98 



EXPERIMENTS WITH SOLUBLE AND INSOLUBLE PHOSPHATES 



The turnips were pulled and weighed on the 28th October. 

 The soil was very dry, and the turnips were almost as clean and 

 free from soil as if they had been washed, all the very small 

 rootlets were struck off, and the shaws were separated from the 

 root close to the bulb. Before making any remarks on the 

 general results of the experiments and their effect on the 

 question at issue, I will tabulate the exact weight of roots and 

 shaws grown on each plot of the first and second sections, ex- 

 ceeding the natural production of the soil, as shown by plot 6, 

 Section I., also giving the cost of the manure per acre which 

 urew the said excess. 



The excess of weights above the net production of the soil show, 

 in the first place, that coprolite, or ground mineral phosphates, 

 do increase the weight of crop, but, owing to the sluggish start 

 \vhich it gives to the plant, it exposes it to the ravages of all the 

 parasites which prey on its leaves, at a stage of its growth when 

 it most requires nourishment, and is not, therefore, suitable on 

 poor soils, or safe to apply alone as a turnip fertilizer, especially 

 if followed by cold or ungenial spring weather. Also, that sol- 

 uble mineral phosphate increases the crop to a greater degree 

 than insoluble, giving it a quicker start and allowing less chance 

 for the operations of all destructive parasites which prey on the 

 plant during its early stages, it being very questionable, however, 

 whether the dissolving of the phosphates is worth the expense 

 of the operation, as a little nitrogen at half the expense would 

 give the same result. 



Animal phosphates, in the shape of bone meal, give the best 

 results of this section, being better than either soluble or insol- 

 uble phosphates from mineral, but the C(3st is nearly double that 

 of raw mineral phosphate, and although it contains a considerable 

 weight of nitrogen, better results are obtained at the same expense 

 by applying the nitrogen in a different foini for turnips. 



