*2.4. Soil Analysis*

Initial soil samples were taken for physicochemical properties (Table 3). Soil samples (0–30 cm) were analyzed for the texture [31], organic matter [32], total P [33]. However, soil samples were extracted through Ammonium Bicarbonate Diphenyl Triamine Penta Acetic Acid (AB-DTPA) solution for determination of available P, NO3-N and extractable K following the method of Soltanpour and Schwab [34] and soil pH (1:5 soil–water) using the method of Mclean [35]. Undisturbed soil samples were collected for soil bulk density (g cm−3) using stainless steel cylinders [36]. Soil phosphatase activity was determined by the method of Tabatabai and Bremner [37], whereas, microbial biomass carbon and microbial biomass phosphorus was determined following the method adopted by Steel and Torriej [38]. For determining post-harvest soil properties, soil samples were collected after 6 days of wheat crop harvesting.

**Table 3.** Physicochemical, biological and biochemical properties of soil.

**Table 3.** *Cont*.

#### *2.5. Statistical Analysis*

The experiment was laid down following the randomized complete block design (RCBD) with split plot design. Different soil amendments (composts and inorganic fertilizers) were assigned with the main plot while PGPRs were placed in sub-plots of the field. Analysis of variance (ANOVA) was conducted with the General Linear Models and means were compared according to the Tukey HSD test with Statistix 8.1 [39]. Two years of data were pooled because there were not interactions between the two years and year was included as a random effect in statistical model.

#### **3. Results**

Means of two-year data (2010–2011 and 2011–2012) are provided here due to the result similarity trend from both the years.

#### *3.1. Yield and Yield Components*

The data for the number of tillers showed 36%, 34%, 30%, 24% and 21% increases with un-inoculated RPEC1, FDP, RPEC2, SPLC and HDP, respectively, over un-inoculated untreated control (Table 4). The treatment RP did not show any significant increase over un-inoculated untreated control. Seed inoculation with PGPRs without any fertilizer treatment did not show any difference with un-inoculated control. However, seed inoculation with *Pseudomonas* sp. in combination with RPEC1 treatment showed a maximum 5% increase in the number of tillers over un-inoculated RPEC1 and FDP.

C—Control (un-inoculated untreated), SPLC—Simple poultry compost, RPEC1—Rock phosphate enriched compost inoculated with *Pseudomonas* species, RPEC2—Rock phosphate enriched compost inoculated with *Proteus* species, RP—Rock phosphate, HDP—Half dose inorganic P fertilizer, FDP—Full dose inorganic P fertilizer.

The data presented in Table 4, showed that there was a significant (*p* ≤ 0.05) effect of PGPR on grain yield of wheat crop. A maximum (18%) increase in grain yield was recorded in plants inoculated with *Pseudomonas* sp. which was 4% higher than inoculation with *Proteus* sp. Without inoculation, maximum (67%) increase in grain yield was recorded with the application of RPEC1 which was 4%, 9% and 16% higher than FDP, RPEC2 and SPLC, respectively over un-inoculated untreated control. However, RPEC2 showed a 52% increase in grain yield over control. The interactive effect of fertilizers × PGPR, was highly significant (*p* ≤ 0.05) for grain yield. *Pseudomonas* sp. inoculated RPEC1 and FDP gave maximum (10%) increase over un-inoculated RPEC1 and FDP treatments, respectively. The *Proteus* sp. in combination with RPEC1 also showed 3% increase over un-inoculated RPEC1 treatment, whereas the treatment RP produced minimum grain yield showing 14% increase over un-inoculated RP treatment.

The data in Table 4 show that the treatment RPEC1 resulted in a maximum increase in dry matter yield which was 3.8%, 16%, 27% higher than FDP, RPEC2 and SPLC respectively, over un-inoculated untreated control. The stimulatory effect of PGPR was recorded on dry matter yield. However, the interactive effect of PGPR and fertilizer treatments was significant for dry matter yield of wheat crop. The combination of *Pseudomonas* sp. with RPEC1 gave the maximum increase (62%) similar to

FDP (60%) while with *Proteus* sp. in combination with RPEC1 showed 56% increase over un-inoculated untreated control. RP inoculation with *Proteus* sp. showed nonsignificant difference with un-inoculated untreated control.

