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AbstractPhosphorus (P) deficiency is a frequent problem in calcareous soils of Pakistan because of P-fixation, which poses significant threats to pearl millet productivity. The use of P-solubilizing bacteria (PSB) is regarded as a promising approach for improving P-availability in soil-plant systems. However, it needs optimization of P application into the soil. Therefore, this 2-year field study was conducted to optimize P doses in combination with PSB (Bacillus sp. MN54) inoculation to improve phosphorus use efficiency (PUE), yield, economic returns, and grain quality of pearl millet. Five P doses, i.e. 0 (native soil P only - control), 30, 60, 90, and 120 kg P2O5 ha−1 combined with and without PSB inoculated seeds were used in the study. The application of 90 kg P2O5 ha−1 + seed inoculation with PSB improved the grain yield by 36.8% and 36.0% during 1st and 2nd year, respectively. The same treatment significantly improved the PUE, grain protein, zinc (Zn), and total grain P contents compared to the control treatment. Furthermore, the highest economic returns (1053.3 and 1050.5 $ ha−1) and benefit:cost ratio were observed under 90 kg P2O5 ha−1 + seed inoculation with PSB during both years. In conclusion, application of 90 kg P2O5 ha−1 combined with PSB seed inoculation is a pragmatic option to improve P uptake, grain yield, PUE, grain quality and economic returns of pearl millet grown on calcareous soils. [ABSTRACT FROM AUTHOR]

Soil legacy phosphorus (P) accumulated due to the long-term continuous application of P fertilizers in agricultural fields accumulated in the soil for years, as sparingly soluble forms. This can be made as a possible soil P source using P-activators. In this study, a laboratory incubation and a pot experiment were conducted to evaluate the potential of some P activators (Phosphorus solubilizing bacteria, phytase, humic acid, oxalic acid) in increasing the availability of residual phosphorus in calcareous soil. For the incubation experiment, the P activators were applied alone and in combination. Soil samples were analyzed at subsequent intervals for soil available P, alkaline phosphatase activity, and sequential P fractions. The results showed that phytase application with humic acid (HA) increased the available soil P (12.4 kg ha−1) and alkaline phosphatase activity (47.42 µg p-nitrophenol released g−1 soil hr−1) followed by phosphorus solubilizing Bacteria (PSB) with humic acid and PSB with phytase treatments. All treatments have a significant effect on different soil P-fractions. A greater reduction in calcium phosphate fraction was noted in phytase and humic acid application. The combined application of P-activators performed better than their sole application. The best three treatments selected from the laboratory incubated experiment were used for the pot experiment with maize, along with the different dosages of P fertilizer. The morphological parameters were observed on the 30th and 60th days of the maize crop. The results of plant height, chlorophyll index, and dry matter production showed that the application of phytase and HA with 100% recommended dose of P was statistically comparable with phytase and HA with 75% recommended dose of P. The findings have illustrated the extent of P release by different P activators in increasing the legacy P availability. The application of phytase and HA with 25% reduced dose of P fertilizers will promote the availability of legacy P in calcareous soils through solubilization. [ABSTRACT FROM AUTHOR]

Background and aims: Proteaceae are a prominent plant family in south-western Australia. Most Proteaceae are 'calcifuge', occurring exclusively on old phosphorus (P)-impoverished acidic soils, with a few 'soil-indifferent' species also found on young P-richer calcareous soils. Calcium (Ca)-enhanced P toxicity explains the calcifuge habit of Proteaceae. However, previous research has so far been focused exclusively on the roles of Ca and P in determining Proteaceae distribution, and consequently there is little knowledge on how other soil-based strategies influence this distribution. We aimed to study the effects of young calcareous soils on four soil-grown Proteaceae and assess differences between calcifuge and soil-indifferent Proteaceae to better understand their natural distribution. Methods: Two calcifuge and two soil-indifferent Proteaceae from south-western Australia were grown in six contrasting soils, including young calcareous, and old acidic soils. Results: When grown in calcareous soils all species showed root growth inhibition, micronutrient deficiency, Ca-enhanced P toxicity, and negative impacts on physiology. Calcifuge species were more sensitive to calcareous soils than soil-indifferent ones, although this varied between genera. Soil-indifferent species tended to produce more cluster roots, release more carboxylates per root mass, and allocate less Ca to their leaves, compared with calcifuges; they also had smaller seeds and were less sensitive to Ca-enhanced P toxicity. Conclusion: We surmise that a combination of these traits allows soil-indifferent species to tolerate calcareous soils. This study provides insight into how Proteaceae respond to young calcareous soils and how this influences their distribution. [ABSTRACT FROM AUTHOR]

Background: Over the years, the excessive P fertilizer application to crop fields resulted in the build up of insoluble phosphorus pool in soil known as legacy phosphorus. This represents a vast and largely untapped resource in soil. The current study was conducted to evaluate the potential of some P activators (Phosphorus solubilising bacteria, phytase, humic acid, farmyard manure) on increasing the plant availability of legacy P in calcareous soil. Methods: A field experiment was conducted with maize hybrid COH(M) 6. The P activators were combined and applied along with the different doses of P fertilizer (100%, 75% and 50% soil test dose of single super phosphate). Result: Farmyard Manure (FYM) application with Humic acid (HA) showed the increased Olsen P under 100% and 75% of P application. The phosphorus activation response of FYM+HA applied plots showed a higher value than other treatments. The maize yield and P uptake obtained with FYM and HA were statistically comparable at 100% and 75% soil test dose of P. The findings have illustrated that even the reduced amount of P fertilizer application can support the crop growth due to the release of legacy P if they are applied along with P-activators such as FYM and HA. [ABSTRACT FROM AUTHOR]

Despite some evidence in greenhouse experiments, the benefits of Bacillus subtilis and Trichoderma asperellum on nutrients uptake by plants under field conditions are unknown. This work aims to study the effect of these microbial inoculants on durum wheat nutrition and yield under Mediterranean conditions where soils may lead to micronutrients and phosphorus deficiencies and where drought may promote low use efficiencies of applied fertilizers. To this end, three experiments were performed in two growing seasons. B. subtilis increased the uptake of nitrogen, phosphorus, and manganese relative to other treatments in the experiment carried out in the first growing season involving two experimental sites. The increased phosphorus uptake was attributed to the increased activity of alkaline phosphatase. In this first season, T. asperellum increased acid phosphatase activity without effect on P uptake and decreased the P to Zn molar ratio in grains, thus improving grain quality for human consumption. In the second season, the effects of microbial inoculants were less evident possibly due to favourable environmental conditions for crops (higher water availability) or phosphate fertilization. Results evidenced that B. subtilis can be effective improving the development and nutrient uptake of durum wheat under more stressful conditions, such as drought stress. [ABSTRACT FROM AUTHOR]

Phosphorus (P) deficiencies are widespread in calcareous soils. The poor availability of nitrogen (N) and P in soils often restricts crop growth. However, the effects of P addition on plant growth and plant nutrient transport changes during the establishment of Leymus chinensis fields in Xinjiang are not clear. We investigated the responses of Leymus chinensis biomass and nutrient absorption and utilization to changes in soil N and P by adding P (0, 15.3, 30.6, and 45.9 kg P ha−1 year−1) with basally applied N fertilizer (150 kg N ha−1 year−1). The results showed that (a) Principal component analysis (PCA) of biomass, nutrient accumulation, soil available P, and soil available N during the different periods of Leymus chinensis growth showed that their cumulative contributions during the jointing and harvest periods reached 95.4% and 88%, respectively. (b) Phosphorus use efficiency (PUE) increased with the increase of P fertilizer gradient and then decreased and the maximum PUE was 13.14% under moderate P addition. The accumulation of biomass and nutrients in Leymus chinensis can be effectively improved by the addition of P fertilizer at 30.6 kg ha−1. Different P additions either moderately promoted or excessively inhibited Leymus chinensis growth and nutrient utilization. [ABSTRACT FROM AUTHOR]

