678 EXPERIMENT STATION RECORD. 



'•Should the iiorceutage of total salts in the soil not materially exceed the lower of 

 the above figures (perhaps up to the limit of 0.175 per cent), nor the carbonate per- 

 centage one-half of the above, we may consider that, for barley at least, the land 

 can be reclaimed by simply treating with gypsum, and deep and thorough culture; 

 while any laud of which the salt content, ascertained by the same method, falls 

 materially below the above Hgure, may be confidently taken into cultivation, even 

 when covered with alkali grass. 



"The limits of tolerance for other culture ijlants doubtless differ greatly, and have 

 to be separately ascertained for each one. . . . 



"The saltbush came up easily from seed on land of which the surfa(;e foot con- 

 tained one-third per cent of salts, but languished, although they did not die, when 

 that amount reached one-half i)er cent ; the surface foot then containing not less than 

 31,000 lbs. of total salts per acre. Where the surface crust (including about half an 

 inch of the surface soil) contained nearly 8 per cent of total salts, of which one-half 

 was Glauber's salt, the rest almost evenly divided between the carbonate and com- 

 mon salt, the young i^lants of saltbush scarcely kejit alive; they died when the accu- 

 mulation rose to over 25 per cent in the first half inch, 0.6 being Glauber's salt and 

 0.1J5 carbonate of soda: a weakness which, under the circumstances, must be consid- 

 ered pardonable.'' 



The charts and tabulated data given show that the proportion of car- 

 bonate of soda (black alkali) decreases as the surface of the soil is 

 approached, and confirms the conclusion "tbat whenever an alkali soil 

 is subjected to the action of stagnant water or of abundant moisture 

 without aeration, the formation of black alkali will take place." 



Investigation of matidre noire, or humus, M. E. Jaffa {Galifor- 

 nia Sta. Npt. 1S95, pp. 35, 36). — The method used by the station in 

 determining humus and nitrogen in humus in soils is as follows: 



"Two portions of 5 or 10 gm. of air-dried soil (depending on ric-hness in humus) 

 are weighed off into prepared filters (about 9 cm.). The soils should be covered 

 with filter pajier, so as to i)revent packing when solvents are poured onthem. 



"They are now treated with dilute hydrochloric acid, from 0.5 to 1 per cent strength 

 (25 cc. concentrated acid to about 800 cc. water), to dissolve out the lime and mag- 

 nesia, which prevent the humus from going into solution Avith alkali hydrates. The 

 treatment with acid is continued until there is no reaction for lime; the acid is then 

 washed out with water to neutral reaction. The funnels (7 cm.) containing the 

 washed soils are now stoppered (cither with a cork or by means of a small piece of 

 rubber tubing with glass plug), and one of them is treated with ammonia water 6 

 to 7 per cent strong, for the determination of hiimus, and the other with potassium 

 hydrate 5 per cent strong, or sodium hydrate 4 per cent, for the estimation of the 

 nitrogen. The mode of operation is the same in both cases, so far as the extraction 

 of the humus is concerned. The lye, ammonic or potassic, is poured on the respec- 

 tive funnels and allowed to remain a few hours. (If started late in the afternoon, the 

 liquid can remain in the funnel all night.) The solution is then allowed to pass 

 through, and the filter washed once with the lye; the funnel is then restoppered nud 

 a fresh quantity of the solvent added to the filter. This treatment is repeated until 

 the filtrate remains colorless. 



"The ammonia solution, or an aliquot of the same, is evaporated in a weighed 

 platinum dish, over the water bath, and the residue dried at 100° C, and weighed. 

 It is then ignited and re weighed ; the loss in weight shows the amount of humus. 

 It is rarely necessary to recarbonate the ash. 



"The potassium or sodium hydrate solution ' is measured, and if much over 100 cc. is 



' Sodium hydrate is preferable to potassium, as sodium sulphate (formed in the flask) 

 is less liable, owing to its greater solubility, to "bump" during the boiling down 

 with sulphuric acid, and the subsequent oxidation. 



