2.1 Experimental setup

A field trial was carried out in the winter of 2016–2017 at the Agricultural Research Institute Swat in Khyber Pakhtunkhwa, Pakistan, located at an Altitude of 984 m, Latitude of 34.14 ^oN, and Longitude of 71.6 ^oE (Fig. S1). The trial was conducted using RCBD with split plot arrangement, and three replications. The Pirsabaq-2005 wheat variety was sown in late November 2016 on a 3 m x 4 m subplot with a seed rate of 120 kg ha⁻¹. The row-to-row distance was kept at 25 cm; while plot to plot distance was kept at 0.5 m. The experimental site had a wheat-maize and maize-alfalfa cropping history.

Compost (Comp) produced from poultry litter was distributed manually among the main plots, which had two levels of 0 and 10 tons ha⁻¹. Trichoderma. harzianum Strain (GB) was provided by Agro Services (PVT) LTD Swat and contains at least 1.0 x 10⁷ colony forming units per gram dry weight. According to the treatment plan, 5 kg ha⁻¹ T. harzianum was first mixed with soil and then manually broadcasted among the subplots. Similarly, P sources, including SSP and RP, were manually broadcasted @ 90 kg ha⁻¹ among the subplots. Urea was applied in a base dose, half at sowing and half at the tillering stage. Moreover, Swat city recorded temperatures between 18.57 and 38.96 °C, with an average temperature of 31.5 °C. Average rainfall and relative humidity were 910 mm and 95.87 %, respectively (Fig. S2).

2.2 Soil and plant analysis

One composite pre-sowing soil sample from the experimental site was collected using a zigzag manner and another after harvest the crop. Pre-sowing soil samples were representative of the soil at the experimental site, whereas post-harvest soil samples were representative of each experimental unit that received various treatments. After being air dried and grounded and passed through a 2-mm sieve, the pre- and post-soil samples were analyzed for the different selected parameters. The soil texture, includes relative proportion of silt, sand, and clay, was determined by Gee's Method (2002). Nelson and Sommers (1996) method was used to determine soil organic matter content. Soil pH and EC were determined by the methods of McLean (1983) and Rhoades and Corwin (1981) respectively. Soil total nitrogen was determined by the method of Bremner (1996). The concentration of P and micronutrients in soil was determined by following the procedure developed by Soltanpour and Schwab (1977). The P content was then determined by spectrophotometer after standardization while the micronutrients (Cu, Fe, Mn, and Zn) were determined by atomic absorption spectrophotometer (Optima 3000 + ). After harvesting, the sample of plant parts were washed, dried, grounded, sieved, and stored in paper bags for future analysis. Plant parts were analyzed for P and micronutrient uptake by following the procedure of wet digestion as explained by Rashid and Ryan. (2004). The following formula was used to calculate the total uptake of P and micronutrients. $$\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{N}\mathrm{u}\mathrm{t}\mathrm{r}\mathrm{i}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{U}\mathrm{p}\mathrm{t}\mathrm{a}\mathrm{k}\mathrm{e}=\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{c}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{o}\mathrm{f}\mathrm{N}\mathrm{u}\mathrm{t}\mathrm{r}\mathrm{t}\mathrm{i}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{i}\mathrm{n}\mathrm{P}\mathrm{l}\mathrm{a}\mathrm{n}\mathrm{t}\times \mathrm{b}\mathrm{i}\mathrm{o}\mathrm{m}\mathrm{a}\mathrm{s}\mathrm{s}$$

The pre-harvest soil was a silt loam composed of 16.6 % clay, 61.1 % silt, and 22.3 % sand. Prior to the experiment, topsoil (0–20 cm) had the chemical and nutrient composition as: total nitrogen 0.06 g kg⁻¹, organic matter content 1.21 g kg⁻¹, nitrate nitrogen 22.40 mg kg⁻¹, ammonium nitrogen 2.5 mg kg⁻¹, available P 3.92 mg kg⁻¹, K 149 mg kg⁻¹, pH 6.9. Micronutrient concentrations, Cu, Fe, Zn, and Mn were 0.39 mg kg⁻¹, 4.81 mg kg⁻¹, 1.79 mg kg⁻¹, and 3.02 mg kg⁻¹, respectively.