On a P-poor, calcareous soil, three upland cotton (Gossypium hirsutum L.) cultivars (ST 402, ST 405, Zeta 2) were tested for 2 years under three P rates (0, 13.1, 26.2 kg P ha-1). Leaf traits (SPAD values; specific leaf area, SLA; carbon isotope discrimination, Δ; 15Nnatural abundance, δ15N) and elements (N, P, K, C, Na, Zn) along with arbuscular mycorrhizal (AM) colonisation were measured at first open flower, full bloom and first open boll stages. Phosphorus addition decreased yield, but had no effect on fibre quality, a response attributed to P-induced Zn deficiency, previously reported for cereals. The best-performing cv., ST 405, had high SPAD and SLA, but the lowest P, N and Zn concentrations, an indication of cultivar's high use efficiency for these nutrients. At full bloom, SPAD was lowest, while SLA was highest. AM increased gradually with growth stages, while N, P, K and Zn concentrations showed an opposite trend, possibly due to a dilution effect. On Mediterranean calcareous soils, P fertilisation should take into account soil Zn levels in order to avoid P-Zn antagonistic relationships, which could impact negatively on yield. [ABSTRACT FROM AUTHOR]

In order for plants to perform well in nutrient-deficient calcareous soils, they have an efficient adaptive technique of root exudate secretion, which contains low molecular weight organic acids. They enhance nutrient release and thereby increase the nutrient availability in calcareous soils. The present study aimed to investigate the effect of concentration and time of incubation of low molecular weight organic acids on P solubilization from calcareous soils collected from various locations of Coimbatore district with varying levels of calcareousness. An incubation experiment was conducted with five calcareous soils with varying levels of free CaCO3 viz., (1, 7.5, 12.5, 17.5 & 21.5%) by incubating with seven different concentrations (0, 20, 40, 60, 80 & 100 mM) of four organic (citric, malic, oxalic and acetic acid) and two amino acids (glycine and lysine) for nine incubation time intervals (5, 10, 20, 30, 60, 120, 240, 960 & 1440 mins) on a factorial experiment based on completely randomized design (CRD). Available P was analyzed to find the solubilization efficiency of various organic and amino acids. The organic acids were more efficient when compared to amino acids in P solubilization, especially citric acid followed by oxalic and malic acids, at 100 mM concentration incubated for 1440 mins. Also, the solubilization increased with increasing concentration and incubation time, irrespective of the soil calcareousness, but the magnitude of phosphorus extraction decreased with increasing soil calcareousness. Incubating the calcareous soils with 100 mM of citric acid for 1440 min solubilized more amount of phosphorus. Hence it can be concluded that addition of 100 mM citric acid will influence the phosphorus release even from highly calcareous soils. [ABSTRACT FROM AUTHOR]

This study has been done to see the impact of phosphorus (P) on the concentration of cadmium (Cd) chemical fractions in two sorts of calcareous soils within the Fars province in Iran. Because of these interactions, we looked at the influence of phosphorus on cadmium fractions. Variables were three levels of Cd (0.0, 30.0 and 60.0 mg kg-1 of soil from CdSO4.8H2O), three levels of p (0.0, 50.0 and 100.0mg kg-1 of soil from Ca (H2PO4)2.H2O, three levels Incubation time (2, 4 and 8 weeks) and two sorts of soil (clay and sandy clay loam). The randomized completed block design (RCBD) was used for this research. After 2, 4 and 8 weeks of treatments, the sequential extraction procedure was done to determine cadmium concentration in WsEx (Water Soluble and Exchangeable), Sorb (EDTA extractable), MnOx (Manganese Oxides), Car (Carbonate), OM (Organic matter), AFeOx (Amorphous Iron Oxides), CFeOx (Crystaline Fe oxides) and Res (Residual) fractions. The results showed that 69.0 to 71.0% of the added Cd was removed within the WsEx, Sorb and MnOx fractions. Cadmium concentration in Sorb, OM and Res fraction was higher within clay soil while cadmium concentration within WsEx and Car fractions were higher within sandy clay loam soil. Adding P as monocalcium phosphate reduced cadmium concentration within WsEx and Sorb fractions while increased Car, OM and Res fractions. The presence of phosphorus reduces the concentration of Cd in those forms that are easily released into soil solution (WsEx and Sorb) from where they'll be absorbed by plants and thus decrease cadmium uptake by plants. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the possibility of three phosphate-releasing bacteria (PSB) increasing the bioavailability of phosphorus (P) in a calcareous soil fertilized with single superphosphate (SSP) and its absorption by the barley (Hordeum vulgare L.) variety Giza 123. The pot experiment, a trial using calcareous soil, was conducted at the experimental farm located in Borg Al-Arab. The inoculated and uninoculated barley seeds were sown on December 1st, 2020 for 60 days. The bacterial isolates were Enterobacter aerogenes (ENPSB 1), Pantoea sp. (ENPSB 2), Enterobacter sp. (ENPSB 3), and their mixture in the ratio (1:1:1) was tested in combination with four levels of single super phosphate SSP (0%, 50%, 75%, and 100% of the recommended dosage for barley (150 kg/Fed.). In a randomized full-block design, each treatment included three replicates. Treatments and their interactions significantly affected the plant's dry weight, and bioavailable P in the soil. When these PSB strains were inoculated together (in a mixed culture), they were able to operate synergistically and were responsible for an increase in plant growth, P absorption, and accessible P in the soil when compared to a single inoculation. Also, plants inoculated with the different PSB isolates had a significant impact on total amino acids as compared with un-inoculated plants. Accordingly, we can reduce SSP application to 75% of the recommended dosage + inoculation with a mixed culture of these PSB to have a major impact on barley growth more than the application of 100% SSP of the recommended dosage without PSB inoculation to maintain environmental and soil health. [ABSTRACT FROM AUTHOR]

Phosphorus (P) unavailability and lack of organic matter in calcareous soils under semiarid climates are major reasons for low maize productivity grown in these conditions. The hypothesis was tested that integrated use of biofertilizers (BF) and P-sources could improve dry matter (DM) partitioning and yield of hybrid maize (CS-200) in the semiarid climate of Peshawar. A field trial was conducted to investigate the impact of two BF-sources, and eight organic and inorganic P-sources combinations (P) on DM partitioning, yield, and yield components of hybrid maize. The research was conducted at the Agronomy Research Farm of The University of Agriculture Peshawar, during summer 2017. Experiment was laid out in randomized complete block design with split plot arrangement, using four replications. Combination of inorganic-P [single super phosphate (SSP) and rock phosphate (RP)] and organic-P (compost and biochar) sources was used as factor-A, and BF [Phosphate Solubilizing Bacteria (PSB) and Trichoderma (TD)] as factor-B. Phosphorus was applied at the uniform rate of 120 kg ha−1 from different sources (08 treatments). The results revealed that P sources and BF had significantly affected all parameters under study. As compared with TD, application of PSB had significantly increased total plant dry weight (TDW), leaf dry weight (LDW), cob dry weight (CDW), husks dry weigh (HDW), stem dry weight (SDW), and roots dry weight (RDW) at both silking and physiological maturity. The highest ear length (EL), more number of grains per row (NGPR), number of rows per ear (NRPE), number of grains per ear (NGPE), heavy thousand grains weight (TGW), higher total biological yield above ground (BY), grain yield (GY), stover yield (SY), harvest index (HI), and shelling percentage (SP) were obtained with application of PSB over TD. As compared with sole biochar (T3), application of organic-P in the form of sole compost (T4) had significantly increased plant TDW (188.8 g & 312.9 g), LDW (34.3 g & 29.0 g), CDW (41.9 g & 176.1 g), HDW (25.9 g & 21.7 g), SDW (85.4 g & 65.6 g), RDW (26.9 g & 15.2 g) at silking and physiological maturity, respectively. Significantly higher yields (GY, SY, BY, HI & SP) and yield components (EL, NGPE, NRPE & TGW) were recorded with sole compost application (T4) or combined application of compost + SSP (T6). Among all possible interactions of BF and treatments (2 x 8 = 16 combinations), the integrated use of PSB x T4, and PSB x T6 was found to the most beneficial combinations for improving DM partitioning, yield and yield components of hybrid maize in the study area. Interestingly, the integrated use of BF with RP (T7 & T8) had more positive effect on DM partitioning, yield and yield components of hybrid maize than sole application of RP (T2). [ABSTRACT FROM AUTHOR]

The long-term application of chemical fertilisers in calcareous soil causes the stable P in soil to accumulate and not be effectively utilised. In this study, whether acidic compost tea (CT) could increase the available P in calcareous soil was evaluated through a pot experiment. The P forms of the samples were analysed using Hedley sequential P fractionation. CT had significant effects on different soil P fractions and P uptake (p < 0.05). Compared with organic fertiliser (OF), acidic CT increased the availability of H2O-P and NaHCO3-P by 15.9% and 12.6%, respectively, it mainly comes from the dissolution of HCl-P and residue-P. CT also promoted the growth and yield of cotton and significantly increased P use efficiency by 13.8% and 31.6% (p < 0.05), respectively, compared with OF, because the H+ in CT reduced the pH of the calcareous soil, promoted the dissolution of stable P in soil, and reduced the fixation of P from the fertiliser. However, the organic matter in CT did not contribute much to the desorption of P. These findings provide a new idea for the activation and utilisation of P in calcareous soil. [ABSTRACT FROM AUTHOR]

