Demand-Driven Technologies for Sustainable Maize ... - IITA

202Figure 1. Relationships between relative response to high P and grainyield at low P of soybean genotypes.with RP application as shown in Figure 1b. Grouping of soybeangenotypes based on grain yield under low P conditions gave threemajor groups of P use effi ciency: effi cient, ineffi cient, and intermediate.Similarly, three P response groups (for both TSP and RP) —responders,nonresponders, and intermediate— were established based on grainyield response to P application (Table 3; Fig. 2). The soybean genotypeTGm1566 which maintained relatively high yields under low soil Pconditions also responded to the application of P fertilizer.The correlation between grain yield and some P use and responseeffi ciency criteria varied with soybean genotypes under low and highP conditions. Grain yield generally had a highly signifi cant correlationwith biomass yield (P ≤ 0.001; r = 0.20), and with P utilization quotientin grain for 0P (r = –0.33) and RP treatments (r = –0.20). Also thecorrelation between grain yield and TSP treatment (r = –0.14), thoughrelatively low, was signifi cant at P ≤ 0.05). Relative response effi ciencyhad a highly signifi cant correlation with grain yield for both RP andTSP treatments. Mycorrhizal infection of roots also had a highly