Sustainable agronomic practices for enhancing the soil quality and yield of Cicer arietinum L. under diverse agroecosystems

Journal of Environmental Management 262 (2020) 110284

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Research article

Sustainable agronomic practices for enhancing the soil quality and yield of Cicer arietinum L. under diverse agroecosystems Rama Kant Dubey a, c, Pradeep Kumar Dubey a, c, Rajan Chaurasia a, c, Harikesh Bahadhur Singh b, Purushothaman Chirakkuzhyil Abhilash a, c, * a b c

Instiute of Environment & Sustainable Development, Banaras Hindu University, Varanasi, 221005, India Dept. of Mycology & Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, 221005, India Agroecosystem Specialist Group, IUCN-Commission on Ecosystem Management, Gland, Switzerland

A R T I C L E I N F O

A B S T R A C T

Keywords: Agricultural soil sustainability indicators Biochar Sustainable yield index Sustainable agriculture Vermicompost

Sustainable agronomic practices are being implemented worldwide to promote the cleaner and planet friendly crop production. Therefore, in the present study, we investigated the effect of agro-waste derived biochar and vermicompost on soil quality and yield in Cicer arietinum L. Field experiment was carried out at three different agro-climatic regions (Varanasi, Sultanpur and Gorakhpur) of Uttar Pradesh, India and periodic soil and crop sampling were done accordingly. Experimental results proven that a significant increase (p < 0.01) in total organic carbon, available N, P and K content was observed under vermicompost followed by biochar amendment at each site. Similarly, irrespective of the experimental site, a significant increase (p < 0.01) in microbial biomass carbon was recorded under vermicompost amendment. Furthermore, the addition of vermicompost increased the grain yield (28–39%) than biochar (23–36%) addition whereas the higher microbial and soil respiration (2–6%) found in former field than the biochar added field (1–3%). Significant correlation (R2¼ 0.61–0.99) was found between the sustainable yield index and soil fertility factors at each site. Assessment of agricultural soil sus­ tainability indicators (ASSI) suggests that the biochar was more effective in enhancing the soil carbon stock (21 � 1.31 Mg C ha 1) and higher glomalin activity (62%). The study also confirmed the increased alkaline phos­ phatase (two fold) and β-glucosidase activity (one fold) along with enhanced urease (45%), soil dehydrogenase activity (36%) under vermicompost amendment followed by biochar. Present study highlights the significance of sustainable agronomic practices for improving the soil quality and agricultural yield while reducing adverse impact.

1. Introduction The loss of soil quality due to organic matter depletion is restraining agricultural productivity around the world. Furthermore, huge popula­ tion demands, limited arable land and loss of soil nutrients coupled with extraneous pressure of agrochemical-based farming are hampering agroecosystem functioning and resilience and leading to their instability (Myers et al., 2014; Kehoe et al., 2017). Additionally, poor agro-waste management and intensive agricultural practices increase greenhouse gas emissions, loss of soil quality and biodiversity leading to environ­ mental instability (Abhilash et al., 2016a,b; Dubey et al., 2015; Ramesh et al., 2019). Owing to these negative effects, organic amendments and other agro-practices are being promoted and tested worldwide as well as in the Indo-Gangetic plain. For instance, Srivastava et al. (2012) studied

the effect of vermicompost and noted significant enhancement in the Allium cepa L. crop growth and soil fertility at the Aurawan Research field, Lucknow, India. In a similar practice, vermicompost containing high humic acid content proved to enhance the soil properties and plant health (Maji et al., 2017). The same study reported that addition of beneficial microbial strains to vermicompost enhanced its performance. In yet another research, vermicompost was applied to improve the growth and yield of tomato (Guti� errez-Miceli et al., 2007). Apart from vermicompost, biochar is another promising agricultural amendment utilized globally with proven positive enhancement in soil properties and crop performances (Herath et al., 2013; Doan et al., 2015; Mehmood et al., 2017). In an experiment conducted by Agegnehu et al. (2016), the impact of biochar, alone and in combination with compost was explored for the betterment of soil health, biomass and yield of maize.

* Corresponding author. Instiute of Environment & Sustainable Development, Banaras Hindu University, Varanasi, 221005, India. E-mail address: [email protected] (P.C. Abhilash). https://doi.org/10.1016/j.jenvman.2020.110284 Received 19 September 2019; Received in revised form 6 February 2020; Accepted 12 February 2020 0301-4797/© 2020 Elsevier Ltd. All rights reserved.

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Journal of Environmental Management 262 (2020) 110284

Additionally, tropical soil having low cation exchange capacity have greater chance of benefitting from biochar addition via increasing the water holding capacity and nutrient availability in soil (Dubey et al., 2020). Although, the positive impact of vermicompost and biochar appli­ cations have been reported previously, knowledge gaps remain in ascertaining their complete agroecosystem response, spatiotemporal variations in these practices and the sustainability aspect associated with natural resource conservation based management practices. Thus there is urgent need of resource conserving agro-practices for better productivity and sustainability of tropical agricultural lands (Dubey et al., 2016). Incorporation of better agronomic practices could preserve the physicochemical and biological integrity of agroecosystems, improve crop nutrient, reduce agrochemical mediated toxicity, loss of soil organic matter and provide nutritious food for all (Goswami et al., 2015; Abhilash et al., 2016a,b; Dubey et al., 2019). In order to manage agricultural resources along with improving soil quality, yield and stability of agroecosystems, the present research studied the impact of adaptive agronomic practices (agro-waste-derived biochar and farmyard waste-cow dung manure based vermicompost amendments) on Cicer arietinum L. (Chickpea) crops at three selected agroecological zones of Uttar Pradesh, India. This study was conducted with common C. arietinum which is an important protein rich pulse crop worldwide. In India, it is a multipur­ pose crop used for human consumption as well as for animal feed. It is a well-known nitrogen-fixing crop in other south Asian countries with India being a major producer (Dubey et al., 2017). Therefore the sus­ tainable management of C. arietinum (a major legume) crop in India is essential for attaining the target of environmental sustainability.

