22 



formed are not taken up by a crop. To obtain the greatest 

 return from manure, or from its residues, it is necessary that 

 the crops produced should be distinctly below the highest 

 which the soil and season would produce with an abundant 

 manuring. It is only when manure is very cheap, or crops 

 are fetching a high price, that high farming will be true 

 economy. 



Even when the quantity of manure applied to the land 

 is insufficient to entirely obliterate the visible effect of the 

 residues of previous manuring, the return in the crop 

 obtained from these residues may be considerably diminished 

 in consequence of this subsequent manuring ; and this will 

 be especially the case when we have to do with a residue of 

 farmyard, or other nitrogenous manure, and are growing not 

 corn but green crops. To make myself clear I must remind 

 you that green crops, as turnips or grass, may vary very 

 much in composition. As an illustration let me take the 

 swedes grown in the experimental rotation field at Eotham- 

 sted. On one portion of this field the swedes have been 

 grown for many years with superphosphate only. On 

 another portion of the field a liberal nitrogenous manuring 

 is applied with the superphosphate. In 1880 the super- 

 phosphate gave nearly 12 tons of swedes, and the mixed 

 manure 22 tons. Analysis showed that 1 ton of swedes 

 grown with nitrogenous manure contained one-half more 

 nitrogen than 1 ton of swedes grown with superphosphate ; 

 the same quantity of soil nitrogen which would produce 

 8 tons of swedes with superphosphate alone would thus only 

 yield 2 tons when high manuring was adopted. Thus under 

 a generous treatment of the land, and especially with the 

 growth of green crops, the apparent effect of residues of 

 nitrogenous manure will be considerably diminished, and 

 their effect will appear partly in an alteration in the composi- 

 tion of the subsequent crops instead of in an increase in their 

 weight. 



It is evident from what has now been said that under the 

 conditions of ordinary agriculture we must not expect to 

 obtain the large returns from residues of farmyard manure 

 which were obtained at Kothamsted and Woburn by leaving 



