12 PEAS AND PExV CULTURE 



cles of the pea roots, assimilate more nitrogen than 

 the plant needs for its growth. If this be true he 

 argues that peas planted with a crop will tend to 

 increase the yield of that crop unless plants are so 

 thick as to interfere with the root development or 

 as to use up too much water in growth. Various 

 experiments have shown that uncultivated soils 

 produce a less number of bacteria than cultivated. 

 A fair proportion of humus favors tubercle develop- 

 ment, yet there is likely to be slight development 

 of tubercles where soil is exceedingly rich in humus. 

 Potash, phosphoric acid, and lime, all favor the pro- 

 duction of root tubercles. 



Inoculation. — There have been many experiments 

 relative to development of root tubercles by treat- 

 ing the soil or the seed with materials carrying great 

 numbers of the desirable bacteria. Kirk^^ made a 

 thorough investigation and declared that his results 

 proved (i) that on land which will already produce 

 a good crop of legumes the inoculation is of little 

 benefit to the crop; but (2) it increases the number 

 of nodules on the root and consequently a quantity 

 of nitrogen is left in the soil for the benefit of the fol- 

 lowing crop, such as grains or roots, which have 

 not the power of providing nitrogen for themselves ; 

 (3) inoculated seed invariably gave better results 

 than the inoculated soil. 



Halsted^^ planted peas on soil where no legumi- 

 nous plants had grown for at least eight years. Por- 

 tions of the plot received a dressing of soil that had 

 recently borne peas. At harvest ten ])lants were 

 taken at random from the treated and untreated 



" N. Z. Dept. of Agri. Annual Rpt., 1905. 

 "N. J. Exper. Sta. Rpt, 1898. 



