Vol. XII. No. 299. 



THE AGRICULTURAL NEWS 



335 



SOIL INVESTIGATIONS. 



SULPHUR IN RELATION TO THE 



MANURING OF RICE. 



The experiments on which the following information 

 is based were conducted by Alice Thompson at the Experi- 

 ment Station, Hawaii, and the results abstracted in the 

 Experiment Station Record, Vol. ^XXIX, No. 3. 



One of the objects of the work was to determine the 

 effect, if any, of fertilizers on the sulphur and chlorine com- 

 position of the plants grown under natural soil conditions, 

 also to determine the amounts of sulphur and chlorine con- 

 tained in the rice field soil and water. 



The rice plants experimented on were analysed during 

 three stages of growth. At the first harvest the effect of 

 ammonium sulphate, superphosphate and potassium sulphate 

 was tried. It was found that the plants of the unfertilized 

 plot (control) showed about 01 per cent, more sulphur than 

 the fertilized plot. The percentage of mineral sulphur was 

 found to be almost four times as high in the roots of the 

 plants as in the filiage. At the .second harvest there wa.s 

 practically no difference in the composition of the plants, 

 although the fertilized plants were much larger and heavier. 

 At the third harvest the fertilizers showed no effect on the 

 composition of the plant. 



RICE ABSORBS SULI'IIUll IN AX ORGANIC FORM. 



The possibility of sulphur fertilization being required 

 by a plant that absorbs about half as much sulphur as it 

 does phosphoric acid is pointed out. The problem is 

 a difficult one, however, since it was proved that under 

 natural conditions, the rice plant obtains its sulphur in an 

 organic form only. An analysis of a rice field soil indicated 

 that the sulphur in the soil is present largely in an organic 

 form, since the acid-soluble and water-soluble sulphur are 

 relatively so small. 



An increase in the total sulithur in the case of pot 

 cultures, particularly when ammonium sulphate was added, 

 seemed to indicate that under these conditions, mineral sulphur 

 is undoubtedly absorbed and utilized by the plant. 



COMPOSITION OF SOIL IN THE 



VIRGIN ISLANDS. 



Samples of soil from two parts of the Botanic Station 

 at Tortola have been analysed in Antigua by Mr. H. A. 

 Tempany, B.Sc, F.I.C., Superintendent of Agriculture for 

 the Leeward Islands. As regards the physical analyses, 

 both these soils show a fairly high percentage of fine silt 

 (about 38 per cent.); one sample contained 14 4 per cent, of 

 stones. The soils are light and easily worked, but at the 

 same time are supplied with a moderate sufficiency of clay 

 constituents; both samples drained freely. Sample A was 

 well supplied with nitrogen (0'179 per cent.) and with organic 

 carbon (1-335 per cent.); in the case of sample B, the amount 

 of nitrogen was somewhat low (0139 [ler cent.), and in view 

 of the fact that the percentage of organic carbon is 1090, it 

 is likely that a good dressing of organic manure might be of 

 benefit. The soils contain 0029 and 0087 per cent, respec- 

 tively of lime. They are therefore deficient in this sub- 

 stance, and a moderate dressing of the mineral would there- 

 fore appear to be advisable. 



METHOD OF ESTIMATING OALOIUM 

 CARBONATE IN THE SOIL. 



No e.xouso is neecieil for presenting the following, 

 account of how the percentage of calcium carbonate 

 in the soil can be determined easily and quickly with- 

 out the employment of any elaborate apparatus. The 

 determination of calcium carbonate (or its equivalent 

 in lime) is one of great practical importance to the 

 planter, and although the determination is chemically 

 simple, most of the gravimetric or weighing methods 

 commonly employed to do it are either inaccurate or 

 else lengthy and complicated. 



Ten grammes of finely divided air-dried .soil are placed 

 in a dry wide-mouthed flask or bottle, and 100 c.c. of 

 roughly quarter-normal acetic acid are added. 



During ten minutes the flask is shaken with a rotary 

 movement every time the bulk of the soil settles, which 

 occurs approximately every thirty seconds. 



The soil is then allowed to settle for the last time, and 

 the liquid contents of the Mask decanted through a dry filter. 

 Schleicher & SchuU's filter hats answer the purpose admirably. 



A control experiment is made with another 10 grammes 

 of .soil, using distilled water as the extracting solvent. 



Twenty-five cubic centimetres of each filtrate is 

 evaporated to dryness in a platinum dish and ignited at 

 a bright red heat for thirty minutes. 



The residues when cool are treated with 10 c.c. of 

 deci-normal acetic acid (or more if necessary). 



Solution is effected in a few minutes, particularly if the 

 residues are gently rubbed with a glass rod tipped with 

 a small rubber bung. 



The excess of acid is then titrated with deci-normal soda 

 or potash and phenolphthalein used as indicator. 



The volume obtained from the control is now subtracted 

 from that obtained from the acid extraction of the soil and 

 the result multiplied by 0-2. The product gives the per- 

 centage of calcium carbonate in the soil. 



The process described above is taken from an 

 article in the West Indian Bulletin, Vol. XIII, No. 8, 

 by H. S. Shrewsbury, F.I.C., Assistant Government 

 Analyst, Trinidad. 



In the Journal of the Royal AgricuUiiral Society ej 

 England, Vol. LXXIII, pp. 1-9, appears an article on the 

 value of soil analy.ses to the farmer, by A. D. Hall, F.IJ,S. 

 In the summary to this account the writer puts forward the 

 following benefits which accrue from analyses: (1) mechanical 

 analysis enables us to classify soils and assign an unknown 

 example to its type; (2) from the type, combined with 

 knowledge of the situation and climate, we may predict its 

 suitability or otherwise for particular crops; (3) chemical 

 analysis will tell us whether a soil is getting acid or needs 

 liming to make it work properly and utilize the manure 

 supplied to it; (4) from chemical analysis we can settle what 

 class of manures ought to be used — whether sulphate of 

 ammonia or nitrate of soda, superphosphate or basic slag; (.5) 

 chemical analysis will often reveal particular deficiencies and 

 the specific need for phosphates or potash, but to do this with 

 any certainty, the composition and behaviour of soils of that 

 type should be known from a previous soil survey. 