The present research utilized agro-wastes based strategy for improving the soil quality, crop productivity and also assessed the sus­ tainability of agroecosystems. The study aimed to investigate the role of natural resource based vermicompost and biochar amendments on (i) C. arietinum crop growth, yield, sustainable yield index (SYI) and nutrient content, (ii) the soil quality (physicochemical, biological properties) including soil and microbial respiration (CO2 efflux) (iii) the relationship of sustainable yield index (SYI) with key soil fertility fac­ tors, and (iv) the key agricultural soil sustainability indicators (ASSI) in each experimental fields. Objectives (ii), (iii) and (iv) further helped in evaluating the overall agro-environmental sustainability. To assess the spatiotemporal variation of the adaptive agronomic practices (vermi­ compost and biochar amendments), the same practices were evaluated at various agroecological zones of Uttar Pradesh, India. In order to un­ derstand the complete agroecosystems response to the adopted prac­ tices, various above and below ground plant-soil parameters were analysed at each experimental site. 2. Material and methods 2.1. Experimental layout Research was carried out (2015–2016) in two different agro-climatic zones and three different subzones i) Varanasi (25.2820� N, 82.9563� E), in Eastern Gangetic plane zone, ii) Gorakhpur (26.7588� N, 83.3697� E) in North Eastern Plains of Agro-climatic zone IV, (iii) Sultanpur (26.2500� N, 82.0000� E) in Central Plains of Agro-climatic zone V of Uttar Pradesh, Northern India (Fig. 1). Season was characterized as winter with a temperature range 9-23 � C and relative humidity 66–86%.

Fig. 1. Picture highlights the details of the three experimental sites, test crop (major protein rich-legume crop in India as well as in South Asia) grown under sustainable amendments (farmyard waste and cowdung manure based vermicompost and paddy straw and rice husk derived biochar): Cicer arietinum L. were grown at Varanasi, Sultanpur and Gorakhpur which is located in different agroecosystems of Uttar Pradesh, India. All experimental sites were farmer’s field. 2

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2.2. Cropping system and amendments

glucosidase, urease activities were assayed through the procedures of Tabatabai (1982), Moscatelli et al. (2012), Kandeler and Gerber (1988). Total glomalin content was estimated by the methods of Wright and Upadhyaya (1998). Experimental crops were also monitored critically for some key sustainability indicator species like earthworms and mil­ lipedes richness (Tripathi et al., 2014). Soil water stable aggregate (WSA) was done by wet sieving methodology (Yoder, 1936).

Present assessment used C. arietinum var. PUSA-262, spacing (plant � row, 10 � 30 cm) as winter or (Rabi crops). Crops were grown in triplicate (field plot of size 7 � 5 m2) using random block design and surface irrigation method without runoff return system. De-weeding was done periodically. Adaptive agronomic-practices (vermicompost and biochar amendments) were adopted in test crop with reduced tillage system in order to test the study objectives. Amendments were given at the rate of 6 ton ha 1 vermicompost and 8 ton ha 1 biochar along with the 75% dose of recommended fertilizers. Control field was maintained under conventional methods of farming with 100% dose of recom­ mended fertilizers. Biochar used was produced from paddy straw and rice husk at obtained at 350 � C. The basic properties of biochar were pH 9.5, total carbon 410 g kg 1, total nitrogen 2 g kg 1, total phosphorus 0.25 g kg 1, potassium 2.1 g kg 1, calcium 1.08 g kg 1 and magnesium 0.46 g kg 1. It was sieved through 2 mm sieve to obtain uniform particle size and oven dried at 105 � C prior to application. Farmyard waste, cow dung manure and Eisenia fetida species of earthworm were used for vermicomposting as suggested by Singh et al. (2013a). Vermicompost contains pH 7.51, electrical conductivity 3.9 ds m 1, total carbon 205.1 g kg 1, total nitrogen 11.9 g kg 1, total phosphorus 17.3 g kg 1, total potassium 21.5 g kg 1, calcium 2.82 g kg 1 and magnesium content 5.1 g kg 1.

2.4. Crop growth and sustainable yield index (SYI) Crop growth-related data (percent germination) from each treatment and control plot were recorded at regular interval. For crop growth measurements, 12 crop plants from each amendment and control plot were harvested at maturity (90 days after sowing). Aboveground shoot parameter was collected by cutting the stem just above the root collar, and for root associated parameter, root biomass washed carefully before maintaining records. Root, shoot length, lateral root, root nodule, fresh and oven dried, root, shoot weight per plant were further recorded. For grain yield, 90 days old (mature) total crop plants in each plot were harvested at maturity and threshed to separate the grains from plant biomass. The total cleaned seed was weighted for seed yield. To get the better idea about the impact of treatments on crop productivity and sustainability factor under diverse agroecosystems, sustainable yield index (SYI) was calculated as per following equation (Singh et al., 1990).

2.3. Soil sampling and analysis

SYI ¼ Y

2.3.1. Soil physico-chemical properties, enzyme and soil and microbial respiration Eight soil subsamples were collected from each field and mixed to form a composite sample considered as one sample from each replicated fields and pre-treatments were done and soil pH, electrical conductivity, moisture content, bulk density, water holding capacity were estimated in accordance of the standard procedural protocols mentioned else­ where (Dubey et al., 2019). Similarly, total organic carbon (TOC) (Estefan et al., 2013; Walkley and Black, 1934), total nitrogen and available nitrogen (AN) (Kalra and Maynard, 1991), available potassium (AK) (Toth and Prince, 1949), available phosphorus (AP), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) (Vance et al., 1987), soil dehydrogenase activity (SDA) (Tripathi et al., 2014), soil and microbial respiration (Dubey et al., 2019) were measured periodically. Initial soil properties were characterized as sandy loam alluvial (48.9% sand, 30.7% silt and 20.4% clay); sandy loam (60.1% sand, 23.3% silt and 17.6% clay) and clay loam (56.3% sand, 24.2% silt and 19.5% clay) at Varanasi, Sultanpur and Gorakhpur sites respectively. Physico-chemical properties of initial soil yielded pH as (7.89 � 0.05, 8.53 � 0.04 and 7.71 � 0.03); electrical conductivity as (0.160 � 0.01, 0.165 � 0.01 and 0.170 � 0.03); moisture content as (3.56 � 0.40, 3.46 � 0.34 and 3.92 � 0.18); and bulk density as (1.27 � 0.02, 1.40 � 0.02 and 1.30 � 0.02) for Varanasi, Sultanpur and Gorakhpur respectively. The initial soil total OC was (3.12 � 0.09, 2.63 � 0.02 and 2.84 � 0.05) while microbial biomass carbon was (139.38 � 0.64, 129.83 � 6.73 and 137.98 � 6.51) at Varanasi, Sultanpur and Gorakhpur sites respectively.

where Y is representing the calculated average yield of an adopted practice across the years, σ is estimated standard deviation and Ymax is the recorded maximum yield across the cultivation. Further harvested plant biomass (stem þ leaf) was crushed and stored in paper packets for analysis of crop nitrogen (Allen et al., 1974), phosphorus (Jackson, 1973), potassium and crude protein content (protein %) (Mariotti et al., 2008).

