Changes in Soil Properties with Combined Use of Probiotic Cultures and Organic Farming Practices in Degraded Soils of Bangladesh

Abstract

A shift in agricultural management from chemical to organic practices is expected to reduce environmental hazards and improve soil health and productivity in Bangladesh. To increase knowledge of the impact of probiotic cultures and organic farming practices on the physical and chemical properties of Bangladeshi soils, an investigation was carried out during the period from July 2016 to June 2019. The study included nine treatments using combinations of probiotic cultures and organic farming practices. The experiment used a randomized complete block design with three replicates. The probiotic cultures and organic practices increased soil moisture content, porosity and silt particle and decreased bulk density, particle density and sand particles. The organic matter content (11.66%), nutrient availability and electrical conductivity (8.96%) increased with the organic practices, while pH of the soil decreased. The largest significant change in the physical properties (p ≤ 0.05) was in the compost + vermicompost + green manuring treatment, while for chemical properties this was in the poultry manure + vermicompost + green manuring. These findings suggest that the above combinations of organic treatments provide most benefit to the soils of the practices considered.

1. Introduction

Intensive cultivation and imbalance in nutrient availability has resulted in degradation of the limited land resources in Bangladesh [1]. While the availability of nutrients in Bangladeshi soils was high in the past, today it is declining at a rapid pace [2]. Mostly plant nutrient requirements in Bangladesh comes from synthetic fertilizers [3] and normally N is used by plants 30.2–53.2% [4], P is less than 25% [5] and K use efficiency is 19% [6]. To meet the needs of an ever growing population, food supply needs to increase globally by 75–100% by 2050 [7] in Bangladesh; this increase is 56–560% [8]. Land intensification and synthetic fertilizers have been widely used in South Asia to increase productivity [9]. However, this creates pressures on natural resources and can result in degradation of the soils due to loss of soil organic matter [10]. It has also been reported that the intensive use of fertilizers has become a global problem, leading to depletion of organic matter and soil fertility [11]. Organic soil amendments for soil fertility and productivity to restore or improve soil health are drawing attention. Combination of organic manures enhances soil properties such as water-holding capacity, soil organic matter and essential nutrients elements [12]. Sustainable agriculture is now a global concern. Sustainability increases farming profitability with positive environmental effects that enforces the soil amendments with organic materials for utilization of nutrients by plants [13].

A good soil should have more than 2.5% organic matter, but in Bangladesh, the majority of soils have low to very low organic matter content, often less than 1.5% [14]. In order to maintain the productivity of soils, increased use for crop nutrition could be made of organic manures, such as crop residues, green manures and animal manures [15]. Applying livestock manures and composts to crops can help to increase soil organic matter and improve the physical properties of the soil [16]. The large poultry industry in Bangladesh [17] provides an opportunity to use poultry manure in organic farming systems, as poultry manure contains high levels of N, P, K and other essential nutrients, making it an excellent organic fertilizer [18,19]. Li et al. [20] highlighted that poultry manure improves pore structure and aggregate stability, and so has an important impact on soil structure formation, moisture content and maintenance of nutrients. Vermicompost is high in both macro- and micro-nutrients (N, P, K, Mn, Fe, Mo, B, Cu and Zn), which increases soil fertility and crop quality [21]. It also improves the physical properties of the soil, such as aggregate formation, bulk density, porosity and moisture holding capacity [22,23].

In Bangladesh, Aus rice is cultivated from March and April after the pre-monsoon rainfall and harvested between July and August [24]. This fallow period of about 2 months between rice harvest and wheat cultivation can be used effectively for growing a suitable legume as a green manure. Green manures have been observed to increase the soil biological and enzymatic activities more than synthetic fertilizers and also result in improvement in soil structural stability and higher water-holding capacity, thereby increasing the availability of nutrients to crops [25]. It also contributes in restoration of soil health [26].

Probiotics, such as the fungal plant symbiont Trichoderma, have been proposed by Hajieghrari and Mohammadi [27] as environmentally-friendly alternatives to chemical fertilizers for improving soil fertility without degrading soils. While other studies have considered the use of probiotics alone, there has been limited work on the combined use of probiotics with organic amendments. Because the fungi are a living component of the soil, this could have a significant impact on their effectiveness for improving crop production. There is still a need to investigate combined use of probiotics to improve soil health. Therefore, in this study, we consider the impacts of combined probiotic and organic amendments on degraded agricultural soils in Bangladesh. This will provide important information for extending the toolset available to Bangladeshi farmers for reducing degradation of soils, improving crop production, and achieving national food security.

