CHAPTER XVHI. 



THE DAMAGE CAUSED BY TOO HEAVY DRESSINGS OF CALCAREOUS 

 MANURE, AND THE REMEDY. 



PROPOSITION 5 continued. 



The injury or disease in grain crops produced by marling has 

 so lately been presented to our notice, that the collection and com- 

 parison of many additional facts will be required before its cause 

 can be satisfactorily explained. But the facts already ascertained 

 will at least show how to avoid the danger of such injury in future, 

 and to find remedies for the evils already inflicted by the injudi- 

 cious use of calcareous manures. 



The earliest effect of this kind observed was in May, 1824, on 

 the field containing experiment 10. The corn on the land marled 

 four years before sprang up and grew with all the vigour and luxu- 

 riance that was expected from the appearance of increased fertility 

 exhibited by the soil, as before described (page 133.) About the 

 20th of May the change commenced, and the worst symptoms of 

 the disease were seen by the llth of June. From having as deep 

 a colour as young corn shows on the richest and best soils, it be- 

 came of a pale sickly green. The leaves, when closely examined, 

 seemed almost transparent, afterwards were marked through their 

 whole length by streaks of rusty red) separated very regularly by 

 other streaks of what was then more of yellow than green ; and 

 next they began to shrivel and die downwards from their extremi- 

 ties. The growth of many of the plants was nearly stopped. 

 Still some few showed no sign of injury, and maintained the 

 vigorous growth which they began with, so as by contrast more 

 strongly to mark the general loss sustained. The appearance of 

 the field was such, that a stranger would have supposed that he 

 saw the crop on a rich soil exposed to the worst ravages of some 

 destructive kind of insects ; but neither on the roots or stalks of 

 the corn could any thing be found to support that opinion. Before 

 the first of August this gloomy prospect had somewhat improved. 

 Most of the plants seemed to have been relieved of the infliction, 

 and to grow again with renewed vigour. But before that time 

 many were dead, and it was impossible that the others could so 

 fully recover as to produce anything approaching a full crop for 

 the land. It has been shown in the report of the products of Exp. 

 10, what diminution of crop was then sustained, and that the evil 

 was not abated in the three succeeding courses of cultivation. 



(155) 



