Impact of Melia composita based agroforestry system under variable spacings on chemical properties and nutrient status of soil

Abstract

Melia composita Willd. (Burma dek) is a fast-growing tree species widely adopted by Punjab farmers in agroforestry systems. The present study was conducted to examine the improvement in soil chemical properties, available macronutrients, and DTPA-extractable micronutrients in soil under different spacings of Melia composita-based agroforestry system in its 9th year of age. The study was carried out in the experiment having three spacings viz., 5 x 3 m, 7 x 3 m (paired at 2.5 m), and 7 x 3 m along with the fallow land (control). Soil sampling was done at four soil depths (0-15, 15-30, 30-45, and 45-60 cm) for analysis. The tree height and DBH were highest in the 7 x 3 m spacing (20.16 m and 23.81 cm, respectively). Soil pH decreased, whereas EC and CEC increased under trees over control, and the influence was higher in 5 x 3 m than other spacings. The concentration of macronutrients and micronutrients was highest in surface soils and decreased with increasing depth. The available N, P, and K in the system were highest in 5 x 3 m spacing (149.5, 41.95, and 194.8 kg ha-1, respectively in 0-15 cm depth) followed by 7 x 3 m (paired row), 7 x 3 m, and control. The DTPA-extractable Zn, Fe, Mn, and Cu were also highest in 5 x 3 m spacing (4.12, 5.98, 13.80, and 0.70 mg kg-1, respectively in 0-15 cm depth) and the lowest were observed under control (1.55, 4.36, 8.03, and 0.41 mg kg-1, respectively in 0-15 cm depth). Based on this study, it is suggested to include Melia composita in cropping systems at 7 x 3 m or 5 x 3 m spacing for good growth of plants and for improvement in soil properties and nutrient content due to the addition of litterfall from the trees.