σ=Ymax

2.5. Statistical analysis Data were subjected to one-way ANOVA followed by DMRT using SPSS Version 16.0 for windows program (Statistical Package for Social Science, Illinois, USA. Means � standard deviation were calculated and the Duncan post hoc multiple comparison tests were applied when the F ratio was significant (α < 0.05). Correlation and regression analysis was performed to find out the relationship between the SYI, TOC, SOC, MBC, SDA, soil respiration, AN, AP and AK using same statistical package. 3. Results and discussion 3.1. Response of soil physicochemical and biological properties The first objective quantified changes in soil properties based on variation in adaptive agronomic practices (vermicompost and biochar amendment) at three experimental sites. The periodicity was kept at two years in order to nullify the background influences of edaphic, regional climatic factors. Soil physicochemical properties (pH, moisture content, TOC, available nitrogen, available phosphorus and available potassium) of both the adopted amendments and control field are presented in Table 1 and Fig. 2 which make it evident that a significant difference (p < 0.05) in the physicochemical properties was recorded between the experimental (vermicompost and biochar amended) and control (without vermicompost and biochar) fields. Biochar amendment increased the soil pH significantly at all sites during both years of study except in the first year at Gorakhpur. Increase in pH clearly indicates the impact of biochar amendment that is also found in other studies; how­ ever, the magnitude of change depends upon the soil structure at each experimental site and alkaline (pH 9.5) nature of biochar as found in our results (Zhang et al., 2012; Taketani et al., 2013). A slight decrease in pH

2.3.2. Analysis of key soil sustainability indicators The soil OC stocks (Mg C ha 1) was determined for each site (Dubey et al., 2019). For rhizospheric soil sample collection, ten plants (at the middle of flowering and fruiting, 60 days after sowing) were randomly selected from each amended as well as control crop and uprooted. Root interface soil was collected in sterile poly-bag after carefully cutting the root biomass from the shoot. All subsamples were pooled together to form a composite rhizospheric soil sample. Isolation of rhizospheric microbe and determination of colony forming unit (CFU) was done by serial dilution method. Plating was done with 0.1 ml of diluted soil suspension on nutrient agar plates and CFU was counted after 24 h in­ cubation at 28 � C (Tripathi et al., 2014). Alkaline phosphatase, β 3

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Table 1A Soil physicochemical properties ofCicer arietinum maintained under sustainable agronomic practices (vermicompost and biochar amendments) at three different experimental sites of Indo Gangetic Plains of India. Data are the means with � (Standard deviation) (n ¼ 4). Mean value followed by same letter (a-d) within a column for particular amendment are not significantly different (p < 0.05) by Duncan post hoc multiple comparison test. Soil physicochemical properties of C. arietinum field maintained under sustainable agronomic practices at Varanasi. Year 2015 2016

Treatments Control Biochar Vermicompost Control Biochar Vermicompost

pH 7.83 8.22 7.03 7.65 8.45 6.88

Moisture content (%) bc

� 0.10 � 0.27ab � 0.56d � 0.13c � 0.26a � 0.33d

3.53 4.18 3.71 3.69 4.31 4.25

c

� 0.76 � 0.95ab � 0.52bc � 0.34bc � 0.94a � 0.56ab

Bulk density (g cm 3) 1.56 � 1.41 � 1.45 � 1.40 � 1.26 � 1.30 �

0.04a 0.02c 0.07b 0.03b 0.02d 0.06c

Water holding capacity (%) 51.79 � 55.07 � 54.49 � 54.41 � 57.85 � 57.25 �

0.46c 1.06b 0.26b 0.49b 1.12a 0.27a

Table 1B Soil physicochemical properties ofCicer arietinum maintained under sustainable agronomic practices (vermicompost and biochar amendments) at three different experimental sites of Indo Gangetic Plains of India. Data are the means with � (Standard deviation) (n ¼ 4). Mean value followed by same letter (a-d) within a column for particular amendment are not significantly different (p < 0.05) by Duncan post hoc multiple comparison test. Soil physicochemical properties of C. arietinum field maintained under sustainable agronomic practices at Sultanpur Year 2015 2016

Treatments Control Biochar Vermicompost Control Biochar Vermicompost

pH

Moisture content (%) b

7.75 � 0.06 7.95 � 0.06a 7.33 � 0.13c 7.68 � 0.10b 7.93 � 0.10a 7.25 � 0.13c

3.57 � 4.01 � 3.91 � 3.58 � 4.09 � 4.03 �

b

0.97 0.54ab 0.50ab 0.70ab 0.61a 0.65a

Bulk density (g cm 1.47 � 1.34 � 1.37 � 1.34 � 1.28 � 1.35 �

3

)

a

0.05 0.02 ab 0.02ab 0.23ab 0.02b 0.02ab

Water holding capacity (%) 48.00 � 53.36 � 52.61 � 49.18 � 55.11 � 54.23 �

2.85b 0.55a 0.91a 2.84b 0.35a 1.00a

Table 1C Soil physicochemical properties ofCicer arietinum maintained under sustainable agronomic practices (vermicompost and biochar amendments) at three different experimental sites of Indo Gangetic Plains of India. Data are the means with � (Standard deviation) (n ¼ 4). Mean value followed by same letter (a-d) within a column for particular amendment are not significantly different (p < 0.05) by Duncan post hoc multiple comparison test. Soil physicochemical properties of C. arietinum field maintained under sustainable agronomic practices at Gorakhpur. Year

