Agronomic evaluation of phosphorus fertilizers developed from sokoto rock phosphate in Nigeria

Abstract

Sokoto rock phosphate (SRP) obtained from Sokoto in the Northern Nigeria was evaluated with some other phosphorus (P) sources viz: Partially acidulated rock phosphate (PARP) and single superphosphate (SSP) in the greenhouse and field studies. These fertilizers were also compared with nitrogen‐phosphorus‐potassium (NPK) 11–12–11–9.7S‐1.4Zn and NPK 10–20–5–6.5S which have 80% of their P as rock phosphate and were formulated through compaction. The fertilizers were applied in the greenhouse at 0–400 mg kg^‐1soil on the Oyo Arenic Haplustalf and Alagba Kandiudult soil. Field trials were carried out at four locations—at Ikenne in the humid, Samara in the subhumid, Gumi and Gusau in the semi‐arid zones of Nigeria. The fertilizers were applied at 0–150 kg P₂O₅ ha^‐1 in the humid zone and 0–100 kg P₂O₅ ha^‐1in the subhumid and semi‐arid zones. Maize was used as test crop in most sites except at Samaru where sorghum was planted. The results of the greenhouse study showed that on the Haplustalf, PARP, and NPK 10–20–5–6.5S gave almost a similar relative agronomic effectiveness (RAE about 70%) as SSP, which was followed by SRP and NPK 11–12–11–9.7S‐1.4Zn (RAE between 50 and 60%). On the Kandiudult, the RAE of the fertilizers increased significantly. The PARP and NPK 10–20–5–6.55S gave high effectiveness (RAE about 90%) relative to SSP. The field trials results indicated that ground SRP was suitable for direct application on slightly acid soil in the humid zone (annual rainfall > 1,200 mm). Its efficiency was fairly moderate in the subhumid and quite low in the semi‐arid zones (annual rainfall <900 mm). The PARP gave higher RAE than SRP and had almost similar efficiency as for NPK 10–20–5–6.5S. The PARP was well comparable to SSP in the humid and subhumid zones and was fairly comparable to the later in the semi‐arid. This suggests that PARP may be suitable for humid and subhumid zones and the physical quality was also superior to SRP and SSP. Application of SRP on soils in the semi‐arid zones of low rainfall gave relatively low yields which could be due to inadequate moisture availability required to enhance P solubilization.     

Effect of sulfur source and rates on yield and yield components of soybean in subtropical soils

Abstract

The supply of sulfur (S) fertilizers, such as phosphogypsum, to new agricultural frontiers has been hindered by the high cost of freight. However, this problem could be resolved by utilizing deposits of rock in the affected regions. Accordingly, a greenhouse study was designed to evaluate the effect of S source and rate on soybean yield. Five S rates (0, 50, 100, and 200?mg kg^?1) and five S sources (S-phosphogypsum, S-Niquelândia rock, S-Araripina rock, S-Grajaú rock, and S-Sulfurgran [90% S0?+?10% bentonite]) were applied to soybean grown in two soil types (Typic Ultisol and Typic Oxisol), which differ in clay content. Regardless of soil type, the application of P-phosphogypsum resulted in a higher grain yield. However, application of the other S sources also improved grain yield as well as total dry weight; S application, in general, improved soybean yield components (number of grains per pod, number of pods per pot, and weight of pods per pot), photosynthetic rate, chlorophyll content, and the S levels of leaves and grains as well as the available sulfate (SO₄^2-) levels in the soil. Therefore, for soybean grown in Typic Ultisol and Typic Oxisol, different S sources effectively improve a variety of variables that ultimately improve grain yield.     

Citric acid loaded nano clay polymer composite for solubilization of Indian rock phosphates: a step towards sustainable and phosphorus secure future

Non-renewable nature of rock phosphate (RP) reserves coupled with open ended nature of P cycle makes it imperative for maximum utilization of available P resources. In this context, use of Indian RPs from Purulia and Udaipur along with citric acid loaded nanoclay polymer composite (CA-NCPC) as P source to costly diammonium phosphate (DAP) was investigated through an incubation experiment followed by a greenhouse experiment with wheat-rice cropping sequence in a Luvisol (pH 5.14, available P 13.5 mg kg^?1). Soil available P, crop yield parameters and dynamics of soil P fractions were taken to judge the efficacy of CA-NCPC in solubilizing RPs. Application of CA-NCPC and DAP resulted in 82% and 69% increase in available P over control, respectively under incubation study. Direct effect of treatment receiving CA-NCPC + RP on yield and P uptake by wheat was comparable with DAP but residual impact of CA-NCPC + RP (16.7 g pot^?1) was better than DAP (13.8 g pot^?1) in rice. The changes in inorganic P fractions were also significant as inclusion of RP increased calcium-P from 16.1 to 61.5 mg kg^?1. Results indicated potentiality of RPs treated with CA-NCPC as an alternate P source which could prove promising amidst P scarcity.     

