164 
Injiuence of Climate on Cultivation. 
the soil until it was decomposed and taken up by the roots of 
plants. By acting in some measure in fixing the nitrogenous 
substances, the vegetable matter might be supposed to prevent 
the wasting effects of rains : no doubt it does that also, but then 
it must be remembered tb.at vegetable manuring answers best in 
the driest climates where there is least waste- from washing. 
Mr. Hannam states this very strongly, in his article on green 
manuring, in ' Morton's Cyclopaedia of Agriculture ' : — " It is 
only after a good crop of depastured seeds that a full crop of 
wheat can be grown upon tlie high and dry wolds and the lime- 
stone and chalk hills that are brought into cultivation in this 
country [south-east of England]. After turnips, barley upon 
such soils succeeds, but it is only upon lea that wlieat can succeed 
fully, when the texture of the soil is light. No doubt manuring 
will answer upon fallow." The decaying vegetable matter seems 
to improve the physical texture of the soil by its attraction for 
moisture : it also, to some extent, regulates the supply of ammonia 
to the plants, by only slowly yielding it up — a matter of much 
economy in the feeding of plants. These influences combined 
have the effect of sustaining vegetation in a comparatively healthy 
state during periods of drought. Though the necessity for 
vegetable manuring is most strongly marked for wheat on light 
soils in dry climates, still all other crops exhibit its beneficial 
effects under similar circumstances. . 
The necessity for seeds as a basis ibr a full crop of V'heat is 
not so much felt where the soil is argillaceous, even in dry 
climates. Soils of this character, by their retentive properties for 
moisture, can maintain the plants in a healthv state during periods 
of drought. The ammonia being also absorbed by the soil and 
rendered in a great measure insoluble, is only taken up by the roots 
as the plants require it ; but as the climate becomes more moist, 
and just in proportion as it can better sustain the healthy growtli of 
grass on light soils, so can it also that of wheat. The increased 
moisture compensates in l)oth cases for the physical deficiencies 
of the soil, and tlie beneficial effects of green manuring are less 
apparent. Vegetable matter may l)e regarded not only as a good 
absorbent of moisture, but as tlie best dilutant of ammonia in a 
dry climate ; in a moist climate it is less needed for tliese ends, 
and its efficacy is not so striking or marked. 
These considerations are by no means in contradiction to the 
sucfcssf ul results of aj)plying soluble manures such as the nitrates 
or salts of ammonia to wheat crops in dry climates. Tlie last num- 
ber of the Journal contains an admiraiile summary of numerous 
experiments on manuring wheat on tlie light lands at Holkham. 
No doubt clover lea forms the basis of success, which so far as 
regards the nitrates is dependent on their ajijilication at intervals 
