Effect of different spacings of poplar-based agroforestry system on soil chemical properties and nutrient status in Haryana, India

A field experiment was conducted during 2013-14 and 2014-15 to study the effect of different spacings, i.e. 5 x 4 m, 10 x 2 m and 18 x 2 x 2 m (paired row) of 7- and 8-yr-old poplar-based agroforestry system on soil chemical properties such as soil pH, electrical conductivity (EC), soil organic carbon (SOC) and available N, P and K. Poplar-based agroforestry system had better available nutrients status in comparison to sole wheat crop. The lowest value of soil pH (7 x 5) was recorded under 5 x 4 m spacing after harvesting of wheat crop during April 2015. The decrease in EC was maximum (67%) under 5 x 4 m spacing followed by 10 x 2 m and 18 x 2 x 2 m spacing with a reduction up to 63% and 61% respectively. SOC increased with the decrease in tree spacing and was maximum (0.74%) under 5 x 4 m spacing; it followed the order 5 x 4 m > 10 x 2 m > 18 x 2 x 2 m > control after harvesting of wheat crop during April 2015. The available soil N, P and K increased significantly under different spacings of poplar-based agroforestry system in all the treatments from their initial values. The highest available soil N (366.3 kg ha(-1)), P (21.4 kg ha(-1)) and K (355.3 kg ha(-1)) were recorded under 5 x 4 m spacing compared to 10 x 2 m and 18 x 2 x 2 m and sole cropping after harvesting of wheat crop during April 2015.