EFFECT OF MTKMXiKN Al.ONK i:,; 



weeds and the same general aspct-t as tlic (•<»iitiminii>l\ 

 iinnianured plot. 



II. Use of Nitrogenous Mdmnrs ah^nr. 



Three of the plots — 17, 5, and 1— show the efVcct of tlic 

 long-continued use of nitrogenous without any mineral iiianun >. 

 Plot 5 has been receiving 86 lbs. of nitrogen as .iimiK.niiiin 

 salts, Plot 17 half the quantity of nitrogen in the sha^x' nt 

 nitrate of soda, and Plot 1 the same half quantity of nitii)L:(n 

 as ammonium-salts, though on this plot dung was ai)pli((l in 

 each of the first eight years of the experiment. It is ww 

 evident when a nitrogenous manure is used alone for uras>, 

 nitrate of soda is far more effective than the ammonium-salts; 

 ('.a., on Plot 17 it has given an average crop of :]."> ewt. 

 against 26 cwt. produced by double the quantity of nitni;_;en 

 in ammonium-salts on Plot 5. 



For this superiority of the nitrate of soda twcj reasons may 

 be traced ; being completely soluble it sinks deeply into the 

 soil, and encourages grasses of a deeply-rooting habit, \\lii(li 

 not only obtain more food from the soil, but also are better 

 al)le to withstand the droughts of spring and early summer. 

 On Plot 17 (nitrate) deep-rooting grasses like Mmdow 

 Foxtail and Downy Oat Grass are prominent, whereas the 

 plots receiving only ammonium-salts are almost wholly occupied 

 l)y Sheep's Fescue and Connnon Bent, whose feeding- roots are 

 close to the surface, where the ammonium-salts are cauulit and 

 retained by the humus in the soil. 



The continued use of large applications of amiiionimii->alt- 

 has also had an injurious effect upon the reaction of the soil, 

 since it behaves as an acid, and C(jntinually remov(\s carlKHiatc 

 of lime. The creeping surface vegetation tends to aceiiniiilatc 

 and decays into a substance resembling peat ; at the same tiim- 

 the vegetation shrinks into tufts, between which ai-e bare 

 patches of l)lack soil, showing- an aeid reaction to liinni- 

 paper. So pronounced had this effect become on Plot .">. 

 which received the larger amount of anunonium-s^ilts, that the 



