WATER SOILS. 555 



the volume of irrigation used per acre. The i|uantities and proportions of the ingre- 

 dients, other tlian common salt, contained in irrigation water also influence in large 

 measure the action of such water on the growth of cane. 



"Cane planted in Ijsimeters grew apparently unchecked with its roots in contact 

 with a soil water containing 195.75 gr. of chlorin to the U. S. gallon. Cane abso- 

 lutely refused to grow where the percentage of chlorin in the soil reached 0.198, the 

 soil containing 28 per cent of its weight of water. 



''('an - in lysimeters irrigated to excess with water containing 200 gr. of salt to the 

 gallon made an apparently normal growth. In other tests with the same amount 

 of salt in the water, but where excessive irrigations were not applied, the cane died. 



"In brackish irrigation water the quantities of lime and magnesia are usually 

 rather high, the latter element being in excess of the former. If it were not for the 

 fact that the lime of the soil is considerably more soluble than the magnesia, where 

 saline irrigation is used the soil water would have an excess of magnesia over lime. 

 The latter condition would l)e decidedly unfavorable to the growth of cane. As the 

 lime is washed from the soil in greater quantities than the magnesia, it is necessary 

 to apply the former element to the land to prevent the soil water from ultimately 

 containing more magnesia than lime." 



■Water-holding- power and irrig-ation of Hawaiian soils; the application 

 of nitrate of soda; the accumulation of salt in Hawaiian soils, J. T. Crawley 

 {Ilairaiian Planters' Mo., 21 {1902), No. 8, pp. 358-363). — Observations on 7 different 

 soils are reported which show that the amount of water in the soils when saturated 

 in the field varied from 22.87 per cent to 29.61 per cent, while in the same soils sat- 

 urated after being dug up the amount of water varied from 31.95 per cent to 39.9 per 

 cent, showing ' ' that in order to obtain the amount of water that any given soil will 

 take up it must be saturated in the field." As a means of determining the amount 

 of water which may be applied to a soil without waste it is proposed that determina- 

 tions of the water content be made in the soil before irrigation and 5 hours there- 

 after, the difference between the two determinations being taken as the absorptive 

 power of the soil. This, multiplied by 9,120, which is the number of gallons of 

 water corresponding to each per cent of moisture in an acre of soil to a depth of 2 ft., 

 gives the number of gallons of water which the soil will absorb. 



Experiments are reported in which nitrate was applied before and after irrigation. 

 "When nitrate was applied after irrigation there were 12 times as much nitrate in 

 the first 6 in. of soil than when applied before the irrigation. In the aliove case a 

 considerable quantity of nitrate of soda was lost through irrigation after putting on 

 the nitrate, but practically all remained in the first 6 in. of soil, when it was apjilied 

 after irrigation." 



Observations on soils which were irrigated with water containing as high as 0.2 

 per cent of soluble salts show that there was very little accumulation of salt in the 

 soils. 



The reversion of superphosphate of lime in the soil, W. F. Sutherst ( Chem. 

 Xeu-K, 86 (1902), No. 2236, ])/>. 170, 171). — Observations on mixtures of superphos- 

 phate with calcium carbonate, magnesium carbonate, and limonite in varying pro- 

 ptirtions are reported which show that the process of precipitation or reversion "does 

 not by any means take place instantly, many days elapsing before all the water- 

 soluble phosphate is rendered insoluble, and that only when a large excess of the 

 reverting agents are present — a state of things not always occurring. ' ' Magnesium 

 carbonate proves to be the most active reverting agent, iron oxid being next, and 

 calcium carbonate last. Since the soil generally contains more iron oxid than 

 magnesium or calcium carbonate the soluVjle phosi^hate is in most cases precipitated 

 chiefly as an iron compound. The author's investigations indicate, however, that it 

 is only from the calcium and magnesium compounds that the root sap takes up phos- 

 phoric acid. 



