Oct. 4, 1913 



Effect of Alkali Salts in Soils on Crops 



Table Y1.— Percentage of germination of New Zealand wheat in soil containing alkali 

 salts in different quantities. Salts added dry 



An examination of Table VI, in agreement with Table V, shows the 

 germination to be greatly reduced by sodium chlorid in concentrations 

 above 3,000 p. p. m., while it ceases entirely at about 6,000 p. p. m. 

 With sodium carbonate a large reduction in germination occurred at 

 about 10,000 p. p. m., but a few plants survived at about 20,000 p. p. m. 

 The sodium sulphate showed about the same results as the sodium car- 

 bonate, while the magnesium sulphate gave over a 50 per cent germina- 

 tion at a concentration of 30,000 p. p. m. In the mixed salts the gyp- 

 sum (calcium sulphate) did not have any great effect, possibly owing to 

 the slowness with which gypsum dissolves. 



On comparing the data in Tables V and VI with those reported in 

 Table I and also others given later in the paper, where the salts were 

 first dissolved and added in solution, it will be found that the salts were 

 more toxic when added in solution than when mixed with the dry soil. 

 This may be due to the slow solution and diffusion of the salt when added 

 dry, which probably helps to explain the common obsen^ation that 

 crops can sometimes be made to grow" in a soil the analysis of which 

 shows a very high total alkali content. It also explains why it is that 

 crops growing on alkali land may look healthy and be growing vigor- 

 ously until irrigated, when they are immediately killed. 



In order to determine more exactly the effect of soil moisture on the 

 toxicity of alkali salts, sand was placed in tin plates, as previously 



