FERTILIZERS. 335 



The topics treated are the elements and sources of plant food, the nature and origin 

 of soils, the number and distribution of soil bacteria, and the chemical changes 

 produced by bacteria. 



FERTILIZERS. 



Contribution to the solution of the question of the extent to 

 which the potash requirements of soil can be determined by- 

 analysis of the plant and the soil, (). Lemmeemann (Landw. Vers. 

 Stat., 4!) (1897), N~os. 4-5,pp. 287-339). — Both field and pot experiments 

 on this subject are reported. Experiments in the field were made on 

 unfertilized soils and those which had received kainit at rates of 1,000 

 to 2,000 kg. per hectare (about 890 and 1,780 lbs. per acre). The crops 

 grown were oats, wheat, and rye. The potash content of the soils was 

 determined by digesting 200 gm. with 400 cc. of 10 per cent hydro- 

 chloric acid on a boiling water bath for 3 hours. The attempt was made 

 first to determine what amount of potash soluble in this reagent is nec- 

 essary in a soil in order to produce normal crops. It was found in these 

 experiments that a soil containing 0.21 per cent of potash soluble in 10 

 per cent hydrochloric acid was not improved for the production of oats 

 by applications of potassic fertilizers, although the yield of wheat and 

 rye on such soils was considerably increased by applications of such 

 fertilizers. No relation was observed between the amount of potash in 

 the soil and that found in the plant. Samples of soil were treated with 

 tV? 45 h I? aD( i 5 P er cent hydrochloric acid, the soil so treated being 

 used in pots for the growth of oats. The object in this case was to 

 determine the exact strength of acid and method of treatment which 

 would remove all of the potash assimilable by oats. The experiments, 

 however, gave negative results because the oats grew best in the soils 

 which had been exhausted with the stronger acid. The author believes 

 this to be due to chemical changes which render the potash not dissolved 

 by the acid more accessible to the roots of the plants and at the same 

 time more assimilable. Contrary to the results obtained in the field, 

 the potash content of oats grown in pots increased with the amount of 

 this substance applied to the soil. 



The liming of soils, H. J. Wheeler (U. 8. Bept. Agr. Farmer's 

 Bui. 77, pp. 19).— This bulletin discusses the use of lime for improving 

 soils, its manurial and chemical action, its physical effects, and its effects 

 on the action of microscopic organisms in the soil. The conditions 

 under which lime may be injurious are pointed out. The influence of 

 lime upon some plant diseases is noted and directions for the applica- 

 tion of lime to soils are given. Fifteen forms of lime used for agricul- 

 tural purposes are described. 



"There are many soils in which lime is deficient, notably in soils derived from 

 granite, mica schist, and sandstone formations. On such soils lime is of direct value 

 in supplying a necessary element of plant food. 



"The indirect value of lime is perhaps more important than its direct action, 

 because probably the majority of cultivated soils contain sufficient lime to meet tin; 

 direct demands of plants. Lime is of indirect value in unlocking the unavailable 

 potash, phosphoric acid, and nitrogen in the soil. 



