Fertilizing the Orchard 81 



Allowing for a dressing of four tons to the acre 

 every second year, this makes an average cost of 

 one pound per acre per annum, which is a very 

 reasonable price to pay for keeping up the humus 

 content of the soil. 



CHEMICAL FERTILIZERS. 



As in many instances it is not possible to obtain 

 sufficient quantities of organic matter to bring on 

 to the land to make up for all the nourishment re- 

 moved from the soil by continuous cropping, 

 chemical fertilizers have to be used to make up the 

 deficiency. As Australian soils generally appear to 

 be somewhat weak in phosphoric acid, phosphates 

 are usually the first kind of manures used to main- 

 tain the crop returns from the land. Commercial 

 varieties of phosphates are of two kinds, the organic 

 classes, such as bone dust and bone superphosphate, 

 and the inorganic forms made from various kinds of 

 phosphatic rock. Of these bone dust is the slowest 

 in its action, lasting about two seasons in the soil 

 before being entirely dissolved. By not being so 

 water soluble as other kinds of phosphates, the 

 manurial properties of bone dust are not so readily 

 leached out of the soil by heavy rains or irrigation, 

 and therefore, although slower, lasts longer in the 

 soil for the roots of plants to feed on. The mineral 

 superphosphates are usually water soluble to a great 

 extent, hence their action on plant growth is rapid, 

 and for this reason their effect is not lasting, there- 

 fore must be applied annually to keep up growth 

 and crop returns. 



Potash as a fertilizer is also needed on most soils 

 that are being continuously cropped. As has been 

 previously mentioned, potash is usually contained 

 in considerable quantities on many classes of clay 



