Introduction

Vermicomposting is a process of composting organic waste material of diverse origin such as domestic, agricultural and industrial through the agency of suitable kind of earthworm species. The worms feed on organic materials, and fragment and digest them in their gut by their own enzymes and with the help of ingested micro-organisms, and excrete nutritionally rich feces or casts. During this process, the nutritional elements in the organic matter are mineralized and concentrated into soluble and readily available forms through microbial action (Edwards 1995). The earthworm casts have been shown to contain increased quantities of important plant nutritional elements such as nitrogen, phosphorus and potassium together with the biologically active substances stimulating plant growth (Lee 1985).

Several studies have examined growth of plants using vermicompost derived from different materials in green house conditions or in field studies (Atiyeh et al. 2000). All such studies indicated beneficial effects of vermicompost on plant growth. Recently, Manivannan et al. (2009) observed favorable effects of vermicompost on the growth and yield of beans and recommended the use of ptb (press mud, sugar cane thrash and fine bagasse) vermicompost alone or in combination with chemical fertilizer for improved productivity. Sutar (2009) reported increased growth and yield of Allium sativum L. (garlic) due to application of vermicompost. Chanda et al. (2011) studied the effect of vermicompost and other fertilizers on the growth of tomato plants and reported significant increase in growth parameters of the plants treated with vermicompost supplemented with chemical fertilizers. Cristina et al. (2010) studied influence of vermicompost on pine (Pinus pinaster Ait.) and reported significant inhibition of aerial and root biomass with high dose of solid vermicompost. Thus, despite large body of scientific evidence showing beneficial effect of plant growth and yield; there is also strong evidence that these effects are not general or constant (Cristina and Jorge 2011).

Therefore, present investigations were aimed to study effect of vermicompost prepared from such novel leaf residues as the tendu leaves to observe its effect on plant growth and yield. The objective of present study was to assess growth and yield of Phaseolus vulgaris when grown in soil (control) and soil with vermicompost alone, soil with urea alone, soil with admixtures of vermicompost and urea under green house conditions.

Methods

Tendu leaf vermicompost

The vermicompost was prepared by inoculating 1 kg shredded and precomposted tendu leaf residues with 20 adult Eudrilus eugeniae worms and incubating the pot at 25 °C temperature for 10 days. The moisture content of the pot was adjusted between 60 and 70 % by sprinkling distilled water. After incubation the vermicomposted material was collected, sieved and stored for further use. The physico-chemical properties of tendu leaf vermicompost were determined by methods described in Trivedi and Goel (1984) and are summarized in Table 1.

Table 1 Physicochemical characteristics of raw and partially decomposed tendu leaf residues and tendu leaf vermicompost (mean ± SE)
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Pot trial studies

Cement pots of 10-kg capacity were filled with clay loam soil from the campus of Regional Agriculture Center, Solapur. The soil was wetted with distilled water to 50 % of water holding capacity and incubated for 48 h before sowing. The pots were added separately with vermicompost, chemical fertilizer (urea) and admixtures of both as per pattern given in Table 2.

Table 2 Admixture pattern of vermicompost and urea in pot trials
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Twenty seeds were sowed per pot at 0.5 cm depth and incubated under green house conditions. The germination percentage was measured 1 week after the emergence of seedlings. Plants were harvested at 60 and 120 days to measure growth and yield, respectively. The shoots and roots were dried at 60 °C for dry weight determination.

Statistical analysis

The experimental data was expressed as mean ± SE and Student’s t test was carried out to determine significant differences of different parameters in different treatments from the control at p ≤ 0.05 level.

Results and discussion

Seed germination

The seed germination percentage of French bean in control soil (T10) was 83.3 ± 1.77 %, which was increased to 96.6 ± 3.3 in 75 % vermicompost treatments (T2). The germination percentage in T1 (100 % vermicompost) and T3 (50 % vermicompost), however, was 90 and 86.6 ± 3.3 %, respectively. The maximum germination percentage (100 %) was observed in T7 (75 % urea + 25 % vermicompost) and T8 (25 % urea + 75 % vermicompost) treatments. The minimum seed germination percentage (83.3 %) was found in T6, T9 and T10 (control soil) treatments (Fig. 1).

Fig. 1
figure 1

The germination percentage of French bean (P. vulgaris) seeds in various treatments of tendu leaf vermicompost and chemical fertilizer (mean ± SE). Data analyzed by Student’s t test at p ≤ 0.05 to calculate significant differences of treatments from the control (T10)

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Plants’ shoot and root length

The maximum shoot length was observed in T2 showing 36 % increase over the control (T10). Among the treatments receiving vermicompost alone, T1 (100 % vermicompost) showed 6.56 % decrease in shoot length while T3 (50 % vermicompost) showed only 10 % increase over that of control. Among the treatments that received urea (chemical fertilizer) alone, T4 (100 % U) showed maximum (30 %) increase in shoot length over control while T5 (75 % U) and T6 (50 % U) showed 13 and 16.5 % increase in shoot length, respectively. Among the admixture treatments T7 (22.8 %), T8 (20.6 %) and T9 (17.1 %) showed significant (p ≤ 0.05) increase over the control (Fig. 2).