Upland rice genotypes evaluation for phosphorus use efficiency

Phosphorus (P) deficiency is one of the most important yield‐limiting factors in acid soils in various parts of the world. The objective of this study was to evaluate the growth and P‐use efficiency of 20 upland rice (Oryza sativa L.) genotypes at low (0 mg P kg^‐1), medium (75 mg P kg^‐1), and high (150 mg P kg^‐1) levels of applied P on an Oxisol. Plant height, tillers, shoot and root dry weight, shoot‐root ratio, P concentration in root and shoot, P uptake in root and shoot, and P‐use efficiency were significantly (P<0.01) affected by level of soil P as well as genotype. Shoot weight and P uptake in shoot were found to be the plant parameters most sensitive to P deficiency, suggesting that these two parameters may be most suitable for screening rice genotypes for P‐use efficiency under greenhouse conditions.     

Introduction of composted rock phosphate and poultry manure enhances winter wheat phosphorus use efficiency,grain yield and soil quality

This field study evaluates the integrated impact of poultry manure (PM), rock phosphate (RP), composted rock phosphate (CRP) and single super phosphate (SSP) on the growth, yield, and phosphorus use efficiency (PUE) of winter wheat and their effect on postharvest soil characteristics. The seven treatments were as follows: T₁ = control; T₂ = SSP full; T₃ = PM full; T₄ = RP full; T₅ = CRP full; T₆ = 50% SSP + 50% CRP (50:50); T₇ = 50% PM + 50% CRP (50:50) at a recommended P rate of 90 kg ha^?1. The combined treatment with PM + CRP produced the highest straw yield of 3582 kg ha^?1, grain yield of 2226 kg ha^?1, P uptake of 21.3 kg ha^?1, and PUE of 18%. The postharvest soil organic carbon, total nitrogen and soil available phosphorus were sig-nificantly higher in integrated treatments.     

Biosolubilization of phosphorus from rock phosphate and other P fertilizers in response to phosphate solubilizing bacteria and poultry manure in a silt loam calcareous soil

‘Phosphate solubilizing bacteria' (PSBs) are able to release unavailable P from native and applied P sources into plant‐available soil pool through their solubilizing and acidifying effects. The effects of three indigenous and one exotic PSBs on P solubilization from different P sources, plant biomass production, and P‐uptake efficiency of maize (Zea mays L.) were examined in an incubation and greenhouse study. For incubation study, surface (0–15 cm) soil was collected from an arable field (Inceptisols) and amended with rock phosphate (RP), single superphosphate (SSP), poultry manure (PM), and RP+PM with and without PSBs. The amended soil was incubated in the control environment at 25 ± 2°C for a total of a 100‐d period to establish relative potential rate of P solubilization of added P sources. A complementary greenhouse experiment was conducted in pots by growing maize as a test crop. Growth characteristics, P‐uptake, and P‐utilization efficiency (PUE) were determined. Phosphate solubilizing bacteria generated a solubilization effect on different P sources by releasing more P into plant‐available soil pool, i.e., 14.0–18.3 µg g^?1 in RP, 5.0–9.9 µg g^?1 in SSP, 1.4–4.4 µg g^?1 in PM, and 4.5–7.8 µg g^?1 in RP+PM compared to their sole application without PSBs. The available P from inorganic SSP declined continuously from the mineral pool (after day 30) and at the end 40% of applied P was unaccounted for. However, P losses were reduced to 28 and 27% when PSBs (PSB₁ and PSB₃) were applied with superphosphate treatments. In the absence of PSBs, the recoveries of applied P (in soil) from RP, SSP, PM and RP+PM were 4, 25, 9, and 12%, respectively, those had been increased to 14, 30, 12 and 15% in the presence of PSBs. Similarly, the plant biomass in RP+PSBs treatments compared to the RP without PSBs increased between 12–30% in first sampling (30 DAG) and 13–30% in the second sampling (60 DAG). The P utilization efficiency (PUE) in plants supplemented with PSBs was 20–73% higher compared to those without PSBs. The detection of oxalic and gluconic acids in culture medium treated with PSBs (7.8–25.0 and 25–90 mg L^?1, respectively) confirmed the production of organic acids by the indigenous bacterial isolates. This study indicate that low P recovery both in plant and soil can likely be improved by using indigenous PSBs and organic amendment poultry manure, which allowed a more efficient capture of P released due to P solubilization.     