**Table 4.** Effects of plant growth promoting rhizobacteria (PGPR), P-enriched compost and inorganic fertilizers on yield and yield components on wheat.

All the treatments sharing common letter are similar otherwise they differ significantly at *p* ≤ 0.05.

#### *3.2. Leaf Chlorophyll, IAA and GA Contents*

Mean data recorded for chlorophyll contents in flag leaves of wheat crop showed that there was a significant (*p* ≤ 0.05) difference for the treatments (Figure 1). Among the un-inoculated treatments, RPEC1 showed the highest (28%) increase which was 2%, 6%, 12% and 25% higher than FDP, RPEC2, SPLC and HDP, respectively. Seed inoculation with *Pseudomonas* sp. resulted in an increase (4%) in chlorophyll content over un-inoculated treatments. However, the interactive effect of treatments (PGPRs × fertilizer) showed 29% increase followed by FDP (27%) over un-inoculated untreated control. While the treatment RP showed a nonsignificant difference when applied in combination with *Pseudomonas* as well as *Proteus* sp.

Data in Figure 2 show that RPEC1 resulted maximum (12%) increase in IAA content, having a similar effect as with FDP, followed by RPEC2 showing a 9% increase, while HDP and SPLC showed a similar effect (i.e., 7% increase) in IAA content over un-inoculated untreated control. The inoculation of seeds with *Pseudomonas* sp. gave higher values of IAA by showing 6% increase over un-inoculated treatments. The interactive effect of PGPR × Fertilizer was nonsignificant except for *Pseudomonas* sp. which showed a 20% increase, when used in combination with RPEC1 and FDP treatments.

The treatment RPEC1 resulted in a 13% increase in GA content, followed by FDP (11%), RPEC2 (9%), SPLC (6%), while HDP resulted only a 4% increase over un-inoculated untreated control (Figure 3). However, seed inoculation with *Pseudomonas* sp. showed a maximum (5%) increase over un-inoculated RPEC2 treatment. The data showed that the treatments RPEC1 and FDP in combination with *Pseudomonas* sp. showed a maximum (16%) increase in GA contents of flag leaves. PGPR inoculation with RP and HDP showed a nonsignificant difference among respective un-inoculated treatments.

**Figure 1.** Effects of PGPR, P-enriched compost and inorganic fertilizers on leaf chlorophyll concentration (μg g−1). C—Control; SPLC—Poultry litter only; RPEC1—Rock phosphate + poultry litter solubilized with *Pseudomonas* sp. during the composting process; RPEC2—Rock phosphate + poultry litter solubilized with *Proteus* sp. during composting process), RP—Rock phosphate + poultry litter; HDP—Half dose inorganic P from Single Super Phosphate-SSP 18% P2O5; FDP—Chemical fertilizer (Single Super Phosphate). All the treatments sharing a common letter are similar, otherwise they differ significantly at *p* ≤ 0.05.

**Figure 2.** Effects of PGPR, P-enriched compost and inorganic fertilizers on leaf IAA concentration (μg g−1) in wheat. C—Control; SPLC—Poultry litter only; RPEC1—Rock phosphate + poultry litter solubilized with *Pseudomonas* sp. during the composting process; RPEC2—Rock phosphate + poultry litter solubilized with *Proteus* sp. during composting process), RP—Rock phosphate+poultrylitter; HDP—Half doseinorganic P from Single Super Phosphate—SSP 18% P2O5; FDP- Chemical fertilizer (Single Super Phosphate). All the treatments sharing common letter are similar otherwise they differ significantly at *p* ≤ 0.05.