Fig. 2
figure 2

The effect of tendu leaf vermicompost and chemical fertilizer on shoot and root length of French bean (mean ± SE). Data analyzed by Student’s t test at p ≤ 0.05 to calculate significant differences of treatments from the control (T10). FW fresh weight, DW dry weight

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The maximum root length was observed in T7 showing 65 % increase over the control followed by T2 and T3 treatment showing 58 and 54.3 % increase, respectively, over the control. T1 treatment showed significantly (p ≤ 0.05) lower root length increase (11.4 %) over the control indicating some deleterious effect at 100 % vermicompost. The increases in root length in all the treatments receiving urea only were significantly (p ≤ 0.05) lower than the vermicompost treatments. Thus there were only 28 % (T4), 8.7 % (T5) and 0.9 % (T6) increase in root length over the control. T9 treatment (5.2 %) also showed decreased root length similar to T1 (Fig. 2).

Plants’ shoot and root fresh weights

The maximum shoot weight increase was in T4 (83 %) followed by T2 (72.3 %). The shoot weight in T1, however, decreased (−9.4 %) significantly (p ≤ 0.05) compared to control. All the treatments receiving urea alone viz. T4 (83 %), T5 (56.8 %) and T6 (51.5 %) showed significant (p ≤ 0.05) increase in shoot fresh weights. Among the admixture treatments maximum increase (38.5 %) in shoot weights was in T7 followed by T9 (29.2 %) and T8 (18.5 %) treatments. The maximum increase (36.6 %) in root fresh weight was observed in T4 treatment followed by T2 (30.25 %). The root fresh weights in T1 decreased (−1.6 %) significantly (p ≤ 0.05) compared to those in control. The increase in root fresh weights in T3 (50 % V) and T5 (75 % U) was similar (8.25 %). Among the admixture treatments significant (p ≤ 0.05) increase (19.82 %) in root fresh weights was observed only in T9 while T7 and T8 showed significantly (p ≤ 0.05) decreased root fresh weights compared to the control (Fig. 3).

Fig. 3
figure 3

The effect of tendu leaf vermicompost and chemical fertilizer on shoot and root fresh weights and shoot and root dry weights of French bean (mean ± SE). Data analyzed by Student’s t test at p ≤ 0.05 to calculate significant differences of treatments from the control (T10)

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Plant shoot and root dry weights

Among the treatments that received vermicompost alone, the maximum increase (46.8 %) in shoot dry weights was observed in T2 whereas shoot dry weight in T1 was lower (−23.4 %) compared to control and only 6 % increase over the control was observed in T3. Among the treatments that received urea alone, the maximum increase (56 %) in shoot dry weight was observed in T4 followed by T5 (50.4 %) and T6 (43.5 %) over the control.

The maximum increase in root dry weights was observed in T4 (41.6 %), whereas the increase in root dry weights in T2 (25 %) and T9 (25.83 %) was similar. Except T3 and T5, rest of all treatments showed reduced root dry weights as compared to control (Fig. 3).

Thousand grain weight

Among the treatments that received vermicompost alone, maximum weight of thousand grains (374.0 g) was observed in T2 with 20.3 % increase over that of control (311.0 g). Among the treatments with chemical fertilizer alone, the maximum weight of thousand grains (398.0) was found in T4 with 28 % increase over that of control. The thousand grain weight in T6 (379.0 g) and T9 (378.0 g) did not differ significantly (p ≤ 0.05) whereas T7 (394.5 g) and T8 (392.2 g) also showed similar increase (26 %) in thousand grain weight over the control (Fig. 4).

Fig. 4
figure 4

The effect of tendu leaf vermicompost and chemical fertilizer on grain weights and grain yield of French bean (mean ± SE). Data analyzed by Student’s t test at p ≤ 0.05 to calculate significant differences of treatments from the control (T10)

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Grain weight per plant and grain yield

The maximum increase in grain weight per plant was observed in T7 (46.9 %) and T4 (46.6 %) compared to that in the control. The grain weight per plant in T7, T8 and T9 did not differ significantly. Among the treatments that received vermicompost alone, T2 showed 80.52 g grain weight per plant with 32 % increase over the control. The interaction effects of vermicompost and chemical fertilizers were significant. The maximum increase in grain yield was in T4 (53.16 %) followed by T7 (51.5 %) and T9 (40.28 %). Among the vermicompost alone treatments, maximum increase in the yield was 37.5 % in T2. These results indicate that the interaction effect of vermicompost and chemical fertilizer was significant (Fig. 4).