Improved management and breeding increased maize (Zea mays L.) yields over the last century, but nutritional efficiency was usually not the focus. This study investigates whether old and recently released flint and dent maize seedlings vary in the phosphorus (P) acquisition and utilization. P use efficiency (PUE) and related traits were measured and compared at two P levels in a calcareous soil. PUE and P acquisition efficiency (PAE) from founder flints to elite flints declined over the last decades. This was associated with smaller root systems, reduced ability to exploit external P, decreased rhizosphere pH and shorter root hairs in low P. Comparing flints with doubled haploid landraces (DH_LR), old and elite dents and hybrids revealed that dents started to acquire exogenous P earlier and had improved PUE. Most DH_LRs had similar PUE as elite flints. When evaluating root traits associated with P efficiency, seed P was also critical, and it is important to stack different root traits to optimize PUE, P utilization efficiency (PUtE) and PAE in breeding programmes. The root hair length, the ability to acidify the rhizosphere and the root diameter in flint and dent pools may be utilized to improve P use in maize germplasm. [ABSTRACT FROM AUTHOR]

Novel adsorbents that remove P from contaminated waters can be potentially used as slow release P-fertilizers. In this study, Mg-Al layered double hydroxide (Mg-Al-LDH) and Mg-Al-LDH functionalized apple wood biochar and hydrochar were prepared to remove phosphate from aqueous solutions and then P-loaded LDH-biochar/hydrochar composites used as fertilizers for maize production in calcareous soils under controlled conditions. After five successive desorption cycles, the LDH, LDH-biochar, and LDH-hydrochar desorbed 18, 22, and 27% of adsorbed-P into a 0.03 M KCl solution, respectively, while, these adsorbents desorbed 52, 63, and 66% of adsorbed-P into a 0.1 M Na2CO3 solution, respectively. Additionally, increasing solution pH from 3.0 to 10 increased P desorption. The results revealed that the P-loaded LDH-biochar and LDH-hydrochar significantly increased available-P, maize shoot and root dry matters, and P uptake as compared with control. The integration of monocalcium phosphate fertilizer with ‎biochar, hydrochar, LDH-biochar, and LDH-hydrochar increased available-P, ‎maize shoot and root dry matters, and P uptake; while P integration with P-loaded LDH-biochar/hydrochar decreased shoot dry matter. Therefore, the P-loaded LDH-biochar/hydrochar can be added to soil as P-fertilizers without any chemical P-fertilizer. Application of biochar, hydrochar, and LDH-biochar/hydrochar accompany with chemical P-fertilizers is recommended to increase available-P and maize growth. [ABSTRACT FROM AUTHOR]

Phosphorus is a major plant nutrient obtained from non-renewable phosphate rock, which is not much available in India. Over and above in this its recovery efficiency in crops hardly exceeds 15-20 per cent. Utmost care is therefore required in its use. Phosphorus applied to soil gets fixed by the formation of insoluble reaction products by reacting with Fe and Al in acid soils and with calcium in saline and alkaline soils. Two techniques used for identification of reaction products are X-ray diffraction and solubility product principle. In addition, phosphate ions are also held on Fe and Al hydroxides by anion exchange. The reaction products identified are variscite and strengite minerals in acid soils and dicalcium phosphate and hydroxy apatite in calcareous soils. Methods to increase phosphorus recovery by crops include: 1) addition of organic matter to soils; 2) addition of sulphur to compost or to ground rock phosphate or directly to soil and use of phosphorus solubilising organisms including VAM/AM along with ground rock phosphate. [ABSTRACT FROM AUTHOR]

To study the effect of applying different phosphorus solubilizers on the insoluble phosphorus in the soil, so as to improve the utilization rate of the insoluble phosphorus. [Method] The indoor soil culture experiment method was used to study the activation effect of different phosphorus solubilizers on the insoluble phosphorus in calcareous soil. [Results] γ-polyglutamic acid treatment can increase the available phosphorus content of the soil, and the highest net increase of the available phosphorus content in the soil treated with phosphate rock powder and γ-polyglutamic acid compared with the control (only treated with phosphate rock powder) 60.10%. [Conclusion] γ-polyglutamic acid can promote the conversion of insoluble phosphorus to available phosphorus in the soil. [ABSTRACT FROM AUTHOR]

In this research, the potential application of phosphate containing zinc-aluminum-layered double hydroxide (Zn-Al-P-LDH) to enhance the availability of P and Zn compared to triple superphosphate (TSP) in a calcareous soil was investigated. First, soil availability of P and Zn at two P levels (18 and 45 mg kg–1) of Zn-Al-P-LDH and TSP were compared in a 70-day incubation procedure. Second, a pot experiment was performed to study the effect of these treatments on growth and on P and Zn uptake by maize. Incubation experiment showed that, in contrast to the TSP, addition of both P levels of LDH increased P availability during the incubation period. Furthermore, the soil-available Zn in LDH was significantly enhanced compared to TSP and control treatments. This observation suggested that ion exchange accompanied by partial dissolution mechanism possibility happened for studied LDH. However, the values of shoot dry weight and leaves P uptake were significantly higher for LDH than TSP treatment just at 18 mg P kg-1 level probably due to its effect on adequate Zn supply along with P. Therefore, Zn-Al-P-LDH might be a candidate as dual-purpose fertilizer if its limitations in terms of high Zn content to be overcome. [ABSTRACT FROM AUTHOR]

Background: P deficiency is very common in alkaline - calcareous soil. Therefore, application of foliar-absorbed fertilizers may be an effective strategy to overcome the low bioavailability of phosphorus in soil, by improving phosphorus use efficiency and reduced nutrients loses. Methods: A field experiment was carried out in 2006-07 growing season at El-Menia (southeastern Algeria) to evaluated the effect of two foliar P (agriphos and leader-start) and three soil P (TSP P 46, Fosfactyl NP 3:22 and NPKs 8:36:13,5+15) on yield and P use efficiency of durum wheat crop Triticum durum Desf. var. Carioca and on available P and total P in soil. Result: Data showed that significant effect of soil P fertilizer on grain yield components (ears m-2, grains ear-1 and the 1000 grains weight), grain P use efficiency and available P in soil. The best values were recorded by NPKs fertilizer, but no differences were observed for these parameters among foliar fertilizer sources. [ABSTRACT FROM AUTHOR]

Non-renewable sources of phosphorus (P) are running out, so it is necessary to recover P from secondary recyclable materials. This study aims to recover P from domestic sewage sludge as Leo/MAP (Leonardite/magnesium ammonium phosphate) composites and use them as phosphorus fertilizer. The characteristics of Leo/MAP composites, solubility, and kinetic of P-release from them were evaluated. The properties of composites were determined by using XRF (X-ray fluorescence) spectroscopy, as well as structural analysis by using SEM.(Scanning electron microscopy) In addition, the effect of Leo/MAP composites was investigated on the responses of the Moldavian Balm (Dracocephalum Moldavica) under greenhouse conditions compared with traditional P-fertilization (TSP (Triple-superphosphates)) – and unfertilized check in terms of morphological characteristics, and concentration of nutrients (P, Mg, and N) in a calcareous soil. Microscopic images of manufactured composites showed they are free of PO (Parasitic ova) and the presence of FC (Fecal coliforms) in the samples was negative. The results showed that P Recovery (%) from domestic sewage sludge increased by application of leonardite, and the solubility and the dissolution rate of P, N, and Mg from composites in HCl (0.5 M) and citric acid (20 g/L) are more than that in water. The kinetic of P release from composites was better fitted the Korsmeyer-peppas equation (R2 = 0.96–0.99) in water, and to the first-order equation (R2 = 0.87–0.98) in citric acid and HCl solutions. The n value of the Korsmeyer-peppas model showed that the mechanism of P release from the composites is based on the Fickian-diffusion (n < 0.45). The highest positive impact of P-fertilization on morphological characteristics, and concentration of nutrients in Moldavian Balm plants were as follows: L 75 /MAP > L 50 /MAP > L 25 /MAP > L 0 /MAP. Therefore Leo/MAP composites, especially with a high amount of leonardite, are applicable to increase the growth of Moldavian Balm in a calcareous soil that is one of the important medical plants with its unique characteristic for human's health. [Display omitted] • In alkaline soil, leonardite can promote the availability of nutrients in MAP. • Solubility of nutrients and kinetic of P release from struvite increased in the presence of leonardite, especially in high amount. • Leonardite/struvite compounds can be utilized as a slow-release phosphorus fertilizer in a calcareous soil. • Leonardite/struvite composites especially with high amount of leonardite (L 75 /MAP) were more effective for increasing growth parameters of Moldavian Balm than commercial P-fertilization (TSP). [ABSTRACT FROM AUTHOR]

