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Anthropogenic activities have added a large amount of heavy metals to the environment. Heavy metal contaminants affect the physiological and biological properties of soil and plant health. Zinc (Zn) is an essential micronutrient and it promotes plant growth and development but a higher concentration of the metal causes reduction in plant growth. The present study was aimed to evaluate the response of Bacillus cereus on maize plants at different concentrations of ZnSO4 (20, 40 and 60 mg kg-1) amended in the soil under pot experiment conditions. The experiment was conducted by using complete randomized design (CRD) with three replications. Higher doses of ZnSO4 inhibited maize growth and nutrient uptake. However, inoculation of maize seeds with Bacillus cereus at 20 mg kg-1 concentration of ZnSO4 increased seed germination about 39% and plant height by 15%. Moreover, 17% increase in leaf length and a 7% increase in leaf number were observed as compared to control at 20 mg kg-1 concentrations of ZnSO4. Reductions in all growth parameters were observed with 60 mg kg-1 concentration of ZnSO4. The Zn uptake was 75% higher in treatment T8 (uninoculated seeds with 60 mg kg-1 concentration of ZnSO4) as compared to treatments which were inoculated and grown under different zinc concentrations. The results suggest that Bacillus cereus has good potential to remediate Zn from soil as well as to reduce the phyto-availibility and phytotoxicity of zinc. [ABSTRACT FROM AUTHOR]

The deficiency of phosphorus (P) is widespread in the soils of Pakistan. Out of 1279 thousand nutrient tons consumption of P fertilizers in the country during the year 2017-18, 85.4% was imported. The most expansive P fertilizers' application is continuously increasing the cost of crop production. The huge amount rock phosphate (RP) found in Hazara area of Pakistan can be utilized as P source by preparing Single Super Phosphate (SSP). The spatial variation in minerology of Hazara RP might have an impact on the availability of phosphorus from these rocks. The experiment was therefore planned to revisit the formulation of SSP for various Hazara locations' rock, for obtaining maximum available P. Three main locations' rock phosphates; Guldania, Kakul and Paswal was collected and ground at 160 mesh level with ± 30% total P2O5 content were treated with various amounts and dilutions of sulfuric acid. The results showed that application of H2SO4 @0.6L + 50% dilution (v/v) per kg Guldania RP gave significantly highest available P content (15.61%), while Kakul RP released maximum P (15.47%) by application of H2SO4 @0.60 L+ 55% v/v dilution, per kg RP. The Paswal RP released maximum P by applying H2SO4 @0.55 L+ 55% v/v dilution, per kg RP. The periodic analysis of the reacted RP showed that availability of P increased with the time span, irrespective of the treatments and locations. However, the highest P in all reacted RP was recorded on day 90. Beyond day 90, the P content showed a declining trend, especially in reacted RP of Paswal and Kakul. These results reveal that with the change in mineralogy of RP, the requirement of H2SO4 for solubilizing P also changes hence, separate formulation will be workable for all the three locations. These results also indicate that Guldania RP has a good and economical potential for SSP preparation. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is one of the most important minerals required for plant growth occupying a strong position among soil macro nutrients. Soil P deficiency is often fulfilled by phosphate fertilizers. P deficiency in soils is due to less total P contents in the soil and fixation of added P from chemical fertilizers as well as other organic sources like manures. The response of plant under P stress or even when it is present in adequate amount is very mild. The basic constraint in the availability of P is its solubilization as it gets fixed both in acidic and alkaline soil. Soil fixed P can only be solubilized by phosphate solubilizing microorganisms (PSMs).These bacteria released different types of organic acids in the soil which make P soluble and available to plants. The potential of these PSMs to solubilize P varies and mainly depends upon mechanism adopted for solubilization, their molecular genetics as well as their ability to release P in soil. The PSMs, having all the characteristics of phytohormone production, nitrogen fixation, as well as, heavy metal decontamination and creating salt stress tolerance in plants, are quite rare for sustainable agriculture. Application of this environment friendly approach for increasing crop productivity as well as its impact on soil and plant health is discussed in this review which will not only open new avenues of research but also provide fruitful information about phosphate solubilizing microbes for sustainable agriculture development. [ABSTRACT FROM AUTHOR]