2.3 Morphological and yield-related traits

Ten plants were randomly selected from each subplot to estimate plant height. A tape measure was used to estimate the plant's height from the soil's surface to the tip of plant. The average was then calculated in centimeters. Similarly, with the help of a measuring ruler, the spikes of five randomly selected plants in each sub-plot were measured, and the average was computed. For biological yield (total dry matter accumulation of wheat), the middle two rows of each subplot were harvested. The plant bundles were sun-dried after harvesting, and they were then weighed by using balance. The biological yield was calculated and converted to kg ha⁻¹ by using the following formula. $$\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{M}\mathrm{a}\mathrm{s}\mathrm{s}\mathrm{a}\mathrm{t}\mathrm{M}\mathrm{a}\mathrm{t}\mathrm{u}\mathrm{r}\mathrm{i}\mathrm{t}\mathrm{y}=\left(\frac{\mathrm{M}\mathrm{a}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{n}\mathrm{K}\mathrm{g}}{\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{t}\mathrm{o}\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{d}\mathrm{i}\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{e}\times \mathrm{r}\mathrm{o}\mathrm{w}\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{g}\mathrm{t}\mathrm{h}\times \mathrm{n}\mathrm{o}\mathrm{o}\mathrm{f}\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{s}\mathrm{s}\mathrm{e}\mathrm{l}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{e}\mathrm{d}}\right)\times 1000$$

The center two rows for the grain yield (kg ha⁻¹) were threshed, cleaned, and weighed. The following formula was used for the calculation of grain yield in kg ha⁻¹. $$\mathrm{G}\mathrm{r}\mathrm{a}\mathrm{i}\mathrm{n}\mathrm{Y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}\left({\mathrm{K}\mathrm{g}\mathrm{h}\mathrm{a}}^{-1}\right)=\left(\frac{\mathrm{G}\mathrm{r}\mathrm{a}\mathrm{i}\mathrm{n}\mathrm{Y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}\mathrm{i}\mathrm{n}\mathrm{K}\mathrm{g}}{\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{t}\mathrm{o}\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{d}\mathrm{i}\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{e}\times \mathrm{r}\mathrm{o}\mathrm{w}\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{g}\mathrm{h}\mathrm{t}\times \mathrm{N}\mathrm{o}\mathrm{o}\mathrm{f}\mathrm{r}\mathrm{o}\mathrm{w}\mathrm{s}\mathrm{s}\mathrm{e}\mathrm{l}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{e}\mathrm{d}}\right)\times 1000$$

2.4 Data analysis

The data obtained on various soils and crop parameters were statistically analyzed using the two-factor analysis of variance (ANOVA) technique using Statistix 8.1 software and MS Excel. Tukey’s HSD test was applied to estimate the differences among the treatments at a 5 % significance level. The figures were made by OriginPro 9.0. To identify the principal components that underlie changes in various treatments in this experiment, the principal component analysis (PCA) and Heatmap with Dendogram were conducted using the statistical package XLSTAT.

3.1 Effect on morphological and yield-related traits of wheat

The statistical analysis of the data revealed that the harmonized TRI, Comp, and P sources predominantly improved wheat morphology and yield compared to single treatment application and control (Table 1). The harmonized TRI + RP + Comp predominantly improved plant height by 108.0 ± 0.61, followed by TRI + SSP + Comp (107.1 ± 0.83), compared to the control (99.8 ± 1.37). The same trend was also recorded for the spike length, as the harmonized TRI + RP + Comp predominantly improved spike length by 9.9 ± 01.5 followed by TRI + SSP + Comp (9.7 ± 0.10), compared to control (7.8 ± 0.15). In the case of grain yield, TRI + SSP + Comp significantly increased grain yield by 4325 ± 54, followed by TRI + RP + Comp (4296 ± 11), compared to control (2765 ± 33). TRI + RP + Comp significantly increased biomass by 9356 ± 222, followed by TRI + SSP + Comp (9092 ± 157), compared to control (7494 ± 141). TRI + RP + Comp performed better than TRI + SSP + Comp and other harmonized and single treatments.