Application of phosphorus (P) fertilizer has achieved a remarkable increase in yield but has also resulted in decreased zinc (Zn) concentration and its bioavailability in cereal grains. Selecting, breeding, and understanding the mechanism for wheat cultivars with high-yield and high-grain Zn under P application is urgent and difficult, with the purpose of alleviating P-Zn antagonism and solving Zn malnutrition globally. In a five-year field experiment on the southern Loess Plateau, China, selected high-yield wheat cultivars with contrasting grain Zn concentrations were assessed for rhizosphere Zn activation, root Zn acquisition, and Zn translocation among plant parts at the key growth stages under different P fertilization rates. Results showed that although the grain Zn concentration decreased with P application, it decreased less and still remained around 49–65 mg/kg in the grain of high Zn (H Zn) cultivars. This was 58–72% higher than that of the low Zn (L Zn) cultivars on soil with 2.7 mg/kg Olsen-P and 0.55 mg/kg DTPA-Zn due to 32.9–55.4% higher shoot Zn uptake in H Zn cultivars at harvest. P application enhanced the rhizosphere Zn activation of H Zn cultivars by 21.6% higher than that of L Zn cultivars at the jointing stage. However, P application inhibited the root Zn acquisition of both types of cultivars, except for that of the H Zn cultivars at the anthesis. The Zn translocation from root to shoot was remarkably enhanced at the grain-filling stage, but much more for H Zn cultivars with P application, with the transfer factor being 154% for H Zn cultivars and 7.9% for L Zn cultivars, respectively. Therefore, H Zn cultivars alleviated the P-Zn antagonism and achieved higher grain Zn concentration than the recommended target of 40–60 mg/kg, by maintaining higher rhizosphere Zn activation at the jointing stage, stable high Zn acquisition at the anthesis, and higher Zn translocation capacity from root to shoot during the grain-filling stage. Breeding and selecting cultivars with excellent acquisition performance and translocation capacity for Zn, accompanied by relatively lower soil available P and reasonable P application, may be an applicable Zn biofortification strategy for wheat and other cereals, overcoming the P-Zn antagonism. • High Zn cultivars achieved higher grain Zn in calcareous soils due to increased Zn uptake. • High Zn cultivars activated more Zn in the rhizosphere soil, particularly during the jointing stage with P application. • Root Zn acquisition of high Zn cultivars was unaffected at key growth stages with P application. • High Zn cultivars exhibited enhanced Zn translocation from roots to shoots during the filling stage with P application. [ABSTRACT FROM AUTHOR]

This study assessed the feasibility of struvite formation as a sustainable alternative for increasing the availability of phosphorus by applying a coated fertilizer. Diammonium phosphate fertilizer granules were coated with sepiolite-chitosan nanocomposites (SCF) to increase the use efficiency of phosphate fertilizer. The phosphorus uses efficiency of SCFs was studied under greenhouse conditions using Zea mays (maize) as the test plant and an efficiency improvement were observed. The phosphorus uptake as the result of available phosphorus increased, when fertilizing with the coated phosphate fertilizers. Suspensions of different-coated fertilizer treatments were prepared in 3 pH levels (6,7,8) and the chemical speciation was assessed by Visual MINTEQ 3.1. Precipitation and dissolution reactions were considered as the struvite formation mechanism. Also, the formation of struvite in a calcareous soil was evaluated in three incubation periods by X-ray diffraction (XRD) technique. The XRD patterns showed the peaks of struvite, while the peak of sepiolite decreased gradually with increasing incubation time that could be explained by the transformation of this mineral to amorphous fibrous silica. Energy Dispersive X-ray (EDX) analyses also showed diffusion of phosphorus into the coating region, probably forming metastable magnesium phosphate that can facilitate the movement of P aside from the fertilizer granule toward the soil matrix. [ABSTRACT FROM AUTHOR]

Increasingly, phosphorus (P) fertilizer is being applied in Inner Mongolia of China to overcome the problem of insolubility of phosphorus in calcareous soil and meet the growth demand of potato plants. As a result, phosphorus use efficiency (PUE) in potatoes decreases continually. In this four-year study in sandy soils, drip fertigating potatoes with phosphorus during the growth season improved phosphorus uptake, plant growth, tuber yield, and PUE. Results show that relative to a single phosphorus application, using a split phosphorus application regime through drip irrigation significantly increased the leaf area index (LAI) and phosphorus uptake rate in the mid and late growth stages of potatoes, and enhanced potato yield and PUE. We concluded that split phosphorus application has the potential to benefit sustainable potato production in Inner Mongolia of China. [ABSTRACT FROM AUTHOR]

China's urban sludge production is huge. The harmless and resource-based disposal of sludge is imminent. Agricultural use is an effective way to dispose sludge after its harmless treatment. Calcareous soil is one of the soil types widely distributed in arid and semi-arid areas of China. The purpose of this study was to clarify the impact of sludge on nutrient status and fertility characteristics of calcareous soil by continuously adding sludge on calcareous soil and to explore the critical value of phosphorus leaching from calcareous soil by adding sludge, so as to provide support to the rational application of sludge in this kind of soil. The typical calcareous soil in the north of China was selected as the object of this study, and the added amount of composted sludge was in accordance with the sludge application amount specified in the control standard for pollutants in agricultural sludge (GB4284-2018). The five treatments of sludge addition amount were designed: 0 t/hm²(Control), 3.75 t/hm²(H1), 7.50 t/hm²(H2), 37.5 t/hm²(H3), 75.0 t/hm²(H4). The pot experiment of two years' continuous planting of winter wheat and summer maize was carried out to analyze the annual and seasonal changes of soil nutrients after adding different levels of composted sludge. The integrated fertility index was determined by Nemero index method according to the relationship between soil available phosphorus Olsen-P and soluble phosphorus CaCl2-P. The relationship between sludge addition and phosphorus leaching critical value was determined. The results showed that the pH values of calcareous soil decreased with the addition of sludge, but the content of soil organic matter (OM), total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), available phosphorus (Olsen-P), available potassium (AK) and soil integrated fertility index (IFI) increased with the increase of sludge addition. During the experiment, the content of soil nutrient in maize season was lower than that in wheat season when the sludge addition was the same in the same production season, and the nutrient content increased with the increase of sludge application years. There was a significant (P<0.05) or extremely significant (P<0.01) positive correlation between the nutrient content and the cumulative application amount of sludge. When the amount of sludge added in each growing season was more than or equal to 37.5 t/hm², the soil nutrient contents of treatments were significantly different from those of control treatments (P<0.05). The phosphorus leaching thresholds calculated by the above method was 28.57 mg/kg in calcareous soils. At this time, the amount of sludge application in the field was 61.39 t/hm². The addition of sludge improved the nutrient and fertility status of calcareous soil, and attention should be paid to the risk of soil acidification and phosphorus leaching caused by excessive application of sludge. [ABSTRACT FROM AUTHOR]

Little is known about the occurrence of phosphorus (P) acquisition processes in the field, especially for faba bean (Vicia faba L.) in calcareous soils. We sampled soil, rhizosphere and plant materials in 12 calcareous field sites in Algeria and performed physicochemical analysis during two growing seasons. Both proton exudation and root exploration increased in P-deficient soils as compared to P-sufficient soils. Inhibition of nitrogen (N) fixation and rhizosphere alkalization were observed in N-rich soils. We also found that calcium (Ca) concentrations in both shoots and roots significantly increased with P-deficiency. The same trend, although less significant, was observed with respect to Ca uptake. These field observations suggested that acidifying roots acquired P from dissolving Ca-P minerals. The concomitant increase of the ratio Ca/P uptake should further enhance their dissolution. Other rhizosphere processes such as the mineralization of organic P should control P acquisition as alkalization occurred in the root zone in response to the inhibition of N fixation. In conclusion, P-acquisition processes in the field were consistent with previous findings made at the laboratory. In addition, the variety of faba bean cultivated by local farmers appeared relatively well adapted to field conditions thanks to the deployment of rhizosphere processes. [ABSTRACT FROM AUTHOR]

