200 Mainiriiiff Jar Ihtji 



(T)) The indications as to the, manurial hcmmIs of the soil with respect 



to supplies of nitrogen, phosphate and potash arc as follows: 



Increased 3delds on 



Nitrato plots Ammonia |)lots 

 (7, !», 11) (8, 10, 12) 



p<'r cent. per cent. 



Kffpct of siii)i)lyiii;^ nitrogen 



[Plots n, 12"compaml with 1. 13] 29±5J 8±5i 



Kflft'ct of supplyini; plio.S|)hatc 



[Plots 9, 1(1 compared with 11, 1-'| 16±8 20±7i 



Effect of supplying potash 



[Plots 7, 8 compared with !), 10) fl±81 f)±7i 



The results indicate a marked response to nitrogenous manuring 

 in the form of nitrate of soda, a much less sharply defined response 

 to phosphate, and no measurable response to potash. The reasons 

 for the poor response to nitrogen wIkmi applied in the form of ammonium 

 salts will be dealt with later. 



In considering the records of experiments of this character the 

 averages can give only a partial indication of the real effects of the 

 differences in treatment of the various plots. It is desirable to study 

 also the changes step by step throughout the whole period of the experi- 

 ment. It is not our intention, however, in the present communication 

 to enter into detailed discussion of the yearly records. We would 

 merely indicate that the yearly records show little falling-oiT as yet 

 in the productivity of the unmanured plots, whilst the plots receiN-ing 

 dung seem to have reached practically the limits of their productive 

 powers, giving on the average a crop which is roughly double that 

 on the unmanured plots. This is the case even on Plot 3 (dunged aiul 

 tuuiianured in alternate years). The records of this plot show a steady 

 iinprovenu'nt in condition with the result that in the later years (prior 

 to the reduction in the dressing of dung in 1913) the yields obtained 

 from this plot were almost ecpial to those obtained from any other 

 plot of the dung series, as the following summary shows: 



Average YiMa {per aerc) for the Five Years 1909-13. 



Plot 2 Plot 3 Plot 4 



cwts. cwts. cwt.s. 



60-8±3-0 47-3±l-8 52-0±2'6 



In 1914 the yield frotn Plot 3 fell considerably below that from the other 

 "dung jjlots, " but it is, of course, too early yet to say whether thi.s 

 is purely a seasonal fluctuation or is to be attributed to the reduction 

 in the dressing of dung in 1913 from 10 tons to fi tons per acre. 



