ON MANURES. 1 1 43 



Chief Sources of Potash. 



Wood-Ashes constituted for a long time the chief source of the 

 supply of potash used for gardening purposes. The incom- 

 bustible part, or minerals, of garden crops and of shrubs and 

 fruit-trees contain from one-fourth to one-third its weight of 

 potash. For this reason the ashes of refuse garden stuff forms a 

 capital dressing for Carrots, Onions, and most plants in pots. 



Kainit is, on account of its low price, in great favour as a 

 cheap form of potassic fertiliser. The crude kainit found in 

 commerce contains 12 per cent, to 13 per cent, of potash, 27 

 per cent.- to 30 per cent, of magnesia, and 30 per cent, of 

 common salt. It is more valuable in light loam than in heavier 

 soils, which it makes more sticky. A fair dressing per acre 

 would be from 3cwt. to 6cwt, mixed with other fertilisers, and 

 worked well into the soil. 



Sulphate of Potash, which is the chief potash salt in kainit, is 

 also sold in a more concentrated form than in that crude salt, 

 and is found in commerce with from 50 per cent, to 54 per cent, 

 of potash, or more than four times the amount per cent, found 

 in kainit. Although its price is considerably higher than that of 

 kainit, growers will find it more advantageous whenever freight 

 and cartage are considerations, the fertiliser being four times more 

 concentrated : icwt. per acre forms a good dressing in con- 

 junction with other manures. 



Chloride or Muriate of Potash is the most soluble of the various 

 salts of potash, and when purified contains as much as 63 per 

 cent, of potash, or 80 per cent, of muriate of potash. It is 

 obtained as a by-product in the manufacture of chlorate of potash, 

 in the purification of nitre and other manufactures. Its use, 

 however, is said to be harmful on certain crops, such as the 

 Sugar Cane and Sugar Beets, in which it lessens the percentage of 

 crystallisable sugar, while Potatoes are rendered waxy, and Tobacco 

 leaves are deteriorated in value ; in the soil it is besides apt to 

 give rise to the formation of common salt, while the sulphate 

 gives rise to the formation of gypsum, which in saline potash 

 especially is of value to plants. 



Chief Sources of Lime. 



Lime applied to soils has a mechanical as well as a chemical 

 effect. It assists in the decomposition of organic matter, and 

 combining with the nitrates as they are formed, produces nitrate 

 of lime, one of the most active of plant-foods ; it sweetens sour 

 soils, such as water-meadow soils and very rich old kitchen-garden 

 soils, by neutralising the otherwise harmful acids; it indirectly 

 supplies plant-food — that is to say, it combines with other 

 substances in the soil, bringing them into an available and 

 assimilable form for the plants to take up ; it is a necessity to 