Because of the high pH of the soil in semiarid regions, phosphorus adsorption is unfavorable. So, considerable amounts of phosphorus fertilizers are used annually, where this fertilizer may affect the plant residues' decomposition. To examine the interaction effects of nitrogen and phosphorus on nitrogen mineralization in calcareous soil, a factorial experiment was performed in a completely randomized design with three replications. The first factor consisted of various C:N ratios (20, 40, and 60 or three levels of nitrogen N1:0, N2:11, and N3:43 kg N ha−1, respectively) and the second factor consisted of various C:P ratios (87, 174, and 260 or three levels of phosphorus P1:0, P2:12, and P3:45 kg P ha−1, respectively), under incubation conditions. The results indicated that the cumulative mineral nitrogen content in all treatments, except for N1P2 and N1P3 treatments, started from a positive amount and remained positive until the end of the incubation period. The highest amount of cumulative mineral nitrogen among treatments was related to N3P1 treatment, while the lowest was associated with N2P3 treatment. Mineralization of nitrogen during 60 d of incubation was the dominant phenomenon, except for the N1P2 and N1P3 treatments which remained in the organic phase. The effect of phosphorus on the cumulative mineralization of nitrogen was significant. With increasing the amount of phosphorus, the total inorganic nitrogen diminished. Nitrogen release begins earlier with lower C:N ratios, and therefore the available nitrogen can be released more quickly to the plant. It is generally concluded that, in calcareous soil, the use of nitrogen fertilizer to adjust C:N ratio and to improve the mineralization of wheat residues will be a suitable option. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted to study the interaction effects of phosphorus and copper on wheat. The soils used were calcareous loamy sand (ls) and non calcareous sandy loam (sl). Four levels of Cu (0, 5, 10 and 20 mg Cu kg−1 soil) and six levels of P (0, 25, 50, 100, 200 and 400 mg P kg−1 soil) were applied in all possible combinations with three replications. Soil pH decreased with Cu application while Olsen P increased with P application in both soils. Growth and yield of wheat improved significantly with graded levels of applied P. However, when any level of P was combined with 20 mg Cu kg−1 soil, severe iron chlorosis of leaves, a drastic reduction in growth and chlorophyll content was observed in calcareous ls only. The results indicated that it was Cu and not P that induced Fe deficiency in wheat grown in alkaline calcareous soil and the Cu requirement of the crop seemed to be much lower in the calcareous ls. Root dry matter, grain and straw yield decreased with increasing levels of applied Cu in ls but in sl maximum increase of 62.5, 74.3 and 63.7 per cent in root, grain and straw yield was observed with a combined application of 400 mg P and 5 mg Cu kg−1 soil over control. Accumulation of Cu in roots decreased the Fe absorption by roots which indicated that Fe chlorosis of wheat leaves is expected when Cu: Fe concentration ratio in root is > 0.30. [ABSTRACT FROM AUTHOR]

Aim: Our aim was to quantify the extent to which nutrient pollution explains arbuscular mycorrhizal fungal community richness and composition. Location: Europe. Time period: 2014–2016. Major taxa studied: Arbuscular mycorrhizal fungi. Methods: We sampled soils of calcareous and acidic grasslands and roots of 34 host plant species across a large geographical gradient of atmospheric nitrogen deposition and soil phosphorus availability. Furthermore, we performed an independent pairwise comparison between fertilized and unfertilized grasslands in Belgium and Iceland to compare results. Results: We found that nitrogen deposition had a significant negative relationship to arbuscular mycorrhizal fungal richness, with a negative community threshold of 7.7 kg N/ha/year corresponding to the greatest reduction in operational taxonomic units. Additionally, we found that soil phosphorus had a significant negative relationship to mycorrhizal fungal richness. Main conclusions: Our results highlight the necessity to revisit the critical loads of atmospheric nitrogen deposition used in European environmental policy, currently set at 10–15 kg N/ha/year. Importantly, our observed threshold of 7.7 kg N/ha/year does not correspond to a critical load below which there is no environmental harm, because the least negative changes in arbuscular mycorrhizal fungal communities were observed at < 5 kg N/ha/year. Therefore, to avoid compromising the policy tenet of no environmental harm with respect to grassland mycorrhizal fungi, areas of zero tolerance to nitrogen pollution should be delimited. Our results also indicate that environmental policy biased towards reducing nitrogen pollution alone will fail to preserve mycorrhizal biodiversity in European grasslands. We advocate increased policy attention to avoid phosphorus enrichment, particularly through agricultural fertilization. Here too, areas of zero phosphorus input, ideally set in the currently unpolluted (or least polluted) areas, seem key for effective environmental policy, because elevated levels of soil phosphorus after phosphorus fertilization are known to be extremely persistent. [ABSTRACT FROM AUTHOR]

Phosphorus (P) unavailability and lack of organic matter in the soils under semiarid climates are the two major constraints that negatively influence dry matter partitioning and yield in maize. Three field experiments were conducted to investigate the impact of phosphorus, organic sources and phosphate solubilizing bacteria (PSB) on dry matter partitioning (DMP) of maize during summer 2014 and 2015. The experiments were carried out at Agronomy Research Farm, The University of Agriculture Peshawar. The results revealed that application of P at the rate of 75–100 kg P ha−1 for open pollinated variety and 120 kg P ha−1 for hybrid maize was more beneficial in terms of higher DMP and accumulation. Application of compost at sowing time along with poultry manure (5 tons ha−1), 2 weeks before sowing of maize increased DMP significantly. The results further suggested that incorporation of legume (faba bean) residues (10 tons ha−1) 1 month before sowing significantly increased DMP in maize as compared to the incorporation of garlic and paper mulberry residues. The results confirmed that seed inoculation with PSB increases the availability of calcium bound-phosphorus under calcareous soils in semiarid climates hence increased DMP and accumulation, and total maize biomass. [ABSTRACT FROM AUTHOR]

Conversion of manures to vermicompost and biochar may alleviate some negative effects of manure application to soil but the efficiency of the produced vermicompost and biochar as compared to their feedstocks is not well-known. In the current investigation, we compared the effects of sheep manure and its derived vermicompost and biochar (pyrolyzed at 400°C for 4 h) on the properties of a calcareous soil that planted with five cultivars of barley (Behrokh, Khatam, Reyhaneh03, Fajr 30 and Nimrooz) for 60 days. Different soil properties and availability of nutrients and barley yield were determined after plant harvest. The biochar significantly increased barley yield rather than control (4.20 vs. 3.57 g pot−1), but sheep manure and vermicompost had no effect on it (3.51 and 3.37 g pot−1, respectively). Fajr 30 and Nimrooz (3.52 and 3.42 g pot−1, respectively) had significantly lower yield than other cultivars. Biochar increased soil pH up to 8.2. Soil salinity was increased by application of all organic materials (increase to 16–36%). Cation exchange capacity (CEC) and organic matter content of soil were also increased by all organic materials application (0.4–0.9 cmol kg−1 and 0.33–0.50%, respectively). All organic materials increased total nitrogen (N), but this increase was the highest with sheep manure application (53%). The availability of phosphorus (P) and potassium (K) was increased significantly by application of all organic materials, and this increase was the highest with biochar application (19 and 309 mg kg−1, respectively). Biochar application had no effect on the availability of micronutrients, but application of sheep manure and vermicompost increased the availability of iron (Fe) (0.62 and 0.48 mg kg−1, respectively) and zinc (Zn) (0.18 and 0.37 mg kg−1, respectively). Generally, organic materials may change the status of soil nutrients via change in soil pH, organic matter content, release of nutrients, increase in soil CEC and formation of soluble complex with nutrients. [ABSTRACT FROM AUTHOR]