Short‐term evolution of phosphorus in an ultisol

Abstract

Evolution of residual phosphate was monitored as function of time on an Ultisol without cropping in a field trial at Sembawa Rubber Research Station, South Sumatra, Indonesia. Three treatments were imposed and either triple superphosphate at a rate of 600 kg ha^‐1 containing 21.54% phosphorus (P) or lime at the rate of 4.14 tons ha^‐1 was applied. During the 20 months of incubation, extractable phosphate as evaluated by hydrochloric acid‐ammonium fluoride (Bray‐I) declined in all treatments. The decrease in the P fertilized plot was more pronounced in relation to the control and the limed soil. Only 56% of P added to the soil was initially recovered as extractable P. This percentage was 30–40% in limed soils. No significant pH difference was recorded for all treated plots except for limed soils. An increase of 1.3 pH units was initially obtained by liming, but the pH dropped to about 0.9 unit after 20 months of incubation. In addition, total P in arable layer remained fairly constant. According to the recoveries of P added referring to 4.3 P 100 g^‐1, half‐life of a single P dose was estimated at 31 months for a P fertilized soil and almost threefold delay for combination of P fertilization and lime application, which was obtained from the following equation:     

Agronomic Efficiency of Indian Rock Phosphates in Acidic Soils Employing Radiotracer A‐Value Technique

Abstract

A greenhouse pot culture study was conducted to evaluate the agronomic efficiency of two rock phosphates from Mussoorie (MRP) and Purulia (PRP) in two acidic soils from Dapoli (Maharashtra) and Aruvanthklu (Karnataka), India, by growing maize (cv. Ganga) as the test crop and using ³²phosphorus (P) single superphosphate (³²P=SSP) as a tracer (A‐value technique). Dry‐matter yield and P uptake increased significantly with the application of P fertilizers compared to control treatment (without P) in both the soils. There was no significant difference with respect to dry‐matter yield among the P fertilizer treatments. However, P uptake by the shoots was found to be significantly higher in the PRP treatment in only Dapoli soil compared to other P fertilizer treatments. Phosphorus derived from fertilizer decreased in rock phosphate treatments compared to standard ³²P‐SSP treatment in both the soils, indicating an excess availability of P from the rock phosphates. A‐values of soil and rock phosphate indicate a relatively higher P availability from Aruvanthklu soil compared to Dapoli soil; A‐values for the rock phosphates were in the order PRP>MRP. The substitution ratio showed that the availability of P from both the rock phosphates were less than SSP in both the soils.     

不同磷源对设施菜田土壤速效磷及其淋溶阈值的影响

土壤中磷的移动性不仅取决于磷的数量且与磷肥形态有关。了解不同磷源（有机肥和化肥）对设施菜田土壤磷素的影响对于指导科学施肥和面源污染防治至关重要。本文选取河北省饶阳县3种不同磷含量的农田土壤（未种植过蔬菜的土壤、种植蔬菜30年的塑料大棚土壤和种植蔬菜4年的日光温室土壤）为研究对象,采用室内培养试验和数学模型模拟方法研究有机无机磷源对设施菜田土壤磷素的影响,确定无机肥和有机肥源土壤磷素淋溶的环境阈值。结果表明添加有机肥和无机磷肥都会显著增加3种不同种植年限设施菜田土壤速效磷（Olsen-P）和氯化钙磷（CaCl₂-P）含量,但增加速度不同。对于未种植过蔬菜的低磷对照土壤,磷投入量高于50 mg·kg^-1（干土）后,无机肥比有机肥显著提高了土壤Olsen-P含量。对于已种植蔬菜30年的塑料大棚土壤,高磷投入时[300 mg·kg^-1（干土）和600 mg·kg^-1（干土）],无机肥比有机肥显著提高了土壤Olsen-P含量,低于此磷投入量时有机肥和无机肥处理之间没有显著差异。3种不同农田土壤CaCl₂-P的含量所有处理均表现出无机肥显著高于有机肥处理,尤其是在高磷量[>300 mg·kg^-1（干土）]投入时表现更加明显。两段式线性模拟结果表明,设施菜田土壤有机肥源磷素和无机肥源磷素淋溶阈值分别为87.8 mg·kg^-1和198.7 mg·kg^-1。随着土壤Olsen-P的增加,添加无机肥源磷对设施菜田土壤CaCl₂-P含量的增加速率是有机肥源磷的两倍。因此,建议在河北省高磷设施菜田应减少无机磷肥的投入,特别是土壤速效磷高于198.7 mg·kg^-1的设施菜田应禁止使用化学磷肥和有机肥,在土壤速效磷低于198.7 mg·kg^-1的设施菜田应加大有机肥适度替代无机肥技术的推广。     