**Figure 3.** Effects of PGPR, P-enriched compost and inorganic fertilizers on leaf GA concentration (μg g−1) in wheat. C—Control; SPLC—Poultry litter only; RPEC1—Rock phosphate + poultry litter solubilized with *Pseudomonas* sp. during the composting process; RPEC2—Rock phosphate + poultry litter solubilized with *Proteus* sp. during composting process), RP—Rock phosphate + poultry litter; HDP—Half dose inorganic P from Single Super Phosphate—SSP 18% P2O5; FDP—Chemical fertilizer (Single Super Phosphate). All the treatments sharing common letter are similar otherwise they differ significantly at *p* ≤ 0.05.

#### *3.3. Plant Phosphorus Uptake and Seed Phosphorus*

The data presented in Figure 4 show that the phosphorus uptake was maximum (70%) due to the application of RPEC1 followed by RPEC2 (63%) and FDP (60%), while RP treatment showed no significant difference compared to un-inoculated untreated control. Seed inoculation with *Pseudomonas* sp. resulted in a maximum (7%) increase in P-uptake over un-inoculated treatments. The interaction of fertilizer treatments and PGPRs showed that RPEC1 in combination with *Pseudomonas* sp. showed maximum increase (88%) in P-uptake followed by *Proteus* sp. inoculated RPEC1 (79%) over untreated un-inoculated control.

The seed phosphorus content showed a 61% increase following application of RPEC1 over un-inoculated untreated control, which was 12%, 17%, 33% and 41% higher than FDP, RPEC2, SPLC and HDP, respectively (Figure 5). The application of *Pseudomonas* sp. alone also resulted in an increase (3.5%) in seed P contents over un-inoculated untreated control whereas the interactive effect of PGPR × Fertilizer was nonsignificant.

**Figure 4.** Effects of PGPR, P-enriched compost and inorganic fertilizers on plant P uptake (kg ha−1) in wheat. C—Control; SPLC—Poultry litter only; RPEC1—Rock phosphate + poultry litter solubilized with *Pseudomonas* sp. during the composting process; RPEC2—Rock phosphate + poultry litter solubilized with *Proteus* sp. during composting process), RP—Rock phosphate + poultry litter; HDP— Half dose inorganic P from Single Super Phosphate—SSP 18% P2O5; FDP—Chemical fertilizer (Single Super Phosphate). All the treatments sharing common letter are similar otherwise they differ significantly at *p* ≤ 0.05.

**Figure 5.** Effects of PGPR, P-enriched compost and inorganic fertilizers on plant P uptake (kg ha−1) in wheat. C—Control; SPLC—Poultry litter only; RPEC1—Rock phosphate + poultry litter solubilized with *Pseudomonas* sp. during the composting process; RPEC2—Rock phosphate + poultry litter solubilized with *Proteus* sp. during composting process), RP—Rock phosphate + poultry litter; HDP— Half dose inorganic P from Single Super Phosphate—SSP 18% P2O5; FDP—Chemical fertilizer (Single Super Phosphate). All the treatments sharing common letter are similar otherwise they differ significantly at *p* ≤ 0.05.

#### *3.4. Soil Properties*

#### 3.4.1. Available P, Nitrate Nitrogen and Extractable Potassium

The post-harvest soil analysis for phosphorus availability showed that the treatments significantly increased the P availability (Table 5). The treatment RPEC1 resulted in a significant increase over un-inoculated untreated control, the value of which was 37%, 82%, and 130% higher than SPLC, HDP and RP, respectively. The PGPR seed inoculation effect was significant (*p* ≤ 0.05) for post-harvest available soil P contents. The phosphorus content was increased (20% and 9%) in the rhizosphere of plants treated with *Pseudomonas* sp. and *Proteus* sp. respectively. In combination with *Pseudomonas* sp., the treatment RPEC1 gave maximum increase (3.43-fold) over un-inoculated untreated control, while RPEC1 in combination with *Proteus* sp. and *Pseudomonas* sp. in combination with FDP showed similar results by giving a 3.17-fold increase over the un-inoculated untreated control. The PGPRs (*Pseudomonas* sp. and *Proteus* sp.) in combination with RPEC2 showed a similar effect for increase [8%] in available P over un-inoculated RPEC2. The treatment RP in combination with *Pseudomonas* sp. resulted in 30% increase over un-inoculated RP, which was 16.5% higher than *Proteus* sp. inoculated RP.