Treatments

pH

2015

Control Biochar Vermicompost Control Biochar Vermicompost

7.83 8.00 7.73 7.33 7.65 7.53

2016

Moisture content (%) � 0.05ab � 0.19a � 0.10b � 0.21d � 0.19bc � 0.05c

3.84 4.50 4.49 3.89 4.59 4.53

� 0.83b � 0.41a � 0.29b � 0.95b � 0.49a � 0.38b

was observed under vermicompost practiced soils. High humic acids of utilized substrate (agro-waste) and phosphorus content of the applied vermicompost could be responsible for this. Changes in pH under both the amendments were more significant during the second year since repeated amendments enhance the level of TOC during the later stage as apparent from Fig. 2 which in turn alters soil biochemistry (more negatively charged soil organic matter and amendment derived anions) leading to changed pH. Similar, increase in the pH under organic amendments was also reported by Zhang et al. (2016). Significant decrease in bulk density was found in both the amendments compared to control at Varanasi, which might be the result of vermicompost and biochar amendment (containing less density organic matter) that induced soil aggregation and increased soil pore volume. Changes in bulk density were insignificant at Sultanpur and Gorakhpur owing to different soil textures (Jones et al., 2012; Herath et al., 2013). Our re­ sults were in accordance with Singh et al. (2013b) who also observed a 13.5% reduction in bulk density under vermicompost amended soil. Moisture content displayed maximum increase (16.8, 14.2 and 17.9%) under biochar amended field compared to vermicompost and corre­ sponding control at all sites (Table 1 A, B and C). This higher moisture content could be due to the biochar that has ability to improve soil hydraulic properties like porosity and water holding capacity as evident from our result (Table 1). A significant increase of 1.4–2.0 and 1.0–1.3 fold in total organic carbon (TOC) was recorded in vermicompost and biochar amendments respectively. At each experimental site, soil available nitrogen also increased by 1.0–1.2 and 1.0–1.1 fold under vermicompost and biochar

Bulk density (g cm 3) 1.56 � 1.45 � 1.47 � 1.50 � 1.39 � 1.42 �

0.08a 0.06ab 0.07ab 0.08ab 0.05b 0.05b

Water holding capacity (%) 54.86 � 57.15 � 55.61 � 55.28 � 57.59 � 56.03 �

0.62b 1.86ab 1.48ab 0.62ab 1.88a 1.49ab

amended field respectively (Fig. 2). Similarly, a 1.2–1.5 and 1.0–1.1 fold increase in available phosphorus and available potassium were found under vermicompost amended plot followed by 1.0–1.1 and 1.00–1.03 fold increase in available phosphorus and potassium in biochar treated field at Varanasi and Sultanpur (Fig. 2). Vermicompost has more labile form of nutrients than biochar, that might be the reason behind the increased TOC, available nitrogen, phosphorus and potassium under vermicompost over control and biochar. Likewise, in the pot experi­ ments, Singh et al. (2013b) reported that enriched vermicompost can improve the soil OC (24.9%); and other (N and P) nutrients. Other than vermicompost, negatively charged surface area of biochar is able to react with positively charged cations leading to greater fertilizer use efficiency and availability of nutrients. Additionally, agro-waste derived biochar utilized in our study acts as a rich source of carbon and other nutrients. Our results were in concordance with previous studies who also recorded the positive impact of organic amendments in different soil conditions (Wang et al., 2017; Steiner et al., 2018; Zuo et al., 2018). Amendments induced changes in the aforementioned soil physico­ chemical properties by changing the pore size distribution of soil mac­ ropores and its surface provides a protected habitat for microbes leading to their altered soil microbiology and expression of soil enzymes. Our results clearly depict that vermicompost and biochar amendments improve biological fertility (soil dehydrogenase, MBC and MBN) of soil differentially. Soil dehydrogenase enzyme responded strongly to ver­ micompost and biochar amendment than the corresponding control at each site. Furthermore, a 26.8, 18.1 and 24.4% increase in soil dehy­ drogenase; 41.3, 11.0 and 34.9% increase in microbial biomass carbon 4

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Fig. 2. Response of soil physicochemical and biological properties of Cicer arietinum field amended with vermicompost and biochar in comparison to control. Data are the mean values of different practices (n ¼ 4) followed by the different letters (a–h) are significantly different at p ¼ 0.05 level of significance under DMRT.

and 29.9, 20.2 and 22.4% increase in microbial biomass nitrogen were recorded at Varanasi, Sultanpur and Gorakhpur site respectively (Fig. 2). Although we have not studied the changes in microbial community structure, the higher soil glomalin activity under biochar-amended soil over control might be a sign of arbuscular fungal dominance which helps in soil carbon stabilization (Table 2). Soil dehydrogenase enzymes and microbial biomass carbon are good indicators of microbial activity involved in organic matter cycling. Therefore, higher magnitude of soil dehydrogenase and microbial biomass in vermicompost and biochar amended fields confirm the nutrient rich organic matter and soil fertility (Romaniuk et al., 2011). Similarly, Tripathi et al. (2014) suggested high dehydrogenase activity in healthy soil. We monitored higher rate of microbial (6.9–14.1%) and soil respi­ ration (2.5–6.6%) in vermicompost amendment whereas biochar

treatment showed reduced rate of microbial (2.5–6.8%) and soil respi­ ration (1.1–2.8%) at Varanasi, Sultanpur and Gorakhpur sites (Fig. 4). In both the amendments, ANOVA results of respiration, demonstrated that microbial respiration is a more sensitive parameter than soil respiration thereby confirming the robust response of soil microbes to these amendments. The higher value of MBC, MBN, dehydrogenase activity, soil and microbial respiration under vermicompost amended field highlighted the role of its humic and fulvic acid, readily available organic component and the easily metabolized carbon and nitrogen. Our findings were in agreement with Masto et al. (2007) that reported 59%, 91% and 51% increase in OC, MBC and soil dehydrogenase activity under organically managed different agricultural crops. In the later stage of the present study, higher residence time of carbon, C, N reten­ tion potential, slower microbial enzymatic activity and CO2 adsorption 5

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Table 2 Sustainably analysis of adaptive agriculturally practiced Cicer arietinum crops in comparison to control at experimental site 1 (Varanasi) where we have found maximum improvements in the soil quality, crop growth and yield. Data are the means with � (standard deviation) (n ¼ 32). Mean value followed by same superscript letter within a column for particular amendment are not significantly different (p < 0.05) by Duncan post hoc multiple comparison test. S.No.