Effect of two moisture regimes on P-release from P treated soils

Understanding phosphorus (P) release under different climatic or moisture regimes will facilitate effective management of plant nutrition. The objective of this study is to evaluate the effect of two soil moisture regimes on P release from Ogun rock phosphate (ORP) and Sokoto rock phosphate (SRP) in two soil types. Soil was poured into soil columns to form lower and top layers. Top layer was mixed with 400 kg ha^?1 P from ORP, SRP, single super phosphate (SSP) and leached with 35.4 cm³ water representing low moisture regime (LMR; 400 mm rainfall) and 106.1 cm³ water for high moisture regime (HMR; 1200 mm rainfall). P concentrations of leachates, available P in soil and soil pH were determined. Cumulative P leached was higher under HMR than LMR in both soils. There was more leaching with SSP (0.41–0.97 mg P) than both phosphate rocks (0.008–0.19 mg P) indicating leaching potential of SSP. Cumulative P leached from SSP treated Olokemeji soils was twice that of acidic Sapoba under LMR while they were similar (Olokemeji, 0.97 mg P; Sapoba, 0.94 mg P) under HMR suggesting that LMR enhances fixation of P in acidic soils. Irrigation of P fertilized soils may reduce P sorption in acidic soils.     

TRENDS OF SOIL CLASSIFICATION IN TANZANIA I. THE EXPERIMENTAL USE OF THE 7TH APPROXIMATION

A review is made of the trends in soil classification in Tanzania, indicating the need for an alternative to the traditional catena concept. An attempt to use the 7^th Approximation is reported, in view of the demand for high category soil classification, using forty-three typical soil profiles and discussing the particular problems related to placing three intimately studied profiles into the orders Alfisol, Ultisol, and Oxisol. An unrevised version of the 7^th Approximation is not recommended for use in Tanzania. However, by using the central concepts of the system and further defining the soil classes at all levels, the use of the 7^th Approximation could greatly assist in the assessment of the nation's soil resources and the ultimate development of agriculture in this country.     

Phosphorus adsorption and desorption in undisturbed samples from subtropical soils under conventional tillage or no‐tillage

The dynamics of P in soil is greatly influenced by the adsorption of phosphate onto Fe‐oxides. Access of phosphate to the surface of these minerals depends on the degree of soil aggregation, which in turn is influenced by soil management system. The primary purpose of this work was to investigate P adsorption and desorption in undisturbed and disturbed soil samples from an Ultisol (Rhodic Paleudult) and an Oxisol (Humic Hapludox) under conventional tillage (CT) or no‐tillage (NT). Phosphorus adsorption and desorption in undisturbed soil was studied by using a continuous flux system containing a P solution for adsorption measurements or deionized water and Mehlich‐I solution for desorption measurements. The Oxisol, which had higher clay, hematite, and goethite contents than the Ultisol, exhibited the highest maximum P adsorption capacity (P_max) values in disturbed samples. Also, the disturbed Ultisol samples had lower P_max values under NT than under CT. The undisturbed soil samples exhibited no significant differences in P adsorption between soil management systems, but P desorption was more marked under NT than under CT. The samples of Oxisol under NT exhibited lower P adsorption rates and higher P desorption rates than the CT samples of the same soil. The decreased P adsorption in undisturbed samples relative to disturbed samples suggests that P adsorption is influenced by physical properties of soil.     

