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Maize plays a vital role in enhancing food security, particularly in regions facing agricultural challenges such as poor soil conditions, erratic rainfall, and limited access to resources. It can be advantageous for smallholder farmers in developing countries, where it can enhance productivity on limited land and under suboptimal soil conditions. One of the potential means for improving crop yield under suboptimal soil conditions, such as acidic soils, is the application of soil amendments. However, the combined effects of functionalized biochar (a pyrogenic carbon) and microbes on phosphorus (P) bioavailability and plant growth performance are still not well understood. This study investigates the optimization of transplanted maize growth in acidic soil through the application of rice husk biochar (RHB) that was oxidized with 10% hydrogen peroxide and inoculated with Pseudomonas aeruginosa, a phosphate-solubilizing bacterium. The oxidized biochar’s pH was adjusted to 6.2 to enhance its effectiveness in challenging soil conditions. Soil properties and maize performance were determined using a pot culture. Results showed that the combined use of 10% oxidized RHB and Pseudomonas aeruginosa significantly increased P availability and phosphatase enzyme activity by 435% and 418%, respectively. Additionally, 10% Oxidized RHB treatment, microbes treatment and combination of biochar and microbes treatment showed yield increment 52%, 51% and 313% respectively, demonstrating the effectiveness of the treatment in improving soil fertility and crop productivity. This improvement in yield might have occurred due to an increase in soil pH, P bioavailability, and a reduction in Al toxicity since there were significant positive relationships between yield and soil pH and available P and a negative relationship with available Al concentration. These findings underscore the potential of integrating oxidized biochar and beneficial microbes, Pseudomonas aeruginosa, to enhance crop performance in acidic soils.

This study was  investigated the P transformation in three soils gathered from different locations (Agricultural researches center in Tel Afar, Ain-Talawi and Sinu in Singar) in north of Iraq representing different gypsum content and land use [wheat (W), vegetable (V), uncultivated (Un)] after incubation period of (0, 5, 10, 30, 60, and 90) days. The soils were treated with 200 mg P kg-1 as superphosphate (S) or 30 g kg-1 soil manure as a cattle manure (A) or compost (p). The appropriate amounts of water were added to bring soil to estimated field capacity. After the specified time of each incubation period, sub-sample of soil analyzed for P, pH, EC and Ca. The results showed that P status affected by amendments and incubation periods. The soil which has more available P was the soil which treated with cattle manure. Generally, P was more available under (V) use compared to (W) use. After 90 days of incubation P solubility generally was higher than after 30 days. It appears from P solubility diagram that the best treatment was (A) which almost located between the two more soluble P compounds DCPD and DCP.

The traditional manure management strategy, based on crop N needs, results in accumulation of phosphorus (P) in soil due to the imbalance of N/P ratio between crop requirement and manure supply. This study was conducted from 2004 to 2013 to evaluate the effects of P-based liquid and solid swine manure (LMP and SMP, for P-based liquid and solid swine manure, respectively) application, in comparison with N-based application (LMN and SMN, for N-based liquid and solid swine manure, respectively), on crop yield and soil residual P under corn (Zea mays L.)–soybean (Glycine max L.) rotation in a Brookston clay loam soil of the Lake Erie basin, ON, Canada. Chemical fertilizer P (CFP) and non-P treatments were included as controls (CK). For liquid manure treatments, corn yield for LMN showed a lower annual corn yield (7.82 Mg ha−1) than LMP (9.36 Mg ha−1), and their differences were even statistically significant at p < 0.05 in some cropping years. The annual corn yield of LMP was also higher than those of SMP (7.45 Mg ha−1) and SMN (7.41 Mg ha−1), even the CFP (8.61 Mg ha−1), although the corresponding yield differences were not significant (p < 0.05) in some cropping years. For soybean, the plots with P application produced an average of 0.98 Mg ha−1 greater annual yields than CK. No significant differences were found between CFP and manure treatments. The annual corn yield of SMN was close to that of the CK (7.19 Mg ha−1). The grain P removal (GPR) of SMN (18.6 kg ha−1) for soybean was significantly higher than that of the other treatments. The above-ground-P uptake (AGPU) in SMN, for both corn and soybean, was significantly higher than that of the other five treatments. The soil test P (STP) presented clear stratification, concentrating in the top 30 cm soil depth after 10 years of application. The contents of STP with LMN and SMN increased from 7.1 mg P kg−1 to 12.4 and 45.5 mg P kg−1, respectively. The sum of STP mass (0–30 cm) with LMP (31.6 kg ha−1) was largely identical to that with CFP (30.1 kg ha−1); however, with SMN (173.7 kg ha−1), it was significantly higher than the rest of the treatments. Manure P source availability coefficients were averaged at 1.06 and 1.07 for LMP and SMP, respectively. The addition of phosphorus-based liquid or solid swine manure can overcome the drawback of traditional N-based applications by potentially reducing the adverse impact on water quality while sustaining crop agronomic production.

