ON THE CONTINUED CULTIVATION OF WHEAT. 21 



By this table it is evident that the only manure which in- 

 creased the proportion of grain during the two last years was 

 the phosphate of lime ; whilst the only salts which increased the 

 whole produce in both these years were the sulphate and muri- 

 ate of ammonia. The manures used in these experiments were 

 sown broad-cast over the ground when the wheat was about four 

 or five inches high, and the effect which they produced on the 

 growth of the plants was very marked ; it generally became 

 most apparent a week or two before the plants came into ear. 

 The salts of ammonia and tlie nitrate of soda caused the wheat to 

 grow rapidly and luxuriantly, and gave the plants a dark green 

 colour. Generally, however, the effect of the manure seemed to 

 go off before the time of flowering, and to produce little or no 

 effect at the time of ripening the grain. The sulphate and 

 phosphate of lime, on the other hand, though they produced very 

 little if any effect at the time of application, evidently influenced 

 the wheat beneficially at the end of the season, when the grain 

 was filling. From this it might be concluded that a better 

 result, as far as the production of grain was concerned, would be 

 obtained by employing a mixture of a salt of lime and a salt of 

 ammonia, than by using either alone ; and this, no doubt, would 

 hold good on all soils like that of the Horticultural Gardens, 

 containing but little lime. 



From the fact just stated, that the ammoniacal manures seemed 

 to lose all effect after a few weeks, it was naturally supposed 

 that, in consequence of the easy solubility of the salts, the whole 

 or greater part of them had in that period been either washed 

 away by the rains or absorbed by the plants. That this, how- 

 ever, was not the case, is proved by the following cui-ious fact : 

 — In the spring of 1845, 1846, and 1847, when the wheat had 

 nearly attained the size at which the manures were to be applied, 

 but still previous to any application whatever, it was very easy 

 to see where the ammoniacal salts and the nitrate of soda had 

 been used the preceding year, as there the wheat was more 

 forward, and the blade had a darker colour and more healthy 

 appearance, than elsewhere. This proved that the diminished 

 influence produced by the manures could not be due to their 

 exhaustion, as enough remained in the soil some months after- 

 wards, and when the soil had been exposed to half a year's 

 rains, to produce a marked effect on the next year's crop. 



