Evaluation of chañar seed cake from biodiesel production as a soil amendment

Abstract

One of the major problems for biodiesel producers is the disposal of the seed cake after expelling oil from seeds. Every ton of biodiesel results in 2.5 to 3 tons of seed cake as byproduct. The physicochemical characteristics of this residue indicate that itcould be converted into valuable organic fertilizer. In order to evaluate the feasibility of using chañar seed cake from biodiesel production as a soil amendment, a greenhouse pot experiment was conducted. Seed cake was applied mixed with soil, at rates of 0, 6, 12 and 24%. A single seedling of chañar per pot was transplanted and after six months, plants were harvested for foliar analyses as well as some physiological characteristics. Seed cake application increased dry biomass production and the shoot concentrations of N and chlorophyll. There were no evident symptoms of phytotoxicity. The application of seed cake at 12% proved superior to the 6% treatment and the control; ahigher dose of seed cake (24%) was not significantly different from the treatment with 12% in terms of dry biomass production of chañar, foliar contents of N, P, Kor total chlorophyll. However, plant aerial biomass was significantly correlated with soil microbial respiration and soil C biomass.