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454 ANNUAL, REPORT OF THE Off. Doc. 



yields as are produced by farm manure. Why? Because the peat 

 does not decay readily so as to furnish plant food either by its own 

 decomposition or by liberating it from the soil; and yet the peat has 

 as great power as farm manure for physical improvement of the 

 soil. 



Manure made from clover hay and heavy grain rations has much 

 greater value than manure made from wheat straw. Why? Is it 

 because they aifect the physical condition of the soil in different 

 waj'S? No. The great dilference in value is due to the difference 

 in plant food and in rapidity of decay. 



At the famous agricultural experiment station at Rothamsted, 

 England, on a held to which no manure and no plant food have been 

 applied, the average yield of wheat has been 13.1 bushels per acre 

 for more than half a century. Land treated with a heavy annual 

 application of farm manure has produced 35.7 bushels of wiieat per 

 acre as an average of 51 years. Another field treated with commer- 

 cial plant food without organic matter has produced 37.1 bushels 

 of wheat per acre as an average during the same time. The latter 

 field received a little less plant food than was furnished in the ma- 

 nure, thus furnishing ample proof of the value of plaut food supplied 

 in manure and showing that the physical eflect of the farm manure 

 was by no means so important. 



Nevertheless the physical effect should not be overlooked. Under 

 certain seasonal conditions this physical ellect may be very im- 

 portant. Thus in the very dry season of 1893 the land fertilized with 

 commercial plant food produced only 21.7 bushels of wheat per acre, 

 while the farm manure plot produced 34.2 bushels the same year. 



In semi-arid regions the physical conditions of the soil and its 

 power to absorb and retain moisture may be the controlling factor in 

 crop yields, but where the aA^erage annual rainfall is 28.21 inches as 

 at Rothamsted) or 37.39 inches (as in Illinois) with a fairly uni- 

 form distribution during the growing season, the physical condition 

 of the soil in relation to crop yields may be compared to the shelter 

 and other physical surroundings provided for live stock. In other 

 words, under normal conditions the controlling factor is food, for 

 crops as well as for live stock. 



While manure has some value for physical improvement and a lar- 

 ger value of its power to liberate plant food from the soil, it should 

 be clearly understood and always borne in mind that the great i aliie 

 of farm manure, especially in profitable systems of permanent agri- 

 culture, is due to the plant food it contains and that the greatest 

 problem in the handling of farm manure is to prevent the loss of 

 plant food. 



The value of the average fresh farm manure is about |2.25 a ton 

 either when determined by chemical analysis on the basis of market 

 values for the plant food contained in the manure, or when deter- 

 mined by the value of the increased crop yields produced when the 

 manure is applied to the fields in ordinary crop rotations. 



This means that a pile of average fresh farm manure containing 

 700 tons is worth |225. If exposed to leaching from heavy rains 

 during only two or three months in the spring the value will be re- 

 duced as a rule fi'om .f225 to about -floO by the loss of plant food 

 without much reduction in total weight. Indeed, the total weight 

 is frequently increased under such conditions, because the rain 