Agricultural Soil Sustainability Indicators (ASSI)

1 2 3 3 4 5 6 7 8 9 10 11

Soil organic carbon stocks (Mg C ha 1) Soil total bacterial counts (106 g 1 soil) Soil total fungal counts (106 g 1 soil) Microbial biomass carbon (μg g 1) Microbial biomass nitrogen (μg g 1) Soil dehydrogenase (μg g 1) β-glucosidase (μg g 1) Urease (μg g 1) Alkaline phosphatase (μg g 1) Glomalin (mg g 1) Water Stable Aggregates (%) Soil macro fauna Earthworms Millipedes/Centipedes Ants

Observed data from second year trial Control

Biochar

Vermicompost

18.11 � 1.29b 25.74 � 1.45b 11.28 � 2.11b 150.23 � 3.1b 27.84 � 0.59b 132.81 � 1.3b 91.65 � 0.305b 132.22 � 0.75b 33.03 � 0.88b 3.27 � 0.88b 19.15 � 1.29b þ þ þ

21.07 � 1.31a 148.91 � 1.97a 121.25 � 1.70a 204.39 � 13.3a 33.81 � 3.64a 172.12 � 2.8a 182.50 � 1.065a 182.76 � 0.73a 108.31 � 0.94a 5.33 � 0.94a 33.54 � 1.10b þþ þþ þþ

19.97 � 1.26a 189.92 � 2.36a 100.04 � 1.95a 214.48 � 13.57a 36.23 � 3.83a 181.08 � 3.00a 191.37 � 0.78a 192.32 � 1.94a 109.19 � 1.23a 4.17 � 0.39a 27.87 � 1.30b þþþ þþþ þþ

The symbols ‘þ‘, ‘þþ’ and ‘þþþ’ indicates ‘low’, ‘medium’ and ‘high’ level of abundance.

to biochar surface could be the reason behind reduced rate of respiration under biochar amended plots. Correlation results of the study further yielded a significant positive correlation (r ¼ 0.808; R2 ¼ 0.65, p < 0.05) between the TOC and soil MBC which was in conjugation with other findings (García-Ruiz et al., 2012; Kumar et al., 2017). Conclusively, our study revealed the impact of adaptive agro-practices (vermicompost and biochar amendments) on several soil characteristics and put forward the valuable relationships between microbial and soil parameters that responded significantly to the adopted amendments.

that the vermicompost favours the growth of beneficial microorganism which promote plant growth and yield (Bosco et al., 2017; Singh et al., 2017; Zuo et al., 2018). Additionally, we reported higher MBC and soil dehydrogenase mediated enhancement in the microbial activity and nutrient availability that results in the higher crop growth and biomass as well as productivity. Pronounced crop growth and yield under bio­ char amendment could be the result of higher nutrient releases from biochar in soil as evident from our results of available N, P and K (Fig. 2). Our results of improved crop root, shoot growth and biomass results are supported by the previous findings conducted among different crops and regions (Zhang et al., 2012; Abhilash and Dubey, 2015; Goswami et al., 2015). We also observed reduced bulk density in biochar and vermi­ compost amended field that might have favoured higher root and plant growth, nutrient uptake and productivity by improving the soil water permeability. The present study ascertained that vermicompost and biochar besides being a source of nitrogen, phosphorus and potassium, provide optimum pH for plant and microbial growth which improves soil health and productivity. Correlation regression analysis performed to cross validate the results yielded significant positive correlation be­ tween root length and grain yield (r ¼ 0.721, p < 0.05). The sustainable yield index (SYI) was highest for biochar (0.88, 0.88 and 0.87) followed by vermicompost (0.87, 0.86 and 0.84) control (0.78, 0.73 and 0.69) at Varanasi, Sultanpur and Gorakhpur site respectively (Fig. 5). There was significant linear relationship between the SYI and soil carbon fractions (TOC, SOC, MBC), key soil microbial enzyme (dehydrogenase activity) and soil available nutrients (available nitrogen, phosphorus and potassium). These relationships validated the role of soil carbon fractions, soil microbial enzymes and nutrient availability in governing plant pro­ ductivity by improving microbial activity and soil health at each experimental site under diverse agroecosystems. The highest significant relationships were found between SYI and TOC (R2¼ 0.96, p < 0.05); SOC (R2 ¼ 0.82, p < 0.05); MBC (R2 ¼ 0.99, p < 0.05); SDA (R2 ¼ 0.90, p < 0.05); AN (R2 ¼ 0.98, p < 0.05); AP (R2 ¼ 0.99, p < 0.05) and AK (R2 ¼ 0.97, p < 0.05) at Varanasi followed by Sultanpur and Gorakhpur. No significant relationship was obtained between the SYI and soil respiration (R2 ¼ 0.08, 0.001 and 0.001; p < 0.05) at Varanasi, Sul­ tanpur and Gorakhpur respectively which again favoured the sustain­ ability of the crop production systems (Table 4). The results confirmed that improving soil quality and crop productivity through agro-waste derived biochar applied as an adaptive agro-practice can significantly improve agroecosystems sustainability in the Indo Gangetic plains of India as well as in other agrarian countries. Along with the crop yield, nutrient contents also responded signifi­ cantly (p < 0.05) to both the amendments. Data in the (Table 3)

