Soil micronutrient pools in a chronosequence of poplar based agroforestry system
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Date
2020
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Punjab Agricultural University, Ludhiana
Abstract
A study was conducted to observe the temporal effect of poplar based agroforestry system on soil micronutrient pools and depth wise distribution of organic carbon and macronutrient content of soil in Ludhiana district of Punjab. The soil organic carbon (SOC) fractions viz., very labile, labile, less labile and recalcitrant carbon were also determined. The observation were recorded in five land use systems viz., sites having poplar based agroforestry system for 10, 20 and 30 years, fodder-fodder rotation and fallow land. Total micronutrients (Fe, Mn, Zn and Cu) followed the order agroforestry system > fodder-fodder > fallow land and with chronosequence of agroforestry system, an increase of 9.8% Fe, 24.8% Mn, 50.8% Zn and 9.2% Cu was observed in 0-15 cm soil depth in sites having poplar for 30 years over 10 years of agroforestry system. Chronosequence of agroforestry system resulted in increase and redistribution of Zn, Fe, Cu and Mn from non available (carbonate and crystalline iron oxides) to readily available (water soluble + exchangeable fraction) and potentially available (organic fraction, manganese oxides and amorphous iron oxides) forms in soil. In surface soil (0-15 cm), Fe and Zn contents in fodder-fodder and fallow land were in the order: residual fraction (RES) > non available (CARB and CFeOX) > potentially available (OM, MnOX and AFeOX) > readily available form (WSEX) and in agroforestry system the order was: residual fraction > potentially available > non available and readily available form. In all land uses, more than 50% of the total Mn content occurred in the relatively inactive and mineral-bound residual form (RES), followed by potentially available (23.1-33.1%), non available (6.3-14.8%) and only small fraction (< 2%) occurred in readily available fraction. Copper content in fodder-fodder and agroforestry system were in the order: residual fraction > potentially available > non available and readily available form. With chronosequence of poplar based agroforestry system, a significant increase of 38.7 %, 39 % and 45.6 % in SOC, TOC and TC, respectively was observed in 30 year poplar sites than 10 year poplar sites in 0-15 cm soil depth. With chronosequence of agroforestry system, stability of organic carbon increased as all the passive C forms increased in 30 year poplar sites over 10 years of poplar plantations. Adoption of poplar based agroforestry” also resulted in the buildup of macronutrients (N, P, K, Ca, Mg, S) in the soil profile and their contents increased with age of plantation cycle. Bulk density and pH decreased with conversion of fallow land to fodder-fodder and agroforestry system but WHC and CEC increased in both cases.
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Citation
Ravinder Kaur (2020). Soil micronutrient pools in a chronosequence of poplar based agroforestry system (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.