362 EXPERIMENTS WITH MIXED MANURES. 



{Cactus Opuntia, — European Indian-Fig) is stuck in, when the roots in- 

 sinuate themselves into every fissure, expand, and finally break up the 

 lava into fi-agments. These plants are thus not only the means of pro- 

 ducing a soil, but they yield also much fruit, which is sold as a refresh- 

 ing food throughout all the towns of Sicily. (Decandolle, quoted in the 

 Quart. Journ. of Agr., IV. p. 737.) 



These are all so many natural mineral mixtures of which we may 

 either directly avail ourselves, or which we may imitate by art. 



Experiments with mixed manures. 



Note. — As a valuable appendix to the preceding observations on 

 mixed manures, I am permitted to insert the following very interesting 

 results obtained during the present season, 1842, from experiments made 

 on the estate of Mr. Burnet, of Gadgirth, near Ayr. The crop to which 

 the several manures were applied waswheatof the ecZfpse variety, sown 

 on the 29th of October, 1841, and reaped on the 15th of August last. 

 The soil is a loam with subsoil of clay, tile drained and trenched plough- 

 ed. It had been in beans the previous year, and gave six quarters per 

 acre, which were sold at 46s. a quarter. No manure had been applied 

 with the bean crop, and except a good dose of lime before sowing the 

 wheat, nothing but the saline mixtures mentioned below was applied 

 with this latter crop. 



The reader will observe here that though the first mixture produced 

 a large increase both of straw and grain, a still larger additional increase 

 was caused by mixing with the substances of which it consisted either com- 

 mon salt or sulphate of soda or nitrate of soda. Each of these three sub- 

 stances produced nearly the same effect. The soda, therefore, more 

 than the acid with which it was combined, must in these cases have act- 

 ed beneficially. The comparatively small proportion of fine flour yield- 

 ed by the nitrated wheat, and the comparatively large proportion ob- 



•The sulphate of ammonia was prepared from urine, and, therefore, contained other ad- 

 mixtures (page 349). The straw was strongest, coarsest, and longest in ripening, where 

 this sulphate was applied. The two guanos produced little luxuriance, but the lots to which, 

 they were applied were soonest ripe. 



