191T1 SOILS FERTILIZEES. 627 



sodium nitrate gave a larger average increase in crops than either dried blood 

 or ammonium sulphate. During the first ten years of the experiment, ammonium 

 sulphate was superior to eitlier sodium nitrate or dried blood, but later the 

 yields declined and crops began to fail on the ammonium sulphate plats. 



None of the plats used In this comparison of sources of nitrogen liave been 

 limed since the experiment was begun. " On the plats where the heaviest appli- 

 cations of sulphate of ammonia have been made there are large areas where all 

 crops fail. This we believe is due to the acidity of the soil, especially since in 

 pot cultures, when soil from tliese most acid plats was limed, the yields of clover 

 were excellent. . . . The nitrate of soda plats are least acid, and the crop 

 yields are probably not reduced by a lack of lime. On some of the dried blood 

 plats the acidity has become too great for a good growth of clover though other 

 crops do not show signs of injury." 



Complete commercial fertilizers, except where ammonium sulphate was 

 used, and barnyard manure were about equally efficient In maintaining the fer- 

 tility of the soil. The heavier applications of each caused the yields during the 

 last five or ten year periods to exceed those of the first five or ten year periods 

 of the experiment. 



Manure applied in different amounts showed that there is economy in light ap- 

 plications when used for general farm crops. The money return per ton of 

 manure, when applied at the rate of 6 tons per acre twice in a rotation, was 

 $3.29 as compared with $2.29 per ton when applied at the rate of 10 tons per acre 

 twice in the rotation. 



Lime either as slaked lime or as carbonate of lime applied alone in large 

 amounts frequently gave a small increase in yields of crops. Burnt lime alone 

 during a period of 35 years gave an average increase of 701 lbs. of total prod- 

 ucts per acre in a rotation, as compared with the untreated plats immediately 

 adjacent. Pulverized raw limestone under the same conditions gave an aver- 

 age increase of 1,334 lbs. of total products in a rotation, as compared with un- 

 treated plats nearest to the pulverized limestone plats. The larger return from 

 burnt lime was where it was used in conjunction with barnyard manure. In 

 this case there was an increase of 1,001 lbs. of produce per acre in a rotation 

 valued at $6.38. Land plaster or gypsum had no measurable effect on the crops 

 grown and did not prevent the soil from becoming acid. 



" For the limestone soils of Pennsylvania it is recommended that manure be 

 applied at tlie rate of about 6 tons per acre for corn, and supplemented with 

 200 lbs. per acre of acid phosphate. For oats which follow the corn, no fertilizer 

 will be required. For the wheat which follows oats, 350 lbs. per acre of acid 

 phosphate, 100 lbs. of muriate of potash, and not more than 10 lbs. of nitrogen, 

 preferably In an organic form, Is recommended. For the clover following wheat, 

 no fertilizer will be required. On timothy occurring the fifth year in a rotation, 

 a top-dressing of 150 lbs. of acid phosphate, 150 lbs. of nitrate of soda, and 50 

 lbs. of muriate of potash will give good results." 



Injurious effect of farmyard manure on the balance of nitrogen in the soil, 

 A. Sabashnikov (Sabachnixov) (Selsk. Khos. i Liesov., 250 {1916), Jan., pp. 

 5-19; abs. in Intemat. Inst. Agr. [Rome], Intemat. Rev. Sci. and Pract. Agr., 

 7 (1916), No. 6, pp. 802, 803; (Them. Ahs., 11 {1911), No. 9, p. 1242).— The chief 

 influence of barnyard manure on the balance of nitrogen in the soil is attributed 

 to the organic matter it contains and not to microorganisms, which are con- 

 sidered of secondary importance. The organic matter In the manure (espe- 

 cially undecomposed straw), being a good source of carbon for the soil micro- 

 organisms, contributes (1) in an aerobic environment to the assimilation of 

 nitrates, ammonia, amids, and gaseous nitrogen, and their deposition in protein 



