cwt. superphosphate } 274
{4 " muriate of potash }

"Here again," said the Doctor, "superphosphate and potash alone give an
increase of only forty-two bushels per acre, while on plot 2, where two
hundred weight of muriate of potash is substituted by two hundred weight
of sulphate of ammonia, the increase is 108 bushels per acre. It
certainly looks as though a manure for potatoes, so far as yield is
concerned, should be rich in available nitrogen."

The following are some of the results in 1869:

Bushels per acre.
1. No manure 176

2. {4 cwt. superphosphate }
{3/4 " sulphate of magnesia } 306
{2 " muriate of potash }
{2 " sulphate of ammonia }

3. 4 cwt. superphosphate 189

4. {4 cwt. superphosphate } 201
{2 " sulphate of ammonia }

5. {4 cwt. superphosphate }
{2 " muriate of potash } 340
{2 " sulphate of ammonia. }

6. {4 cwt. superphosphate } 249
{2 " muriate of potash }

"This is a very interesting experiment," said the Doctor.
"Superphosphate alone gives an increase of thirteen bushels.
Superphosphate and potash an increase of seventy-three bushels. The
potash, therefore, gives an increase of sixty bushels. Superphosphate
_and_ ammonia give twelve bushels more than superphosphate alone, and
the reason it does not produce a better crop is owing to a deficiency of
potash. When this is supplied the ammonia gives an increase (plots 5 and
6) of ninety-one bushels per acre."

In 1870 the above experiments were repeated on the same land, with the
same general results.

In 1871 some experiments were made on a sharp, gravelly soil, which had
been over-cropped, and was in poor condition. The following are the
results:--

Bushels per acre.
1. {9 cwt. superphosphate } 186
{3 " sulphate of ammonia }

2. {9 cwt. superphosphate }
{3-1/2 " muriate of potash } 204
{3 " sulphate of ammonia }

3. No manure 70

4. {9 cwt. superphosphate }
{3-1/2 " muriate of potash } 205
{3 " sulphate of ammonia }

5. 20 tons farm-yard manure 197

"On this poor soil," said the Doctor, "the ammonia and superphosphate
gave an increase of 116 bushe