Application of recycled slaughterhouse wastes as an organic fertilizer for successive cultivations of bell pepper and amaranth

Abstract

The effects of ‘bovine-blood-rumen-digesta-mixture’ (BBRDM), an organic fertilizer prepared from recycled rural slaughterhouse wastes on the yield of vegetable crops and soil health were studied. Sophisticated waste management technologies are difficult to apply in rural abattoirs due to poor infrastructure and low waste generation resulting in environmental as well as human health hazards. Bovine blood and rumen digesta (3:1) were mixed and dried at 100−120 °C for 6−8 hours using a tray dryer to obtain BBRDM (N/P/K = 7.63:1:1.16; C/N = 4.68). Application of 6 g BBRDM kg−1 of soil showed two-fold higher yields of bell pepper in comparison with the control as well as N/P/K = 10:26:26+urea treatment. Plants fertilized with 13 g BBRDM kg−1 of soil died after second phase of application due to the presence of labile C fraction in BBRDM. Crop yield was two-fold higher during residual cultivation of amaranth after 12 weeks of bell pepper cultivation in soils treated with BBRDM in comparison to the other treatments. The abundance, diversity and composition of bacterial communities were superior in soils fertilized with BBRDM compared to soils cultivated with chemical fertilizer as revealed by V3-V4 16S rRNA gene sequencing. Air-soil methane fluxes recorded in soils of the abattoir waste dumping sites ranged from 13.13–28.55 μg g−1 hr−1 which were around 150 times higher than those emitted from soils of BBRDM treated bell pepper pots. Recycled slaughterhouse wastes promoted healthy growth of plants and abundance of soil beneficial microbes. This recycling methodology may be advantageously adopted in rural slaughterhouses.