Introduction

Sorghum is produced in many countries of the world and it is the fifth major cereal crop in the world in terms of tonnage after maize, wheat, rice and barley. Traditionally, sorghum has been known for being nutrient-use efficient and managed with low fertilizer rates, but yields can be increased with higher fertilizer application rates. Many studies have been published on N, P, or K fertilizer response in sorghum (Elkased and Nnadi, 1987; Kayuki et al., 2007), but these studies were limited to single nutrients and did not include a combination of nutrients. 

Composting is the biochemical conversion of organic wastes by naturally occurring or inoculated microbes to organic fertilizer through biological processes (Gautam et al., 2010). It is done by different group of microorganisms including bacteria, fungi and actinomycetes such as Pseudomonas sp., Bacillus sp., Aspergillus sp., Streptomyces rectus, Thermopolyspora bispora, Thermomonospora fusca, Thermoactinomyces sp. and Thermomonospora curvata (Zeng et al., 2011). Fungal species such as Aspergillus, Penicillium, Tricoderma plays important role in the decomposition of various kind of waste material. Fungi are responsible for decomposing more than 80% of the cellulose (Betts and Dart,1988). The success of the composting process and the usefulness of compost as an organic amendment are determined by microbial activity (Chroni et al., 2009). Bio-degradation of agricultural waste into compost and incorporation into soil may enhance the nutrient recycling and maintain soil fertility (Gaind and Pandey, 2006).

The quality of compost prepared by microbes is mostly dependent on its raw materials (Wang et al., 2004). However, other characters that can make good-quality compost are C:N ratio, moisture content, pH and the presence of plant growth-promoting microorganisms (Fourti et al., 2011). Compost is rich source of nutrients with high organic matter content and use of compost can be beneficial to enhance soil organic matter status. Physical and chemical properties of soil can be improved by using the compost, which may ultimately increase crop yield. Physical properties like bulk density, porosity, water permeability and hydraulic conductivity were significantly improved when compost was applied in combination with chemical amendments (Hussain et al., 2001). Application of compost not only benefits crop plants as it contains beneficial microbes that help the plants to mobilize and acquire nutrients but also promotes plant growth and inhibits plant pathogens (Perner et al., 2006). Gopalakrishnan et al. (2020) reported that sorghum bagasse compost prepared with potential microbes significantly enhanced plant growth promotion (PGP) traits of sweet sorghum (Sorghum bicolor (L.) Moench) including the plant height, leaf area, leaf weight, root weight, root length, shoot weight, panicle weight, seed number and seed weight over the bagasse compost prepared without microbes. Thus, this study was aimed to investigate the effect of prepared bio-compost on plant growth promotion trait of Sorghum.

Materials and Methods

2.1.  Preparation of bio-compost using microbes

Sugarcane trash (W₁) and banana pseudostem (W₂) were collected, chopped into 2-3 cm pieces and dried followed by inoculation of microorganism’s viz. Bacillus subtilis and Schizophyllum commune as per treatments. This experiment was conducted using factorial CRD with three repetitions. In this, Factor I was Substrates i.e. Sugarcane trash (W₁) and Banana pseudostem (W₂); Factor II was Microorganism’s i.e. Control (M₀), Bacillus subtilis (M₁), Schizophyllum commune (M₂) and Bacillus subtilis+Schizophyllum commune (M₃); Factor III was conditions i.e. Unsterilized (S₀) and Sterilized (S₁). Treatment wise initial and final composition viz. organic carbon, nitrogen, C:N ratio, P₂O₅ and K₂O of bio-composts were measure using standard methods i.e. organic carbon by Walkley and Black (1935), nitrogen and potassium by Jackson (1973) and phosphorus by Kitson and Mellon (1944).

2.2.  Pot experiment

A Pot experiment was set up using factorial CRD with two repetitions at the College of Agriculture, Navsari Agricultural University, Waghai to test the prepared bio-compost on sorghum plants (GJ-42). A total of 32 (16 treatments×2 replications) pots were taken and filled with 1 kg soil. Four seeds were sown on each pot and recommended doses of fertilizer (10t prepared compost ha^-1, 40 kg N ha^-1 as urea and 40 kg P₂O₅ ha^-1 as SSP) were applied in mg kg^-1. Irrigation was done with distilled water as per the requirement. After germination, 2 healthy plants of each pot were maintained. After 1 month of sowing, the plants were harvested and observations on plant height, root length, fresh weight and dry weight of the plant were recorded.