2. Materials and Methods

2.1. Experimental Field

The work was conducted at the Institute of Biological Sciences (IBSc) Laboratory and its experimental field and Plant Pathology Laboratory, Department of Agronomy and Agricultural Extension, University of Rajshahi, Bangladesh during the period from July 2016 to June 2019. The experimental field is located at 24°17′ N latitude and 88°28′ E longitude, at a height of 20 m above the sea level. It is part of the Agro-ecological Zone-11 (High Ganges River Floodplain (13,205 sq km). predominantly highland and medium highland. Soils are slightly alkaline in reaction. General fertility level is low [28]. The soil characteristics are given in

Table 1. Initial physical properties of soil.

Moisture Content (%)	Particle Density (g/cc)	Bulk Density (g/cc)	Porosity (%)	Sand (%)	Silt (%)	Clay (%)	Textural Class
19.40	2.65	1.27	51.34	47	40	13	Loam

and

Table 2. Initial chemical properties of soil.

pH	Organic Matter (%)	K cmol (+)/kg	Total N (%)	P (µg/g)	S (µg/g)	Zn (µg/g)	EC (µs/cm)	C:N
8.10	1.20	0.150	0.07	26.30	12.50	0.75	145	10:1

:

For the two years before 2016, the field had been used to grow barley.

2.2. Soil Sample Collection and Analysis

Soil samples were collected from nine randomly selected locations in the experimental field before and after treatment during the three years study. Collected samples were packed in a polythene bag and were sent to the Department of Soil Science, Bangladesh Agricultural University, Mymensingh, for determination of moisture content, particle density, bulk density and textural class. The chemical properties, pH, organic matter, N, P, K and electrical conductivity (EC), were determined in the Soil Resource Development Institute (SRDI) laboratory, Shyampur, Rajshahi, Bangladesh. The methodologies are described in more detail below.

2.3. Experimental Design and Treatments

The experiment was laid out in a randomized complete block design with three replicates. Three wheat varieties were grown (BARI wheat-28 (V₁), BARI wheat-29 (V₂) and BARI wheat-30 (V₃). Nine soil amendments were used as control (T₀), rice straw + vermicompost + green manuring (T₁), cow dung + vermicompost + green manuring (T₂), compost + vermicompost + green manuring (T₃), poultry manure + vermicompost + green manuring (T₄), Trichoderma harzianum + vermicompost + green manuring (T₅), mung bean residue + vermicompost + green manuring (T₆), Trichoderma viride + vermicompost + green manuring (T₇) and chemical fertilizer (T₈). The size of each plot was 5.0 m², with a distance of plot-to-plot of 0.5 m, bed-to-bed of 0.25 cm, and 1 m from surrounding the boundary. The total number of plot units was 81. Before sowing, the crop residues (rice straw and mung bean residues), cow dung, compost and poultry litter (10 t ha⁻¹ fresh weight) vermicompost (5 t ha⁻¹ fresh weight) and Trichoderma spp. suspension (1 × 10⁶ cfu @ 5 kg ha⁻¹) were applied, depending on the treatment. The basal dose for the synthetic fertilizer treatment was one-third urea (200 kg ha⁻¹), triple super phosphate (160 kg ha⁻¹), muriate of potash (45 kg ha⁻¹), and gypsum (115 kg ha⁻¹) [29]. The remaining urea was administered 21 days and 55 days after sowing. The chemical properties of organic fertilizers are shown (Table S1).

2.4. Crop Cultivation and Harvesting

During the 2016–2017 cropping year, seeds were sown on 25 November 2016, likewise in the 2017–2018 and in 2018–2019; seeds were sown on 27 November 2017 and 25 November 2018. Seeds were sown in line following seed-to-seed and line-to-line distance 4 cm and 20 cm with a depth of about 4–5 cm opened by a specially made iron hand tine. The sown seeds were covered by soil manually. The seed rate was followed 120 kg ha⁻¹ as per the Bangladesh Agriculture Research Institute. The plots were infested with weeds. Two times hand weeding at 30 and 50 DAS was carried out. The major infesting weed species were Chenopodium album, Cyperus rotundus L., Amaranthus spinosus L. and Cynodon dactylon. Wheat crops were irrigated considering the presence of soil moisture. The crop provided 3 irrigations at crown root initiation (21 DAS), flowering (55 DAS) and grain filling (75 DAS) stages (BARI 2014). In every application, the flood method of irrigation was followed. When pests and diseases appeared, necessary control measures were taken.

After examining their proper maturity, the crops were harvested. The harvested crop of each plot covering 1 m² was bundled individually, tagged properly and taken to the clean threshing floor. Then the crops were threshed, cleaned and winnowed separately and necessary data were collected. The grain and straw yield of each plot were recorded and finally converted into t ha⁻¹.

