Comparison of growth, biomass and nutrient distribution in five promising clones of Populus deltoides under an agrisilviculture system

Variations in growth, above- and below-ground biomass and nutrient distribution were examined in five clones (G3, G48, 65/27, D121 and S7C1) of Populus deltoides grown under agrisilviculture system in sub-humid tropics of Central India. The monoclonal blocks were planted at 4 × 5 m in a randomized block design with three replications. Diameter at breast height (dbh) and tree height were consistently higher in clone 65/27 and lowest in clone S7C1. Mean annual increments (MAI) in dbh and height were 1.6 and 1.3 times higher in clone 65/27 compared to clone S7C1. Total biomass varied from 48.5 to 62.2 Mg ha−1 in six-year-old clones. In rank order, the total biomass of clones was: 65/27 > D121 > G48 > G3 > S7C1. Stem wood accounted 60.4–68.9% to total biomass followed by coarse roots (12.2–18.9%), branches (12.3–15%), leaves (3.02–6.9%) and fine roots (1.5–2.7%). Root–shoot ratio ranged from 0.2 to 0.35. It was highest in clone G48 and lowest in clone S7C1. In six-year-old clones, total N ranged from 184.3 to 266.3 kg ha−1, P from 16.8 to 31.1 kg ha−1 and K from 81.9 to 128.7 kg ha−1. Total N and P were highest in clone 65/27, while K in clone G48. Nutrients were lowest in clone S7C1. In general, maximum nutrients (N, P and K) were allocated to above-ground components (leaves > stem > branches) than below-ground components. Available N, P and K in the soil improved significantly after six years of planting. It was higher in 0–20 cm and decreased with soil depth. At 0–20 cm soil depth, N increased from 14.9% to 24.1%, P from 17.2% to 23.3% and K from 3.1% to 5.1% under different clones. The yield of both soybean and wheat reduced under poplar clones. Yield losses in soybean ranged from 10.1% to 33% and wheat from 15% to 30.3% under different clones. The management strategies for reducing tree-crop competition and nutrient export from the site under P. deltoides based agrisilviculture system for achieving sustainable production are discussed.