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THE GENESEE FAEMEE. 



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PLOWING IN GREEN CROPS. 



AVuEN a plant is burnt in the air, the ashgs which remain are termed by chemists the 

 inorganic constituents ; that which is burnt away, the organic : and though this defini- 

 tion is not strictly correct, it is sufficiently so for all practical pui*poscs. The great store- 

 house of the orr/anic elements of plants, is the atmosphere ; the inorganic elements are 

 obtained by plants only from the soil. The amount of produce whicii a soil destitute 

 of organic matter will annually yield by the disintegration of its inorganic elements, may 

 be considered the natural yield of the land. What that amount will be, will depend, 

 within certain limits, on the abundance or scarcity of these mineral constituents of the 

 plants grown ; but plants can not gTOw at all without organic matter, or those elements 

 which the atmosphere will supply. Now, in what quantity*will the atmosphere supply 

 these to the plants, providing there is a sufficiency of mineral matter ? This depends on 

 the kind of plants, the length of the gi'owing season, and the quantity of rain and num- 

 ber of rainy days in that season. It has indeed been supposed by some eminent chem- 

 ists, that the atmosphere would supply an unlimited amount of organic constituents to 

 the plants, and that therefore the yield of any given crop would be in exact proportion 

 to the quantity of inorganic matter existing in the soil in an assimilable condition ; — that, 

 if there were only mineral elements sufiicient in an acre for five bushels of wheat and 

 straw, only five bushels would be grown ; but if there were sufficient for fifty bushels, a 

 produce of fifty bushels per acre would be obtained. To the first proposition we of 

 course agree, thinking that up to the amount of j^roduce for which the atmosphere 

 supplies sufficient organic matter, the yield will be in exact proportion to the mmeral 

 matter available in the soil ; so that the point at issue between the " mineral theory" 

 and " ammoniacal theory" advocates, is, the amount of organic matter which the atmos- 

 phere annually supplies to certain crops, — and there is no subject of more importance 

 connected with agricultural chemistry, affecting as it does the reason of all our systems 

 of agricultui'e, rotation of crops, the value of manuring substances, and in fact everything 

 connected with agricultural operations. 



Without therefore attempting to settle the question as to whether soils are easily 

 exhausted of their mineral constituents or not, we will give some results of experiments 

 by Mr. Lawes, that, so far as wheat is concerned, entirely satisfy us that to obtain large 

 crops, it is absolutely necessary to supjjlg organic matter in the soil ; or, in other words, 

 that the atmosphere will not supply sufficient organic matter for a large crop of wheat. 



The experiments were commenced in 1843. The soil a rather heavy loam, or what 

 is generally known as a good wheat soil. Four grain crops were taken from the field 

 the four years preceding the experiment, without any manure of any kind being supplied. 

 The field devoted to the experiments contains fourteen acres. It is divided into thirty- 

 three portions, which have been sown with wheat (and the whole crop of wheat and 

 straw removed) every year. One plot has been left unmanured since the commence- 

 ment ; another supplied with fourteen tons of barn-yard manure per acre each year, 

 and one with the ashes of fourteen tons of barn-yard manure ; some with " Liebig's 

 Patent Wheat Manure," and others with all kinds of chemical mineral manures, alone 

 and in various combinations; some with rice at the rate of one ton per acre, rape cake 

 in various quantities, and sulphate and muriate of ammonia alone and in conjunction 

 with all kinds of mineral manures. The detailed results of such extensive experiments 

 can not of course be given ; and in fact, a mere summary of them would occupy more 

 room than our space will admit. Sufiice it to say, then, that the average yield of dressed 

 grain per acre, of seven successive crops on the continuously unmanured plot, was 1 7|- 

 bushels. The average yield of nine plots, the first year dressed with a variety of artifi- 

 cial mineral manures corresponding to the ash of wheat and straw, was 16f bushels. 



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