3.2 Effect on post-harvest SOM conent (%) and soil P concnetration (mg kg⁻¹)

The statistical analysis of the data revealed that the harmonized TRI, Comp, and P sources predominantly improved SOM and soil P concentration compared to single treatment application and control (Fig. 1). Soil organic matter content was significantly higher in the soil collected from TRI + SSP + Comp (2.28 ± 0.11 %), followed by TRI + Comp (2.16 ± 0.05 %), TRI + RP + Comp (2.12 ± 0.10 %) whereas less SOM content was found in the SSP (1.46 ± 0.05 %) and TRI (1.52 ± 0.06 %), compared to the control treatment (1.20 ± 0.03 %) (Fig. 1a). Tukey's HSD test revealed that there are significant differences among the treatments for the 9 groups, which can be observed in the figure, even though the treatments' effects on SOM are significant at p < 0.05.

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Fig. 1

The influence of treatments on soil a) organic matter (%), and b) phosphorus (mg kg⁻¹). Bars are the values of three replicates (means) and contain standard deviations of means (n = 3). In each panel, bars with different letters differ significantly from each other at 5 % significance level (p < 0.05).

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The highest P concentration was found at TRI + SSP + Comp (13.60 ± 0.11 mg kg⁻¹), followed by SSP + Comp (12.43 ± 0.12 mg kg⁻¹), TRI + SSP (11.25 ± 0.12 mg kg⁻¹), TRI + RP + Comp (9.47 ± 0.26 mg kg⁻¹), while the lowest concentration was found at the TRI (6.15 mg kg⁻¹) and control (Fig. 1b). Tukey's HSD test showed that there are significant differences between the treatments for all 11 groups except TRI + SSP + Comp, even though the treatments' effects on soil P are significant at p < 0.05.

3.3 Effect on post-harvest soil micronutrient concentration (mg kg⁻¹)

The data analysis showed that the harmonized treatments of TRI, Comp, and P sources significantly improved micronutrient concentration in soil for wheat crop growth compared to single treatment application and control (Fig. 2). It can be seen in Fig. 2a, that the highest Cu concentration was recorded at the treatment combination of TRI + Comp (0.720 ± 01 mg kg⁻¹), followed by TRI + SSP + Comp (0.660 ± 02 mg kg⁻¹), TRI + RP + Comp (0.630 ± 02 mg kg⁻¹), TRI + RP (0.590 ± 02 mg kg⁻¹) and TRI + SSP (0.580 ± 08 mg kg⁻¹), compared to the control (0.350 ± 01 mg kg⁻¹). The concentration of Fe was observed differently with the treatments compared to other micronutrients. The highest Fe concentration was found at sole TRI (7.690 ± 08 mg kg⁻¹) followed by TRI + Comp (6.610 ± 03 mg kg⁻¹), TRI + RP + Comp (7.360 ± 13 mg kg⁻¹), TRI + SSP + Comp (7.150 ± 06 mg kg⁻¹), TRI + RP (6.760 ± 05 mg kg⁻¹), and SSP + Comp (6.620 ± 35 mg kg⁻¹), respectively. Meanwhile, the lowest Fe concentration was found at RP (5.92 ± 0.24 mg kg⁻¹), compared to control (4.64 ± 0.06 mg kg⁻¹) (Fig. 2b). The maximum concentration of Zn was recorded at TRI + Comp (4.07 ± 0.16 mg kg⁻¹), followed by TRI + RP + Comp (3.61 ± 0.08 mg kg⁻¹), TRI (3.52 ± 0.05 mg kg⁻¹), TRI + RP (3.48 ± 0.06 mg kg⁻¹) and TRI + SSP + Comp (3.17 ± 0.05 mg kg⁻¹), whereas, minimum concentration was recorded at the plot with RP (1.42 ± 0.11 mg kg⁻¹), compared to control (1.12 ± 0.07) (Fig. 2c). TRI + Comp had the highest concentration of soil Mn (4.430 ± 08 mg kg⁻¹) compared to TRI + SSP + Comp (3.490 ± 25), TRI (3.450 ± 19), TRI + RP + Comp (3.380 ± 46), and TRI + RP (2.480 ± 04 mg kg⁻¹) (Fig. 2d).

