-feeders, and require their food in a readily available
condition. It is found desirable, therefore, to supplement farmyard
manure by readily available artificial manures. Potatoes repay the
application of a mixed manure containing all the fertilising
ingredients--nitrogen, phosphoric acid, and potash--better than most
crops.

_Highland Society's Experiments on Potatoes._

The nitrogen is, according to the Highland Society's experiments, best
applied in the form of nitrate of soda. Sulphate of ammonia does not
seem, when farmyard manure is also applied, to have an equally valuable
effect, as it influences the size of the tuber, producing an undue
proportion of small potatoes. When no farmyard manure is applied,
however, sulphate of ammonia seems to have a good effect, especially in
wet seasons.

With regard to the nature of the phosphatic manure to be applied,
superphosphate is to be preferred. Potatoes make large demands on
potash, and consequently require potassic manures. In consequence of the
fact that they receive large applications of farmyard manure, the
necessity for adding potash in the form of artificial manures does not
generally exist. Potash, if applied in too large quantities, has been
found to exert a deleterious effect. We have already pointed out that
muriate of potash tends to produce a waxy potato.

_The Rothamsted Experiments with Potatoes._

The Rothamsted experimenters have very fully investigated the conditions
of the manurial requirements of potatoes. In these experiments potatoes
were grown year after year in the same field. It was found that the
effect of mineral manures alone was greater than the effect of
nitrogenous manures alone, and that of mineral manures phosphates, as a
rule, had a better effect than potash; that under the action of the
growth of potatoes a greater exhaustion of phosphates than of potash
takes place in the soil; and lastly, that it is essential to have an
abundant supply of the different fertilising ingredients in order to
grow successful crops. In the Rothamsted experiments, the slow action of
farmyard manure in supplying fertilising ingredients to the potatoes is
strikingly demonstrated. Thus, although farmyard manure was applied at
such a rate that more than 200 lb. of nitrogen were added to the soil,
the result was inferior to that obtained from the application of 86 lb.
of nitrogen applied in the form of readily available artificial manure.

_Effect of