630 EXPERIMENT STATION RECORD. 



"The amount tolerated varies with the variety of the same plant, as shown in the 

 grape. 



"The amount of alkali tolerated by the various cultures varies with the nature of 

 the soil. It is lowest in heavy clay soils and fine-grained soils, in which the down- 

 ward movement of plant roots is restricted; and highest in loam and sandy soils, in 

 which the roots have freedom of penetration. 



"Some plants, such as the saltbush and alfalfa, are quite susceptible to alkali salts 

 when young, but when the roots penetrate deeply, and the ground is heavily covered 

 with the foliage of the plant, they are immune to a very large extent. 



' ' Lands neavily charged with alkali may often be made productive for certain crops 

 by the application of irrigation water in sufficient amount to leach the salts down to 

 a depth of several (5 or 6) feet, and by preventing their subsequent rise by proper 

 mulching, or cultivation until the foliage of the plant itself will prevent evaporation 

 of the soil moisture from the surface of the ground. Alfalfa culture has thus been 

 made highly profitable in lands once so strongly charged with alkali as to kill all 

 vegetation. 



" The reclamation of lands charged with carbonate of soda by neutralization with 

 gypsum often renders possible the profitable planting of such crops as withstand 

 large amounts of common salt or of glauber salt. 



" The effects of carbonate of soda are seen in the yellowing of the leaves of the 

 tree caused by its corrosive action on the root-crown, whereby the proper flow of 

 sap and food supply to the leaves is prevented. The effect of common salt is seen in 

 the falling of the leaves from the newer branches, and in the blackening and curling 

 of the leaves of pears. 



"Sulphate of soda (glauber salt) is hurtful only when present in very large 

 amounts, most cultures doing well in more than 10,000 lbs. per acre in 4 ft. depth; 

 saltbush, hairy vetch, alfalfa, and sorghum grew well in more than 61,000 lbs. 



"Barley is better adapted to alkali land than is wheat, for it will withstand the 

 effects of twice the amount of carbonate of soda and common salt. Of course, the 

 carbonate may be neutralized with gypsum, and in the absence of much common 

 salt will permit of the growth of excellent crops of wheat; but where the amount of 

 common salt exceeds 5,000 lbs. barley should be given the preference over wheat." 



The relation of lime and magnesia to plant growtli, 0. Loew and D. W. May 

 ( U. S. Dept. Afjr., Burmu of Planl Tndmlnj Bui. 1, pp. 5S, pis. 5).— This bulletin dis- 

 cusses the liming of soils from a physiological standpoint, explaining in detail the 

 physiological role of calcium and magnesium in plant growth (E. S. R., 11, p. 1008), 

 and showing the ratio between lime and magnesia in the soils of different countries, 

 and reports water, sand, and soil cultures to determine the proper ratio of lime and 

 magnesia for certain plants, including cowpeas, privet, tobacco, barley, oats, wheat, 

 and beans. The nitrates, sulphates, and carbonates of calcium and magnesium were 

 used in the sand and soil cultures in various combinations and proportions (on the 

 basis of molecular weights). In the water (cultures only the more soluble nitrates 

 and sulphates were employed. 



The principal results are thus summarized: 



"Soil analyses show that lime and magnesia are widely distributed in soils, and 

 generally in sutticient quantities for the direct needs of plants. They are not always 

 in the best proportions to each other, from a physiological standpoint, for favoring 

 plant growth. 



"Magnesia in a soil in great excess over lime, in a finely divided or soluble condi- 

 tion, is noxious to the growth of plants. With a great excess of lime over magnesia 

 the physiological action of the plant is hindered, and it exhibits phenomena of star- 

 vation. An excess of lime counteracts the poisonous effects of magnesia, while the 

 more favorable proportion of the two bases obviat<^s the poor nutrition of the plant. 



"The best proportion of soluble lime to soluble magnesia for the germination and 

 growth of plants is about molecular weight 5 to 4, or actual weight 7 to 4. 



