102 EXPERIMENTS WITH SOLUBLE AND INSOLUBLE PHOSPHATES. 



extent as would warrant their economical use alone above farm- 

 yard manure ; tliird, that the addition of nitrogen increases the 

 crop to a considerable extent, while the addition of potash and 

 phosphates to the nitrogen increases the weight of crop still 

 further, — all these manures combined producmg a surplus of 

 crop over that of farmyard manure alone, far more than equiva- 

 lent to the cost of these manures. 



In reference to the diseased or unhealthy state of the turnips 

 in the dissolved bone and superphosphate plots of Section I., 

 I fortunately have still in stock a portion of the manures, from 

 the l)ulk of which I had drawn the quantity for these plots. 

 The manures were analysed by Dr Macadam of Edinburgh, 

 during April 1879, who certified the one to be bones and acid ; 

 the other to be mineral phosphate and acid. I thought that it 

 might be possible that the manures may have contained some 

 poisonous matter, after seeing the condition of the turnips 

 during the autumn months ; I therefore drew a sample of the 

 dissolved bones in October, and sent it to J. Falconer King 

 of Edinburgh, with miniite instructions to test for poisonous 

 matter. He duly reported that he had carefully analysed and 

 tested the manure, and found no trace of any substance in 

 its composition which would prove injurious to plant life. This 

 report, while very satisfactory to the manufacturers of the 

 manure, leaves me quite as much in the dark as ever in regard 

 to the cause of the inihealthiness of the turnips. The only 

 cause which looks feasible may be an excess of sulphuric acid 

 in the soil, seeing that the plots treated with the manures con- 

 taining it were the only unhealthy ones. In regard to the 

 quality of the turnips grown by the various manures, I thought 

 it necessary only to test those turnips grown on the plot with 

 no manure ; also those on the superphosphate plot, the nitrate 

 of soda and coprolite combined plot, the farmyard and artificial 

 manure combined from the general crop of the field. All these 

 turnips being of the M'Combie's Aberdeen yellow species, I 

 judged it prudent also to test the Swedish turnips of another 

 portion of the field. I gave the chemist to whom I sent the 

 turnips, instructions to ascertain the quantity of water only 

 contained in the composition of the turnips. I pulled average 

 turnips out of each of the di^dsions to which I have referred — 

 as nearly as possible about the same size — and subjoined are the 

 results : — 



Percentage 

 of Water. 

 No-manure plot — Yellow turnips . . . 89-50 

 Superphospliate „ „ . . .. 88-24 



Nitrate of Soda and Coprolite — Yellow turnips 92-12 

 Farmyard and Artificial „ „ . 89-70 



Swedish turnips . 88-39 



