PRESIDENTIAL ADDRESS. 373 



circulation from the soil to the plant, and from the plant to the animal, and so, 

 to a large extent, back to the soil again ; and (/i) to the accumulation of nitrogen 

 in the form of humus. Poor unprofitable grass is chiefly associated with clay, 

 and it is fortunate that it is precisely on such land that clover responds so 

 markedly to phosphatic manuring. But conspicuous results have alsobeenobtained 

 on deep peat,-* on light stony loam,-''' on thin chalk,''" and on chalk covered by 

 clay with flints.^' iMiddleton has very fully discussed the conditions under which 

 phosphatic dressings may be expected to give results '- and ascribes an important 

 place to soil moisture, on which white clover is directly very dependent. The only 

 conspicuous case of failure of phosphates to improve pasture was encountered in 

 Norfolk, where a ' manuring for mutton ' experiment was started in 1901. The 

 soil at that station was a hot dry sandy gravel containing 60 per cent, of sand, 

 and there both basic slag and superphosphate were unable to produce any 

 improvement. Wood and Berry attribute this result partly to the presence of 

 abundant natural supplies of citric soluble phosphoric acid, but chiefly to lack 

 of moisture. ^^ In reporting on the R.A.S.E. experiments Carruthers and 

 Voelcker in 1900 had already called attention to the dependence of basic slag 

 on soil moisture.^''. 



We may now look at the effect of supplementing phosphates with certain 

 other substances. And, first of all, as regards potash. At most of the 

 manuring-for-mutton stations both in England and Scotland there was a plot 

 devoted to the elucidation of the effect of this substance, and although in the 

 great majority of cases the phosphates-plus-potash plot has shown more live- 

 weight increase than phosphates alone, it is only in very rare instances that the 

 gain has been a profitable one. Even on thin soil overlying chalk potash has had 

 little action on pastures. There are several rather conspicuous instances of 

 quite moderate dressings of potash doing positive harm. Thus, at Cockle Park, 

 whereas potash gave an appreciable increase in live weight in the first nine years, 

 it proved positively and progressively injurious during the next two six-year 

 periods. Even on a ' light stony loam ' in Perthshire Wright found that 

 although in the first two years potash when added to slag gave a conspicuous 

 return, in the next three years ' the advantage was wholly with the slag alone 

 plot.' The most notable beneficial effect of potash was obtained in Dumfries- 

 shire on a station where the mineral soil was overlaid by ten feet of peat.^^ 

 There the use of kainit supplying 100 lb. of potash per acre at the beginning 

 of the experiment has in seven years produced 70 per cent, more meat than 

 phosphate (slag) alone, while the financial gain has been improved by nearly 

 50 per cent. 



IPotash has had great influence both on the yield and composition of the hay 

 on the meadow at Rothamsted, and 'it would seem that this substance has more 

 effect On a meadow than on a pasture. The reason is probably to seek in file 

 fact that in a pasture the top layers of the soil are constantly being enriched 

 by the potash brought from the subsoil by plants and returned through their 

 excreta. In any case, pasture plants on clay soil are in possession of abundant 

 supplies of potash, and it is only where pasture occupies sandy, gravelly or 

 peaty soil that this manurial element need be seriously considered. 



Lime as an addition to superphosphate was tested at the three original 

 manuring-for-cotton experiment stations, a total of 30 cwt. per acre being applied. 



28 Wright, Report on Experiments on the Improvement of poor permanent 

 pasture bv manuring, Bulletin No. 54, West of Scot. Coll. Agric. 1910, p. 173 



2» UuL, p. 187. 



'" Somerville, ' Poverty Bottom.' an Experiment in increased Food Produc- 

 tion, Miscellaneous Publications of the Board of Agriculture, 1918. 



31 Somerville, ' Influence on the Production of Mutton of Manures applied 

 to Pasture,' Suppl. Jour. Board of Agric. 1911, p. 11. 



32 Cambridge University Dept. of Agric, 5</t Anvual Bcport on Experiments, 

 p. 13; and the 'Improvement of Poor Pastures,' Jour. Agric. Science, vol i , 

 p. 122. 



" Wood and Berry, ' Soil Analysis as a Guide to the Manurial Treatment 

 of Poor Pastures,' Jour. Agric. Science, vol. i., p. 114. 

 3* Op. cit., pp. 131-2. 

 3= Bulletin No. 54 of the West of Scotland Coll. of Aqric, 1910. 



1919. J,y 