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Fig. 2

The influence of treatments on soil a) Cu, b) Fe, c) Zn, and d) Mn in mg kg⁻¹. Bars are the values of three replicates (means) and contain standard deviations of means (n = 3). In each panel, bars with different letters differ significantly from each other at 5 % significance level (p < 0.05).

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3.4 Effect on soil P and micronutrients uptake by wheat plants

The harmonized treatments showed a significant (P < 0.05) effect on soil P and micronutrient uptake by wheat plants (Fig. 3). When compared to other doses and the control, the P uptake by wheat plants was significantly (P < 0.05) higher with the treatment combinations TRI + RP + Comp (510 %) and TRI + SSP + Comp (474 %). Other treatments, either alone or in combination, resulted in the following trends in P uptake by wheat plants: TRI + Comp (345 %), TRI + RP (330 %), TRI + SSP (244 %), RP (49 %), and SSP (48 %) (Fig. 3a). The TRI + RP + Comp treatment combination significantly increased Cu, Fe, Zn, and Mn uptake by 106 %, 111 %, 63 %, and 137 %, respectively. TRI + SSP + Comp increased Cu, Fe, Zn, and Mn uptake by 88 %, 104 %, 58 %, and 128 %, respectively (Fig. 3b-e).

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Fig. 3

The influence of treatments on the uptake of soil a) P, b) Cu, c) Zn, d) Mn, and e) Fe in kg ha⁻¹. Bars are the values of three replicates (means) and contain standard deviations of means (n = 3). In each panel, bars with different letters differ significantly from each other at 5 % significance level (p < 0.05).

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3.5 Multivaraite and cluster analysis for the studied varaibles

To investigate the association between the studied variables under the harmonized effect of TRI, Comp and inorganic sources of P a multivariate analysis such as Pearson’s correlation, principal components analysis (PCA) and Heatmap with Dendogram was performed. The correlation between the studied variables as affected by the single or combined treatments is presented in Table 2. As can be seen, Pearson’s correlation analysis indicated that all the investigated variables showed a strong positive association except for soil P and micronutrients, which exhibit weak but positive association. There was no evidence of a negative association, demonstrating the efficacy of the treatments on soil fertility and wheat productivity. Similarly, the results obtained from PCA revealed that soil P and micronutrient uptake, and wheat productivity attributes were more closely associated with TRI + RP + Comp and TRI + SSP + Comp. These results further proved that the uptake of P, and micronutrient by wheat plants was highly correlated with the availability of P and micronutrients in the soil, as well as the concentration of soil organic matter (SOM). The first principal component (PC1) and PC2 explained 82.7 % and 8.56 % of the total variation, respectively (Fig. 4). Additionally, a Heatmap coupled with Dendogram was analyzed, and the colors scale revealed that the effects of the harmonized treatments were more pronounced towards TRI + RP + Comp and TRI + SSP + Comp (darker to darker red). The Dendogram displayed two separate data clusters or groups. The course of treatment where the TRI, Comp, and inorganic sources of P fertilizers were harmonized or administered in combination, as illustrated in the green tree cluster, made the apparent differentiation. The single treatments were clustered or grouped separately in a red tree (Fig. 5). Overall, the multivariate and cluster analysis of the data showed that the harmonized treatments significantly increased SOM, soil P, and micronutrient concentration, which subsequently regulate P and micronutrient uptake, resulting in improved soil fertility, wheat growth, and production.

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Fig. 4

Biplot with a 95% Confidence Ellipse for the principal component analysis of the variables under investigation.

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Fig. 5

Heatmap with Dendo-gram for the studied variables under single or combined TRI, Comp and inorganic P sources application.

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