622 
Rotation of Crops. 
that the land was practically fallowed for the barley ; and now 
in the case of the fourth crop — the wheat — there was the pre- 
paration either of the growth of a leguminous crop leaving a 
highly nitrogenous residue, or of fallowing. Then with super- 
phosphate alone, the produce of barley, and the yield of nitro- 
gen in it, were less than without manure where the turnips 
had been removed, but more where they had not, and where, 
therefore, there was an available nitrogenous residue from the 
roots ; and now in the wheat, the effects on the available supply 
of nitrogen, on the one hand of the growth and removal of a 
leguminous "crop, and on the other of actual fallow, are obser- 
vable. Lastly, with the mixed manui'e the influence of the 
direct supply of nitrogen for the first crop of the course is 
obvious. But, as the amounts of nitrogen taken up were not 
very much more than where none had been supplied, it is 
evident that in both cases much must have been due to 
the influence of the preceding leguminous crop or fallow. 
Upon the whole there can be no question that, so far as 
nitrogen is concerned, the supply within the soil in a condition 
of combination and of distribution available to the wheat is 
increased, both by fallow, and by the growth of a leguminous 
crop, especially of clover ; and, further, that such accumulation 
of available nitrogen by fallow, and of nitrogenous crop-residue 
by the growth of leguminous crops, is the greater when the soil 
and subsoil are not abnormally exhausted of organic nitrogen. 
Lastly, it is to be observed that, under all conditions of 
manuring, or other treatment, there was, both in the rotation 
and in the continuous wheat crops, more than twice, and in 
some cases considerably more than twice, as much of the total 
nitrogen of the produce stored up in the grain as in the straw. 
Hence, in the sale of the grain, and the retention of the straw 
for home use, by far the greater part of the nitrogen of the 
crop is exported from the farm. 
The Amounts of Total Mineral Matter ( Ash) in the 
Rotation, and in the Continuous Crops. 
The results are given in Table VII. for each of the four 
descriptions of crop, in exactly the same form as those for the 
total dry matter and the nitrogen, in Tables V. and VI. re- 
spectively. 
The record is deserving of careful study, as showing the 
very various, and sometimes very large, amounts of mineral or 
ash-constituents taken up from the soil, and stored up in the 
different crops, or parts of the crops. But, it must suffice here to 