3.2. Crop growth, sustainable yield index (SYI) and nutrient turnover For the present study, maximum (p < 0.05) germination capacity was recorded as vermicompost > biochar > control at each experimental site (Table 3). Root lengths were enhanced by 1.3 and 1.2 fold under vermicompost and biochar respectively and site wise trends were in order of Varanasi > Sultanpur > Gorakhpur (Fig. 3). Maximum lateral root formation was recorded under vermicompost treated field at Var­ anasi. Significant increase in the number of lateral roots was observed under vermicompost (66, 50 and 47%) and biochar (56, 35 and 40%) at Varanasi, Sultanpur and Gorakhpur respectively in comparison to the control. We also recorded a 62, 58 and 59% along-with 46, 52 and 41% higher root dry biomass in vermicompost and biochar amendments at Varanasi, Sultanpur and Gorakhpur sites (Fig. 3). Similarly, other crop growth related parameters like shoot length demonstrated maximum improvement at Varanasi (1.2 and 1.0 fold) followed by Gorakhpur (1.1 and 1.0 fold) and Sultanpur (1.1 and 1.0 fold) under vermicompost and biochar amendments during the second-year trials. A highest significant increase of 29, 18 and 26% under vermicompost and 20, 13 and 18% under biochar treatment was recorded for shoot dry biomass at Varanasi (Fig. 3). In general, ANOVA results confirmed the robust (p < 0.05) response of root, shoot length, lateral root and root, shoot dry biomass plant 1 under vermicompost treatment, followed by biochar over con­ trol during both years of study. The first and second-year crop yield and nutrient content results are provided in Table 3 and (Fig. 3). Vermi­ compost amendment showed maximum (28–39%) increase whereas biochar demonstrated (23–36%) increase in grain yield over the control. Basic nutrient property results suggested that the nutrient rich agrowaste derived vermicompost is a good source of labile nitrogen which might have enhanced the C. arietinum growth and biomass (root, shoot parameters) as well as productivity at each site as apparent from our study. Vermicompost could also be a contributing factor towards plant growth due to its direct (changes plant metabolism by induced uptake of humic and fulvic acid) and indirect (increases plant nutrient uptake) action modes (Spokas et al., 2012). Furthermore it has also been noted 6

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Journal of Environmental Management 262 (2020) 110284

Fig. 3. Response of growth characteristics and yield of Cicer arietinum crop amended with vermicompost and biochar in comparison to control field. Data are the mean values of different practices (n ¼ 12) followed by the different letters (a–e) are significantly different at p ¼ 0.05 level of significance under DMRT.

7

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Journal of Environmental Management 262 (2020) 110284

Fig. 4. Spatiotemporal response of soil and microbial respiration to the adaptive agronomic practices (vermicompost and biochar amendments) at three different experimental sites (Varanasi, Sultanpur and Gorakhpur) under diverse agroecosystems. Table 3A Germination and nutrient content results of Cicer arietinum crop grown under adopted agronomic practices at diverse agroecosystems. Response of germination and nutrient content of C. arietinum crops amended with vermicompost and biochar in comparison to control at Varanasi site. Data are the means with � (Standard de­ viation) (n ¼ 4). Mean value followed by same letter (a-d) within a column for particular amendment are not significantly different (p < 0.05) by Duncan post hoc multiple comparison test. Year

Practices

Germination capacity (%)

2015

Control Biochar Vermicompost Control Biochar Vermicompost

87.93 88.65 90.70 97.25 99.03 99.53

2016

� 0.36d � 0.57bc � 0.41bc � 0.44cd � 0.44ab � 0.26a

Plant nitrogen content (mg g 1) 5.01 6.75 7.40 5.17 6.96 8.10

� 0.27d � 0.46c � 0.45b � 0.39d � 0.44bc � 0.32a

Plant phosphorus content (mg g 1) 3.11 � 3.41 � 3.73 � 3.13 � 3.43 � 3.83 �

0.09b 0.16a 0.47a 0.09b 0.21a 0.40a

Plant potassium content (mg g 1)

Plant crude protein %

3.99 � 0.30b 4.08 � 0.12eb 4.35 � 0.36ab 4.00 � 0.12b 4.19 � 0.14ab 4.51 � 0.36a

3.69 � 4.22 � 4.63 � 3.73 � 4.35 � 5.07 �

0.17d 0.29c 0.28b 0.24d 0.27bc 0.20a

Table 3B Germination and nutrient content results of Cicer arietinum crop grown under adopted agronomic practices at diverse agroecosystems. Response of germination and nutrient content of C. arietinum crops amended with vermicompost and biochar in comparison to control at Sultanpur. Year

Practices

Germination capacity (%)

Plant nitrogen content (mg g 1)

2015

Control Biochar Vermicompost Control Biochar Vermicompost

87.75 � 0.44d 98.50 � 0.57bcd 98.73 � 0.61abc 88.0 � 0.5cd 98.88 � 0.46ab 99.48 � 0.28a

5.38 6.52 7.18 5.46 6.76 7.90

2016

� 0.14d � 0.50c � 0.47b � 0.18d � 0.45bc � 0.23a

Plant phosphorus content (mg g 1) 3.06 � 3.27 � 3.37 � 3.11 � 3.32 � 3.55 �

0.15b 0.18a 0.37a 0.11b 0.20a 0.35a

Plant potassium content (mg g 1)

Plant crude protein %

3.88 � 0.43a 3.92 � 0.44a 4.23 � 0.21a 3.91 � 0.36a 3.99 � 0.25a 4.35 � 0.14a

3.61 � 4.08 � 4.49 � 3.78 � 4.22 � 4.94 �

0.08d 0.31c 0.29b 0.10d 0.28bc 0.15a

Table 3C Germination and nutrient content results of Cicer arietinum crop grown under adopted agronomic practices at diverse agroecosystems. Response of germination and nutrient content parameters of C. arietinum crops amended with biochar and vermicompost in comparison to control at Gorakhpur. Year

Practices

Germination capacity (%)

2015

Control Biochar Vermicompost Control Biochar Vermicompost

85.48 98.43 98.53 85.83 98.95 99.40

2016

� 0.42d � 0.49bc � 0.61bc � 0.50cd � 0.65ab � 0.26a

Plant nitrogen content (mg g 1) 4.96 6.63 7.21 5.48 6.88 8.01

� 0.43c � 0.51b � 0.37b � 0.22c � 0.45b � 0.22a

Plant phosphorus content (mg g 1) 3.10 � 3.41 � 3.45 � 3.15 � 3.40 � 3.63 �

8

0.08b 0.18ba 0.39a 0.04b 0.20a 0.26a

Plant potassium content (mg g 1)

