30 



about three-fourths as much as the entire crop would be worth if incor- 

 porated in the soil. If we turn the crop under, then, in the one case, 

 we get its full manurial value. If, on the other hand, we feed it and 

 carefully save and apply the excreta, or if we pasture and so manage 

 that the droppings are evenly distributed, we have the food value and 

 about three-fourths of the manurial value. The sum of these two in 

 the great majority of instances will be greater than the full manurial 

 value. 



There are, of course, conditions under which the crop cannot be 

 profitabl)' fed, either because of the absence of stock necessary to con- 

 sume it or because of the location of the field. In such cases the turning 

 under of the entire crop may, of course, be wisest. 



There can be no doubt that the latter practice is much more often in 

 place upon light and sandy soils than upon the better soils. Upon the 

 light and poor soils legumes, not finding nitrogen in the soil, are forced 

 to take it from the air. Upon the richer soils they would take it from 

 the soil itself and there would be no essential increase in this element 

 as a result of green-manuring. 



This has been very strikingly shown by Julius Kiihn. Kiihn's experi- 

 ments were carried out in 1891 at Halle, Germany. The soil was a 

 good medium loam. It had produced wheat in 1890. After the wheat 

 was harvested a mixture of 194 pounds of peas, 44 pounds of vetch and 

 35 pounds of yellow lupine seed per acre was sown. The resulting 

 crop was ploughed under the last of October and rye was sown. The 

 quantity of green material ploughed in amounted to 8,G50 pounds per 

 acre. This supplied about 50 jjounds of nitrogen In the spring of 

 1892 the field was sown to barley, and also an adjoining field, not green- 

 manured. The crops were practically equal under the two methods of 

 treatment. In this case, then, green-manuring produced no ai^preciable 

 benefit. Kiihn estimated that the crop ploughed in would have been 

 worth for feeding about thirteen dollars per acre. 



On the other hand, the same experimentor fovmd that on a sandy loam 

 soil green-manuring with field peas sown in the rye stubble after har- 

 vesting increased the crop of barley the following year to the same ex- 

 tent as an application of about 175 pounds of nitrate of soda. In the 

 latter case green-manuring paid, while in the first it was attended with 

 loss. 



Numerous experiments in the United States, a few of which will be 

 noticed later, establish beyond a doubt the possible benefits of green- 

 manuring upon the lighter and poorer soils. It is important to point 

 out, indeed I have already, in what has been said concerning eating 

 one's cake and having it too, called attention to the fact, that even when 

 the catch-crop is fed the manurial value of its stubble and roots may be 

 considerable. Especially is this true concerning the legumes (clover- 

 like plants). 



A great deal of work to determine the manurial value of the .stubble 

 of different crops has been carried out at the Storr's School Experiment 

 Station, Connecticut. Some of the leading results of Professor Wood's 

 investigations are shown in the following table : — 



