On Permanent and Temporary Meadows and Pastures. 221 
speedily the equilibrium which is favourable to good cultivation. 
Analysis gives an equally clear idea as to the amount of cal- 
careous and nitrogenous matter which exists in the soil. If it is 
poor in lime, lime must be laid on with those crops which 
follow the breaking-up of the grass-land, for the purpose of 
rendering assimilable the nitrogen which is necessary to their 
well-being. But lime ought only to be employed in moderation, 
so as not to overstep the mark, and so bring about too active a 
nitrification, which would cause the grain-crops to be laid, and 
prodigally waste the nitrogenous materials which are accumu- 
lated in the soil. 
These reserves are precious, and if on the one hand it is 
useful to draw upon them, it would be a very shortsighted policy 
to waste them recklessly. As the most luxuriant vegetation can 
only absorb annually a small quantity of nitrogen, it is important 
to introduce lime only in such proportions as to render assi- 
milable the quantity of nitrogen necessary for the growing crop. 
One must be guided in this matter by the appearance of the 
crop. If of scant growth, and of poor colour, the quantity of 
lime should be increased. On the other hand, it should be 
diminished if the growth is too quick, the colour too deep, the 
ripening difficult, and the laying of the crops frequent. When 
the soil is rich in lime, the employment of lime is not only 
useless, but will certainly be positively prejudicial, for the 
reasons I have given. In such a case the difficulty will be to 
regulate the action of the lime which the plough brings up and 
mixes with the superficial nitrogenous layer. The most simple 
means of effecting this is to gradually mix the superficial humus- 
holding layer with the subjacent lime by shallow ploughing at 
first, and subsequently by ploughing deeper and deeper. But 
since good cultivation demands a soil deeply stirred, the plough 
may be followed by a subsoiler, so that the soil may be stirred 
to a suitable depth. 
In certain cases we may by a deep ploughing bury the super- 
ficial layer, and afterwards bring it up again gradually by 
shallow ploughings, keeping the soil in a suitable state of light- 
ness. These methods are based on the fact, that nitrification, 
which decomposes nitrogenous matter, and makes it assimilable, 
only takes place in the superficial layers of the soil which are 
permeable to the oxygen of the air. 
After some years of cultivation, carried on under the conditions 
which I have indicated, the land can be laid down to grass 
again, if it is deemed expedient ; but in the great majority of 
cases it will be found preferable to continue arable cultivation, 
for it will continue to be remunerative so long as the soil remains 
rich in nitrogenous matters. 