Phosphorus (P) availability is usually low in soils around the globe. Most soils have a deficiency of available P; if they are not fertilized, they will not be able to satisfy the P requirement of plants. P fertilization is generally recommended to manage soil P deficiency; however, the low efficacy of P fertilizers in acidic and in calcareous soils restricts P availability. Moreover, the overuse of P fertilizers is a cause of significant environmental concerns. However, the use of arbuscular mycorrhizal fungi (AMF), phosphate–solubilizing bacteria (PSB), and the addition of silicon (Si) are effective and economical ways to improve the availability and efficacy of P. In this review the contributions of Si, PSB, and AMF in improving the P availability is discussed. Based on what is known about them, the combined strategy of using Si along with AMF and PSB may be highly useful in improving the P availability and as a result, its uptake by plants compared to using either of them alone. A better understanding how the two microorganism groups and Si interact is crucial to preserving soil fertility and improving the economic and environmental sustainability of crop production in P deficient soils. This review summarizes and discusses the current knowledge concerning the interactions among AMF, PSB, and Si in enhancing P availability and its uptake by plants in sustainable agriculture.

Soil phosphorus (P) availability in lowland tropical rainforests influences the distribution and growth of tropical tree species. Determining the P-acquisition strategies of tropical tree species could therefore yield insight into patterns of tree β-diversity across edaphic gradients. In particular, the synthesis of root phosphatases is likely to be of significance given that organic P represents a large pool of potentially available P in tropical forest soils. It has also been suggested that a high root phosphatase activity in putative nitrogen (N) -fixing legumes might explain their high abundance in lowland neotropical forests under low P supply. Here, we measured phosphomonoesterase (PME) activity on the first three root orders of co-occurring tropical tree species differing in their N-fixation capacity, growing on soils of contrasting P availability in Panama. Our results show that root PME activity was higher on average in P-poor than in P-rich soils, but that local variation in PME activity among co-occurring species within a site was larger than that explained by differences in soil P across sites. Legumes expressed higher PME activity than nonlegumes, but nodulated legumes (i.e., actively fixing nitrogen) did not differ from legumes without nodules, indicating that PME activity is unrelated to N fixation. Finally, PME activity declined with increasing root order, but the magnitude of the decline varied markedly among species, highlighting the importance of classifying fine roots into functional groups prior to measuring root traits. Our results support the hypothesis that low-P promotes a high root PME activity, although the high local variation in this trait among co-occurring species points toward a high functional diversity in P-acquisition strategies within an individual community.

Despite that organic phosphorus (Po) is a source of bioavailable P during the early stage of soil development, it remains unclear whether P availability or organic carbon (C) mineralization is the main regulator of Po mineralization. In this study, the P availability (labile inorganic P, Pi) and the potential organic C mineralization (β-glucosidase activity) were investigated at the Hailuogou Chronosequence and a reference site (35–125 and ∼1400 years after glacier retreat, respectively) to decipher their relationships with the potential Po mineralization (acid and alkaline phosphomonoesterase activities). Labile Pi displayed no trend in the soil profile, whereas it was significantly higher at the reference site than the young sites. Enzyme activities decreased down the soil profile, but this trend weakened for specific activities (enzyme activity per microbial biomass C). Enzyme activities and specific activities displayed no trend with the succession stage. Potential Po mineralization was more related to potential organic C mineralization ( R 2  = 0.41–0.69, p  < 0.0001) than P availability ( R 2  = 0.05–0.09, p  ≤ 0.05). By increasing the specific activity of β-glucosidase, the microbial biomass C:P ratio decreased to reach the value of 8:1. Probably, the phosphate in the excess of microbial demand was released as the by-product of C mineralization. At the young sites of the chronosequence, the significant correlation between Po and C concentrations in the surface mineral horizon ( R 2  = 0.85, p  < 0.0001) suggested that the mineralizations of Po and organic C were linked to each other. The results suggested that the demand for C may drive the microbial mineralization of soil Po during the early stage of soil development, and the phosphate released by the Po mineralization may serve as a potential source of labile Pi for plants.