RESIDUAL EFFECTS OF PHOSPHORUS SOURCES IN GRAIN AMARANTH PRODUCTION

Productivity of grain amaranth can be improved at a reduced cost through combined use of low-cost rock phosphate (RP) phosphorus sources as well as selection of amaranth varieties with high phosphorus (P) use efficiencies. Rock phosphate sources are known to exhibit differences with respect to grain yield, disease tolerance and P use efficiency (PUE) in amaranth varieties. However, very little is known about their residual release of P. It is probable that the differential performances exhibited by the RPs might be a function of their P residual properties after cropping. Based on these premises this study was carried out to evaluate the residual effects of P sources under continuous croppings for grain amaranth production. The study was a factorial experiment with four replications. Four P sources: single super phosphate – SSP, ogun rock phosphate – ORP, sokoto rock phosphate – SRP, and control; three amaranth varieties: NH84/493, NH84/445 and NH84/452 were factorially combined with two soil types: Kandiudult and Haplustalf. In order to monitor the residual effects of the P sources the experimental plots were cropped consecutively three times. Results from the study revealed that sandy loam Haplustalf was better than the clayey Kandiudult soil in improving grain amaranth yield under continuous cropping system. Grain yield and relative agronomic efficiency (RAE) decreased with continuous cropping for SSP but increased with continuous cropping for ORP and SRP till second cropping, thereafter there was a decrease. Averaged over the three continuous consecutive croppings, SRP and ORP were 68.9% and 73.5% as effective as SSP in increasing grain yield respectively. It was concluded therefore that ORP and Haplustalf soil are best options for grain amaranth production under continuous cropping system.     

Soil‐solution speciation by MINEQL+4.6 model and plant uptake of Cd and Zn by barley (Hordeum vulgare L.) after application of different phosphate fertilizers

A greenhouse experiment was conducted to investigate the immediate effect of application of mono‐ammonium phosphate (MAP), single superphosphate (SSP), and triple superphosphate (TSP) fertilizers containing varying concentrations of Cd on (1) chemical speciation of Cd and Zn in soil solution by chemical‐equilibrium calculations (MINEQL+4.6 model), (2) growth of barley plants, (3) concentrations of Cd, P, and Zn in soil solution and plant tissue, as well as total plant accumulation of Cd, P, and Zn, and (4) monitoring pH and element changes during incubation periods following phosphate application. Results show that, in general, the pH of soil solution increased during the first 40 d of incubation, then declined. Also, at the end of incubation period, pH of soil solution was affected by fertilization source and fertilization rate. The concentration of Cd in soil solution changed with time. Phosphate fertilization (p < 0.05) or fertilizer source (p < 0.05) showed consistent effects. Also, the application of phosphate fertilizers with three rates significantly increased Zn concentrations in soil solution during the first half (0–30 d) of incubation period and then decreased but still more than in the control. In general, application of different sources of phosphate at 100 g kg^–1 did not change the dominant forms of Cd in soil solution during all incubation time intervals. Speciation of Zn in the control after 30 d of incubation had changed, in comparison to 10 d of incubation, and the dominant forms were Zn²⁺, ZnOH⁺, ZnHCO₃, ZnCO₃(aq), and Zn(OH)₂(aq). Adding phosphate fertilizer significantly increased both shoot and root dry weight compared to control, indicating P was a growth‐limiting factor in the control plants. The Zn concentrations in shoot and root were lower in the TSP‐ and SSP‐fertilizers treatment than those in the MAP and fertilizer treatments at all rates of fertilization. Adding phosphate increased the Cd : Zn and P : Zn ratios in the shoot and root tissue, with the effect being greater with increasing fertilization rate. Phosphate fertilization greatly increased the total accumulation of Cd of barley compared with the control plants (p < 0.001), with the effect being greater with increasing fertilization rate. Source and rate of fertilizers, and their interactions had significant effect (p < 0.05) on Cd accumulation in the whole plant.     

