for Twenty Years in succession on the same Land. 
307 
Average annual produce and increase hij Rape-calie. 
Rape-calvc is estimated to contain, on tlie average, about 4'75 
per cent, of nitrogen. It also contains a large amount of car- 
bonaceous organic substance, and about 8 per cent, of mineral 
matter. It has been applied on 4 plots each year ; on one alone, 
on one with superphosphate, on one with the " mixed alkali- 
salts," and on one with both superphosphate and the mixed 
alkali-salts. For the first 6 years 2000 lbs. = 95 lbs. nitrogen, 
were applied per acre per annum ; but during the next 1-i years 
only 1000 lbs. = 47-5 lbs. nitrogen. Table XXXVIII. (p. 308) 
shows the produce over the first 6 years with the larger amount, 
over the last 14 years with the smaller amount, and both produce 
and increase over the whole 20 years. 
It is first to be observed that where the rape-cake is used 
without superphosphate, Plots 1 and 3, there is much less defi- 
ciency of produce, both corn and straw, compared with Plots 
2 and 4 with superphosphate, than in the experiments with 
ammonia-salts without, compared with those with, superphos- 
phate. The fact is that the rape-cake itself supplies some 
phosphates ; so that superphosphate has less effect when added 
to it than to ammonia-salts. The general result is, that the 
rape-cake alone, and the rape-cake and mixed alkali-salts, yield 
considerably more of both corn and straw than ammonia-salts 
alone, or ammonia-salts and mixed alkali-salts ; but, where used 
with superphosphate, there is more produce of both corn and 
straw from a less amount of nitrogen supplied as ammonia- 
salts, or nitrate of soda, than from a larger quantity in rape- 
cake. 
Thus, over the first 6 years, rape-cake in amount supplying 
95 lbs. of nitrogen per acre per annum was applied, and over 
the same period ammonia-salts = 82 lbs. of nitrogen. But 
where each was used with superphosphate, whether without or 
with the addition of the mixed alkali-salts, there was more 
produce of both corn and straw by the ammonia-salts than by 
the rape-cake. In fact, there was not much less barley-grain, 
though a greater deficiency of straw, with superphosphate and 
ammonia-salts = only 41 lbs. of nitrogen, than with super- 
phosphate and rape-cake = 95 lbs. of nitrogen. 
Over the next 14 years the application of rape-cake was 
reduced to 1000 lbs. per acre per annum = 47-5 lbs. nitrogen ; and 
where ammonia-salts = 82 lbs. nitrogen had previously been 
applied, the quantity was also reduced to one-half = 41 lbs. 
nitrogen. The result in each case was that, with superphosphate 
and the reduced amount of nitrogenous manure, there was an 
average annual produce of about as much corn, though less 
VOL. IX. — s. S. y 
