204 Journal of Agricultural Research voi. iv, N03 



(6) The total yields in the second crop throughout are much larger 

 than in the first crop, indicating almost certainly an improvement in 

 the soil and climate during the growth of the first crop and the next 

 period between the two crops. 



(7) The toxicity of sodium chlorid and sodium sulphate is plainly 

 discernible in the second crop, even at the lowest concentrations em- 

 ployed. Note the difference between this statement and statement i. 



(8) In the case of sodium carbonate it seems probable that a slight 

 toxicity exists also, even at the lowest concentration. Such toxicity is 

 not nearly so marked, however, as in the cases of the two other salts. 



(9) It is remarkable to note the high yields obtained in the sodium- 

 carbonate series of the second crop, as well as the uniformly poor agree- 

 ment between duplicate pots in the series. 



(10) In general, it is a striking fact not easily accounted for that 

 once toxicity does manifest itself it does not seem to become notably 

 more acute as the quantity of salt present increases. 



The behavior of the cultures at the lowest concentrations in the first 

 crop is probably to be attributed to an improvement in the physical, 

 chemical, and biological condition of the heavy clay-adobe soil through 

 the salt applications. At the same time the control soils had improved 

 during the growth of the first crop and especially during the period 

 intervening between the two crops much more markedly than the soils 

 treated with the smallest quantities of salts. This improvement was 

 doubtless wrought by good crumb formation in the soil through alter- 

 nate wetting and drying at first and later by thorough drying during 

 the period of rest. After such improvement, therefore, the control pots 

 showed marked superiority over the pots nearest them in the series 

 which during the same period had changed but slightly, except in the 

 case of the sodium-carbonate series. While, therefore, the yields of the 

 control pots had trebled in the second crop, they remained practically 

 the same at the lowest sodium-chlorid and sodium-sulphate concentra- 

 tions. It remains true, however, that generally the yields of the second 

 crop were superior to those of the first, a fact to be attributed, in addi- 

 tion to the above-mentioned causes, to the seasonal and climatic differ- 

 ences obtaining between the periods of growth of the two crops. 



ANTAGONISM BETWEEN SODIUM CHLORID AND SODIUM SULPHATE 



Table II gives the results obtained in two successive crops in the 

 series of experiments on antagonism between sodium chlorid and sodium 

 sulphate. The toxic quantity of sodium chlorid used throughout was 

 0.2 per cent, and sodium sulphate was added in varying quantities up to 

 0.5 per cent. 



