Poultry Manure as an Organic Fertilizer with or without Biochar Amendment:Influence on Growth and Heavy Metal Accumulation in Lettuce and Spinach and Soil Nutrients

This pot-based study investigated the influence of poultry manure and 1:1 mixture of poultry manure+biochar(produced from farmyard manure[FYM]or wood),on the biomass production and concentration of heavy metals in leaves of lettuce and spinach.The concentration of mineral nitrogen(N)and soluble inorganic phosphorus(P)of soils cultivated with these vegetables was also investigated.The application of poultry manure or FYM biochar in soil as 10%(equivalent to 60 t ha^(-1),an estimated 1726.8 kg ha^(-1)N in poultry manure and 1353.9 kg ha^(-1)N in FYM)and 15%amendment(equivalent to 90 t ha^(-1),an estimated 2590.2 kg ha^(-1)N in poultry manure and 2030.8 kg ha^(-1)N in FYM)significantly decreased biomass production of lettuce as compared to control(no fertilizer added)treatment.However,mixture of poultry manure with wood-derived biochar at both application rates(i.e.,10%and 15%)and with FYM biochar at lower application rate(i.e.,10%)caused 2-3-fold increase in aboveground plant biomass and 2-14-fold increase in root biomass(p<0.05).Furthermore,as compared to control treatment,a significant~2-3-fold increase in aboveground plant biomass was also observed in response to mixture of poultry manure with wood-derived and FYM derived biochars at 10%amendment rates.As compared to control treatment,concentration of mineral N and soluble inorganic P were higher in soils of all other treatments.In spinach,amendment of poultry manure or its co-amendment with biochar of FYM significantly increased aboveground plant biomass at 7%(equivalent to 42 t ha^(-1))as compared to 3%and 5%amendment rates(equivalent to 18 and 30 t ha^(-1)respectively).The concentration of soil mineral N and soil soluble mineral P was not different between treatments.In lettuce,wood-derived biochar did not reduce concentration of heavy metals(i.e.,manganese(Mn),copper(Cu),iron,(Fe),cadmium(Cd),lead(Pb),nickel(Ni)and cobalt(Co)than FYM-derived biochar while in spinach,as compared to poultry manure,co-amendment of poultry manure with wood-derived biochar reduced concentration of heavy metals,indicating differential responses of crops to organic amendments.