324 EXPERIMENT STATION RECORD. 



" The percentage of crops which show au increase in growth caused by the 

 addition of potassium fertilizers, decreases from 86.7 with soils containing less 

 than 50 parts per million of active potash to zero in soils containing 800 to 

 1,000 parts per million of active potash. The effect of the potash decreases 

 with the active potash in the soil. 



" The percentage of crops injured by the potash increases with the quantity 

 of active potash in the soil. 



" The effect of the addition of potash to the soil upon the average weight of 

 the crop in the pot experiments decreases with the quantity of the active potash 

 in the soil. When the soil contains more than 200 parts per million of active 

 potash, addition of potash does not increase the average weight of the crop, but 

 often decreases the crop. 



" The average percentage of potash contained in 235 crops increased with the 

 percentage of active potash in the soil. The average quantity of potash removed 

 from the soil by the crops increases with the quantity of active potash in the 

 soil. Relatively enormous quantities of potash are removed by the crops in 

 these pot experiments. Expressed in terms of bushels of corn equivalent to the 

 potash removed, the quantity averaged 5S.6 bu. in soils containing less than 

 50 parts per million of active potash and 413.8 bu. in soils containing 600 to 

 800 parts per million. 



" Deficiency of plant food is a relative term and depends upon the growth 

 which can be made under the conditions of the experiment. Soils containing 

 less than 50 parts per million of active potash were deficient in 87 per cent of 

 the pot tests and the average crop without potash is 67 per cent of that with 

 potash, and yet these soils gave up enough potash to the crop to produce 58 bu. 

 corn to the acre, on the average. 



"There is a loss of active potash consequent upon the cropping of the soil. 

 The loss is approximately one-half of the potash talsen up by the plant when 

 the active potash exceeds 100 parts per million. When the active potash is 

 between 50 to 100 parts per million, the loss is about one-fifth of the potash 

 taken up by the plant. When the active potash is about 50 parts per million 

 or less, there may be no observed loss." 



The feeding' of plants with mineral matter through the leaves, L. Hiltneb 

 (Prakt. Bl. Pflanzenbaii u. Schutz, n. scr., 10 {1912), No. 1, pp. 6, 7, fig. 1; 

 Deut. Obstbau Ztg., 1912, No. 7, pp. IJfS, lJ,.'i, fig. 1).—A brief account is given of 

 the growing of raiie plants in sterile sand practically free from potash, certain 

 of the plants receiving no application of potash while in other cases a 2 per 

 cent solution of potassium sulphate was painted upon the leaves from time to 

 time but no potash was applied to the soil. The plants grown in sterile sand 

 without potash made practically no growth while those on which the potash 

 solution was applied to the leaves grew and matured normally. 



Results of cooperative fertilizer tests on clay and loam soils, J. B. Abbott 

 and S. D. Conner (Indiana Sta. Bui. 155, pp. 99-132, figs. 7). — Duriug the past 

 8 years about 225 cooperative fertilizer tests on clay and loam soils have 

 been undertaken by the station, mainly with corn and wheat, but also including 

 cats, potatoes, cannery tomatoes, and one or more experiments with each of 15 

 other crops of less general importance. Such of the results of the corn, wheat, 

 oats, potato, and tomato experiments as are deemed of value, one timothy ex- 

 periment, and a few miscellaneous experiments, are included in this bulletiu. 



The, results of these experiments are summarized as follows : 



"In the com fertilization experiments, complete fertilizer gave the largest 

 average increase, but phosphoric acid and potash gave the largest average 

 profit. In the amounts used on corn, nitrogen caused a small average increase 

 and was used at a loss, potash caused a larger average increase and was used 



