Nutrient return through litterfall from poplar plantation having different spacings in an agroforestry system

An investigation into nutrient return via litterfall was conducted in a poplar (Populus deltoides Bartr.) plantation employing three distinct spacing configurations [5 × 3 m, 7 × 3 m (paired at 2.5 m), and 8 × 2.5 m] within an agroforestry system over the plantation’s 4^th, 5^th, and 6^th years of growth. After six years, trees planted at 8 × 2.5 m spacing exhibited significantly greater diameters at breast height (22.05 cm) and heights (19.47 m) compared to those at the other spacings. Litterfall accumulation over the 4^th, 5^th, and 6^th years was statistically highest in the 7 × 3 m (paired row) spacing, with totals of 6.54, 7.61, and 7.53 t/ha, respectively, and lowest in the 8 × 2.5 m spacing, with totals of 4.55, 4.90, and 5.40 t/ha, respectively. The average nutrient return of nitrogen (N), phosphorus (P), and potassium (K) over these years was significantly greater in the 7 × 3 m (paired row) spacing, with values of 65.41, 7.38, and 55.53 kg/ha, respectively, compared to the other spacings. Soil organic carbon (OC), available N, P, and K content were all elevated compared to initial levels, with the highest concentrations found under the 7 × 3 m (paired row) spacing, measuring 4.47 g/kg, 158.3 kg/ha, 18.23 kg/ha, and 199.1 kg/ ha, respectively. These findings suggest that poplar-based agroforestry systems contribute positively to soil health through the addition of litterfall. Nonetheless, further research is needed to quantify the contribution of litterfall nutrients to the overall nutrient requirements of the agroforestry system.