The present study was aimed to evaluate the role of Plant Growth Promoting Rhizobacteria (PGPR) in P solubilisation from rock phosphate through composting with poultry litter, and further to study the effects of prepared enriched composts on growth, yield, and phosphorus uptake of wheat crop. Various phosphorus-enriched composts were prepared from rock phosphate and poultry litter (1:10) with and without inoculation of plant growth promoting rhizobacterias (Pseudomonas sp. and Proteus sp.). Results showed that the rock-phosphate-added poultry litter had higher total phosphorus, available (Mehlic-3 extracted) phosphorus, microbial biomass (carbon and phosphorus), and lower total organic carbon, total nitrogen, and carbon/nitrogen ratio over poultry litter alone. Inoculation of Pseudomonas sp. with rock phosphate-added poultry litter showed maximum increase in available phosphorus (41% of total phosphorus) followed by Proteus sp. inoculation (30% of total phosphorus) over uninoculated treatment (23% of total phosphorus) on the 120th day of composting. Microbial biomass (carbon and phosphorus) increased up to Day 45 and tended to decrease till the 120th day of composting, irrespective of the treatments. However, in pot experiments, wheat seeds receiving inoculation with plant growth promoting rhizobacterias, subsequently treated with rock phosphate-enriched compost proved highly stimulatory to plant height, phosphorus uptake, grain yield, and seed phosphorus content over uninoculated untreated control. The plant growth promoting rhizobacterias inoculation can be a sustainable source releasing phosphorus from low grade rock phosphate through composting and application of rock phosphate-enriched compost can be an alternative to chemical fertilisers for better crop production. [ABSTRACT FROM PUBLISHER]

Phosphorus deficiency is wide spread in soils of Pakistan. It is imperative to explore the potential and economics of indigenous Hazara rock phosphate for preparation of single super phosphate fertilizer. For the subject study rock phosphate was collected from Hazara area ground at 160 mesh level with 26% total P₂O₅ content for manual preparation of single super phosphate fertilizer. The rock phosphate was treated with various concentrations of sulfuric acid (98.9%, diluted or pure) in the field. The treatments comprised of 20 and 35% pure acid and diluted with acid-water ratios of 1:5, 1:2, 1:1 and 2:1 v/v for acidulation at the rate of 60 liters 100 kg-1 rock phosphate. The amount was prior calculated in the laboratory for complete wetting of rock phosphate. A quantity of 150 kg rock phosphate was taken as treatment. The respective amount of acid was applied with the spray pump of stainless steel or poured with bucket. After proper processing, chemical analysis of the products showed a range of available P₂O₅ content from 9.56 to 19.24% depending upon the amount of acid and its dilution. The results reveal at that 1:1 dilutions gave the highest P₂O₅ content (19.24%), lowest free acid (6 %) and 32% weight increase. The application of acid beyond or below this combination either pure or diluted gave hygroscopic product and higher free acids. The cost incurred upon the manual processing was almost half the prevailing rates in the market. These results lead to conclude that application of sulfuric acid at the rate of 60 liters 100 kg-1 with the dilution of 50% (v/v) can yield better kind of SSP from Hazara rock phosphate at lower prices. [ABSTRACT FROM AUTHOR]

Sulfur deficiency arising due to intensive cultivation, use of sulfur free fertilizers and reduction in atmospheric sulfur depositions has become a major issue limiting crop production in many parts of the world. Elemental sulfur could be a good source of available S, but its slow oxidation is a problem for its efficient use as a sulfur fertilizer. Main objective of the study was to assess the effect of organic amendments (OA) and elemental sulfur (ES) on microbial activities, sulfur oxidation and availability in soil. A laboratory incubation experiment was carried out for a 56 days period using two sulfur deficient alkaline soils. Organic amendments (OA), i.e., farmyard manure (FYM), poultry litter (PL) and sugarcane filter cake (SF), were applied (1% w/w) with or without elemental sulfur (ES) at 50 mg kg−1. Application of ES alone or in combination with OA significantly increasedCO2-C evolution, microbial biomass, and enzyme activities in the soils, except dehydrogenase activity (DHA) which was not affected by ES application. Combined application of OA and ES had a more pronounced effect on microbial parameters compared to ES or OA applied alone. Ratios of dehydrogenase activity-to-microbial biomass C and arylsulfatase activity-to-microbial biomass C were high in ES+FYM and ES+SF treatments, respectively. Elemental sulfur got sufficiently oxidized resulting in significant improvement in plant available S. Relatively more ES was distributed into C-bonded-S than ester bonded-S. Increase in sulfur availability in ES+OA amended soils was the combined function of sulfur oxidation and mineralization processes through improved microbial activity. [ABSTRACT FROM AUTHOR]