Phosphorus (P) in an essential non-renewable resource in agriculture and zinc (Zn) deficiency is an important micronutrient imbalance in calcareous soils. Inoculation with Bacillus subtilis QST713 and amendments with readily available C for soil microorganisms is known to enhance the uptake of some nutrients by plants. We hypothesized that these practices may also improve P and Zn uptake. However, since Zn and P are antagonistic nutrients, it is also relevant to assess if a potential enhancement of P nutrition worsens Zn uptake by plants. An experiment with wheat (Triticum durum L) was performed involving three factors: (i) treatments affecting rhizospheric microorganisms: control without treatment, cellulose as readily C source for microorganisms, and inoculation with B. subtilis QST713, (ii) soil type: Vertisol and Alfisol, and (iii) P source: unfertilized control, and rock phosphate. The supply of cellulose improved total P uptake by plants in both soils independently of the P supply. Overall, inoculation with B. subtilis also provided benefits on P uptake, despite this effect varied depending on soils and P supply. B. subtilis improved Zn concentration in grains by 24% relative to untreated control, while the effect on total Zn uptake by plants was non-significant. This explained the increased Zn harvest index with B. subtilis. The improvement of P uptake by B. subtilis and cellulose did not lead to an antagonistic effect on Zn, whose uptake by plants increased linearly with increased P uptake (R2 = 0.68; P <.001). These results provide evidence of the benefits of agricultural practices affecting microbial properties of the rhizosphere in improving P supply to plants. B. subtilis increased Zn accumulation in edible parts, thus promoting a biofortification effect. [ABSTRACT FROM AUTHOR]

Over 650 Proteaceae occur in south-western Australia, contributing to the region's exceptionally high biodiversity. Most Proteaceae occur exclusively on severely nutrient-impoverished, acidic soils (calcifuge), whilst only few also occur on young, calcareous soils (soil-indifferent), higher in calcium (Ca) and phosphorus (P). The calcifuge habit of Proteaceae is explained by Ca-enhanced P toxicity, putatively linked to the leaf cell-specific allocation of Ca and P. Separation of these elements is essential to avoid the deleterious precipitation of Ca-phosphate. We used quantitative X-ray microanalysis to determine leaf cell-specific nutrient concentrations of two calcifuge and two soil-indifferent Proteaceae grown in hydroponics at a range of Ca and P concentrations. Calcium enhanced the preferential allocation of P to palisade mesophyll (PM) cells under high P conditions, without a significant change in whole leaf [P]. Calcifuges showed a greater PM [P] compared with soil-indifferent species, corresponding to their greater sensitivity. This study advances our mechanistic understanding of Ca-enhanced P toxicity, supporting the proposed model, and demonstrating its role in the calcifuge distribution of Proteaceae. This furthers our understanding of nutrient interactions at the cellular level and highlights its importance to plant functioning. [ABSTRACT FROM AUTHOR]

Tomato production, multiple regression model, change point, phosphorus index. [Extracted from the article]

Keywords: Phosphorus; Fractionation EN Phosphorus Fractionation 19 21 3 02/10/21 20210201 NES 210201 The recent article by Barrow et al. ([1]) concerning "The soil phosphate fractionation fallacy" is a welcome cautionary paper for phosphorus scientists to question how they approach the interpretation and practical use of phosphorus fractions in understanding the nature of soil phosphorus. I will not revisit their discussion, but reflect more broadly on my experience of the usefulness of phosphorus fractionation in driving forward a functional understanding of soil phosphorus behaviour, and more specifically, plant phosphorus acquisition. Implicit in those assumptions is that acid extractable phosphorus fractions, representing Ca-P, (and as has been made clear in these two articles, Fe-P) are less available to roots than a bicarbonate extractable fraction. [Extracted from the article]

Knowledge on P release characteristics and availability of different forms of soil phosphorus can be useful for crop production. Kinetics of P release and distribution of inorganic P from in calcareous soils at summit, shoulder, back slope, foot slope and toe slope of three soil toposequences (Fars province southern Iran) were determined and the relationship between P release and soil properties with phosphorus form was investigated. The kinetics of P release in the soils was determined by successive extraction with 0.01 M CaCl2 over a period of 72 hours. The kinetics of P release followed Elovich, power function and first order kinetic models. The results demonstrated that the pattern of P desorption was similar in all topographic units of the three regions at all times. The highest amount of P release was observed in the lower part of the slope specially in Eghlid and Abadeh (xeric and aridic regimes). Generally, the average content of cumulative phosphorus release and most forms of phosphorous and physical and chemical characteristics in Eghlid soils were greater than other studied soils. Different P forms were determined by sequential extraction; the fractionated inorganic P forms namely apatite type and dicalcium phosphate possessed the highest and the lowest amounts of P reserve in the soils, respectively. As a result, P release and various P forms distribution within the soil profiles along toposequences varied in different topographic units and increased down the slope with an irregular trend. Due to such variability, P fertilizers are recommended by consideration of the physiographic units. [ABSTRACT FROM AUTHOR]

Diffusive gradients in thin films (DGT) technology has been increasingly proved to be a promising tool for accurately predicting plant-available phosphorus (P) in soil using air-dried samples. However, the effects of the air-drying process on DGT-measured P are unknown compared to those of using moist samples in which plant roots survive throughout a growing season. We investigated the differences between the Olsen P and DGT P values in 58 air-dried and moist soil samples. The results showed that the discrepancy in the DGT P values between air-dried and moist samples increased with an increase in the organic P concentration in soils. It was presumed that the air-drying process converted some easily mineralized organic P into its inorganic form, thereby allowing it to be measured by the DGT method. The DGT P values in moist samples can be calculated from the values obtained in air-dried samples using the following equation:. However, the Olsen P values were highly correlated (R2 = 0.95) when using air-dried and moist samples, although significant differences were observed. We concluded that the effects of air-drying on predicting soil available P using the Olsen P method can be neglected due to the high correlation relationship. The availability of easily mineralized organic P needs to be further explored. [ABSTRACT FROM AUTHOR]

In an attempt to investigate variations in availability of native and applied phosphorus (P) with time, twenty five calcareous soil samples were treated with 0, 50 and 500 mg P kg−1 soil and incubated at 80–90% of field capacity moisture content in an open door glasshouse for a period of one year. Soil samples were taken out at certain intervals for P extraction with Olsen extractant under moist condition. Results indicated that following wetting the mean value of native Olsen-P decreased initially and then increased gradually with time of incubation. Generally, the short term (24 h) recoveries were not correlated with long term ones. The recovery of added P with time was described properly by the following new proposed model: R = 100/(1 + ktb), where R is percent recovery at time t, and k and b are empirical parameters. The values of k constant at 50 and 500 mg P kg−1 were in the ranges of 0.40 to 1.22 (0.84 ± 0.25, on average) and 0.04 to 0.52 (0.23 ± 0.14, on average), respectively. The corresponding respective values of b constant also ranged from 0.05 to 0.32 (0.15 ± 0.06, on average) and 0.12 to 0.92 (0.46 ± 0.23, on average). [ABSTRACT FROM AUTHOR]

Biochar is a carbon-rich material produced through pyrolysis of biological material under controlled conditions. An incubation experiment was carried out in a calcareous soil to determine the temporal effect of maize biochar produced at three different temperatures 300, 400, and 500°C on soil chemical properties and nutrient availability. The variations in potassium (K), phosphorus (P), mineral nitrogen (MN), ammonium-nitrogen (NH4 +-N), nitrate-nitrogen (NO3--N), soil organic carbon (SOC), cation exchange capacity (CEC) and pH was evaluated by adding biochar in soil @ 0, 1.0 and 1.5% for incubation period (10, 20, 30, 40 and 50 weeks). Results revealed that soil pH was decreased with biochars (B300 and B400), particularly @ 1%. At the end of incubation, CEC was increased (12%) over control with B300 added @ 1%. The SOC and K contents significantly increased by increasing pyrolysis temperature, biochar rate and incubation time. The highest increase in SOC (51%) and K (367%) was observed with B500 @ 1.5% over control. The N contents (NH4 +, NO3-) increased with increasing incubation time; highest NH4 +-N (97%) and NO3--N (118%) were observed @ 1.5% B300. Likewise, MN increased (107% over control) @ 1.5% B300. The available P increased in first 30 weeks but after that, it was decreased with increase in time. However, an increase of 65% in P over control was observed @1.5% B300. It is concluded that addition of B300 @ 1.5% improved the soil chemical properties and nutrient availability of the calcareous soil that needs to be verified further in field experiments. [ABSTRACT FROM AUTHOR]