Liming and sulfur amendments improve growth and yields of maize in Rubona Ultisol and Nyamifumba Oxisol

Aluminum toxicity is a major limitation to crop production on highly weathered and leached soils in Rwanda. Moreover, sulfur though widely deficient in Rwanda acidic soils has received little attention by soil fertility researchers. A field experiment on maize response and soil nutrients status to liming materials of travertines at 3.4 t ha^?1, ash wood 1.2 t ha^?1 of CaO equivalent and sulfur at 10 kg ha^?1 combined with NPK at 80, 60, and 45 kg ha^?1 respectively was conducted in Rubona Ultisol and Nyamifumba Oxisol. Results revealed that travertine and wood ash increased the soil pH from 4.7 to 5.8 or higher and decreased exchangeable Al³⁺ and H⁺ to near 0 cmolc kg^?1. Soil nutrients generally increased to high or medium ranges for crop production. Leaf dry biomass, plant height and maize grain yields were significantly higher in Rubona Ultisol than in Nyamifumba Oxisol. Plots that received wood ash, with NPKS or with NPK, generally had higher maize yields, followed by those which received travertines and NPKS or NPK which had maize growth response as compared to the control plots which received NPK only. Thereby, a combination of wood ash with NPKS or NPK, travertines with NPKS was found to neutralize soil aluminum toxicity, increase soil nutrients status to required levels for plant growth and increase maize yields significantly.     

Effect of phosphite phosphorus on alfalfa growth

Abstract

Phosphite (PO^‐3‐P) was compared to phosphate (PO₄ ^‐3‐P) at 2.5, 5, 10, 20, and 40 mg ? kg^‐1) in a P‐deficient soil in a greenhouse pot study with alfalfa (Medicago sativa L.). Alfalfa growth (g dry matter pot^‐1) and ? accumulation (g ? pot^‐1) were measured by clipping each pot 3 times on 30‐day intervals. Although there was a significant (P<.05) growth response to ? during the first 30‐day growth period, it was significantly less from PO₃ ^‐3 than from PO₄ ^‐3‐P at the 10, 20, and 40 mg kg^‐1 rate. The growth response to ? continued through the next 60 days with only the 40 mg kg^‐1 PO₃ ^‐3‐P being significantly lower than PO₄ ^‐3‐P. During the first and second growth periods, there were no significant effects of PO₃ ^‐3‐P on total ? uptake, as compared to PO₄ ^‐3‐P, except at 40 mg kg^‐1. Tissue concentrations of PO₃ ^‐3‐P at 40 mg kg^‐1 dropped successively from 150, to 50, to 10 ppm during the first, second, and third growth periods. This suggests that 40 mg kg^‐1 of soil‐applied PO₃ ^‐3‐P had largely oxidized to PO₄ ^‐3‐P by 90 days after application.     

Not All Phosphate Fertilizers Immobilize Lead in Soils

The effects of six phosphate (P) fertilizers in mobilizing and immobilizing water-soluble lead (Pb) were determined in a contaminated soil (Alfisol from Shaoxing) from China and four Australian soils (an Oxisol from Twonsville Queensland and three South Australian soils from Cooke Plains (Typic Palexeralf)), Inman Valley (Vertisol), and Two Wells (Natric Palexeralf). The fertilizers tested were single superphosphate (SSP), triple superphosphate (TSP), monoammonium phosphate (MAP), diammonium phosphate (DAP), monocalcium phosphate (MCP), and dicalcium phosphate (DCP) to produce an initial P concentration of 1,000 mg/L. The Chinese soil contained 16,397 mg/kg total Pb, but the Australian soils were uncontaminated. The four Australian soils were each spiked with 1,000 mg Pb/kg soil (as Pb(NO₃)₂) and incubated for a month. Single superphosphate treatments decreased total soluble Pb in soil solution to 2–14 % of those of the nil-P (0P) treatment in the four Pb-spiked soils and to 48 % in the Chinese Pb-contaminated soil. The DAP treatment followed by the MAP treatment greatly increased the total soluble Pb in soil solution up to 135–500 % of the 0P treatment, except in the Two Wells soil. MCP could decrease the total soluble Pb in Cooke Plains, Inman Valley, Shaoxing, and Two Wells soils while increase it in the Queensland soil; DCP decreased the total soluble Pb in Cooke Plains and Queensland soils while increased it in the Shaoxing and Inman Valley soils. There were close relationships between the total soluble Pb, total soluble Al, and total soluble Fe in the water extracts of each. Soluble Al and Fe ions in soil solution increased soluble Pb concentrations. We conclude that not all phosphate fertilizers immobilize Pb in soils equally well. SSP and TSP are excellent Pb-immobilizing fertilizers, while MAP and DAP are strong Pb-mobilizing fertilizers. MCP and DCP are either Pb-immobilizing fertilizers or Pb-mobilizing fertilizers depending on their reactions with individual soils.     