2.5. Moisture Content

Moisture content of the soil was determined by the gravimetric method [30]. The moisture content, $P_{\mathrm{wat}}$ (% by weight), was calculated using the following formula

$$P_{\mathrm{wat}}=\frac{M_{\mathrm{wet}}-M_{\mathrm{dry}}}{M_{\mathrm{wet}}}\times 100$$

where $M_{\mathrm{wet}}$ is the weight of sample before drying (g) and $M_{\mathrm{dry}}$ is the weight of sample after oven drying (g).

2.6. Particle Density

The particle density, $D_{\mathrm{p}}$ (g cm⁻¹), was determined using the following formula [30],

$$D_{\mathrm{p}}=\raisebox{1ex}{$M_{\mathrm{wet}}$}\!\left/ \!\raisebox{-1ex}{$V_{\mathrm{s}}$}\right.$$

where, $M_{\mathrm{wet}}$ is mass of the fresh soil (g), and $V_{\mathrm{s}}$ is the solid soil volume (cm³).

2.7. Bulk Density and Porosity

A core sampler was used to determine bulk density. The bulk density, $D_{\mathrm{b}}$ (g cm⁻³), was estimated as shown by the formula [31],

$$D_{\mathrm{b}}=\raisebox{1ex}{$M_{\mathrm{dry}}$}\!\left/ \!\raisebox{-1ex}{$V_{\mathrm{s}}$}\right.$$

where, $M_{\mathrm{dry}}$ is the mass of the oven dry soil core (g), and $V_{\mathrm{s}}$ is the volume of the soil (cm³). Here, the internal volume of the core sampler was calculated using the equation given below:

$$V_{\mathrm{s}}=\pi r^{2}h$$

where, $r$ is the radius of the core sampler (cm) and $h$ is the height of the sampler (cm).

The porosity, $\phi$ (%), was calculated using the following formula:

$$\phi =100-\frac{D_{\mathrm{b}}}{D_{\mathrm{p}}}\times 100$$

2.8. Textural Class

The hydrometer method was used to determine soil texture [32]. A correction of the hydrometer reading was made as the hydrometer was calibrated at 68 °F [33].

The percentage of sand, silt and clay were calculated as follows:

$$P_{\mathrm{silt}+\mathrm{clay}}=\frac{H_{40}}{M_{\mathrm{dry}}}\times 100$$

$$P_{\mathrm{clay}}=\frac{H_{120}}{M_{\mathrm{dry}}}\times 100$$

$$P_{\mathrm{sand}}=100-P_{\mathrm{silt}+\mathrm{clay}}$$

$$P_{\mathrm{silt}}=P_{\mathrm{silt}+\mathrm{clay}}-P_{\mathrm{clay}}$$

where $P_{\mathrm{silt}+\mathrm{clay}}$ is the silt + clay content, $P_{\mathrm{clay}}$ is the clay content, $P_{\mathrm{sand}}$ is the sand content and $P_{\mathrm{sand}}$ is the sand content (all in % by weight); $H_{40}$ is the corrected hydrometer reading after 40 s and $H_{120}$ is the reading after 2 h; and $M_{\mathrm{dry}}$ is the dry mass of the soil (g).

The textural classes were determined by Marshall’s Triangular Coordinate [34], following the USDA system.

2.9. Chemical Properties Analysis

The samples were dried in the open air and dusted using a wooden roller. Each sample was sieved at 2 mm to remove coarse concretions, stones and organic waste. Jackson’s method of measuring soil pH with a glass electrode pH meter was used [35]. Wet digestion was used to estimate the organic carbon content of the soil, and the amount of organic matter was calculated by multiplying organic carbon by the Van Vemelon factor (1.724) [36]. The semi-micro Kjeldahl method was used to determine the total nitrogen in the soil [37]. After producing blue color with molybdate-ascorbic acid, available P was evaluated colorimetrically at 882 nm wavelengths [38]. The exchangeable potassium was measured using an atomic absorption spectrophotometer following the methodology outlined by Jackson [39]. The EC was calculated electrometrically using a conductivity meter, as described by Ghosh et al. [40].

2.10. Statistical Analysis

For comparison of the means of different soil parameters, the least significant difference (LSD) test was used because of pairwise comparison such as ‘Initial value versus 1st year value’, ‘1st year value versus 2nd year value’ and ‘2nd year value to 3rd year value’ through Crop Stat (Version 7.2).

3. Results and Discussion

3.1. Soil Physical Properties

3.1.1. Soil Moisture

At the beginning of the experiment, the initial moisture content of the experimental plot was recorded (19.40%). After application of amendment treatments, the moisture content varied significantly (

Table 3. Changes of soil moisture content (%) as influenced by soil amendments.

