1022 THE COMPLETE GRAZIER. BOOK xi. 



from exhausting the land, experience has indicated, year after year, 

 that we improve it. This is probably due to the fact that the most 

 luxuriant mangel plants leave in the soil a much greater residue, in 

 the shape of fine rootlets, than do the poorer ones, and that these 

 rootlets decay next year and furnish manure for the oats. Added to 

 this there is a much greater quantity of tops, which are left on the 

 land and ploughed in as green manure. If the manure made by con- 

 suming the roots were carted on to the land as it is in actual farm 

 practice the increased fertility would be still more apparent. In fact, 

 we believe that heavy crops cannot be systematically grown without 

 raising the condition of the land, and, as a general rule, the more 

 produce that we take off a field not spasmodically, but year after 

 year the better is the condition of the soil and the greater its 

 capability for growing large crops in the future, provided that liberal 

 manuring be kept up. If it be not kept up the condition will, of 

 course, gradually lapse back to its normal state, but no permanent 

 exhaustion will be apparent. It would probably pay better to give a 

 higher rent for land on which heavy crops had been raised by high 

 manuring in ordinary rotation cropping for ten years, than a lower 

 rent for a neighbouring farm on originally similar soil, where, for a 

 like time, meagre crops had been grown. 



BEANS, PEAS, CLOVER, VETCHES, &c. These and other leguminous 

 crops vary in their rnanurial requirements from the crops already 

 considered, inasmuch as they are far less responsive to nitrogenous 

 manuring. It has been amply proved 1 that leguminous plants are 

 able to obtain a part and, if necessary, all of their nitrogen, from the 

 nitrogen of the air, this being apparently fixed and assimilated by the 

 aid of micro-organisms which are found in the nodules which occur 

 on the roots of such plants. Beyond the nitrogen that they receive 

 in dung, therefore, it is not generally found to be economical to apply 

 nitrogen for these crops. Some striking field experiments bearing upon 

 this point have been made by Mr. James Mason, of Eyiisham Hall, Oxon. 



Mineral manures may be used, that is to say, manures supplying 

 phosphates and potash ; and it has been already said that sulphate of 

 lime or gypsum is found useful on some soils, all the leguminous crops 

 assimilating comparatively large quantities of lime. 



ROTATION GRASSES. When, however, clover is grown in association 

 with rye-grass, or other grasses, nitrogenous manuring should not be 

 neglected, especially if such a mixture of grasses is sown as will last 

 for two or more seasons. 



Rotation grasses will stand freely heavy manuring, and afford one of 

 the best opportunities of producing large quantities of green fodder 

 from the land. As the farmer with this crop looks only to an im- 

 mediate yield, and not to the maintenance of a fine herbage and good 



1 See "The Sources of the Nitrogen of our Leguminous Crops," by Sir J. B. Lawes and 

 Dr. J. H. Gilbert, in the "Journal of the Royal Agricultural Society," Vol. II., Third 

 Series, 1891 (pages 657 to 702). 