C—Control (un-inoculated untreated), SPLC—Simple poultry compost, RPEC1—Rock phosphate enriched compost inoculated with *Pseudomonas* species, RPEC2—Rock phosphate enriched compost inoculated with *Proteus* species, RP—Rock phosphate, HDP—Half dose inorganic P fertilizer, FDP—Full dose inorganic P fertilizer. Soil samples for nutrient and biological analyses were collected two days after wheat harvesting.

**Table 5.** Effects of PGPR, P-enriched compost and inorganic fertilizers on post-harvest soil of wheat in field experiments.

All the treatments sharing a common letter are similar otherwise they differ significantly at *p* ≤ 0.05.

Mean data for post-harvest soil nitrate-nitrogen showed significant differences with the application of fertilizer treatments (Table 5). The treatments RPEC1 and RPEC2 resulted a 36% increase followed by SPLC, FDP and HDP showing 29%, 26% and 14% increase over un-inoculated untreated control, respectively. The treatment RP showed nonsignificant difference with the control. There was a nonsignificant effect of seed inoculation on NO3-N over un-inoculated control. However, the maximum increase was recorded by the application of *Pseudomonas* sp. which was 4% higher over un-inoculated control treatments. The interactive effect of PGPR and fertilizer treatments was nonsignificant with SPLC, RP, HDP and FDP, while the treatments RPEC1 and RPEC2 showed 36% and 35% increases over un-inoculated untreated control. The mean data showed that all the treatments increased extractable potassium except RP (Table 5). A maximum increase (15%) in the content of extractable K was recorded following the treatment RPEC1 followed by SPLC and RPEC2 which were significantly similar in their effect by showing 11% and 12% increase over un-inoculated untreated control, respectively. The treatments FDP and HDP also showed similar effects and increased extractable K by 7% over control. Seed inoculation with *Pseudomonas* sp. showed 2% increase in seed phosphorus contents over un-inoculated untreated control. The interactive effect of PGPR × Fertilizers, was nonsignificant, whereas *Pseudomonas* sp. inoculation in combination with RPEC1 showed maximum (17%) phosphorus contents over un-inoculated untreated control.

#### 3.4.2. Alkaline Phosphatase and Microbial Biomass

Alkaline phosphatase activity was significantly (*p* ≤ 0.05) increased as a result of different treatments (Table 5). The treatment RPEC1 resulted a maximum increase (29%) over un-inoculated untreated control, which was 5.6%, 11%, 13.5% and 19% higher than RPEC2, SPLC, FDP and HDP respectively. *Pseudomonas* sp. inoculation showed 8% increase over un-inoculated treatments, which was 2.5% higher than *Proteus* sp. inoculation. Significant (*p* ≤ 0.05) increase in alkaline phosphatase activity was recorded due to the combine effects of PGPRs with different fertilizer treatments. The inoculation of *Pseudomonas* sp. in combination with the treatment RPEC1 showed maximum (43%) increase over untreated un-inoculated control. The treatments RPEC2 and SPLC in combination with *Pseudomonas* sp. and RPEC1 in combination with *Proteus* sp. showed similar effect and increased the alkaline phosphatase activity by 34% over un-inoculated untreated control. The treatment FDP in combination with *Pseudomonas* sp. showed a 23% increase over untreated un-inoculated control; the effect of which was significantly similar to un-inoculated RPEC2 treatment. The PGPRs (*Pseudomonas* sp. and *Proteus* sp.) in combination with HDP showed a similar effect but significantly lower percentage increase than un-inoculated HDP treatment.