	2016–2017			2017–2018			2018–2019
Treat.	Initial	Final	Change	Initial	Final	Change	Initial	Final	Change
T0	19.40	16.73	−2.67 *	16.73	15.47	−1.27 *	15.47	13.47	−2.00 *
T1	19.40	17.85	−1.55 *	17.85	18.17	+0.32 ns	18.17	18.65	+0.48 ns
T2	19.40	18.65	−0.75 *	18.65	19.05	+0.40 ns	19.05	19.77	+0.72 *
T3	19.40	19.33	−0.07 ns	19.33	19.93	+0.60 ns	19.93	20.80	+0.87 *
T4	19.40	17.33	−2.07 *	17.33	17.57	+0.23 ns	17.57	17.93	+0.37 ns
T5	19.40	17.10	−2.30 *	17.10	17.27	+0.17 ns	17.27	17.53	+0.27 ns
T6	19.40	18.05	−1.35 *	18.05	18.40	+0.35 ns	18.40	18.95	+0.55 ns
T7	19.40	16.90	−2.50 *	16.90	16.98	+0.08 ns	16.98	17.20	+0.22 ns
T8	19.40	16.07	−3.33 *	16.07	14.27	−1.80 *	14.27	12.13	−2.13 *
LSD(0.05)		0.41			0.71			0.69
CV (%)		1.30			2.40			2.40

T₀ = control, T₁ = rice straw + vermicompost + green manuring, T₂ = cow dung + vermicompost + green manuring, T₃ = compost + vermicompost + green manuring, T₄ = poultry manure + vermicompost + green manuring, T₅ = T. harzianum + vermicompost + green manuring, T₆ = mung bean residues + vermicompost + green manuring, T₇ = T. viride+ vermicompost + green manuring, T₈ = chemical fertilizer, NS = Not significant difference between initial and final values, * = Significant (p ≤ 0.05) CV = Coefficient of variation, LSD = Least significant difference.

). The most significant gain of soil moisture was recorded in T₃ (+0.87%) but major decline was found in T₈ (−2.13%) followed by T₀ (−2.00%). Soil amendments with compost, vermicompost and green manure were directed to improving soil water-holding capacity [41]. This might be due to the effect of the nature and decomposition rate of organic matter added to the soil, and may be due to the improvement of the soil physical property such as the aggregation of soil particles that enhance the water-holding capacity. The present finding is also consistent with the findings of Vengadaramana and Jashothan [42] and Desta [43].

3.1.2. Bulk Density

Bulk density is a vital factor that explains soil quality, productivity and porosity [44]. The higher significant decrease of bulk density was noted from T₃ with the value −0.08 g cc⁻¹, an oppositely higher significant increase was recorded from T₈ (+0.10 g cc⁻¹) and in T₀ (+0.06 g cc⁻¹) (

Table 4. Changes of soil bulk density (g cc⁻¹) as influenced by soil amendments.

	2016–2017			2017–2018			2018–2019
Treat.	Initial	Final	Change	Initial	Final	Change	Initial	Final	Change
T0	1.27	1.30	+0.03 ns	1.30	1.34	+0.04 ns	1.34	1.41	+0.06 *
T1	1.27	1.24	−0.03 ns	1.24	1.21	−0.03 ns	1.21	1.17	−0.04 ns
T2	1.27	1.23	−0.04 *	1.23	1.20	−0.03 ns	1.20	1.15	−0.05 ns
T3	1.27	1.22	−0.05 *	1.22	1.16	−0.07 *	1.16	1.08	−0.08 *
T4	1.27	1.24	−0.04 *	1.24	1.18	−0.05 ns	1.18	1.14	−0.04 ns
T5	1.27	1.24	−0.03 ns	1.24	1.21	−0.04 ns	1.21	1.17	−0.03 ns
T6	1.27	1.24	−0.04 *	1.24	1.20	−0.04 ns	1.20	1.15	−0.05 ns
T7	1.27	1.25	−0.02 ns	1.25	1.24	−0.01 ns	1.24	1.20	−0.03 ns
T8	1.27	1.32	+0.05 *	1.32	1.39	+0.07 *	1.39	1.49	+0.10 *
LSD(0.05)		0.03			0.05			0.05
CV (%)		1.30			2.30			2.50

NS = Not significant difference between initial and final values, * = Significant (p ≤ 0.05).

). Reduction bulk density is treated as physical properties improvement of soil that could be achieved by addition of organic manures [45]. The reason for such variable result may be for the potentiality of compost in improving soil physical characters including aggregation of soil particles. Brown and Cotton [46] also stated that organic fractions reduce the total weight of soil which results in minimal bulk density.

3.1.3. Particle Density

Generally, we observed that due to addition of organic manure, the particle density of the soil was decreased (

Table 5. Changes of soil particle density (g cc⁻¹) as influenced by soil amendments.

