ENGLISH AGRICULTURE. 173 



soda is added it appears to develop the action of the super- 

 phosphate, and a better result is obtained. 



Additions of sulphate of potash, sulphate of magnesia, and 

 chloride of sodium (common salt) often produce a consider- 

 able increase on mangel, but it is open to the view that 

 the effect is a good deal owing to the common salt rather 

 than to the magnesia or even the potash. Yet in a crop 

 like mangel, which is a heavy yielder and a rapid grower, 

 a mixture of fertilizers approaching to the composition of 

 a general manure assists in its development. An argument 

 in favour of the view that potash salts and salts of soda 

 and magnesia are not usually required in ordinary practice 

 may be supported by the fact that the mangel plots at Roth- 

 amsted are like most of the experiments there conducted, 

 successive cultivations, year after year. A crop such as 

 mangel grown consecutively upon the same land would draw 

 heavily upon the potash and magnesia of the soil much 

 more so than would mangel grown at the usual intervals in 

 ordinary farming. There would consequently be a probable 

 lack of potash and other mineral ingredients induced. With 

 this consideration in view we may well wonder that dress- 

 ings of potash salt produced so little effect. We may also 

 reasonably conclude that in combination with a good dressing 

 of farmyard manure they would produce no visible effect, 

 especially as potash, soda, magnesia, and lime abound in 

 farmyard manure. 



Next with reference to manuring permanent pastures. The 

 herbage in such pastures is of a very mixed character indeed. 

 It is a very different thing to manure permanent pasture 

 grounds, and to manure a wheat field or even a field of turnips 

 or mangel wurzel. You have plant requirements of all sorts 

 plants searching after food in different layers of the soil ; you 

 have leguminous plants, and plants of gramineous order, and 

 you have also plants of a mixed weedy character, spoken of 



