116 EXPERIMENT STATION RECORD. 



«ick soils can best bo cured by materials wliicli restore the original acid 

 reaction ; acid canal sediment and moor peat turf are best for this purpose. The 

 same change can be brought about by use of acid artificial fertilizers, but they 

 are not so effective if the abnormal condition is marked. A sick crop can be re- 

 stored to health by the innnediate application of manganese sulphate; this has 

 no beneficial effect if applied beforehand, as it does not remain in an effective 

 form in the soil. The explanation of the effect of manganese sulphate is not 

 found in an insufiicient content of manganese in the soil. 



The properties of the humate-silicate compounds in sick and normal soils 

 vary as follovi^s: Normal soils contain more alkali-soluble (in 5 per cent am- 

 monia) compounds. The composition of these compounds easily soluble in 

 ammonia is the same in sick and normal soils, while the difiiculty soluble in 

 normal soils contains more silicic acid, iron, and aluminum; the insoluble in 

 sick soils contains more lime and also more iron than in the normal soils, though 

 the total iron content of sick soils is lower than that of normal soils. The 

 insoluble compounds in sick soils, like the soluble, are poorer in silicic acid than 

 in normal soils; the latter contain more colloidal silicic acid than the former. 



The capacity for absorbing potassium and ammonia is higher in sick than in 

 normal soils, or at least never lower. In both soils a great deal of the amount 

 absorbed is easily washed out and the amount washed out is greater in the 

 case of the sick soil ; in an alkaline reacting humate this goes into solution. 



Sick and normal soils vary in respect to physical properties. Normal soils 

 under most conditions when sampled in the field seem to contain more moisture, 

 which may be ascribed to the higher content of organic matter. Sick soils 

 have a looser structure and contain organic matter which swells more with the 

 addition of moistur& than that contained in normal soil. 



Considering the differences in properties of sick and normal and of those 

 recovering — both soil and crop — it is to be concluded that the alkaline reaction 

 (including the action of added nitrates) of the soil plays an important part in 

 the occurrence of " oat sickness." It is suggested that by the increased " au- 

 toxidation " which is the result of this alkaline reaction, great quantities of 

 compounds (peroxids) injurious to plants are formed and the favorable action 

 of the manganese sulphate is due to the catalytic decomposition of these inju- 

 rious peroxids. 



Experiments with soils, fertilizers, and farm crops, C. A. Mooers ( Ten- 

 nessee Sta. Bui. SG, pp. 35-76, 83-88; Rpt. Coop, and Ed. Work Agr. 2Iiddlc 

 Tenn. 1907-8, pp. 7--'iS, 55-60). — This reports the results of two years' experi- 

 ments which were undertaken primarily for the purpose of securing information 

 regarding the fertilizer requirements of various soil types in middle Tennessee. 

 The experiments were as a rule made on fortieth-acre plats of as uniform soil 

 as it was possible to secure. Chemical analyses were made of the soils. 



The systems of fertilizing employed included the use of rarious mixtures of 

 chemical fertilizers, farm manure, and green manure (cowpeas). The crops 

 used in the fertilizer experiments were wheat, corn, sorghum, millet, tobacco, 

 cantaloups, buckwheat, peanuts, clover, and potatoes. 



The results of the experiments agree in showing that the soils of the Central 

 Basin are as a rule well supplied with the mineral elements of plant food (phos- 

 phoric acid, potash, and lime). Occasionally, however, areas were found which 

 responded to phosphatic fertilizers. The principal requirements of the soils 

 seem to be nitrogen and organic matter. The sandy loam soils of the Cumber- 

 land Plateau were found to be very deficient in phosphoric acid and lime. The 

 gray soils of the Highland Rim were apparently particularly deficient in phos- 

 phoric acid, although also in need of potash. The limestone soils of this area 