	2016–2017			2017–2018			2018–2019
Treat.	Initial	Final	Change	Initial	Final	Change	Initial	Final	Change
T0	2.65	2.65	+0.00 ns	2.65	2.66	+0.01 ns	2.66	2.67	+0.01 ns
T1	2.65	2.64	−0.01 ns	2.64	2.63	−0.01 ns	2.63	2.61	−0.02 ns
T2	2.65	2.63	−0.02 ns	2.63	2.63	−0.01 ns	2.63	2.61	−0.02 ns
T3	2.65	2.63	−0.02 ns	2.63	2.61	−0.02 ns	2.61	2.61	−0.02 ns
T4	2.65	2.63	−0.02 ns	2.63	2.61	−0.02 ns	2.61	2.60	−0.01 ns
T5	2.65	2.64	−0.01 ns	2.64	2.63	−0.01 ns	2.63	2.61	−0.02 ns
T6	2.65	2.63	−0.02 ns	2.63	2.61	−0.02 ns	2.61	2.60	−0.01 ns
T7	2.65	2.64	−0.01 ns	2.64	2.62	−0.02 ns	2.62	2.61	−0.01 ns
T8	2.65	2.66	+0.01 ns	2.66	2.68	+0.02 ns	2.68	2.70	+0.02 ns
LSD(0.05)		0.02			0.03			0.03
CV (%)		0.40			0.60			0.70

NS = Not significant difference between initial and final values.

). From the comparison of different amendment treatments, T₂ and T₃ showed the higher capability to reduce particle density (−0.02 g cc⁻¹) of soil round the study period. To maintain good soil quality, organic amendment is the best option [41]. It may be due to higher organic matter concentration in organic manure and its impact on soil physical properties improvement. This strong association was previously notified by Celik et al. [47] and Rasoulzadeh and Yaghoubi [48].

3.1.4. Soil Porosity

Indeed, porosity is an essential part of soil structure that allows air and water movement in the soil. The porosity of experimental soil was increased by the application of organic amendments (

Table 6. Changes of soil porosity (%) as influenced by soil amendments.

	2016–2017			2017–2018			2018–2019
Treat.	Initial	Final	Change	Initial	Final	Change	Initial	Final	Change
T0	51.34	50.94	−0.40 *	50.94	49.58	−1.36 ns	49.58	47.37	−2.21 *
T1	51.34	52.91	+1.57 *	52.91	53.90	+0.99 ns	53.90	55.00	+1.09 ns
T2	51.34	53.26	+1.92 *	53.26	54.29	+1.03 ns	54.29	55.93	+1.64 ns
T3	51.34	53.50	+2.16 *	53.50	55.80	+2.31 *	55.80	58.74	+2.83 *
T4	51.34	52.98	+1.64 *	52.98	54.73	+1.76 *	54.73	56.33	+1.63 ns
T5	51.34	52.82	+1.48 *	52.82	54.15	+1.33 ns	54.15	54.98	+0.83 ns
T6	51.34	53.04	+1.70 *	53.04	54.29	+1.25 ns	54.29	55.81	+1.52 ns
T7	51.34	52.84	+1.50 *	52.84	52.79	−0.05 ns	52.79	53.81	+1.02 ns
T8	51.34	50.38	−0.96 *	50.38	48.14	−2.24 *	48.14	44.74	−3.40 *
LSD(0.05)		0.02			1.74			1.92
CV (%)		1.20			2.00			2.20

NS = Not significant difference between initial and final values, * = Significant (p ≤ 0.05).

). After three years, the significant increase of soil porosity (+2.83%) was recorded in T₃ and the second most (+1.82%) from T₂ but the most significant decrease (−3.40%) was noted in T₈. Organic manures make soil porous, resulting in good aeration for the plant. [49]. This might be due to the fact of addition of organic manures increasing the organic matter status of soil including particle-binding agents and thus leading to improved soil porosity. Conversely, due to lack of organic matter in the chemical-fertilizer-treated plot (T₈), it decreases. These results are in agreement with the findings of Woignier et al. [50]. Furthermore, Marinari et al. [51] reported that addition of organic fertilizers and compost increased total soil porosity of the soil.

3.1.5. Sand and Silt Particle

Most of the values for sand particles of the experimental soil were affected by various soil amendments especially in the final year of the study (

Table 7. Changes of soil sand particle (%) as influenced by soil amendments.

