NURSERY PRACTICE FOR PRAIRIE-PLAINS PLANTING 47 



TREATMENT OF ALKALINE SOILS 



The important factor in the infertility of black alkali soils, according 

 to Breazeale and McGeorge (6), is the poor carbon dioxide relation- 

 ship. Carbon dioxide was found to be either completely absent or 

 markedly deficient. In addition, the high alkalinity of such soils 

 caused a marked depression or even cessation of nitrate and phosphate 

 absorption. Even though there be an abundance of soluble phos- 

 phates, they are unavailable to the plant at a pH of 8.5 or higher, 

 the optimum pH for absorption of phosphates and nitrates being 

 around 6.8. For this reason treatment with sulfur o.r some other 

 acidifying material will benefit the soil. It will be further benefited 

 by addition of large amounts of organic matter such as manure, 

 which in decomposing will greatly increase the supply of carbon 

 dioxide and at the same time counteract the puddled condition 

 prevalent in black alkali soils. 



McGeorge (23), in studying the decline of citrus-growing areas in 

 Arizona found that the clay in these black alkali areas had the peculiar 

 property of fixing sodium in the base-exchange complex of the soil. 

 Practical reclamation measures involve leaching out the alkali or 

 neutralizing it with a calcium salt such as calcium sulfate. Acidifying 

 of the soil or water was suggested. High pH of water was found to 

 be a serious problem in Arizona in midsummer when the water some- 

 times reached a pH of 8.5. He found citrus trees generally well 

 developed and in healthy condition when the soil pH was 8.45 or less. 

 In extremely alkaline soils calcium starvation may be a factor in poor 

 growth of plants. 



If black alkali is present the soil can be improved with gypsum 

 (calcium sulfate), sulfur, or other acid-forming material. These ma- 

 terials are applied at the rate of 200 to 1,000 pounds per acre, and as 

 high as 2 tons in case gypsum is used. 



If a thin layer of impervious soil is found within 3 or 4 feet of the 

 surface, and is underlain by a more porous material such as sand, it 

 will be feasible to lay tile to drain localized alkali spots. 



There are other measures that can be used to supplement under- 

 drainage. Among these are scraping the salts from the surface of 

 the soil at a time when the soil is rather dry and when a high propor- 

 tion of the salts are located in the top inch of soil. Also recommended 

 are deep tillage, good cultivation, avoidance of leaky irrigation ditches, 

 and heavy applications of manure. None of these measures are 

 substitutes for underdrainage. They merely supplement it. 



SOIL TESTING AND INTERPRETATION 



Soil tests can be of aid in determining the method of handling 

 alkali soils. A suggested method is to sample several of the alkali 

 spots from the surface to a depth of 2 or 3 inches and then at the 

 1-, 2-, 3-, and 4-foot levels. 



Field test kits developed by Truog, Spurway, and other investi- 

 gators can be of aid to the nurseryman in determining the type of 

 alkalis present and to gage the approximate treatment needed. 



The minimum test should include pH, chlorides, sulfates, and a 

 test for presence of carbonates. These tests might well be supple- 

 mented by a laboratory test for total soluble salts and a test for 

 sodium. 



