xviii CONTENTS. 



ed. Mr. Robertson's experiments with bone-dust. Soils 

 most profited by bone-manure. The action of phosphates 

 on soil and plant. Quantity used per acre. 

 Lime. Its extensive use as a manure. Its composition. 

 Kunkur. Quicklime. Action of lime on clay and soils in 

 general. The liberation of alkaline silicates from their 

 unassimilable compounds. Lime a powerful aid to the 

 mechanical operations of agriculture. Shell-sand. Its 

 extensive use in Ireland and France. Quantity used per 

 acre. Lime increases the assimilable store of inorganic 

 plant-food, resulting in a corresponding increase of the 

 outturn. Its use must go hand in hand with a careful 

 restoration to the soil of what is withdrawn. If not, lime 

 will enrich the father and impoverish the son. Experiments 

 of lime-manuring at Oberbobritzsch. Mr. Robertson's 

 experiments on the Madras Model Farm. Quicklime has 

 the greatest effect on stiff, clayey, or marshy soils. The 

 permanent improvement of the soil effected by lime, and 

 its effects upon different crops. The action of lime on soil 

 and plant 134 



CHAPTER VIII. 



GYPSUM, NITRATE OF POTASH, AND AMMONIA. 



Gypsum allied to lime in its composition and general effects. 

 Preferable for green crops and grass-lands. Dr. Pinkers' 

 experiments. How Gypsum is applied. Its effects upon 

 leaves and stems. Highly appreciated in Europe. Aden 

 pumice. Mr. Smith's experiments on clover and wheat. 

 Mr. Robertson's experiments. Refuse of soda-water 

 manufactories. 



Nitrate of potash. Sora Khar. Mr. Robertson's experi- 

 ments. Consumption of nitrates steadily increasing. 

 Quantity per acre, and mode of application. Effect on the 

 plant. Common salt checks the tendency of saltpetre to 

 make the crop run into grass. Ammoniacal liquor of 

 gas-works. Its usefulness for kitchen plants, and mode of 

 application ,. 151 



