Abstract
Opportunity costs seriously limit the large-scale production of bio-organic fertilizers (BOFs) both in China and internationally. This study addresses the utilization of amino acids resulting from the acidic hydrolysis of pig corpses as organic nitrogen sources to increase the density of TrichodermaharzianumT-E5 (a typical plant growth-promoting fungi, PGPF). This results in a novel, economical, highly efficient and environmentally friendly BOF product. Fluorescence excitation-emission matrix (EEM) spectroscopy combined with fluorescence regional integration (FRI) was employed to monitor compost maturity levels, while pot experiments were utilized to test the effects of this novel BOF on plant growth. An optimization experiment, based on response surface methodologies (RSMs), showed that a maximum T-E5 population (3.72 × 108 ITS copies g−1) was obtained from a mixture of 65.17% cattle manure compost (W/W), 19.33% maggot manure (W/W), 15.50% (V/W)hydrolytic amino acid solution and 4.69% (V/W) inoculum at 28.7°C after a 14 day secondary solid fermentation. Spectroscopy analysis revealed that the compost transformation process involved the degradation of protein-like substances and the formation of fulvic-like and humic-like substances. FRI parameters (PI, n, PII, n, PIII, n and PV, n) were used to characterize the degree of compost maturity. The BOF resulted in significantly higher increased chlorophyll content, shoot length, and shoot and root dry weights of three vegetables (cucumber, tomato and pepper) by 9.9%~22.4%, 22.9%~58.5%, 31.0%~84.9%, and 24.2%~34.1%, respectively. In summary, this study presents an operational means of increasing PGPF T-E5 populations in BOF to promote plant growth with a concomitant reduction in production cost. In addition, a BOF compost maturity assessment using fluorescence EEM spectroscopy and FRI ensured its safe field application.
Highlights
Trichoderma species exhibit extremely high levels of ecological adaptability through their symbiotic colonization of plants and saprophytic existence in all soil types
The coefficient of determination (R2, 0.9992 > 0.8) demonstrated good fit with the response model [28], with 99.92% of the T-E5 population sample variation explained by this model
The results of our present study show that the BOF and planted with cucumber (BOFc) treatment increased chlorophyll content levels, shoot lengths, and shoot and root dry weights by 8.5%, 37.9%, 26.9%, 17.0%, respectively, relative to the OF and planted with cucumber (OFc) condition results, and that this response can be attributed to the presence of large quantities of the PGPR strain (T. harzianumT-E5) and biologically active metabolites
Summary
Trichoderma species exhibit extremely high levels of ecological adaptability through their symbiotic colonization of plants and saprophytic existence in all soil types. Their capacity to improve plant growth and promote health in agricultural systems has been well documented. Bio-organic fertilizers (BOFs) that contain Trichoderma spp. and animal manure have been shown to promote plant growth and control Fusarium wilt in cucumber plants [5, 11, 12, 13]. There is need to develop alternative waste organic nitrogen sources to both replace defatted rapeseed meal in order to reduce BOF production costs and to identify an optimum secondary co-solid-fermentation process to ensure a maximum PGPF (Trichoderma spp.) population in BOFs
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