378 
Field Experiments on Boot-Crops. 
' 3. Next to the dung in order of efficiency follows the mixture- 
of superphosphate, muriate of potash, and sulphate of ammonia^ 
This mixture gave an increase over the average yield of the un- 
manured plots of 3 tons 8 cwts. 97 lbs., and in a more favourable 
season the increase would probably have been more conspicuous, 
4. A somewhat less favourable result than on Plot 2 was 
obtained on Plot 6, where, instead of sulphate of ammonia, 
nitrate of soda was applied in conjunction with superphosphate 
and muriate of potash. Comparing the produce of Plot 6 with 
that of Plot 4, on which mineral superphosphate and muriate 
of potash were used, it will appear that in the dry season of 
1869 the addition of nitrate of soda to these fertilizing matters 
had rather an injurious than a beneficial effect. 
5. Muriate of potash, in conjunction with mineral superphos- 
phate, it will be seen by the preceding results, gave a considerable 
increase, differing only by 5 cwts. from the increase of Plot 2, 
which, in addition to 4 cwts. of superphosphate and 2 cwts. of 
muriate of potash, received 1 cwt. of sulphate of ammonia. 
Potash-salts and superphosphate thus appear to constitute a 
valuable manuring mixture for potatoes. 
6. The results obtained on Plot 4 and Plot 8 clearly show 
that muriate of potash cannot be successfully replaced in artificial 
manures by muriate of soda (common salt), for, wliilst 4 cwts. 
of mineral superphosphate mixed with 2 cwts. of muriate of 
potash, gave a produce of 7 tons 100 lbs. of potatoes, the same 
quantity of mineral superphosphate mixed with common salt 
produced only 4 tons 17 cwts. 36 lbs., or the increase over the 
average yield of the unmanured plot was 3 tons 3 cwts. 77 lbs. 
on the plot upon which potash was used, and only 1 ton 5 cwts. 
33 lbs. on Plot 8 where common salt was employed. 
7. Peruvian guano, it is well known, is a capital manure for 
potatoes, especially on light soils. In the experiments at Blenner- 
hasset, however, it produced scarcely 1 ton of increase, a result 
which finds its explanation in the fact that June, July, and 
August, in 1869, were unusually dry. In such seasons as that 
of 1869, Peruvian guano and indeed all manures rich in ammonia 
do not act nearly so well as fertilizers as in seasons in which a 
good deal of rain falls during the summer months. 
Nitrogenous or ammoniacal matters, unless washed into the 
soil by copious rains, and thereby distributed through a large 
mass of soil, appear to check the growth of root-crops ; and for 
this reason it would appear desirable to apply such manures 
quite early in the spring and to sow them broadcast. 
