VALrK OF FAI.'M\AIM) \l WIIM Km 



maiuire. Even wlion \hv plant docs not cntiiclx fail it lias 

 been often nt)tieeil that, if a spoil uf liot weather comes in the 

 early part of the season, the plant on the dnn^ed plots will lie 

 growing vigorously when that on the othei- plots is still 

 struggling for exislenee. Later on, when all ihe jilani i^ 

 •established, the ditierences are not so marked, an<l in la\onial)|r 

 seasons the crop on the plots manured with artilieials ri\al> 

 the crop grown with dung, if due allowance be made for the 

 larger amount of nitrogen actually supplied to tlie dunged plots. 



The right-hand portion of the diagram Fig. 14, page KM. 

 shows the effect of the successive additions of other niti-ogeiions 

 manm'es to dung. 



Considering first the crops on Plot 1, in each series (see 

 Table XL., page 98), we find that notwithstanding the large 

 amount of nitrogen which the dung supphes, and its accunuila- 

 tion in the soil, yet dressings of quickly-acting nitrogenous 

 manures will still bring about an increase of crop, 'i'he 

 amount of nitrogen annually supplied to Plot 1-0 is mnch 

 greater than is removed by the crop, hence there nuist be a 

 considerable accumulation of nitrogen from year to ycai- in the 

 soil of this plot. Nevertheless, these reserves cannot become 

 active quickly enough for the needs of so rapidly growing a 

 plant as the mangel, hence the increase which is seen when a 

 further addition of active nitrogen in the shape of ammoninm- 

 ^alts or of nitrate of soda is made. 



When more than 86 lb. per acre of nitrogen is adde<l, as on 

 Plot 1 C, which receives 98 lb. of nitrogen as rape cake, or 

 as on Plot 1 AC, which receives 184 lb. of nitrogen as rape 

 ■cake and ammonium- salts, no further increase of crop is >. i n, 

 the average remains stationary at 24 tons per acic The (r(»p 

 has, in fact, attained its maximum, and is limited, noi b\ the 

 amount of nitrogen and other plant food available, bm l.\ its 

 restricted period of growth, or l)y a scarcity of water, sindiiiht, 

 and other factors of development. 



Turning to a comparison of Plots 1 and 2, some interesting 

 results are to be seen ; both receive a sinnlar dressing of 



