Response of Leucaena diversifolia (Schlecht.) Benth seedlings to Rhizobium inoculation in Macolod and Luisiana soils

The screening experiment (Experiment 1) showed that among the four local Rhizobium isolates (Ld PL, LTD, LdCR, LdCI) screened for effectiveness under laboratory condition, Ld PL (Puting Lupa isolate) and LdCR (Carranglan isolate) were the two best Rhizobium inoculants for Leucaena diversifolia. Results obtained from experiment 2 suggested that inoculation of L. diversifolia with the two best local Rhizobium isolates (LdPL and LdCR) and an Australian strain (CB 81) significantly affected growth, dry matter production, nodulation, nitrogen content and uptake of the seedlings. Experiment 3 showed that inoculation of L. diversifolia with Rhizobium isolate LdCR resulted in an increase in height, diameter, shoot biomass, nodule number, nodule dry weight and N uptake of the seedlings. Soil type significantly and independently affected all the growth parameters except for root/shoot ratio. The interaction of Rhizobium inoculation in both Macolod soil and Luisiana soil markedly improved the nodulation and N uptake of the seedlings. Addition of nitrogen fertilizer in the form of urea (46% N) significantly influenced growth, dry matter production, nodulation, N content and N uptake. Local Rhizobium isolate LdCR can substitute for an estimated amount of about 84.40% and 65% of the nitrogen requirements of L. diversifolia in Macolod and Luisiana soil, respectively. In experiment 4, inoculation of the test host with the best Rhizobium source, LdCR significantly enhanced height, nodule number and nodule dry weight by as much as 12%, 96.3% and 94%, respectively relative to the uninoculated ones and contain 9% more N and 14% more K in their tissues. The combined effect of lime levels and inoculation influenced significantly the height, nodulation, nutrient content, and nutrient uptake. Correlation and regression analyses revealed that shoot and biomass was highly correlated with nodule dry weight and N uptake.