The data on various growth and yield parameters of French bean such as germination percentage, shoot and root length, shoot and root fresh as well as dry weights, grain weight per plant, thousand grain weights etc. revealed that they were significantly (p ≤ 0.05) higher in vermicompost treatments compared to control treatments. The significant increase in the yield of French bean due to application of tendu leaf vermicompost might be due to increased content of available nutrients in the vermicompost, increased number of beneficial kinds of micro-organisms, increased enzyme activities as well as presence of plant growth stimulating substances like gibberellins, cytokinins, auxins etc. in the vermicompost. The presence of biologically active substances in the vermicompost might have increased the availability of nutrients in soil and their uptake by the plant due to improved root system.

It is well-known that vermicompost is rich in essential nutritional elements for plant growth, beneficial micro-organisms, plant growth promoting substances and different types of enzymes and as such the vermicompost can be applied alone or in combination with other organic or inorganic fertilizers to obtain better yields of different crops (Bano et al. 1987).

There are several other reports on favorable effect of vermicomposts on various plants (Kale et al. 1987; Vadiraj et al. 1992). Atiyeh et al. (2000) reported that the shoot dry weights of raspberry plant soil mixed with vermicomposted pig wastes weighted more than those grown in unfertilized control soil, and were as great as those in soil receiving a chemical fertilizer treatment.

However, an important observation made by us during our investigations is that the application of tendu leaf vermicompost at a level of 100 % N through vermicompost resulted in significantly (p ≤ 0.05) decreased growth parameters as compared to the treatments that received tendu leaf vermicompost at a level of 75 or 50 % N through vermicompost alone. This is indicative of some detrimental effect of tendu leaf vermicompost application above certain threshold concentrations on the growth of French bean plant. These observations corroborate with the reports of Cristina et al. (2010) who stated that substitution of peat with higher dose vermicompost resulted in detrimental effect on Pine seedling growth, and beneficial effects were observed only at lower doses of vermicompost in potting media.

The data showed that combined application of various levels of chemical fertilizer (urea) with tendu leaf vermicompost resulted in significant (p ≤ 0.05) increase in growth and yield of French bean compared to control. The maximum grain yield of French bean (42.12 q/ha) was recorded in T7 treatment that received combined application of 25 % N through vermicompost plus 75 % N through urea followed by T9 treatment that received combined application of 50 % N through urea plus 50 % N through vermicompost. These results suggest that the quantity of chemical fertilizers for French bean could be reduced by 25–50 % due to combined application of vermicompost with chemical fertilizer. These results are comparable with those reported by Kale (1998) who suggested that the quantity of chemical fertilizers could be reduced to 25–50 % due to application of vermicompost for plants like brinjal, tomato, radish and carrot.

The combined application of tendu leaf vermicompost and chemical fertilizer (urea) increased the growth and yield of French bean (P. vulgaris) significantly (p ≤ 0.05). The maximum grain yield of French bean was obtained due to combined application of tendu leaf vermicompost at 25 % N through vermicompost plus 75 % N through urea followed by combined application of 50 % N through urea plus 50 % N through vermicompost. The increase in the yield due to above treatments accounted for almost similar yields as that of 100 % recommended dose of NPK fertilizers and 23.8 % increased yields over 75 % recommended dose of NPK fertilizers and 29.5 % increased yields over the 50 % recommended dose of NPK fertilizers.

Most of the growth and yield parameters in of French bean (Figs. 1, 2, 3 and 4) in T4 (100 % N through urea) do not differ significantly (p ≤ 0.05) from T7 (25 % N through vermicompost plus 75 % N through urea) and T9 (50 % N through vermicompost plus 50 % N through urea) though the chemical fertilizer quantity is reduced to 25–50 % compared to T4. This might be due to the contribution made by the quantity and quality of vermicompost in increasing growth and yield of the plant in these treatments. Similarly most of growth and yield parameters in T2 (75 % N through vermicompost) and T8 (25 % N through urea plus 75 % N through vermicompost) do not differ significantly (p ≤ 0.05) indicating the potential of vermicompost to contribute nitrogen and other plant growth promoting substances that can compensate decreased levels of chemical fertilizer. Moreover, growth and yield parameters in all treatments except T1 differ significantly (p ≤ 0.05) than the control soil (T1).

Conclusion

The pot trial experiments suggest that the quantity of chemical fertilizers for French bean plants could be reduced by 25–50 % due to combined application of tendu leaf vermicompost with chemical fertilizer. Moreover, application of tendu leaf vermicompost alone at higher concentrations (100 % N through vermicompost) may reduce certain growth parameters and yield of P. vulgaris plants.