SOILS FERTILIZERS. 319 



relation to niaintiiining the soil fertility. Ceueral information is given regard- 

 ing commercial fertilizers, soil correctives and stimulants, and their use. 



The duration of the action of manures, A. D. Ham. (Jour. Roy. Agr. Soc. 

 Englund, 7.', (1913), pp. 1 J 0-1 26). —Thlfi article is based upon results of experi- 

 ments begun at Kothamsted in 1004 with an alternating rotation of wheat and 

 root crops on " eight sets of five [ilats; five for nitrogenous manures — dung made 

 from roots and hay only, cuke-fed dung, shoddy (wool waste). Peruvian guano, 

 rap(? dust, and three for i)hosphatic manures — bone meal, superphosphate, and 

 basic slag. Once during each rotation a dressing of superphosphate and sul- 

 phate of potash was applied equally to all the nitrogen plats; similarly for the 

 corn [grain] crops a dressing of sulphate of ammonia was given alike to all the 

 phosphatic plats. For each manurial .series there was one check plat un- 

 manured." 



Of the manured plats "one received the manure in 1004, but remained un- 

 manured in 100.5, lOOC. and 1007; a second plat was manured in 1006, but not in 

 1!K)7 ; the third in 1007. Thus in 1007, by which year the experiment was in full 

 swing, there was a plat that had been manured in that year, another that had 

 been manured in the previous year ; a third two years previously ; and a fourth 

 three years previously. In 1008 it was considered that the manure applied in 

 1004 to the first plat had been exhausted by the four crops grown with it, and 

 the manuring was renewed on that i)lat ; on the second plat it was renewed in 

 1000. and so on ; the result being that in any year after 1007 there was a crop 

 grown on some plat with the manure; on a second plat with the residue of the 

 manure after one crop had been taken; on a third with the residue after two 

 crops; and on a fourth with the residue after three crops; while there was a 

 further check plat that had never received the manure." 



The conclusions reached are summarized as follows: "As regards farmyai'd 

 manure we can distinguish between the nitrogenous compounds introduced by the 

 consumption of cakes and other concentrated feeding stuff and the compounds de- 

 rived from the straw and the undigested residues of such coarse foods as hay. 

 The former will have an immediate effect on the first crop, and to a much smaller 

 extent on the second crop, after which they disappear: the latter compounds 

 act slowly, do not waste, and have a measurable value for many years, though 

 for practical purposes we may neglect their action after the fourth year. 



"Among nitrogenous fertilizers ammonium compounds and nitrate of soda 

 have no perceptible action after the first year; Peruvian guano, rape cake, and 

 similar fertilizers containing proteins leave very little residue after the first 

 year, and none after the second. On the other hand, nitrogenous fertilizers of 

 the wool, hair, bone class are slowly acting and nonwasting; their effect may 

 be expected to persist for at least four years. 



" Phosphatic fertilizers, even when soluble like superphosphate, do not waste 

 in the soil, and their residues continue to be effective until they have been 

 exhausted by the crops. 



" To one other point attention may be called, though it does not arise strictly 

 out of these experiments. It is seen that the residues of active nitrogenous 

 fertilizers are wasted; this wastage takes place in the winter, for soils in the 

 autumn after the crop has been removed become very rich in nitrates, which 

 usually disappear before the spring. Hence, especially in rich soils, there will 

 be a great economy if before the winter the land can be occupied by a rapidly 

 growing catch crop which will convert these fugitive nitrates, etc., into insol- 

 uble plant material, afterwards plowed in to become available for another 

 crop." 



Intei-preting fertilizer tests, C. E. Thokne (Jour. Amer. 8oc. Agron., 5 

 (1913), No. S, pp. 129-137). — ^A reply to criticisms of the plan of fertilizer 



