture, vol. 5, no. 1, Oct. 5, 
1915. 