Due to the scarcity of water, raw sewage effluents are often used to irrigate arable suburban soils in developing countries, which causes soil contamination with toxic metals. Soil microorganisms involved in biochemical transformations are sensitive to heavy metals contamination. The study was designed to investigate the effect of organic amendments on the microbial activity of cadmium (Cd), lead (Pb) and zinc (Zn) fractions and their bioavailability in soils contaminated with wastewater irrigation. Three metal contaminated soils under wastewater irrigation were collected, ground, sieved and added to incubation jars. Two organic amendments: wheat straw and chickpea straw, were applied (1% w/w) to the soil before incubation for 84 days at 25 °C. The CO2-C evolution after 1, 2, 3, 5, 7, 10 and 14 days was measured and thereafter was also measured weekly. Soil samples collected at 0, 14, 28, 42, 56, 70 and 84 days after incubation were analyzed for microbial biomass carbon (MBC). Sequential extraction for metal fractionation of samples was carried out collected at 0, 28, 56 and 84 days. Three soils differed significantly in evolved MBC and ∑CO2-C. Chickpea straw addition significantly increased soil MBC as compared to the wheat straw. Organic amendments significantly increased ∑CO2-C evolution from the soils, which was higher from chickpea straw. The addition of crop residues did not affect total Pb, Cd and Zn contents in soils. The concentration of exchangeable, carbonate bound and residual fractions of Pb, Cd and Zn decreased (6–27%), while the organic matter bound fraction increased (4–75%) with straw addition. Overall, the organic amendments improved microbial activity and reduce the bioavailability of toxic metals in wastewater irrigated soils. Furthermore, organic amendments not only reduce economic losses as they are cheap to produce but also minimize human health risks from heavy metals by hindering their entry into the food chain. [ABSTRACT FROM AUTHOR]

Continuous application of phosphate (P) mineral to soil renders apatite addition during each crop growing season which is of great concern from a sustainable agriculture viewpoint. Use of efficient phosphate solubilizing microbes (PSB) is one of the most effective ways to solubilize this apatite mineral in the soil. The current study targeted hydroxyapatite mines to explore, isolate and characterize efficient P solubilizers to solubilize apatite in the soil. Efficiency of isolated microbes to solubilize rock phosphate (hydroxyapatite) and tri-calcium phosphate (TCP) as well as indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate deaminase (ACC) activity were tested. Identification and phylogenetic analysis of bacterial and fungal isolates were carried out by 16S rRNA and internal transcribed spacer (ITS) rDNA sequence analyses, respectively. The isolated bacterial strains were identified as Staphylococcus sp., Bacillus firmus, Bacillus safensis, and Bacillus licheniformis whereas fungal isolates were identified as Penicillium sp. and Penicillium oxalicum. Results showed that the impact of identified strains in combination with three phosphate fertilizers sources (compost, rock phosphate and diammonium phosphate (DAP)) was conspicuous on maize crop grown in pot. Both bacterial and fungal strains increased the P uptake by plants as well as recorded with higher available P in post-harvested soil. Penicillium sp. in combination with compost resulted in maximum P-uptake by plants and post-harvest soil P contents, compared to other combinations of P sources and bio-inoculants. Screening and application of efficient P solubilizers can be a better option to utilize the indigenous phosphate reserves of soil as well as organic amendments for sustainable agriculture. [ABSTRACT FROM AUTHOR]

