8 



Relative gro^vth of wheat plants on Portsmouth sandy loam ivith various 



treatments. 



The above table shows that this soil, although thoroughly cultivated, 

 well supplied with commercial fertilizers, and subject to a systematic 

 rotation of crops, in which cowpeas are frequently grown, has responded 

 in a marked degree to many of the manurial treatments. 



Cowpeas have produced decidedly the largest increase in growth, 

 applications of 2 tons and 5 tons giving increases of 57 and 104 per 

 cent, respectively, and by supplementing this treatment with small 

 amounts of lime, the gain has been increased to 99 and 138 per cent. 

 The tops of young cowpeas were used in a green state, and the amounts 

 given in the above table are calculated to water-free substance. Two 

 and one-half tons of water-free tops per acre would be a good yield where 

 cowpeas are grown for the purpose of plowing under as a green manure, 

 although larger yields are sometimes secured. The roots of the cowpeas 

 will probably equal about one-half the weight of the tops, and not only 

 possess a manurial value, but have a marked beneficial effect upon the 

 soil as a result of- their extensive penetration. It is quite possible for 

 the benefits derived from the roots and stubble of a crop of cowpeas to 

 equal the benefits secured by plowing under the tops, and thus the tops 

 may be removed for forage or hay and still the soil be improved. 



Lime has also produced very marked results on this soil, giving 

 increases of 47 and 40 per cent for applications of 1,000 and 2,000 

 pounds per acre, respectively. The same applications, when used in 

 addition to cowpeas, produced gains over and above that resulting from 

 the cowpeas amounting to 42 and 34 per cent, and when used in con- 

 nection with a complete commercial fertilizer consisting of 200 pounds 

 per acre each of sodium nitrate, potassium sulphate, and acid phos- 