通过施用碱性矿渣和作物残茬生物炭以促进酸性老成土中盐基饱并降低土壤酸度

This investigation was conducted by using alkaline slag and crop straw biochars to reduce acidity of an acidic Ultisol through incubation and pot experiments with lime as a comparison. The soil was amended with different liming materials： lime（1 g kg^-1）,alkaline slag（2 and 4 g kg^-1）, peanut straw biochar（10 and 20 g kg^-1）, canola straw biochar（10 and 20 g kg^-1） and combinations of alkaline slag（2 g kg^-1） and biochars（10 g kg^-1） in the incubation study. A pot experiment was also conducted to observe the soybean growth responses to the above treatments. The results showed that all the liming materials increased soil p H and decreased soil exchangeable acidity. The higher the rates of alkaline slag, biochars, and alkaline slag combined with biochars, the greater the increase in soil p H and the reduction in soil exchangeable acidity. All the amendments increased the levels of one or more soil exchangeable base cations. The lime treatment increased soil exchangeable Ca^2＋, the alkaline slag treatment increased exchangeable Ca^2＋ and Mg^2＋ levels, and the biochars and combined applications of alkaline slag with biochars increased soil exchangeable Ca^2＋, Mg^2＋ and K^＋ and soil available P. The amendments enhanced the uptake of one or more nutrients of N, P, K, Ca and Mg by soybean in the pot experiment. Of the different amendments, the combined application of alkaline slag with crop straw biochars was the best choice for increasing base saturation and reducing soil acidity of the acidic Ultisol. The combined application of alkaline slag with biochars led to the greatest reduction in soil acidity, increased soil Ca, Mg, K and P levels, and enhanced the uptake of Ca, Mg, K and P by soybean plants.     

Comparative Effects of Rock Phosphates on Arbuscular Mycorrhizal Colonization of Trifolium pratense L.

Abstract

The effect of five rock phosphates with different solubility (from Algeria, North Florida, North Carolina, Senegal, and Morocco) and that of single superphosphate (SSP) alone or with lime was investigated on the root colonization of red clover with indigenous arbuscular mycorrhizal fungi (AMF). In a pot experiment, the phosphorus (P) sources were applied at four rates (0, 100, 400, and 1600 mg total P₂O₅ kg^?1 dry soil) to an acidic sandy soil (Nyírlugos) and to an acidic clay loam soil (Ragály). The arbuscule content of the roots was more sensitive to various rock phosphates than the infection frequency. No mycorrhizal colonization of roots was observed in the Nyírlugos soil at the 1600 mg P₂O₅ kg^?1 level of SSP or in either soil at the 1600 mg P₂O₅ kg^?1 level of SSP+lime, indicating that the mycorrhizal dependency of the host was eliminated by the highest soluble P concentrations in the soil.     

Evaluation of common bean genotypes for phosphorus use efficiency

A greenhouse experiment was conducted to evaluate phosphorus (P)‐use efficiency of 10 promising genotypes of common bean (Phaseoius vulgaris L.) with short and normal growth duration. The genotypes were grown on an Oxisol at 25 mg P kg^‐1 (low P) and 150 mg P kg^‐1 (high P) of soil. Shoot and root dry weight, root length, P concentration in the shoot, and P uptake in the shoot were significantly (P<0.01) affected by soil P concentration and genotype. However, P level did not effect root length and genotype had no effect on root dry weight. On the basis of P‐use efficiency (mg dry weight of shoot/mg P accumulated in the shoot) genotypes were classified as efficient and responsive (ER), efficient and nonresponsive (ENR), nonefficient and responsive (NER), and nonefficient and nonresponsive (NENR). From a practical point of view, genotypes which produce a lot of dry matter in a soil with a low P level, and respond well to added P are the most desirable because they are able to express their high yield potential in a wide range of P environments. Novo Jalo and Pérola genotypes fall into this group. Genotypes Irai, Jalo Precoce and L93300166 fall into the ENR group. Genotypes Carioca, Rosinha G‐2, and Xamengo were classified NER, whereas, genotypes L93300176 and Diamante Negro were classified as NENR. There were no differences between short and normal growth duration genotypes in P‐use efficiency.