10 



BULLETIN" 502, U. S. DEPAETMENT 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. * =i= * 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, 0.3 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. 



Table III. — *S'«/^ content of sh ale-land soil. 





Parts per 100,000 of soil by weight. 



Substance. 



First 

 foot. 



Second 

 foot. 



Third 

 foot. 



Fourth 

 foot. 



Fifth 

 foot. 



Sixth 

 foot. 



Average. 



Sodium chloride (NaCl) 



Sodinm sulphate (NazSO^) 



Ma^esium sulphate (MgSOO . . 

 Sodium bicarbonate (NaHCOs). 

 Calcium sulphate (CaSO^) 



178 

 44 

 278 

 116 

 680 



92 

 231 

 535 

 116 

 1,373 



132 

 141 

 377 

 149 

 720 



337 



1,166 



615 



116 



3,425 



• 132 



53 

 615 

 132 



8,837 



46 



620 



436 



116 



4,337 



153 

 376 

 476 

 124 

 3,229 



Nitric add (NOa) 



1,296 

 89 



2,347 

 600 



1,519 

 600 



5,659 

 556 



9,769 

 353 



5,555 



188 



4,358 

 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. 

 19l5. 



