Global warming promotes soil calcification and salinization processes. As a result, soil phosphorus (P) is becoming deficient in arid and semiarid areas throughout the world. In this pot study, we evaluated the potential of phosphate-solubilizing bacteria (PSB) for enhancing the growth and P uptake in maize under varying levels of lime (4.8%, 10%, 15% and 20%) and additional P supplements (farmyard manure, poultry manure, single super phosphate and rock phosphate) added at the rate of 45 mg P2O5 kg−1. Inoculation and application of P as organic manures (Poultry and farm yard manures) improved maize growth and P uptake compared to the control and soils with P applied from mineral sources. Liming adversely affected crop growth, but the use of PSB and organic manure significantly neutralized this harmful effect. Mineral P sources combined with PSB were as effective as the organic sources alone. Furthermore, while single supper phosphate showed better results than Rock phosphate, the latter performed comparably upon PSB inoculation. Thus, PSB plus P application as organic manures is an eco-friendly option to improve crop growth and P nutrition in a calcareous soil under changing climate.

Phosphate-solubilizing bacteria (PSB) reduce the negative effects of soil calcification on soil phosphorus (P) nutrition. In this incubation study, we explored the ability of PSB (control and inoculated) to release P from different P sources [single super phosphate (SSP), rock phosphate (RP), poultry manure (PM) and farm yard manure (FYM)] with various soil lime contents (4.78, 10, 15 and 20%) in alkaline soil. PSB inoculation progressively enriched Olsen extractable P from all sources compared to the control over the course of 56 days; however, this increase was greater from organic sources (PM and FYM) than from mineral P sources (SSP and RP). Lime addition to the soil decreased bioavailable P, but this effect was largely neutralized by PSB inoculation. PSB were the most viable in soil inoculated with PSB and amended with organic sources, while lime addition decreased PSB survival. Our findings imply that PSB inoculation can counteract the antagonistic effect of soil calcification on bioavailable P when it is applied using both mineral and organic sources, although organic sources support this process more efficiently than do mineral P sources. Therefore, PSB inoculation combined with organic manure application is one of the best options for improving soil P nutrition.

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Low availability of phosphorus (P) in calcareous soils is a major problem for sustainable improvement in cereals crops yield. A higher amount of calcium in soils precipitates the P, thus making it immobile in soil. Inoculation of arbuscular mycorrhizal fungi (AMF) and phosphate solubilizing bacteria (PSB) could be helpful in the sustainable management of immobile P in soil. However, their combined use in releasing P from rock phosphate (RP) in alkaline calcareous soils have been little investigated. In this regard, two successive field experiments were conducted to assess the interactive inoculation potential of AMF and PSB strain Bacillus sp. PIS7 with RP on the yield and P uptake of maize (Zea mays L.) and wheat (Triticum aestivum L.) crops in alkaline calcareous soil. The first field experiment was conducted in a complete randomized block design with 10 treatments and three replications by inoculating maize seeds with AMF and Bacillus sp. PIS7 inoculum alone and in combination with RP. Their performance was compared with single super phosphate (SSP) inorganic fertilizer. Afterward, the residual effects of inoculated AMF and Bacillus sp. PIS7 were investigated on wheat as a subsequent crop. Maize and wheat yield parameters, P uptake, AMF root colonization, and PSB population was measured. The results of both trials indicated the beneficial effects of AMF and Bacillus sp. PIS7 with RP in increasing the plants grain yield and P uptake until the second season after inoculation, as compared to controls. Likewise, maize and wheat roots colonization, PSB population density, and post-harvest soil properties were also improved by the combined inoculation of AMF and Bacillus sp. PIS7 with RP. It is concluded that PSB solubilizes the unavailable forms of P in combination with RP fertilizers in soil, and AMF ultimately transfers it to plants for growth promotion. Moreover, the combined inoculation of AMF and PSB with ground RP had more potential to improve maize-wheat yields and P uptake comparable to those obtained by using expensive phosphatic fertilizers in P deficient calcareous pH soils.

Increasing soil organic matter (SOM) contents improve the resilience of productive soil for future sustainability particularly in poor soil (<1% SOM). This study sought to elucidate how tillage and N fertilizer sources affect soil bulk density, soil organic carbon (SOC) and soil total N (TN) in 0‐ to 20‐cm soil depth. Treatments included minimum till (MT), conventional till (CT), deep till (DT), and twelve N treatments (60 and 120 kg urea N ha−1, 10 and 20 Mg farmyard manure [FYM] ha−1, 10 Mg soybean residue [SR] ha−1 and their combinations along with a control). The experiment was designed in randomized complete block design with split plot arrangement. Soil bulk density increased for DT toward the end of the experiment than CT or MT. The sequestration rates of SOC of MT was 22% higher than DT. The FYM retuned more SOC than SR, however SR returned more TN than FYM. Application of FYM as well as SR sequestered more C than urea or control. Conclusively, SOC returned was increased with 10 Mg FYM ha−1 along with 30 kg urea N ha−1 but TN with 10 Mg SR ha−1 in CT plots. This practice can therefore increase soil quality and productivity, and thus is considered a sustainable approach for soils deficient in organic matter. Core Ideas Minimum tillage improved C stock than shallow or deep tillage. The addition of urea increased SOC contents in SR plots than FYM. C Stocks in FYM and SR fertilized plots was about 3‐ to 4‐fold greater than control. Soybean residue build N stock principally in less plowed plots.

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Phosphorus (P) deficiency is the main hurdle in achieving sustainable crop production ps especially in calcareous soils. Using bio-fertilizers like phosphate solubilizing bacteria (PSB) could be a useful approach for sustainable P management as they improve P availability in soil via dissolution, desorption and mineralization reactions. In addition, application of organic amendments with PSB could further ameliorate soil conditions for sustainable management of immobilized nutrients in calcarious soils. Therefore, we performed pot experiment to study the role of PSB in nullifying antagonistic effects of liming (4.78, 10, 15 and 20%) on P availability from poultry manure (PM), farm yard manure (FYM), single super phosphate (SSP) and rock phosphate (RP) in alkaline soils. PSB inoculation improved wheat growth, P availability and stimulated soil acidification over control regardless of P sources and lime levels. Soil calcification adversely affected plant growth, P nutrition, induced soil salinity and alkalinity, however, PSB and manures application potentially nullified such harmful effects over mentioned traits. Individually, organic sources were superior than mineral sources however, the performance of mineral fertilizers with PSB was at par to sole application of manures. Furthermore, application of RP with PSB proved as effective as sole SSP. Therefore, using PSB as bio-fertilizer has huge potential for improving P availability in calcareous soils.