Results and Discussion

C:N ratio and nutrient composition is important parameter of compost. The initial and final composition of prepared bio-compost is presented in Table 1. The lowest C:N ratio of 13.02 was observed in W₁×M₃ ×S₀, Lowest organic carbon of 17.85% was reported in W₁×M₃×S₀, highest nitrogen and P₂O₅ content of 1.37 and 0.40%, respectively was observed in W₁ ×M₃×S₀ and highest K₂O content of 2.68% was observed in W₂×M₃×S₀. This decrease in C:N ratio and increased nitrogen content might be due to C loss in substrate as well as increased N content by metabolic activities of microorganisms. Similar results were also reported by Shamini and Fauziah (2014); Diallo et al. (2017); Premalatha et al. (2017); Dhapate et al. (2018) and increased nutrient content may be due to the decomposition of complex molecules into simpler molecules with releasing of elements. These results are in agreement with the finding of Awasthi et al. (2014); Lakshmi et al. (2019) and Gopalakrishnan et al. (2020).

Table 1: Initial and final composition of bio-compost

The bio-compost prepared by applying different treatments of microorganisms was tested on sorghum plants in a pot experiment with regards to various plant growth parameters. Effect of different prepared compost on root length of sorghum was found non-significant at 30 days after sowing (DAS) in a pot experiment (Table 2 and 3 and Photo 1 and 2). Whereas, shoot length was significantly affected by substrates (W) and microorganisms (M) in which W₂ (banana pseudostem) reported significantly higher shoot length of 24.69 cm while M₁ and M₃ among microorganisms, were equally found significant for shoot length (26.63 cm) followed by M₂ (22.44 cm). The conditions and all the interactions were found non-significant.

Table 2: Effect of different treatments on root length (cm) of sorghum at 30 DAS

Table 3: Effect of different treatments on shoot length (cm) of sorghum at 30 DAS

Photo 1: Pot experiment

Photo 2: Root and shoot length of sorghum at 30 DAS

Photo 2: Continue..

Bio-compost prepared by using different substrates had a significant effect on the green and dry biomass yield of sorghum (Table 4 and 5 and Figure 1). Banana pseudostem (W₂) yielded relatively higher green (8.84 g) and dry (2.03 g) biomass of sorghum than sugarcane trash (W₁). Microorganisms also affected significantly in respect of green and dry biomass of sorghum in which M₃ (cellulolytic + lignolytic) recorded the highest green (11.93 g) and dry (2.58 g) biomass of sorghum. The green and dry biomass yields of sorghum were also significant in different conditions. Among these, S₀ (unsterilized) reported higher green (8.66 g) and dry (1.99 g) biomass of sorghum.

Table 4: Effect of different treatments on green biomass (g) of sorghum at 30 DAS

Table 5: Effect of different treatments on dry biomass (g) of sorghum at 30 DAS

Figure 1: Green and dry biomass yield of sorghum as affected by different factors

The interaction effect of different factors on green biomass was found non-significant for most of the interactions except M×S. Among these, M₃×S₀ (12.88 g) recorded significantly higher green biomass which was at par with M₁×S₀ (11.95 g). Same interactions were analyzed for dry biomass of sorghum in which W×M and M×S interactions were found significant. W₂×M₃ recorded higher dry biomass of 2.92 g followed by W₂×M₁ (2.62 g) which was at par with W₁×M₁ (2.38 g). Considering M×S interactions, M₁×S₀ exhibited significantly higher (2.85 g) dry biomass of sorghum which was at par with M₃×S₀ (2.66 g). Higher-order interaction for green and dry biomass remained non-significant. The beneficial effect of such substrate, microorganism and condition on growth parameters of sorghum was also reported by Mawahib et al. (2015). Similar results had been also reported by Mahalakshmi and Naveena (2016) and Premalatha et al. (2019) in other crops. Gopalakrishnan et al. (2020) also reported enhancement of sweet sorghum growth parameter viz. plant height, leaf area, leaf weight, root weight, root length, seed number and seed weight by sorghum bagasse compost prepared with microbes.

Conclusion

This experiment demonstrated the effect of prepared bio-compost on plant growth promotion trait of sorghum. Overall it was observed that the compost prepared by using different substrates, microorganisms and conditions had a profound effect on various growth parameters of sorghum. Various growth parameters like shoot length, green and dry biomass were found to increase with the application of compost prepared from banana pseudostem (W₂), cellulolytic+lignolytic microorganism (M₃) and in unsterilized condition (S₀).

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