	2016–2017			2017–2018			2018–2019
Treat.	Initial	Final	Change	Initial	Final	Change	Initial	Final	Change
T0	47.00	48.00	+1.00 ns	48.00	49.33	+1.33 ns	49.33	50.67	+1.33 ns
T1	47.00	46.33	−0.67 ns	46.33	46.00	−0.33 ns	46.00	45.00	−1.00 ns
T2	47.00	46.00	−1.00 ns	46.00	44.67	−1.33 ns	44.67	42.67	−2.00 *
T3	47.00	46.00	−1.00 ns	46.00	44.33	−1.67 *	44.33	42.00	−2.33 *
T4	47.00	46.67	−0.33 ns	46.67	46.00	−0.67 ns	46.00	44.67	−1.33 ns
T5	47.00	46.67	−0.33 ns	46.67	46.00	−0.67 ns	46.00	45.00	−1.00 ns
T6	47.00	46.33	−0.67 ns	46.33	46.00	−0.33 ns	46.00	44.67	−1.33 ns
T7	47.00	46.67	−0.33 ns	46.67	46.33	−0.33 ns	46.33	45.33	−1.00 ns
T8	47.00	48.33	+1.33 *	48.33	50.00	+1.67 *	50.00	52.00	+2.00 *
LSD(0.05)		1.01			1.51			1.60
CV (%)		1.30			2.00			2.10

NS = Not significant difference between initial and final values, * = Significant (p ≤ 0.05).

). Treatment T₈ resulted in an increase in the sand particle (+2.00%) over the initial, followed by T₀ (+1.33%). Whereas, the maximum decrease of sand particles were recorded from T₃ (−2.33%) followed by T₂ (−2.00%). On the contrary, the most significant increase in the percent silt particle was recorded by T₃ having a value of +2.67%. However, compared to the initial value, a significant decline of silt particles was found in T₈ (−3.00%) and T₀ (−2.67%). Analyzed data showed the decrease of sand particles, whereas, there was an increase of silt particles through all the organic amendments, mostly by the treatment T₃ (Table 7 and

Table 8. Changes of soil silt particle (%) as influenced by soil amendments.

	2016–2017			2017–2018			2018–2019
Treat.	Initial	Final	Change	Initial	Final	Change	Initial	Final	Change
T0	40.00	38.67	−1.33 *	38.67	36.33	−2.33 *	36.33	33.67	−2.67 *
T1	40.00	41.00	+1.00 ns	41.00	42.00	+1.00 ns	42.00	43.67	+1.67 ns
T2	40.00	41.33	+1.33 *	41.33	43.00	+1.67 ns	43.00	45.33	+2.33 *
T3	40.00	41.67	+1.67 *	41.67	43.67	+2.00 *	43.67	46.33	+2.67 *
T4	40.00	40.67	+0.67 ns	40.67	42.00	+1.33 ns	42.00	44.00	+2.00 *
T5	40.00	40.67	+0.67 ns	40.67	41.67	+1.00 ns	41.67	43.00	+1.33 ns
T6	40.00	41.00	+1.00 ns	41.00	42.00	+1.00 ns	42.00	44.00	+2.00 *
T7	40.00	40.33	+0.33 ns	40.33	41.00	+0.67 ns	41.00	42.00	+1.00 ns
T8	40.00	38.00	−2.00 *	38.00	35.33	−2.67 *	35.33	32.33	−3.00 *
LSD(0.05)		1.20			1.85			1.91
CV (%)		1.80			2.80			2.80

NS = Not significant difference between initial and final values, * = Significant (p ≤ 0.05).

). Such variation may be due to the result of organic matter addition, which prohibits the dispersion of particles and helps to improve soil structure and texture. It was reviewed by many researchers that organic manure improves the soil structure and texture. This finding is in line with the opinion of Adesodun et al. [52] and Mahmood et al. [53].

3.2. Soil Chemical Properties

3.2.1. Soil pH

Soil pH related to soil acidity or alkalinity is an important issue for soil fertility, which did not show remarkable deviation from its initial alkaline status under all the treatments applied in this study (

Table 9. Changes of soil pH as influenced by soil amendments.

	2016–2017			2017–2018			2018–2019
Treat.	Initial	Final	Change	Initial	Final	Change	Initial	Final	Change
T0	8.10	8.17	+0.07 ns	8.17	8.20	+0.03 ns	8.20	8.27	+0.07 ns
T1	8.10	8.10	+0.00 ns	8.10	8.03	−0.07 ns	8.03	7.97	−0.07 ns
T2	8.10	8.03	−0.07 ns	8.03	7.93	−0.10 ns	7.93	7.83	−0.10 ns
T3	8.10	8.00	−0.10 ns	8.00	7.87	−0.13 ns	7.87	7.77	−0.10 ns
T4	8.10	8.20	+0.10 ns	8.20	8.27	+0.07 ns	8.27	8.30	+0.03 ns
T5	8.10	8.10	+0.00 ns	8.10	8.07	−0.03 ns	8.07	8.00	−0.07 ns
T6	8.10	8.03	−0.07 ns	8.03	7.93	−0.10 ns	7.93	7.87	−0.07 ns
T7	8.10	8.10	+0.00 ns	8.10	8.07	−0.03 ns	8.07	8.03	−0.03 ns
T8	8.10	8.23	+0.13 ns	8.23	8.37	+0.13 ns	8.37	8.53	+0.17 ns
LSD(0.05)		0.15			0.21			0.17
CV (%)		1.10			1.60			1.30

NS = Not significant difference between initial and final values.

