and Magazine of the Ceylon Agricultural Society- 



191 



ON THE SELECTION OF PHOSPHATES. 



{Reprinted from '' Farm and Home. ,: ) 

 [Printed as a leaflet used in replying to en- 

 quiries from farmers and planters as to which 

 kind of phosphate would be most suitable for 

 their particular kind of soil. We feel sure that 

 as to the selection of the three kinds of phosphate 

 — superphosphate, basic slag and basic super- 

 phosphate—the last is specially suitable to Cey- 

 lon soils which are deficient both in lime and 

 vegetable matter. — A. M. & J. F.] 



The very general manner in which all kinds of manures 

 appear to be forced upon the farmer's notice adds very 

 considerably to his difficulty in making a selection. It 

 would certainly be a convenience if the merits of any parti- 

 cular fertiliser were put forth by the sellers in a modified 

 and somewhat restricted manner, that fertilisers should 

 not be described as suitable for all soils and all crops, but 

 rather for certain soils and certain crops. If this were 

 done, the future results would be more satisfactory to 

 sellers and buyers. With a view of assisting in the selec- 

 tion during the coming season, the following remarks are 

 offered in regard to the three principal kinds of phosphate 

 fertilisers and the particular soils for which they are res- 

 pectively adapted. 



SUPERPHOSPHATE 



supplies phosphate of lime in the most soluble form that 

 can be obtained, and is specially suitable for all good, 

 arable "soils containing plenty of lime. When carefully 

 manufactured from high-class mineral phosphates, the per- 

 centage of phosphate of lime rendered soluble in water, 

 and therefore readily available, varies from 25 per cent, to 

 35 per cent., and where carriage is costly, the higher quality 

 will be found to be the most economical. In order, however, 

 to get the full benefit from this valuable fertiliser, it is 

 absolutely necessary that the soil should contain plenty of 

 lime— at least 5 per cent.— because the acid phosphate, 

 which is harmful to vegetation, requires to be neutralised 

 by the alkali lime, and rendered alkaline before it can be 

 absorbed by the minute rootlets of the plant. Anyone can 

 soon see the injurious effect of throwing superphosphate 

 over the leaves of plants, and the minute rootlets are still 

 more sensitive. The superior value of water-soluble 

 phosphate of lime is due to the fact that its great solubility 

 promotes more perfect and extended diffusion through the 

 soil, and not, as is sometimes supposed, to the direct 

 absorption by the rootlets of the acid phosphate of lime. 

 Pure dissolved bones are superior to superphosphate, 

 because they supply nitrogenous organic matter, in addi- 

 tion to phosphate of lime ; but hitherto manufacturers, out 

 of deference to the purchaser's desire to soe the bones in 

 the manure, have not carried the dissolving process with 

 sulphuric acid sufficiently far to render the bones com- 

 pletely soluble, as the term dissolved bones would 

 naturally lead us to conclude was the case. Consequently, 

 as most of the phosphate of lime and nitrogen compounds 

 still remain in an insoluble form such so-called dissolved 

 bones are naturally more suitable for soils somewhat 

 deficient in lime rather than for soils which abound in lime. 



BASIC SLAG (THOMAS' PHOSPHATE) 



when first introduced as a fertiliser, about the year 1883. 