Drought is a major constraint in drylands for crop production. Plant associated microbes can help plants in acquisition of soil nutrients to enhance productivity in stressful conditions. The current study was designed to illuminate the effectiveness of desert rhizobacterial strains on growth and net-return of chickpeas grown in pots by using sandy loam soil of Thal Pakistan desert. A total of 125 rhizobacterial strains were isolated, out of which 72 strains were inoculated with chickpeas in the growth chamber for 75 days to screen most efficient isolates. Amongst all, six bacterial strains (two rhizobia and four plant growth promoting rhizobacterial strains) significantly enhanced nodulation and shoot-root length as compared to other treatments. These promising strains were morphologically and biochemically characterized and identified through 16sRNA sequencing. Then, eight consortia of the identified isolates were formulated to evaluate the growth and development of chickpea at three moisture levels (55%, 75% and 95% of field capacity) in a glass house experiment. The trend for best performing consortia in terms of growth and development of chickpea remained T2 at moisture level 1 > T7 at moisture level 2 > T4 at moisture level 3. The present study indicates the vital role of co-inoculated bacterial strains in growth enhancement of chickpea under low moisture availability. It is concluded from the results that the consortium T2 (Mesorhizobium ciceri RZ-11 + Bacillus subtilis RP-01 + Bacillus mojavensis RS-14) can perform best in drought conditions (55% field capacity) and T4 (Mesorhizobium ciceri RZ-11 + Enterobacter Cloacae RP-08 + Providencia vermicola RS-15) can be adopted in irrigated areas (95% field capacity) for maximum productivity of chickpea. [ABSTRACT FROM AUTHOR]

Organic materials from various sources have been commonly adopted as soil amendments to improve crop productivity. Phosphorus deficiency and fixation in alkaline calcareous soils drives a reduction in crop production. A two-year field experiment was conducted to evaluate the impact of rock phosphate enriched composts and chemical fertilizers both individually and in combination with plant growth promoting rhizobacteria (PGPR) on wheat productivity and soil chemical and biological and biochemical properties. The present study demonstrates significant increments in crop agronomic and physiological parameters with Pseudomonas sp. inoculated RPEC1 (rock phosphate + poultry litter + Pseudomonas sp.) over the un-inoculated untreated control. However, among all other treatments i.e., RPEC2 (rock phosphate + poultry litter solubilized with Proteus sp.), RPC (rock phosphate + poultry litter), HDP (half dose inorganic P from Single Super Phosphate-SSP 18% P2O5) and SPLC (poultry litter only); RPEC1 remained the best by showing increases in soil chemical properties (available phosphorus, nitrate nitrogen, extractable potassium), biochemical properties (alkaline phosphatase activity) and biological properties (microbial biomass carbon and microbial biomass phosphorus). Economic analysis in terms of Value Cost Ratio (VCR) showed that the seed inoculation with Pseudomonas sp. in combination with RPEC1 gave maximum VCR (3.23:1) followed by RPEC2 (2.61:1), FDP (2.37:1), HDP (2.05:1) and SPLC (2.03:1). It is concluded that inoculated rock phosphate (RP) enriched compost (RPEC1) can be a substitute to costly chemical fertilizers and seed inoculation with Pseudomonas sp. may further increase the efficiency of composts. [ABSTRACT FROM AUTHOR]

Abstract: Field experiments were conducted for two seasons to investigate the direct and residual effect of phosphorus enriched compost (PEC) prepared by composting poultry litter (PL) with rock phosphate (RP) and inoculating with effective microorganisms (EM) on the wheat during 2010-11. Both experiments were conducted consecutively, in the same lay out of randomized complete block design with three repeats. Various doses of PEC (6, 4, 2 Mg ha-1) were compared with simple poultry-litter compost (PLC) as 8 Mg ha-1, single super phosphate (SSP) fertilizer as 100 kg P O ha-1 and control. The results showed that PEC 2 5 at 6 Mg ha-1gave 14.7% and 7.7% increased paddy yield and 14.7% and 11.9%-increased total dry matter yield over PLC at 8 Mg ha-1 and SSP, respectively. The highest soil post-harvest extractable P content of 5.42 mg kg-1and rice-plant P uptake (17.50 kg ha-1) were also recorded in the treatment PECat 6 Mg ha-1 as compared to other treatments. The residual effects of PEC applied at the rate of 6 Mg ha-was superior by producing 36.2%, 14.2% and 7.0%increased grain yields over those of control, PLC and SSP, respectively. The post-harvest soil extractable P value and plant P uptake were significantly higher in the treatment where PEC was applied to the previous crop at 6 Mg ha-1 over rest of the treatments. It was concluded that PEC has the potential to improve yield of two consecutive crop i.e. rice and wheat yields when applied at 6 Mg ha-1. [ABSTRACT FROM AUTHOR]