). The increment of soil pH was noted higher (+0.17 unit) in T₈ and the next (+0.03 unit) in T₄ while the maximum decrease (−0.10 unit) of pH was observed in T₂ and T₃. The change of pH was linked with the presence of an N-based compound or ammonia-containing materials [54]. This decline was possibly associated with the application of organic manures which may produce organic acids and push the change to neutral line [55]. Brautigan et al. [56] used organic amendments as a means of reducing soil pH in alkaline soil.

3.2.2. Soil Organic Matter

After completion of a three year trial, the organic matter content of our experimental soil under different soil amendments slightly increased. The treatment T₃ greatly improved the organic matter status of the soil (+0.14%) but the lowest decline (−0.17%) was recorded with T₈ (Figure 1). Organic agriculture was supported by Al-Tawaha et al. [57] for the improvement of soil organic carbon and nutrients availability with positive effects on soil and environment. The gain of organic matter may be for the cumulative action of different organic amendments inputs which led to an increased accumulation. Many researchers report a similar result on organic matter enhancement by adding organic manures [58,59].

3.2.3. Total Nitrogen

At the last year of the study, treatment T₄ and T₃ were found to show the maximum significant increase in total nitrogen with the value of + 0.013% and +0.010% (

Table 10. Changes of soil total nitrogen (%) as influenced by soil amendments.

	2016–2017			2017–2018			2018–2019
Treat.	Initial	Final	Change	Initial	Final	Change	Initial	Final	Change
T0	0.070	0.045	−0.025 *	0.045	0.031	−0.015 *	0.031	0.022	−0.010 *
T1	0.070	0.051	−0.019 *	0.051	0.054	+0.001 ns	0.054	0.056	+0.003 ns
T2	0.070	0.057	−0.014 *	0.057	0.061	+0.005 *	0.061	0.068	+0.007 *
T3	0.070	0.063	−0.008 *	0.063	0.069	+0.007 *	0.069	0.079	+0.010 *
T4	0.070	0.068	−0.002 ns	0.068	0.084	+0.016 *	0.084	0.097	+0.013 *
T5	0.070	0.070	−0.001 ns	0.070	0.076	+0.006 *	0.076	0.084	+0.008 *
T6	0.070	0.056	−0.015 *	0.056	0.058	+0.003 ns	0.058	0.062	+0.005 *
T7	0.070	0.066	−0.004 *	0.066	0.070	+0.004 ns	0.070	0.075	+0.005 *
T8	0.070	0.050	−0.020 *	0.050	0.039	−0.011 *	0.039	0.024	−0.015 *
LSD(0.05)		0.003			0.004			0.003
CV (%)		3.100			3.800			2.700

NS = Not significant difference between initial and final values, * = Significant (p ≤ 0.05).

). On the other hand, total nitrogen was reduced (−0.015%) under the treatment T₈. The synthetic nitrogen does not retain in soil for long time because of faster availability to plants and higher leaching loss. In case of organic amendments, the increment might be due to the addition of biomass and also biological nitrogen fixation capability [60]. This was also credited by adequate supply of organic matter and higher percentage of N supplied by poultry manure. The presence of N stimulated the microbial activity that ultimately helped in decomposition of organic manures and the residual effect was retained in the soil. This result is in line with the findings of Omara et al. [61].

3.2.4. Available Phosphorus

Phosphorus is a major plant nutrient that has an important role in stem elongation, development of the root system and disease prevention which results in a better crop and yield [62]. The statistical analysis indicates mostly significant differences among the various soil amendments on available phosphorus, where the value + 4.05 µg g⁻¹ led to a higher increase but −1.07µg g⁻¹ was indicated as the reduction by T₃ and T₀, respectively (

Table 11. Changes of available phosphorus (µg g⁻¹) as influenced by soil amendments.

	2016–2017			2017–2018			2018–2019
Treat.	Initial	Final	Change	Initial	Final	Change	Initial	Final	Change
T0	26.30	12.96	−13.35 *	12.96	12.26	−0.70 ns	12.96	11.19	−1.07 ns
T1	26.30	23.49	−2.82 *	23.49	24.42	+0.93 ns	23.49	25.85	+1.44 ns
T2	26.30	25.65	−0.66 ns	25.65	29.36	+3.72 *	25.65	31.54	+2.18 *
T3	26.30	26.09	−0.22 ns	26.09	31.50	+5.42 *	26.09	35.55	+4.05 *
T4	26.30	25.22	−1.09 *	25.22	27.33	+2.11 *	25.22	29.34	+2.02 *
T5	26.30	19.23	−7.07 *	19.23	20.52	+1.29 ns	19.23	21.57	+1.05 ns
T6	26.30	21.41	−4.89 *	21.41	22.96	+1.55 *	21.41	24.14	+1.18 ns
T7	26.30	16.79	−9.51 *	16.79	17.70	+0.91 ns	16.79	18.60	+0.90 ns
T8	26.30	15.13	−11.18 *	15.13	16.53	+1.40 ns	15.13	17.50	+0.98 ns
LSD(0.05)		1.00			1.43			1.87
CV (%)		2.60			4.00			4.80

NS = Not significant difference between initial and final values, * = Significant (p ≤ 0.05).

