98 The Rothamsted Barley Experiments. 



Mineral manures alone gave very poor crops, and the 

 quantity of both grain and straw fell off considerably during 

 the later years, but superphosphate of liine alone gave more 

 than salts of potash, soda, and magnesia, and not much less 

 than the mixture of all. It may be concluded that the soil 

 was not relatively deficient in any of the mineral constituents 

 which the manures supplied : and, from the falling off in 

 the produce both without manure and with purely mineral 

 manure, it is probable that the growth of the crop under such 

 conditions is gradually exhausting the available nitrogen 

 accumulated within the soil from previous cultivation, 

 manuring, and cropping. Mixed mineral manure, containing 

 salts of potash, soda, and magnesia, with superphosphate of 

 lime, gave, of barley, much more grain, rather less straw, 

 but considerably more total produce than of wheat. It is 

 probable that, with the autumn manuring for the wheat, the 

 various constituents are distributed by the rains, or enter 

 into less soluble combinations, or both, during the winter ; 

 that hence there is less active root development in the upper 

 and more highly nitrogenous layers of the soil in the spring, 

 and that hence the barley is more rapidly exhausting the 

 accumulated nitrogen of the surface soil than the wheat. 

 The distinction between " condition " and " fertility " is well 

 illustrated by the mineral-manured and by the unmanured 

 plots, for it is apparent that the condition of the soil, as 

 distinguished from its normal or natural fertility, is, at 

 any rate, so far as available nitrogen is concerned, being 

 gradually worked out by the growth of the crop. 



Nitrogenous manures alone (ammonia- salts or nitrate of 

 soda) gave much more barley than mineral manures alone ; 

 the produce declined much less in the later years ; and 

 for twenty years in succession even fair, though not large, 

 crops were obtained. Whilst over the twenty years the 

 average annual produce was, by the mixed mineral manure 

 (4 0), only 27^ bushels of grain and 14| cwt. of straw, that 

 by the 2001b. of ammonia-salts (1 A) alone was 32 J bushels of 



