412 
Field Experiments on Potatoes. 
On comparing the effects which the different manures produced 
on the stiffer clay-loam with those which the same manures 
exhibited on the lighter sandy soils in the preceding experiments, 
several striking differences will at once be noticed. 
1. On the light sandy soils the mixture of mineral super- 
phosphate with potash-salts and sulphate of ammonia had a 
much more beneficial effect upon the potato crop than on the 
stiffer clay-loam. On the former this mixture was equal in its 
results to the application of a heavy dressing of rotten dung, 
whilst on the latter dung on an average produced more than 
double the increase which was obtained on plot 2, on which the 
artificial manure, composed of superphosphate, potash-salts, and 
sulphate of ammonia, was used. 
2. Nitrogenous or ammoniacal constituents appear to be far 
less useful in a potato manure intended for stiffish soils con- 
taining a fair proportion of clay than in fertilisers intended to be 
applied to potatoes on light sandy soils. 
Neither the addition of sulphate of ammonia, nor that of 
nitrate of soda, to superphosphate and potash-salts, materially 
augmented the increase which was obtained on the clay-loam by 
superphosphate and potash-salts on plot 4. 
Practically speaking the yield of potatoes was as large oiu 
plot 4 without sulphate of ammonia as on plot 2 manured with 
the same compound, and the addition of 2 cwts. of sulphate of 
ammonia. 
3. Farmyard manure, it will be noticed, gave by far the best 
result, which no doubt was due — at least in part — to^ the 
mechanical effect which dung is well known to exert on retentive 
soils. 
4. Common salt had a more decidedly prejudicial effect on 
the clay-loam than on the lighter soils. 
5. On the whole we learn from the preceding field-trials that 
compound artificial manures tell far more favourably on potatoes 
when grown on light soils than upon heavier land, into the 
composition of which clay enters more largely than is the case 
with sandy soils. 
In future experiments upon clay soils it is very desirable to 
try the efficacy upon potatoes of a purely mineral superphosphate 
by itself, as well as in conjunction with potash-salts, and also 
that of potash-salts alone. 
Potato Experiments made in 1869 hy Messrs. Coleman and Hull 
at Escricli Park Home Farm, near York. 
In conclusion I have the pleasure of reporting on some 
extremely interesting and successful experiments on potatoes 