 was little appreciated by scientific men of high authority, 

 on account of its origin as a hard, fused, refuse, rock 

 like material from the iron-ore blastfurnaces, and its little 

 solubility, only about six parts being dissolved by HO parts 

 of ordinary water. Farmers, however, in the Midland 

 counties were induced to take small quantities for trial, 

 chiefly on their old grass land, and as the results on cer- 

 tain soils, rich in vegetable matter, but poor in lime, were 

 satisfactory, scientific authorities were obliged to admit 

 its agricultural value as a fertiliser on certain soils. It 

 is important to recognise the fact that basic slag is only suit- 

 able for certain kinds of land, such as damp, heavy clay defi- 

 cient in lime.but containing plenty of acid vegetable matter, 

 which, in the presence of moisture rapidly decomposes 

 the powdered slag, and liberates lime as well as phosphoric 

 acid in a condition readily available for plant food. It is 

 a mistake to recommend basic slag as being suitable for 

 all soils. Farmers know that its application, though most 

 beneficial to certain land, has failed to produce any bene- 

 ficial results upon other kinds of land. It is more econo- 

 mical to adapt the manure to the soil rather than to adapt 

 ortry to adapt, the soil to the manure. Basic Slag varies 

 in its contents of phosphate of lime from 30 iper cent, to 40 

 per cent., and sometimes 45 per cent., and lime from 40 

 per cent, to 50 per cent., also in the fineness of the grind- 

 ing, so that it is necessary Lo stipulate for a guarantee as 

 to its chemical composition and mechanical condition, 



for the grinding should be such that 80 per cent, to 90 per 

 cent, should pass through a sieve of 10,000 holes to the 

 square inch. It has been stated that this material contains 

 as much as 20 per cent, of free caustic lime, imt this is 

 not the case, because any such quantity would indi- 

 cate a wasteful method of manufacture, for lime is 

 only added in sufficient quantity to remove the phospho- 

 rous and silica originally present in the iron ore. The 

 actual amount of free caustic lime in ordinary slag does 

 not exceed 3 per cent to four per cent, and its mild alka- 

 line character, as compared with quicklime, can easily be 

 ascertained by putting equal quantities of these materials 

 into tumblers of cold water and testing the solution after 

 standing and stirring for a few minutes. Most of the lime 

 is present in a combined form, such as phosphate of lime 

 and basic silicate of lime from which latter compound 

 it derives the name of basic slag. In order to dissolve such 

 compounds, it is requisite that the soil water should be 

 acid, for, as already pointed out, ordinary water has but a 

 very slight dissolving effect upon such a hard fused mass, 

 however finely ground the powder may be. It will be 

 gathered from the foregoing remarks that basic slag, 

 though a most useful manure, can only be profitably applied 

 to certain kinds of soil. 



BASIC SUPERPHOSPHATE 

 consists of superphosphate which has been made alkaline 

 by the admixture of finely-ground or lightly-slaked lime 

 in sufficient quantity to convert the original monocalcic 

 or water-soluble phosphate into di-calcic, or citric-soluble 

 phosphate,, with a slight excess of caustic Jime. This ferti- 

 liser was introduced in the spring of 1901, and is manu- 

 factured by a syndicate consisting of ten of the largest firms 

 in England, Scotland and Ireland, so that there should be 

 no difficulty in obtaining it anywhere. The material has 

 a white appearance, and is in a very light, powdery state, 

 occupying fully two-and-a-half times the space of 

 slag, and, when sown broadcast by hand, does not fall 

 between the fingers before delivery, as in the case of slag. 

 It contains about 35 per cent of lime, and 26 per cent 

 of phosphate of lime, which, though not soluble in water, 

 is readily soluble in a very weak solution of 

 citric acid, containing one part of citric acid in 1,030 

 parts of water, which represents an aridity less than that 

 possessed by the acid juices of the rootlets of plants, so 

 that all the phosphate of lime so dissolved may be fairly 

 regarded as available plant food. It combines the valua- 

 ble alkaline character of basic slag with the well-known 

 solubility of superphosphate, but is free from the defects 

 of these opposite manures — namely, the comparative in- 

 solubility of slag and the injurious acidity of superphos- 

 phate. If one part respectively of basic superphosphate 

 and basic slag "are separately exhausted with 1,000 parts 

 of weak citric acid solution (1 in 1,000) for twenty- 

 four hours, with occasional stirring, it will be found that 

 !I0 per cent, of the former has been dissolved, compared with 

 40 per cent, of the latter. The new manure is intended to 

 occupy an intermediate position between acid superphos- 

 phate and alkaline slag, and to be applied for interme- 

 diate descriptions of soil. It is not intended to supersede 

 the use of superphosphate upon good arable land containing 

 plenty of lime, nor is it intended to take the place of well- 

 ground slag upon sour grass land, damp, heavy clay or rich 

 vegetable soils ; but it is specially intended for soils de- 

 ficient in lime, such as light clay, gravel, granite and 

 sandy soils. 



JOHN HUGHES, 

 Agricultural Analyst for Herefordshire. 

 Analytical Laboratory, 79, Mark Lane, London, E C. 



HONEY IN CALIFORNIA. 



Interesting Consular Report. 



In his report on the trade and commerce of 

 the States of California, Nevada, and Utah, and 

 the territory of Arizona, just issued Mr Consul- 

 General Hearn has some interesting references 

 to the honey yield of California. It was pre- 

 dicted during last summer that the output of 

 the year would be very small, but in fact it was 

 almost double that of 1906, the total being esti- 

 mated at 8,700,000 lb. That bee keepers in the 

 State consider 100 to 300 hives sufficient for any 

 otie farm. The honey gathering is usually from 

 April to September, depending upon the 

 weather and the length of the blooming period 

 of the bee forage. The extracting season com- 

 mences in ».vlay or June and is usually about six 