Mean data showed that the fertilizer treatments significantly (*p* ≤ 0.05) improved the microbial biomass carbon contents (Table 5). Significant increase (65%) was recorded in microbial biomass carbon contents in RPEC1 treatment over control; the increase for RPEC1 was also 9%, 22%, 30%, 43%, and 60% higher than that of RPEC2, SPLC, FDP, HDP and RP, respectively. Inoculation of seeds with *Pseudomonas* sp. showed maximum (16%) increase in microbial biomass carbon over un-inoculated treatments, the values of which were 8% higher than *Proteus* sp. inoculated treatments. The interactive effect of PGPR inoculation to seeds and fertilizer treatments was also significant with microbial biomass carbon contents. Among the *Pseudomonas* sp. inoculated treatments, RPEC1 showed 89% increase in microbial biomass carbon over un-inoculated untreated control, while the treatment RPEC2 showed 74% increase, which was significantly similar with *Proteus* sp. inoculated RPEC1 treatment. However, *Proteus* sp. inoculated RPEC2 increased microbial biomass carbon by 63% and showed a nonsignificant difference with un-inoculated RPEC1 treatment. *Pseudomonas* sp. in combination with FDP showed a nonsignificant difference with un-inoculated RPEC2 but was 13% higher than the un-inoculated FDP treatment. The treatment RP in combination with *Pseudomonas* sp. increased microbial biomass by 10% over untreated un-inoculated control.

The data in Table 5 show that microbial biomass phosphorus (MBP) increased significantly (*p* ≤ 0.05) with the application of fertilizer treatments than the un-inoculated untreated control. The maximum increase (1.75-fold) in MBP was recorded from the treatment RPEC1 which was 7%, 37% and 83% higher than RPEC2, SPLC and FDP, respectively while FDP showed nonsignificant difference with HDP. The treatment RP showed a nonsignificant difference with un-inoculated untreated control. There was also a significant effect of PGPR on microbial biomass phosphorus. *Pseudomonas* sp. inoculation increased microbial biomass P by 33% over un-inoculated treatments, the values of which were 14% higher than *Proteus* sp. inoculated treatments. *Pseudomonas* sp. inoculation with RPEC1 showed a maximum increase (2.7-fold) in MBP followed by RPEC2 (2.43-fold) over un-inoculated untreated control. The treatment RPEC1 in combination with *Proteus* sp. showed an (61%) increase over un-inoculated untreated control which was at par with *Pseudomonas* sp. inoculated SPLC. The treatments FDP, HDP increased (46%) microbial biomass P showing nonsignificant difference with each other and RP showed 12% increase in microbial biomass P with PGPR inoculation over un-inoculated untreated control.

#### *3.5. Economic Analysis*

The economic analysis of applied treatments (Table 6) in terms of value cost ratio (VCR) showed that RPEC1 performed best with and without seed inoculation. Among the un-inoculated treatments, RPEC1 showed maximum VCR (2.72) followed by RPEC2 (2.14), FDP (1.94) while the minimum (0.06) VCR was received from RP. Seed inoculation with *Pseudomonas* sp. in combination with RPEC1 superseded all of the treatments resulting in maximum VCR (3.23). Hence, rock phosphate enriched compost alone or more so in combination with phosphate solubilizing bacteria (PSB), can perform better than chemical fertilizers. The economic analysis revealed that RPEC could be an economically feasible substitute to costly chemical fertilizers for sustainable crop production.

**Table 6.** Economic Analysis of the applied products presented as value cost ratio (VCR).

Increase in yield = Yield of treatment − Yield of control, Increased yield value = Grain price × increase in yield, Net return = Increased yield value − cost of inputs, Value cost ratio (VCR) = Increased yield value/cost of inputs, Poultry litter = Rs. 1.5 kg−1, Rock phosphate = Rs. 5 kg−1, Single super phosphate (SSP) = Rs. 25 kg−1, Urea = Rs. 30 kg−1, Labor charges for compost preparation = Rs. 5250, Seed inoculant = Rs. 200 L−1, Wheat grain price = Rs. 30 kg−1, SPLC—Simple Poultry litter, RPEC1—Rock Phosphate Enriched Compost solubilized with *Pseudomonas* sp., RPEC2—Rock phosphate enriched compost solubilized with *Proteus* sp. 1S-Seed inoculation with *Proteus* sp., 2S—Seed inoculation with *Pseudomonas* sp., RP—Rock phosphate, HDP—Half dose of inorganic fertilizer, FDP—Full dose of inorganic fertilizer. Rs—Refer to national currency (Rupees).