420 SECTIONAL TRANSACTIONS.— M. 



group of ealt-soluble constituents increases correspondingly less rapidly. Owing to- 

 these regularities the total nitrogen content is a good index, within each variety, of the 

 effects of the amounts of the separate proteins on the so-called ' quality ' of the grain. 

 A knowledge of yield and nitrogenous composition has an important practical 

 bearing since there is a wide range in prices between high-class malting barley and 

 low-grade barley used for stock feeding. A range which is greater than that between 

 different grades of any other cereal. The ' quality ' is therefore a valuable and 

 important characteristic, and conditions affecting ' quality ' are worthy of study. 

 The reason why particular attention has been paid to the nitrogenous composition 

 is that it has been noted in the past that high quality in barley is chiefly associated 

 with low nitrogen content, while in the future there may be an even closer connection 

 between value and nitrogen content ; for it has been shown that the latter can be 

 used to predict from the barley two quantities of importance in the resulting malt — 

 ' extract ' and ' permanently soluble nitrogen.' 



(c) Dr. E. M. Crowther. — Influence of Fertilisers on the Yield and 



Composition of Potatoes. 



Although the yields of potatoes are more influenced by factors, such as season, 

 soil type, potato variety, and disease than by the artificial fertilisers used, progress 

 in recent years in the study of potato manuring has already greatly modified the 

 practical use of fertilisers for this crop. The potato is primarily a dung crop. Formerly, 

 with liberal supplies of dung the addition of phosphates probably sufficed, but under 

 modern conditions there is much evidence that phosphatic responses occur only in 

 very deficient soils or in highly farmed land where nitrogen and potash supplies are 

 liberal. The importance of an adequate balance between nitrogen and potash has 

 been established. Although high grade potassium salts are especially favoured, the 

 adverse effects of high chloride and sodium contents are shown only in occasional 

 years. 



The influence of fertilisers on potato quality is still obsciire, in spite of the 

 dogmatism of the text books and the confident assertions of salesmen. As potatoes 

 are not important industrial raw materials in this country, there has been little 

 attempt to standardise potato quality even in arbitrary terms. Further, the English 

 taste differs completely from the Continental ones. At present, potatoes are graded 

 almost entirely by variety and type of soil. A preliminary fertiliser trial with quality 

 tests and chemical analyses on the tubers was carried out on a large scale in 1929 by 

 Rothamsted and the Research Laboratories of Messrs. Lyons. Here, too, the 

 difference between two experimental centres (Rothamsted on heavy loam soil and 

 Woburn on sandy loam soil) proved greater than those due to fertilisers at either 

 centre. There was evidence that the nitrogenous manures increased the nitrogen 

 content and decreased the values assigned to consistency and flavour. Potash manures 

 reduced the dry matter and nitrogen contents and increased the values assigned to 

 consistency and flavour. 



(Appreciable effects on flavour were obtained only at Woburn.) Effects due to 

 the form of potash used were slight ; potassium chloride gave the best consistency ; 

 both dry matter and nitrogen in the tubers decreased with increasing amounts of 

 chloride. The variations between replicated plots are so great that field experiments 

 must be very carefully designed before reliable results may be expected. 



(d) Dr. Winifred E. Brenchley. — Meadow Hay. 



Fertilisers exercise an indirect, as well as direct, action on yield on grass and 

 arable land by influencing the growth of plants other than the desired crop, so varying 

 the degree of competition to which the crop is subjected. 



The competition of weeds or undesirable plants is a much more important factor 

 n determining yield than is generallj'' recognised. 



On arable land the type of manuring that is favourable to good crop production 

 also favours the growth of weeds. If seasonal conditions encourage the germination 

 and growth of weed seeds before the crop makes headway the competition causes 

 serious reduction of crop yield, which is frequently more marked with heavy than 

 with light manuring. The potential weed flora may be very abundant, quantitative 

 experiments at Rothamsted showing that the numbers of viable weed seeds buried 

 in the soil may run into hundreds of millions per acre with certain types of fertilisers. 