Abstract Soil microorganisms exuding organic acids have the potential to solubilize inorganic phosphorus (P), which could improve the P availability to plants growing on calcareous soil. The gluconic acid exuding bacteria Pseudomonas protegens CHA0 can solubilize P under glucose rich in vitro conditions, but evidence on the effectiveness in soil is lacking. This discrepancy in P solubilization between in vitro and in vivo is common for many P solubilizing bacteria. Possible causes for this discrepancy are rarely explored in soil using mechanism oriented approaches. Proposed reasons for limitation of bacterial P solubilization in soil are low persistence of the inoculant or low glucose availability in the plant rhizosphere. To test these two hypotheses we investigated the solubilization of 33P labeled synthetic hydroxyapatite (Ca33P) by the gluconic acid producing P. protegens CHA0 wild type and the mutant strain CHA1198 lacking the capacity to produce this acid, in a plant growth experiment with wheat (Triticum aestivum) and an incubation experiment. Neither in the plant growth- nor in the incubation experiment solubilization of Ca33P by strain CHA0 was detected, in spite the inoculated strain persisted in the rhizoplane of wheat and in the sterilized soil amended with glucose. No detected P solubilization in the sterilized inoculated soil suggests that glucose availability was the main limiting factor. The comparison of the results obtained from the two bacterial inoculants suggested that overall microbial activity, i.e., via protonation due to respiration, increased inorganic P mobilization. P solubilizing bacteria should be evaluated using a tracer and an appropriate bacterial control in order to reveal the mechanisms involved in increased plant available P in soil inoculated with P solubilizing bacteria. Highlights • P. protegens CHA0 wild type did not increase Ca33P solubilization in soil compared to its mutant. • Microbial competition was not a limiting factor for P solubilization. • Glucose addition did not increase P solubilization by the wild type. • Overall microbial activity increased inorganic P mobilization. [ABSTRACT FROM AUTHOR]

High levels of phosphorus (P) often induce zinc (Zn) deficiency in plants grown on Zn-poor soils. We investigated P-induced Zn deficiency in durum wheat (Triticum durum L. 'Carpio') grown on 16 noncalcareous and 31 calcareous soils differing in levels of available (Olsen) P and available (diethylenetriaminepentaacetic acid (DTPA)-extractable) Zn using micropots. A completely randomized factorial design with two levels of P (0 and 40 mg P kg−1 soil) and Zn (0 and 3 mg Zn kg−1 soil), i.e. four treatments ('control', + P, + Zn, and + PZn), were used. Grain yield of control plants depended mainly on the Olsen P level. Phosphorus had a negative effect on yield in 6 soils with Olsen P/ZnDTPA > 25, and Zn a positive one in 5 soils with Olsen P/ZnDTPA > 50; and the + PZn treatment generally resulted in the highest yield. Grain Zn concentration of control plants was negatively correlated with growth and Olsen P. Calcareous soils were less sensitive to P-induced Zn deficiency than noncalcareous soils because phosphate is sorbed by calcite rather than being co-adsorbed with Zn on the Fe oxides. Co-application of P and Zn to soil at low and application of Zn at high Olsen P ensured both maximum yield and grain Zn bioavailability. [ABSTRACT FROM AUTHOR]

Background and aims: Although phosphorus (P) application is known to affect the zinc (Zn) nutrition of crops, the underlying mechanisms and effects of soil type are unclear.Methods: A greenhouse pot experiment was conducted with wheat, two soils (calcareous and acid), and nine P fertilizer rates (0, 50, 100, 200, 400, 1000, 2000, 3000, and 5000 mg P2O5 kg−1 soil).Results: The effects of P application on the Zn content of shoots and roots in wheat and on the levels of available Zn in soil differed on the two soils. The wheat dry weight on both soils was highest with 2000 mg P2O5 kg−1. Total Zn accumulation was reduced above 2000 mg P2O5 kg−1 on the acid soil and above 100 mg P2O5 kg−1 on the calcareous soil. Available soil Zn declined when the Bray-P concentration reached about 34 mg kg−1 in the acid soil and when the Olsen-P concentration exceeded 200 mg kg−1 in the calcareous soil. Shoot Zn concentrations were negatively related to available soil P on the two soils.Conclusion: The negative effects of increasing P application rates on Zn accumulation by wheat differed between the two soils. The effects showed no close relationship to available soil Zn. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is one of the least available of all essential nutrients in the soil and its concentration is generally below that of many other macronutrients. An experiment was conducted to study the phosphorus use efficiency (PUE) of the sorghum and blackgram in soils of varying calcium carbonate content using radiotracer phosphorus (32 P). The pot culture experiment was conducted during 2017-2018 at Radioisotope (Tracer) Laboratory, Department of Soil Science and Agricultural Chemistry, Tamil Nadu Agricultural University, Coimbatore. The treatment structure of the pot culture experiment comprised of four types of soils and two levels of phosphorous (control and recommended level of phosphorus as phosphoric acid) with sorghum and blackgram as test crop. The results of the pot culture experiment showed that the grain yield of sorghum and blackgram decreased with increasing calcareousness of the soil. Lowest grain yield recorded was 14.14 g pl-1 for sorghum and 2.20 g pl-1 for blackgram in strongly calcareous soil (S4). In both sorghum and blackgram non calcareous soil (S1) was recorded the highest total P uptake (101.24 mg pl-1), (37.07 mg pl-1) respectively. Among crops, blackgram recorded the highest per cent Pdff (69.71%) than the sorghum (24.31 %). The highest sorghum per cent Pdfs (100 %) was observed with control (T1) which differed significantly from P application (75.70%), in blackgram the highest per cent Pdfs in blackgram (67.35 %) was recorded in slightly calcareous soil (S2) and the lowest % Pdfs (60.04 %) was registered in strongly calcareous soil (S4). Mean Phosphorus Use Efficiency (PUE) showed significant difference in non-calcareous soil (27.13 %) followed by slightly calcareous soil (23.81%). The mean lowest efficiency was observed in strongly calcareous soil (19.41%). Blackgram recorded higher PUE than sorghum in all the soils. [ABSTRACT FROM AUTHOR]

The objectives of the present study was to evaluate biological nitrogen fixation, P and K uptake ability of 31 soybean mutant lines (induced by Gamma irradiation) and their parent cultivar at greenhouse level. Initially, 10 Rhizobial isolates and strains were tested for infectiveness and symbiotic effectiveness using Leonard jars, and the strain Bradyrhizobium japonicum strain RS 152 was selected as the most efficient strain. The experiment was conducted under proper greenhouse condition with a randomized complete block design on a soil with no indigenous rhizobia and low nitrogen and phosphorus content. Thirty-one soybean mutant lines and two inoculated and un-inoculated wild cultivar blanks were replicated three times. Each pot contained 3.5 kg air-dried homogenized soil, and at the time of planting each seedling was inoculated with l mL of inoculum RS 152 containing approximately 9 × 108 cells per mL. During about 4 months of growth, the plants were irrigated to maintain the soil moisture approximately 0.8 field capacity. The plants were harvested at the plant developmental stage of pod filling (R6), and several parameters, such as dry matter of shoot, nodule and roots, number of nodules, and proportion and amount of Nitrogen derived from air (Ndfa% and N-fixed) were measured. According to the results, in most parameters, the mutant lines were significantly different with each other and also with the L17 parent soybean cultivar. The mutant line 5 showed the maximum value of %Ndfa (73.068) compared to the cultivar L17 (48.762), indicating significant increase of biological nitrogen fixation, by about fifty percent, through physical mutagenesis. In addition, the mutant lines 21 and 31 had higher phosphorus and potassium uptake than the others, however, significant differences were observed for phosphorus uptake capacity compared to the cultivar L17. Although more detailed studies are needed to evaluate effects of these mutations on nitrogen fixation, macroand microelements absorption capacity, and also on yield and quality parameters, these findings show that gamma irradiation could be helpful to induce new nutritional properties in soybean and release new mutant cultivars. [ABSTRACT FROM AUTHOR]

In this research, phosphorus (P) desorption was investigated using DMTHFO as an "infinite" sink for 10 calcareous soils over a period of 1-35 days and the kinetic data was related to soil properties and P uptake by maize (Zea mays L.). First- and second-order, and simple Elovich equations adequately described P desorption kinetics, however parabolic, exponential and zero order equations provided the best fits to the data. A systematic relationship exists between the second order rate parameter (k2) and the clay content of the soils. There are positive relationships between P desorption rate constants (for zero order, Elovich and parabolic equations), and both dry matter and P content of maize shoots and also for roots. These relationships indicate that P desorption rate may be a limiting factor for maize growth in these soils. The DMT-HFO technique may be used to assess the long-term availability of P to plants. [ABSTRACT FROM AUTHOR]