Soil chemical fumigation is an effective and popular method to increase agricultural productivity. However, the broad-spectrum bioactivity of fumigants causes harm to soil beneficial microorganisms involved in the soil phosphorous cycle, such as soil phosphorus solubilizing microorganisms (PSMs). We review the effects of soil chemical fumigation on soil phosphorus cycling, and the potential underlying mechanisms that ultimately lead to altered phosphorus availability for crops. These complex processes involve the highly diverse PSM community and a plethora of soil phosphorus forms. We discuss phosphatizing amendments aimed at counteracting the possible negative effects of fumigation on phosphorus availability, phosphorus use efficiency, and crop yields. We also emphasize distinguishing between the effects on soil phosphorus cycling caused by the chemical fumigants, and those caused by the fumigation process (e.g. plastic mulching). These are typically conflated in the literature; distinguishing them is critical for identifying appropriate amendments to remediate possible post-fumigation soil phosphorus deficiencies.

Phosphate-solubilizing bacteria represent a bioalternative in making soil-immobilized phosphorus (P) available to plants, and consequently improve agriculture sustainability and reduce nutrient pollution. In this study, we examined whether Rhizobium sp. B02 inoculation can affect the soil P fractions. Moreover, we investigated how inoculation influences the growth, physiological traits, and productivity of the maize crop. Field tests were carried out to evaluate the combined application of strain B02 and reduced doses of P fertilizer. Soil P fractionation was performed after crop harvesting, assessing the P dynamics. To study the plant response, samplings were carried out in three phenological stages—the vegetative stage of the 7 fully emerged leaves with leaf collars (V7), the vegetative stage of the tassel (VT), and the reproductive stage of physiological maturity (R6). Using 50% of P fertilizer recommended, the strain inoculation increased the labile inorganic P fraction by 14% compared to the control treatment at the same dose, indicating that it favored the Pi mobility. Under these same conditions in the V7 and VT phenological stages, the inoculation significantly improved shoot length (28 and 3%) and shoot dry weight (9.8 and 12%). B02 inoculation increased grain yield by 696 kg ha −1 using 50% of the recommended rate of P fertilizer, phenocopying the complete P fertilization treatment without inoculation. Therefore, Rhizobium sp. B02 inoculation replaced 50% of P fertilizer in maize and increased the soil P availability.

Crop straw retention is believed to effectively promote soil phosphorus (P) availability. However, little is known about how specific components of crop straw, such as cellulose and lignin, regulate soil P availability, which depends on several processes, including the reactions catalyzed by phosphomonoesterase activities. Of the genes encoding alkaline phosphomonoesterase, phoD are ubiquitous in soil. Here, we studied the effects of cellulose and lignin on soil P fractions and phoD-harboring bacterial community in P-deficient upland and paddy soils. In the upland soil, cellulose amendment significantly increased microbial P assimilation and decreased soil citrate-P and HCl-P fractions, suggesting that cellulose mediated the conversion of soil P fractions from the non-labile to the labile P pool (e.g., microbial P) via microbial enrichment. Lignin significantly increased soil Olsen-P content, but scarcely influenced P-related microbial parameters after incubation for 60 days. Therefore, lignin directly increased soil available P via competitive P adsorption by lignin functional groups, rather than by altering soil microbial processes. Compared to upland soil, a smaller effect of both cellulose and lignin on phoD gene abundance, alkaline phosphomonoesterase activity, and phoD-harboring bacterial community was observed in paddy soil, suggesting that the carbon inputs may be unable to promote organic P availability under oxygen-deficient conditions. Our results highlight the contrasting mechanisms of soil P availability regulation via cellulose or lignin in P-deficient soils.

Abstract PurposeFe-modified biochar could promote soil organic phosphorus (Po) mineralization and phosphorus (P) bioavailability; however, the role of biochar and Fe-modified biochar in driving the mineralization of Po by phoD-harboring bacteria in soil aggregates was less known, especially in saline-alkali paddy soil.MethodsA 5-year paddy field experiment was conducted in Yellow River Delta, in which four fertilization treatments were designed: no fertilization (Control), inorganic fertilizer (NPK), NPK + biochar (BC), and NPK + Fe-modified biochar (FeBC).ResultsCompared with NPK treatment, the proportion of macroaggregates in BC and FeBC treatments was significantly increased by 10.42% and 24.67%, respectively. And the mean weight diameter was also increased under biochar treatments. Redundancy analysis (RDA) indicated that oxalate-extractable Fe was a main factor in the stability of soil aggregates, which was significantly increased in FeBC treatment. Meanwhile, the relative abundance of phoD-harboring bacteria was increased in both BC and FeBC treatments, which was driven by the content of soil organic carbon. And the diversity of phoD-harboring bacteria was positively correlated with Po mineralization. Meanwhile, compared with NPK treatment, the activity of alkaline phosphatase in macroaggregate was increased by 39.1% in FeBC treatments, which also promoted the mineralization of soil Po.ConclusionsTherefore, biochar addition, especially Fe-modified biochar combined with mineral fertilization, was a better strategy in improving soil aggregate structure and promoting Po mineralization in saline-alkaline paddy soil.