Macronutrient status of soils under different plantation cycles of poplar (Populus deltoides bartr.) based agroforestry system in Punjab

The study was conducted to determine depthwise (0–15, 15–30, 30–60 and 60–90 cm) available primary (N, P and K) and secondary (Ca, Mg and S) macronutrients in five land use systems viz., sites having continuous poplar (Populus deltoides)-based agroforestry system (AFS) for 10, 20 and 30 years (Y), fodder (pearlmillet/sorghum)-fodder (oats/berseem) rotation (F-F) and fallow land. Available N, P and K in different soil layers were generally lowest in fallow land (62.7, 16.78 and 120.5 kg/ha, respectively in surface depth) and increased significantly with adoption of AFS and were highest in 30 Y plantation site of AFS (183.1, 43.53 and 195.2 kg ha⁻¹, respectively in surface depth). These were highest in surface and declined with increase in depth. In 0–15 cm soil depth, an increase of 13, 84.3 and 29.6% in exchangeable Ca, exchangeable Mg and available sulphur was observed in mature (30 Y) plantation sites over young (10 Y) plantation sites of AFS. The macronutrient index value was low for N, medium to high for P and low to high for K in different treatments. Therefore, the long-term adoption of poplar based agroforestry helps in improving the soil health, productivity and sustainable agriculture.