Plant crude protein %

3.87 � 0.30a 3.92 � 0.28a 4.08 � 0.20a 3.91 � 0.14a 4.07 � 0.20a 4.33 � 0.43a

3.73 � 4.15 � 4.51 � 3.80 � 4.30 � 5.01 �

0.27c 0.32b 0.23b 0.14c 0.28b 0.14a

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Journal of Environmental Management 262 (2020) 110284

Fig. 5. Sustainable yield index of C. arietinum crop maintained with adaptive agronomic practices (vermicompost and biochar amendments) at three different experimental sites (Varanasi, Sultanpur and Gorakhpur) under diverse agroecosystems.

could be due to the cumulative impact of higher (62%) glomalin activity and water stable aggregates (75%) under biochar followed by vermi­ compost practiced field where comparatively lower (27% and 45%) improvements were noted for the same. Highest glomalin activity and water stable aggregates under biochar amended field might have induced the soil macro-aggregation, organo-mineral and surface-ligand reactions, resulting in less SOC depletion. Previous research also found that the biochar can help in improving the soil carbon status via altering the soil structure (Herath et al., 2013). Soil enzymes such as β-glucosidase, urease, and alkaline phosphates are the important enzymes responsible for carbon, nitrogen and phos­ phorus mineralization and turnover in the soil (Hartmann et al., 2015). Soil enzyme results demonstrated the utmost increase (p < 0.05) in response of alkaline phosphatase (two fold) followed by β-glucosidase (one fold), urease (45%) and dehydrogenase activity (36%) under ver­ micompost practiced field. Similarly, two fold, 99%, 38% and 29% in­ crease in alkaline phosphatase, β-glucosidase, urease and soil dehydrogenase activity was found under biochar amendment during second-year trials. The higher soil enzyme activity may be due to the increased microbial (bacterial and fungus) counts, TOC, availability of nutrients and water retention potential of biochar and vermicompost amendments. Increased microbial biomass carbon and nitrogen results in our study bear testimony to the aforesaid result for soil enzymes (Table 2). Other organic farming practices have also been reported for optimizing soil pH and enhanced carbon content which acts as an energy source for soil microbes resulting in pronounced cell multiplication, MBC and soil enzyme activity (Moscatelli et al., 2012). Similarly, the soil enzyme activities were also responded significantly in compost-amended wheat field (Calderon et al., 2018). In accordance with our study, García-Ruiz et al. (2012) reported a significant 3, 1 and 4 fold increase in phosphatase, β-glucosidase and dehydrogenase respec­ tively under compost added soil. There was a positive correlation (r ¼ 0.89; p < 0.01) between TOC and soil dehydrogenase activity shows the enhanced microbial activity stimulated by the amendments. These re­ sults are in agreement with previous study (Kumar et al., 2017). Among all studied soil enzyme, alkaline phosphatase confirmed significant pronounced activity under both the amendments. Alkaline phosphatase is known for organic phosphate mineralization and acts in response to the poor phosphorus availability in soil. Vermicompost and biochar amendments had significantly higher alkaline phosphatase activity suggesting the improved soil phosphorus in amended field. Decreasing phosphorus availability is a foremost dread for Indian and global agri­ culture, thus the implementation of biochar-based agro-practices can alleviate the crisis of phosphorus deficiency. Subsequent to the alkaline phosphatase, β-glucosidase was the second most responsive enzyme to vermicompost (Moscatelli et al., 2012; García-Ruiz et al., 2012) thereby

indicates a 56, 44 and 46% increase in N content followed by 22, 14 and 15% increase in P and a 12, 11 and 10% increase in K content of the crop under vermicompost amended field at Varanasi, Sultanpur and Gor­ akhpur respectively. The crude protein content in the crop was also increased by > 1.3 fold under vermicompost followed by biochar treated field. Nitrogen and phosphorus were more influencing nutrients under both the amendments than potassium. Growth, productivity and nutrient contents of C. arietinum improved effectively in the present study since the agro-waste and cow dung manure-derived biochar and vermicompost amendments improved the soil structure, water re­ lationships, nutrient availability, microbial biomass and enzymatic ac­ tivity of soil. The soil structures, water relationships, nutrient availability, microbial biomass and enzymatic activity characteristics were assessed in our study through estimation of bulk density, water holding capacity, moisture content, initial nutrients content estimation of amendments, available NPK, MBC, MBN, soil dehydrogenase and other enzyme activity followed by evaluation of relationships between them (Tables 1, 3 and 4 and Fig. 2). A previous study by Agegnehu et al. (2016) suggested that biochar and compost amendment lowers nutrient leaching and increases plant nitrogen and phosphorus contents. Simi­ larly, increased performance of organic amendments has also been noted in different crops (Doan et al., 2015; Calderon et al., 2018; Zuo et al., 2018). Furthermore, several studies have highlighted that ver­ micompost and biochar can alter plant growth and productivity depending upon the soil and other environmental factors (Khan et al., 2015; Yang et al., 2015). Therefore, the present study validated the spatiotemporal variation in the adopted amendments and found signif­ icant increase in the crop growth, biomass yield, sustainable yield index, nutrient and protein content at each experimental site located in the diverse agroecological zones of Uttar Pradesh India. Besides, application of these adaptive agro-practices in different parts of the world would positively benefit agro-environmental sustainability. 3.3. Agricultural soil sustainability indicators (ASSI) Sustainable yield index and its relationships with the soil parameters have already been discussed in previous section and indicated the sus­ tainability aspect of the adopted practices. Apart from the aforemen­ tioned parameters, another sustainability assessment has been done by assessing the Agricultural Soil Sustainability Indicators (ASSI). For this, SOC, microbial load, MBC, MBN, soil enzymes and diversity of soil macro-organisms were considered (Table 2). It is obvious from Table 2 that the study recorded a significant difference among the respective values of the ASSI between the amended field and control. The SOC stock was improved by 16% and 10% under biochar and vermicompost amendments respectively. Highest SOC stock in biochar amendment 9

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Journal of Environmental Management 262 (2020) 110284

Table 4 Relationship between key soil fertility factors and sustainable yield index of C. arietinum crops managed under adaptive agronomic practices (vermicompost and biochar amendment) at Varanasi, Sultanpur and Gorakhpur sites under diverse agroecosystems. Soil independent parameters’

