Biological Nitrogen Fixation by Local and Improved Genotypes of Cowpea in Burkina Faso (West Africa): Total Nitrogen Accumulated can be used for Quick Estimation

Figure 4

Relationship between the observed values of N derived from the atmosphere by cowpea genotypes cultivated with different fertilizer treatments (observed Ndfa-ID) and calculated values (calculated Ndfa-ID) from the model equation between total N yields and N derived from the atmosphere with the isotopic dilution method (Ndfa-ID). Number of values: 21; each value represents the mean of 4 values. Data from Bado et al. (2006).