). Such increment of P may be due to the residual effect of organic manures application to soil. The outcome is in harmony with the result of Geng et al. [63]. Organic amendment with compost, cow dung and poultry manure plays a vital role in retention of P in available form and improving P status in soil [64].

3.2.5. Exchangeable Potassium

Chemical fertilizer and organic manures are the major source of K input to soil. At the end season of the study, exchangeable potassium ranged from +0.015 to −0.008 (cmol (+) kg⁻¹), where the upper value (+0.015 cmol (+) kg⁻¹) was demonstrated by the treatment T₄ and the lower one was observed in T₀ (−0.008 cmol (+) kg⁻¹) (

Table 12. Changes of soil exchangeable potassium (cmol (+) Kg⁻¹) as influenced by soil amendments.

	2016–2017			2017–2018			2018–2019
Treat.	Initial	Final	Change	Initial	Final	Change	Initial	Final	Change
T0	0.150	0.088	−0.063 *	0.088	0.085	−0.002 ns	0.085	0.078	−0.008 ns
T1	0.150	0.110	−0.040 *	0.110	0.118	+0.007 ns	0.118	0.122	+0.004 ns
T2	0.150	0.118	−0.033 *	0.118	0.123	+0.005 ns	0.123	0.130	+0.008 ns
T3	0.150	0.123	−0.028 *	0.123	0.133	+0.010 ns	0.133	0.145	+0.012 *
T4	0.150	0.133	−0.018 *	0.133	0.145	+0.013 *	0.145	0.160	+0.015 *
T5	0.150	0.128	−0.023 *	0.128	0.135	+0.008 ns	0.135	0.143	+0.008 ns
T6	0.150	0.114	−0.036 *	0.114	0.122	+0.008 ns	0.122	0.130	+0.009 ns
T7	0.150	0.125	−0.025 *	0.125	0.130	+0.005 ns	0.130	0.136	+0.006 ns
T8	0.150	0.105	−0.045 *	0.105	0.110	+0.005 ns	0.110	0.120	+0.010 *
LSD(0.05)		0.007			0.010			0.009
CV (%)		3.300			5.000			4.200

T₀ = control, T₁ = rice straw + vermicompost + green manuring, T₂ = cow dung + vermicompost + green manuring, T₃ = compost + vermicompost + green manuring, T₄ = poultry manure + vermicompost + green manuring, T₅ = T. harzianum + vermicompost + green manuring, T₆ = mung bean residues + vermicompost + green manuring, T₇ = T. viride+ vermicompost + green manuring, T₈ = chemical fertilizer, NS= Not significant difference between initial and final values, * = Significant (p ≤ 0.05) CV= Coefficient of variation, LSD = Least significant difference.

)_. Some earlier workers mentioned the similar findings as found in the present study [65]. Abubakar and Ali [66] also evaluated the effect of poultry manure as an alternate refill of NPK.

3.2.6. Electrical Conductivity

Excepting T_0, there was found positive deviation of EC over the initial by application of different treatments in the last year of the study (Figure 2). The maximum influence (+13 µs cm⁻¹) from the start (145 µs cm⁻¹) to the end (181 µs cm⁻¹) of the study was recorded by the application of a poultry manure combination treatment (T₄) followed by compost combination treatment (T₃) (+13 µs cm⁻¹). The increase of EC can occur due to the application of organic manures that led to water-holding capacity and made available selected soil nutrients with its reasonable mineralization and sorption of ions. These results are in harmony with the findings of Carmo et al. [67] and Bhatt et al. [68].

4. Conclusions

Organic soil amendments such as probiotics and organic manure have the capacity to change the physical and chemical properties of soil. Green manure, vermicompost, compost and chicken manure may all be viable options in this regard. The organic manures’ breakdown and nutrient release capabilities could be employed to restore and improve soil health. In comparison to other manures, organic manures, especially compost and poultry manure, were healthier sources for improvement of soil physical and chemical characteristics. As a result, based on amendment requirements of farmers in the examined region, combinations of compost + vermicompost + green manure and poultry manure + vermicompost + green manure might be recommended for soil amendment.