Sustainable cropping system indicator

Regression equations

Coefficient of determination (R2)

Total organic carbon (TOC)

Sustainability Yield Index (SYI)

Y (V) ¼ 19.546x - 13.794 Y (S) ¼ 21.377x - 14.711 Y (G) ¼ 14.216x - 7.7562 Y (V) ¼ 214.64x - 163.76 Y (S) ¼ 126.29x - 87.766 Y (G) ¼ 97.155x - 60.866 Y (V) ¼ 1560.1x - 1172 Y (S) ¼ 148.06x þ 28.521 Y(G) ¼ 977.65x - 625.57 Y (V) ¼ 14.558x þ 133.44 Y (S) ¼ 2.3711x þ 147.97 Y (G) ¼ 1.9118x þ 142.32 Y (V) ¼ 1281.1x - 946.07 Y (S) ¼ 180.17x - 34.16 Y (G) ¼ 598.49x - 347.41 Y (V) ¼ 797.97x - 575.63 Y (S) ¼ 184.45x - 65.064 Y (G) ¼ 99.406x þ 17.962 Y (V) ¼ 100.53x - 76.117 Y (S) ¼ 39.676x - 24.139 Y (G) ¼ 30.714x - 15.795 Y (V) ¼ 271.64x - 110.49 Y (S) ¼ 177.81x - 30.354 Y (G) ¼ 229.18x - 65.728

0.96** 0.85* 0.85* 0.82* 0.68* 0.61* 0.99** 0.88* 0.83* 0.08ns 0.001ns 0.001ns 0.90* 0.82* 0.72* 0.98** 0.84* 0.83* 0.99** 0.98** 0.87* 0.97** 0.88* 0.86**

Soil organic carbon stock (SOC) Microbial biomass carbon (MBC) Soil respiration (SR) Soil dehydrogenase activity (SDA) Soil available nitrogen (AN) Soil available phosphorous (AP) Soil available potassium (AK)

Where ns, representing no significant relationship and *, **, denotes significance at p < 0.05 and 0.01. V, S and G are the experimental site i.e. Varanasi, Sultanpur and Gorakhpur respectively.

4. Conclusion

altering the soil biochemistry and crop productivity. In vermicompost amendments, increased expression of β-glucosidase indicates the improved SOC and soil health via microbial mediated mineralization. Urease regulates the nitrogen mineralization and control the labile ni­ trogen content of soil. The present study found higher urease activity under amended plots suggested the higher availability of nitrogen which further supports to the nutrient efficient agriculture. Vermicompost amended strawberry also exemplified the urease mediated resource efficient agro-practices (Zuo et al., 2018). In another practice, Maji et al. (2017) reported the 28% increased urease activity under enriched ver­ micompost amended soil that helps in maximizing the crop growth and biomass. Besides soil enzymes, our study also noted 42% and 30% in­ crease in soil microbial biomass carbon and nitrogen under vermicom­ post followed by biochar amended field, thereby suggested the enriched microbial biodiversity. Thus our finding can significantly add the sus­ tainability aspect to the previous agricultural studies (García-Ruiz et al., 2012; Doan et al., 2015). Apart from aforementioned ASSI, significant increase (4 and 9-fold as well as 6 and 7-fold higher total bacterial and fungal counts) in the soil microorganism population was also found under biochar and ver­ micompost amendment respectively. Increased abundance was also monitored for soil macro-organism population like annelids and insects (earthworms, millipedes, centipedes and ants) under adopted agro­ nomic practices (Table 2). Our findings are in support with a metaanalysis which identified the impact of organic farming on biodiver­ sity and found 50% higher species loads and richness of insects and soil organisms under practiced field (Bengtsson et al., 2005; Chintala et al., 2014; Calderon et al., 2018). Assessment of soil quality and its sus­ tainability indicators are essential to detect the soil system functionality that sustains the crop, human and environmental health simultaneously (Romaniuk et al., 2011; Mete et al., 2015). Present study validated the significant (p < 0.05) improvements in the key soil sustainability in­ dicators under adopted agronomic practices (vermicompost and biochar amendment) over the control at each sites. These indicators can be utilized at landscape level to monitor the current status of soil health and its sustainability component in agriculture, horticulture, olericulture, floriculture, agroforestry practices and other type of wide scale plantations.

Sustainable agronomic practices have enhanced the agricultural resource use efficiency and agro-environmental sustainability at each experimental site of Indo Gangetic Plains of Uttar Pradesh, India. Therefore such practices can be utilized for improving food production with reduced environmental risks. Since, the vermicompost and biochar amendments improved the soil quality, crop growth, yield, nutritional quality, sustainable yield index and soil sustainability indicators. Hence, the adopted practices of the study could be suitable for a variety of other crops grown in different parts of the agrarian countries. Although the present study confirmed the vermicompost amendment as a potential practice for improving grain yield and crop nutrients at each experi­ mental site, however, it also results in an enhanced rate of microbial and soil respiration lead to environmental instability. Comparatively, the biochar amendment enhanced the soil fertility and crop characteristics at a slightly slower rate but was able to reduce the rate of microbial and soil respiration. Thus the biochar based amendments are the promising practices as it has improved the soil quality, crop productivity, nutri­ tional quality of agro-produce, soil carbon stock with the reduced rate of CO2 efflux from agroecosystems. Therefore, the wide-scale employment of such agro-wastes derived cost-effective practices can further help in achieving the targets of cleaner crop production, agro-environmental sustainability and sustainable development goals (SDGs). The adopted agronomic practices could be better customized through precise de­ livery methods, competent nutrient-release kinetics and exploration of underlying soil-organics interactions. Further research is needed to develop efficient technologies for massive production of agro-waste based vermicompost and biochar. Author’s statement Conceived by: RKD, HBS, PCA. Experimental design, filed work and data collection: RKD, PKD, RC, HBS, PCA. Initial Draft: RKD. Reviewing: RKD, PKD, RC, HBS, PCA. Final editing: RKD, PKD, RC, HBS, PCA. 10

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Journal of Environmental Management 262 (2020) 110284

Declaration of competing interest

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