Sustainable Management with Mycorrhizae and Phosphate Solubilizing Bacteria for Enhanced Phosphorus Uptake in Calcareous Soils

Subhan Danish,Rahul Datta,Shah Saud,Martin Brtnicky,Muhammad Adnan,Fazli Wahid,Shah Fahad,Manzer H. Siddiqui,Tereza Hammerschmiedt,Zhen Yue

doi:10.3390/agriculture10080334

Abstract

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.

Highlights

Plant growth and mineral nutrition depend largely on the phosphorus (P) content of the soil.Phosphorus is the second essential macronutrient required for plant development and productivity [1,2]and is involved in almost all the major metabolic and most important plant biochemical processes [3].In many agricultural soils, P is abundantly distributed in both inorganic and organic forms, but its concentration and availability to plants is limited due to fixation, precipitation, and formation of soils complexes with other soil nutrients [4]
The grain yield of maize recorded in the treatment supplied with super phosphate (SSP) (3460 kg·ha−1 ) and rock phosphate (RP) +
The grain yield of SSP was almost equivalent to the treatments having combined inoculation of arbuscular mycorrhizal fungi (AMF)

Summary

Introduction

Plant growth and mineral nutrition depend largely on the phosphorus (P) content of the soil.Phosphorus is the second essential macronutrient required for plant development and productivity [1,2]and is involved in almost all the major metabolic and most important plant biochemical processes [3].In many agricultural soils, P is abundantly distributed in both inorganic and organic forms, but its concentration and availability to plants is limited due to fixation, precipitation, and formation of soils complexes with other soil nutrients [4]. Plant growth and mineral nutrition depend largely on the phosphorus (P) content of the soil. Phosphorus is the second essential macronutrient required for plant development and productivity [1,2]. P is abundantly distributed in both inorganic and organic forms, but its concentration and availability to plants is limited due to fixation, precipitation, and formation of soils complexes with other soil nutrients [4]. In order to compensate for this deficiency and sustain crop productivity, high doses of chemical P fertilizers are nowadays widely applied in agricultural soils [5]. The repeated use of chemical fertilizers at supra-optimum rates in modern agriculture is expensive [6] and has the potential to adversely affect the environment [7], soil microbial population [8]. The north-western region of Pakistan contains millions of tons of recoverable

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