184 Report on sonic features of Scottish Af/riculture. 
per acre of farmyard-manure is laid in tliem. Upon this is 
sown the following mixture of artificial manures, the quantities 
being per imperial acre : — 4 cwts. of Peruvian guano, 4 cwts. of a 
mixture of superphosphate and American crushed bones, 4 cwts. 
of half-inch raw bones, and, last season, about 2 cwts. of German 
kainit. In reference to the last-mentioned suljstance, and also 
to muriate of potash, it is worthy of record that Mr. Drennan has 
found that if it be freely applied to the land the potatoes exhibit 
an increased tendency to become diseased. Less manure is used 
when the potatoes are planted after the first week of April. 
The setts are partly cut and partly small potatoes, the latter 
being preferred if they have been raised before they are quite 
ripe enough for market. Mr. Drennan retains these small 
unripe potatoes when raising for the early Glasgow and New- 
castle markets. About 12 cwts. of potatoes are required to plant 
an acre. The setts having been covered by splitting the drills 
with the double-mouldboard plough, this implement is used again 
in the course of two or three weeks, having been preceded by a 
light chain-harrow. When the plants begin to peep through, 
generally early in May, a light saddle-harrow is used for the 
purpose of lightening their covering, and making them a little 
earlier if possible, — a great point when early potatoes are grown. 
After this, about the 20th of May, a drill grubber is passed 
through them, and then the plants are hoed ; and about the 
beginning of June, or a little earlier in a forward year, they are 
earthed up with the double-mouldboard plough. If the crop is 
to be raised in July for the early market, the plants remain undis- 
turbed from this time until the roots are lifted ; but if it is 
decided not to raise them until the middle of August or later, 
they are earthed up once more, in the same manner as before, to 
keep down annual weeds and prevent green potatoes from peer- 
ing through the surface. Mr. Drennan prefers the latter system, 
as with highly-manured land he gets a larger crop of potatoes, 
and, remarkable though it may seem, a much better crop of 
wheat the following year. The common explanation of this cir- 
cumstance is, that with early raising the manure is wasted by 
exposure to the sun during the hottest part of the season. For 
the early crop the drills are 26 inches apart, but for the later the 
distance is increased to 27 or even 28 inches. As the rule, no 
catch-crop is taken after potatoes ; even the early potatoes have 
not been lifted in time for several seasons. 
Potatoes are harvested with Hanson's patent potato-digger. 
The early crop may yield from 4 to 6 tons per acre, according to 
the time of raising ; but at the season of the year when they are 
raised the growth of the tubers is very rapid, and if left until 
the latter half of August the same crop may be doubled in weight 
