Performance of Melia dubia under different planting densities: effects on growth and carbon sequestration

The experiment was conducted in alfisols having moderate water holding capacity (10% to 18% at field capacity), with acidic soil pH (5.5), low organic carbon content (0.30%), low in available nitrogen (235 kg ha -1 ), medium in available phosphorus (32 kg ha -1 ) and medium in available potash (299 kg ha -1 ).The experiment consisted of six spacing, viz.S 1 (24 m 5 m), S 2 (20 m 5 m), S 3 (16 m 5 m), S 4 (12 m 5 m), S 5 (10 m 5 m) and S 6 (8 m 5 m) which accommodated 83, 100, 125, 166, 200 and 250 trees per hectare, respectively.These were laid out in strip plot design and replicated four times.After ten years of planting, the results revealed that there was wide variation in tree height, girth at breast height (GBH) and canopy spread with different spacings.The tree height was significantly higher in S 1 (14.02m), followed by S 2 (13.99 m) and S 3 (13.04m).A similar trend was observed for GBH (125.39,117.03 and 105.36 cm, respectively), canopy spread N-S (8.89, 8.61 and 8.27 m, respectively) and E-W direction (8.35, 8.17 and 7.86 m, respectively).Variation in tree biomass accumulation was also found.The maximum total biomass was recorded with the spacing of S 4 (91.74 tonne ha -1 ), followed by S 6 (81.44 tonne ha -1 ) and S 5 (79.85 tonne ha -1 ).The higher above-ground biomass of M. dubia in S 1 is due to wider canopy spread and vigorous growth.Similarly, higher tree carbon was sequestered with the spacing of S 4 (157.81tonne ha -1 ), followed by S 6 (140.10 tonne ha -1 ).The least carbon was sequestered with S 3 (124.94tonne ha -1 ).Apart from it also enhanced nutrient content in the soil, viz.soil organic carbon (0.69%), Available nitrogen (295.0 kg ha -1 ), Phosphorus (29.72 kg ha -1 ) and potassium (298.0 kg ha -1 ).There is an improvement in soil pH (6.65) compared to the initial status.Finally, it can be concluded that M. dubia planting at a wider spacing of 24 m 5 m will be effective with respect to tree height, GBH and canopy spread after ten years of planting.But the spacing of 12 m 5 m helped in enhancing the soil health and sequestering 157 tonnes of carbon per hectare.