BARLEY. 77 



manure and rape-cake (Series 4, plot 4), it ranged from 62£ 

 bushels in 1857 to 21 bushels in 1887. 



Looking to the average produce of each of the five eight- 

 yearly periods, it is seen that, under all conditions of manur- 

 ing, even in the case of the rape-cake with its annual accumu- 

 lation, there is a general tendency to reduction in produce Gradual 

 from the first and second periods to the third and fourth, r . ed ^^ 

 and still more in the fifth period compared with the third and mpro 

 fourth. Then, again, the average produce is in every case 

 lower over the second than over the first twenty years. But 

 examination of the details shows that there was, nevertheless, 

 frequently more than average produce in individual years 

 during the latter half of the whole period. There was, in 

 fact, great fluctuation due to season; but there is also 

 evidence of reduction due to exhaustion in some cases. 



The bottom line of the tables, which shows the percentage 

 reduction in the amount of produce over the second twenty- 

 years compared with the first twenty, enables us to dis- 

 criminate in some degree between the effects of exhaustion Effects of 

 and those of season. exhaustion 



It is seen that the four plots of Series 1 show a reduction 

 over the second twenty years of from about 30 to 40 per 

 cent, or about twice as much as in the case of either of the 

 other series. There is here evidence that in the case of 

 Series 1, without nitrogenous manure, much of the reduction 

 over the second half of the period was due to nitrogen Nitrogen 



exhaustion. exhaustion. 



In Series 2, with ammonium-salts, there is about 21 per 

 cent reduction on plot 1, where the ammonium-salts are used 

 alone, nearly as much on plots 2 and 3 with defective 

 mineral manuring, and only about 12 per cent where full Effect of 

 mineral manures are used in addition. mineral 



to-o-t t -i i • i •• i> manures. 



In Series 3, with sodium nitrate, there is a reduction or 

 about 23 per cent where the nitrate is used without mineral 

 manure, of 21 per cent where it is used with potash, soda, 

 and magnesia, but without phosphate (plot 3), and of only 

 14 to 17 per cent where phosphates were used in addition to 

 the nitrate. 



Lastly, in Series 4, with rape-cake, which contains a con- 

 siderable amount of mineral matter, there is a reduction of 

 about 18 per cent on plots 1, 3, and 4, but of only about 14 

 per cent on plot 2 with superphosphate only as the mineral 

 manure. 



As already intimated, that there should be any reduction influence 

 in the yield over the second half of the period where rape- °^ ason ' 

 cake with its annual residue and accumulation is used, is exhaustion 

 evidence that part of the reduction is due to an average of andphos- 

 less favourable seasons over the later period. But that there ^xhaustton. 