One of the strategies of the plants growing in phosphorus (P)-deficient environments is to exudate low-molecular-weight organic acids (LMWOA). Thus, we aimed to investigate the effect of LMWOA on phosphorus uptake of barley from either fertilizer or inherited soil phosphorus. The experiment was set up in full factorial arrangement in completely randomised design with two phosphorus (0 and 50 mg P kg-1), five organic acids, LMWOA (malic acid, oxalic acid, citric acid, acetic acid, ascorbic acid), and four organic acid rates (0, 10, 20, and 30 mmol kg-1). The effects of LMWOA on yield in descending order were: oxalic acid > ascorbic acid > malic acid > acetic acid > citric acid. The maximum P concentration in grain was obtained at 30 mmol kg-1 LMWOA treatments. As a result, it was found that oxalic acid was the most effective LMWOA in increasing nutrient uptake induced grain yield with and without phosphorous fertilizer application. [ABSTRACT FROM AUTHOR]

Four types of plant residues (fruit waste, potato, sunflower, and wheat) with wide ranges of carbon to nitrogen (C/N) and carbon to phosphorus (C/P) ratios were added to the soil at the rate of 20 g kg−1 (dry weight basis) and incubated for two months. In soils treated with plant residues, the P sorption ranged from 62.0% (potato) to 96.6% (wheat) and from 12.6% (fruit waste) to 50.6% (wheat) when 20 and 1500 mg P kg−1 were added to the soils, respectively. In general, incorporation of plant residues decreased maximum P sorption capacity but increased bonding energy. The maximum P sorption capacity was reduced from 586 mg kg−1to 500, 542, and 548 by wheat, fruit, and potato residues, respectively, but increased to 665 mg kg−1 by sunflower residue. At higher P addition, the highest percentage of desorbed P was observed in soils treated with wheat residue (49.9%); followed by fruit waste (46.5%), potato (43.5%), sunflower (38.8%) and control soils (37.0%). It indicated that the P content of the organic residues had an important role in the sorption and desorption of P in calcareous soils. Among organic residues, sunflower residue showed high sorption and low desorption of P in soils, indicating a higher potential of this organic residue for P retention and reducing surface and groundwater contamination in calcareous soils. [ABSTRACT FROM AUTHOR]

The present study investigated kinetics of phosphorus (P) release from some calcareous soils employing DGT technique. For these purpose, DGT were deployed in ten calcareous soils for different time periods between 4 h and 21 days and the accumulated P were used to calculate the distribution coefficient for labile metal, K dl , desorption rate constants (k − 1 ) and the rate at which the soil system can resupply P from solid phase to solution (Tc) using the DIFS model. The values of K dl calculated from DIFS ranged from 0.67 to 198 cm 3 /g. Response times (Tc) were so short in six studied soils with low Olsen-P. A short response time means that the rapid resupply from the solid phase and slow depletion over time of the available P pool occurs. By contrast, the four rests of the soils have a longer response time (about 40 min) and so little the resupply from the solid phase, leading to a progressive depletion. The P desorption rate (k − 1 ) parameter derived from DIFS were from 9.9 ∗ 10 − 6 to 21.12 ∗ 10 − 4 s − 1 with a mean 4.54 ∗ 10 − 4 and well-correlated with the content and/or the concentration of P in corn shoot (r = 0.74, P < 0.05) and root (r = 0.71, P < 0.05) confirming the importance of P desorption rate in plant P nutrition in the calcareous soils. In these study, the close correlation was obtained between clay and calcium carbonate equivalent concentration with P desorption rate that demonstrate DGT technique sensitive to soil properties and may allow the study of root-induced changes in rhizosphere. [ABSTRACT FROM AUTHOR]

The effect of cattle manure and sulfur fertilizer on seed yield and oil composition of pumpkin (Cucurbita pepovar. Styriaca) under inoculated withThiobacillus thiooxidanswas investigated in a factorial study based on a randomized complete block design. Experimental factors consisted of cattle manure (M) (M0: 0, M1: 10; and M2: 20 t ha−1), sulfur (S) (S0: 0, S1: 250; and S2: 500 kg ha−1) andT. thiooxidans(B): inoculated (B1) and non-inoculated (B0). Results demonstrated that the application ofT. thiooxidans, cattle manure, and S fertilizer decreased the soil pH. The largest number of seed per fruit (367), highest fruit yield (70.57 t ha−1), seed iron (Fe) content (16.26 mg 100 g−1), and seed yield (111 kg ha−1) was obtained when 20 t ha−1 manure was applied in combination with 500 kg ha−1 S inoculated withT. thiooxidans. In this condition, the content of S, Fe, phosphorus (P), and nitrogen (N) in plant shoots was increased by 44.8%, 22.58%, 33.89%, and 10.38%, respectively, compared to the control. Moreover, the highest content of seed protein was observed in 10 t ha−1manure and 500 kg ha−1 S fertilizer inoculated withT. thiooxidans. When 250 kg ha−1 S fertilizer was applied, 20 t ha−1manure decreased seed P content sharply. At the rate of 500 kg ha−1 S fertilizer, the highest content of seed P was obtained from 20 t ha−1manure. Totally, 20 t ha−1cattle manure, along with 500 kg ha−1 S fertilizer as well asT. thiooxidansinoculation, improved oil and seed yield of medicinal pumpkin. [ABSTRACT FROM PUBLISHER]

In confined animal feeding operations, such as dairies, manure is amended to soils at high rates leading to increases in P and organic matter in the soils. Phosphorus reacts with soil-Ca to form Ca-P minerals, which controls P availability for leaching and transport through the watershed. In this research, the effects of manure sourced dissolved organic matter (DOM) on P sorption on calcite were measured at different reaction times and concentrations. Reactions were monitored in 1% and 10% manure-to-water extract solutions spiked with P. When manure-DOM was present, a significant reduction in P sorption occurred (2–90% absolute decrease) compared to samples without manure-DOM. The greatest decrease occurred in the samples reacted in the 10% manure solution. XANES spectroscopic analysis showed that at 1% manure solution, a Ca-P phase similar to hydroxyapatite formed. In the calcite samples reacted in the 10% manure solution, K-edge XANES spectroscopy revealed that P occurred as a Ca-Mg-P phase instead of the less soluble hydroxyapatite-like phase. Results from this study suggest that in manure-amended calcareous soils, increased DOM from manure will decrease P sorption capacity and increase the overall P concentration in solution, which will increase the mobility of P and subsequently pose greater risks for impairment of surface water quality. [ABSTRACT FROM AUTHOR]

The foliar status and the factors affecting the foliar chemistry in a natural Aleppo pine forest grown on calcareous soils in Greece were examined. It was found that the Aleppo pine needles had significantly higher calcium (Ca) concentrations, but significantly lower concentrations of magnesium (Mg), potassium (K), phosphorus (P), iron (Fe) and manganese (Mn) than the respective average concentrations of natural Aleppo pine forests in Spain. It was also found that only foliar Ca and Mn had a significant correlation with the exchangeable Ca and available Mn in soils, respectively. Principal component analysis showed that the nature of the calcareous parent material, (colluvial rocks and hard limestones) were the main factors affecting both foliar and soil chemistry. This finding is important as colluvial soils always coexist with other soil types in hilly and mountainous regions containing calcareous material. [ABSTRACT FROM PUBLISHER]

In a field trial, Dalbergia sissoo biochar was used to investigate its potential for improving growth, yield and nutrient recovery of wheat (Triticum aestivum L.), at varying fertilizer rates under calcareous soil. Two biochar levels (0.0 and 1.0% of soil weight) were used along with five fertilizer rates i.e. 0, 25, 50, 75 and 100% of recommended inorganic fertilizer dose (RFD). Seeds of wheat cultivar Faisalabad-2008 were sown in the field using 2 factorial-randomized complete block design. At reduced fertilizer rates, biochar application improved plant growth parameters i.e. plant height, spike length, number of tillers hill-1 and grain yield over the respective treatments having inorganic fertilizer without biochar. Regarding nitrogen (N), phosphorus (P) and potassium (K) content, the highest statistical results were achieved at reduced fertilizer doses along with biochar application i.e. N and P content in wheat straw and grain at 50% RFD, straw N and P uptake at 75% RFD, grain N and K uptake at 50% RFD and grain P uptake at 75% RFD. The highest N, P and K recovery was calculated in the treatments having 50% RFD + biochar with 95%, 25% RFD + biochar with 38% and 25% RFD with 117%, respectively. In comparison with control treatment (without fertilizer and biochar), biochar application improved soil CEC up to 40%. With biochar application, no any significant change was observed in other soil chemical properties i.e. pH and EC. The results suggested that 1.0% biochar along with reduced fertilizer doses, could be effectively used to improve wheat growth, yield, nutrient content and nutrient uptake under field condition. Moreover, 1.0% biochar along with 75% of RFD can be effectively used in place of 100% RFD to get the highest yield. [ABSTRACT FROM AUTHOR]