Dec. 6. 1915 Influence of Growth of Cowpeas on Soil Properties 447 



under adjacent, similarly treated, fallowed plots. (See " Historical 

 summary.") 



Although there is a wide range in the total bacterial count under the 

 respective treatments, the only certain conclusion which can be drawn 

 is that under cowpeas we have larger numbers of bacteria than where 

 no crop is on the land. The ammonifying and nitrifying efficiency of 

 these soils as affected by the summer's treatment seemed to have been 

 only influenced by the varied conditions noted, but no correlations can 

 be drawn. Thus, briefly summing up, it might be said that the main- 

 tenance of soil structure from spring to fall by the growth of cowpeas on 

 the land is due partially to the shading effect of the foliage, which, like 

 the artificial shade, resists the compacting effect of beating rains and 

 baking sun. Besides this, there seems to be a marked correlation between 

 the friability of the soil under cowpeas and the bacterial flora present. 

 Where present in largest numbers, they possibly bring about a greater 

 production of active humus and so maintain the looseness of the soil. 



SUMMARY 



(i) The data given show conclusively that cowpeas tend to maintain 

 the friability of loose and compact seed beds. 



(2) It was also noted that, while cowpeas take more water from the 

 soil than evaporates from uncultivated adjacent lands, the removal of 

 water is from below the second foot of soil. 



(3) Land that was plowed and left uncultivated or plowed and seeded 

 to cowpeas contained a greater quantity of nitrates in the soil at the 

 end of the season than unplowed land similarly treated. 



(4) The bacterial activities of the soil upon which cowpeas were grown 

 tended to show that the soil organisms are probably a factor in prevent- 

 ing the packing of soil, as also is the mechanical shade effect of the crop 

 grown upon the land. 



