144 ACTION OF SOIL ON FOOD OF PLANTS IN MANURE. 



In these respects tlie successes of the agriculturist 

 would be still greater if the nutritive substances con- 

 tained in the manure principally used, namely, farm-yard 

 manure, were more uniformly mixed and distributed, 

 because this would lead to a more uniform distribution 

 of them in the soil. 



Farm-yard manure is a very irregular mixture of 

 decaying straw and vegetable remains, combined with 

 soKd animal excrements, the latter constituting the 

 smaller portion of the whole mass : it is soaked with 

 fluids which hold ammonia and potash in solution. If a 

 hundred samples be taken from a hundred different parts 

 of a dung-heap, the analysis of each sample will show 

 different proportions of nutritive constituents : hence it is 

 evident that by a dressing with farm-yard manure hardly 

 two spots in the soil will receive the same amount of 

 nutritive substances. 



The spot occupied by a duiig-heap on a field during 

 rainy weather, will be marked in the whole period of 

 vegetation, and often even in the second year by a more 

 luxuriant growth of plants, especially of cereals, though 

 the plants growing on it will not always furnish a per- 

 ceptibly greater yield of grain. If the potash and 

 ammonia received by this spot above what was required for 

 the formation of grain, had been more evenly distributed, 

 and thus accessible to the plants in other places, the yield 

 of corn from those plants would have been increased ; 

 whereas the excessive accumulation in one place merely 

 increased the yield of straw. The unequal distribution 

 of the other ingredients of farm-yard manure in the soil 

 leads to a similar inequality in the developement of 

 the several parts of the cereal plants. On an ideal 

 field, with the nutritive substances supposed to be distri- 

 buted with perfect uniformity, and all accessible to the 



