SOILS FERTILIZERS. 1017 



of the oxidatidii. Tlu> most of the rota I'dat ion was due to the action of the 

 potassiuni itself and not to the formation of acid conditions in the solution. 

 Sodium or anunonium salts of the same acid were more favorable to oxidation 

 than the cori'esponding potassium salt. 



" Phosphates usually prodnceil material increases in the oxidation in solu- 

 tions to which they were added. 



" Chlorids and sulphates, when combined with a suitable base, like sodium, 

 are somewhat beneficial to oxidation, but are not as favorable as the corre- 

 sponding? nitrate would be. 



"The presence of toxic orf;;anic substances in solution was extremely delete- 

 rious to the oxidizing power of plants. The oxidizing power of the plants, 

 especially in the in-esence of nitrates, was able to alleviate the toxicity of such 

 solutions. 



"The process of oxidation by roots is largely, if not entirely, due to the 

 activity of a peroxidase produced by the roots. This oxidizing enzym is most 

 active in neutral or slightly alkaline solutions. The activity of the enzym 

 may be inhibited by the jiresence of acid and also by the conditions in solutions 

 where i)utrefacti()n processes occur." 



Soil im^provement work, S. D. Conner (Indiana Sta. Rpt. 1908, pp. 39-^2). — 

 A brief statement is made regarding the cooperative soil improvement experi- 

 ments which have been conducted in 45 different localities in 3.3 counties of the 

 State, and a fuller account is given of two such experiments on peat soil in 

 Xewton and Henry counties and one on a clay soil in Scott County. The peat 

 soils have been found to be greatly benefited by applications of potash, while in 

 the clay and loam soils phosphorus ai»pears to be the element most needed. 

 These soils are also much benefited by ground limestone and slaked lime. 



Soil fertility, T. F. Hunt (PcnnHyJi-ania Sta. Bui. 90, pp. 26, charts 7).— This 

 is a summary of the results of a series of fertilizer experiments on a clay loam 

 soil of limestone origin which have been carried on for 25 years at this station. 



The more important facts brought out by the results are that phosphoric 

 acid is the only fertilizing constituent which produced an increase in yield when 

 used alone. A larger increase, however, was obtained when both phosphoric 

 acid and i)otash were used. The productive i)Ower of the soil was maintained 

 during the 25 years by applying in alternate years 48 lbs. of phosphoric acid 

 and 1(»() lbs. of potash per acre in a rotation in which clover occurred once in 

 4 years, but a material increase in yield resulted from the addition of 24 lbs. 

 of nitrogen per acre to the mineral fertilizers. Nitrate of soda gave better 

 results as a source of nitrogen than either dried blood or sulphate of ammonia. 

 An acid condition, proving especially injurious in later years to corn and clover, 

 resulted fnmi the continued ai>iilicatl<)n of sulphate of anunonia. 



The crop producing power of the soil was maintained during the 25 years 

 without the use of any yard manure. " Without the addition of any organic 

 matter to the soil, except the roots and stubble of the crops raised, the fertility 

 has been fully maintained. In other words, a complete commercial fertilizer 

 and yard manure having maintained the crop producing power equally well in a 

 4 years' rotation containing clover. Comparatively small quantities of yard 

 manure applied on alternate years, viz, to the corn and wheat, have produced 

 marked increase in yield comiiared with plats receiving no fertilizer. . . . 

 The addition of 4,000 lbs. of quick lime applied once in 4 years to plats receiving 

 no fertilizer has caused flu; decrease in yield, but when applied in connection 

 with () tons of yard manure the products produced were e(iual to those produced 

 by an application of 10 tons of manure without lime." 



The general conclusion arrived at is that economic farm management under 

 the conditions obtaining in these experiments retiuires the use of yard manure 



