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1.
Abstract

An agronomic evaluation of phosphate rock (PR) on acid soils of Guarico and Anzoategui States was conducted to measure the effect on soil available phosphorus (P), grain yields of sorghum (Sorghum bicolor (L.) Moench) and soybean [Glycine max (L.) Merr.], and P absorption by these crops. Field experiments were established using a complete randomized block design with three replications. The treatments used were: triple superphosphate (TSP), North Carolina phosphate rock (NCRPR), compacted NCRPR with TSP at 60–40% and 70–30% (NCRPR 60/40 NCRPR 70/30), compacted Venezuelan Monte Fresco phosphate rock 60–40% and 70–30% (MFPR 60/40, MFPR 70/30), finely ground Monte Fresco phosphate rock (MFPR), finely ground Navay phosphate rock (NPR), and a check plot with no P source added. Five rates were applied, 0, 50,100,150, and 200 P2O5/ha, broadcasted and incorporated prior to planting. A basic fertilization of N, K, S, Mg, and Zn was uniformly applied to ensure an adequate supply of these nutrients. Soybean seeds were inoculated with Bradyrhizobium japonicum. Soil samples were taken before planting and at harvest, and plant samples taken at critical growth stage (flowering) for tissue analysis, Crop grain yields were measured at 12% moisture content. The relative agronomic effectiveness (RAE) was calculted by the formula: RAE (%( = Yield of the rock ? Yield of check plot/Yield of TSP ? Yield of check plot × 100 Maximum yields in all cases were obtained with TSP, however, in most cases there were no statistically significant differences between TSP and NCRPR as received or compacted (60/40 and 70/30). The compacted Venezuelan phosphate rocks also gave significantly higher yield and RAE responses showing the potential of these P sources for annual crops in the country. The finely ground Venezuelan phosphate rocks increased yields and RAE as compared to the check plot, but they gave the lowest response of all P sources. Soil available P after harvest had a tendency to increase where any source of P was applied or when the rates increased. The increment in soil available P was more evident when TSP and NCRPR as received and compacted were used. The lowest increments were reached with finely ground Navay phosphate rock. Leaf P concentration values were between the sufficiency range, except for those treatment where Monte Fresco and Navay finely ground phosphate rocks were applied at the rate of 50 kg P2O5/ha and for the check plot.  相似文献   

2.
ABSTRACT

Dissolution of phosphate rocks (PR) in soils requires an adequate supply of acid (H+) and the removal of the dissolved products [calcium (Ca2 +) and dihydrogen phosphate (H2PO4 ?)]. Plant roots may excrete H+ or OH? in quantities that are stoichiometrically equal to excess cation or anion uptake in order to maintain internal electroneutrality. Extrusion of H+ or OH? may affect rhizosphere pH and PR dissolution. Differences in rhizosphere acidity and solubilization of three PRs were compared with triple superphosphate between a grass (Brachiaria decumbens) and a legume (Stylosanthes guianensis) forage species at two pH levels (4.9 and 5.8) in a phosphorus (P)-deficient Ultisol with low Ca content. The experiment was performed in a growth chamber with pots designed to isolate rhizosphere and non-rhizosphere soil. Assessment of P solubility with chemical extractants led to ranking the PRs investigated as either low (Monte Fresco) or high solubility (Riecito and North Carolina). Solubilization of the PRs was influenced by both forage species and mineral composition of the PR. The low solubility PR had a higher content of calcite than the high solubility PRs, which led to increased soil pH values (> 7.0) and exchangeable Ca, and relatively little change in bicarbonate-extractable soil P. Rhizosphere soil pH decreased under Stylosanthes but increased under Brachiaria. The greater ability of Stylosanthes to acidify rhizosphere soil and solubilize PR relative to Brachiaria is attributed to differences between species in net ion uptake. Stylosanthes had an excess cation uptake, defined by a large Ca uptake and its dependence on N2 fixation, which induced a significant H+ extrusion from roots to maintain cell electroneutrality. Brachiaria had an excess of anion uptake, with nitrate (NO3 ?) comprising 92% of total anion uptake. Nitrate and sulfate (SO4 2 ?) reduction in Brachiaria root cells may have generated a significant amount of cytoplasmic hydroxide (OH?), which could have increased cytoplasmic pH and induced synthesis of organic acids and OH? extrusion from roots.  相似文献   

3.
Abstract

An experiment was conducted on some soils of Mesa de Guanipa, which are sandy, acid (pH 5.5), and have low levels of available P, K, Ca, and Mg. These soils are located at the Agropecuaria Guanipa farm in El Tigre, Anzoategui State, Venezuela. The main objective was to evaluate rates and sources of P, and rates of K on soybean yield (variety FP‐3), which is an activity of the project “Maximum soybean yields in Venezuela”;, financed by the Potash and Phosphate Institute of Canada. The rates and sources of P were 0, 75, and 150 kg P2O5/ha as triple superphosphate (TSP) and diammonium phosphate (DAP). Rates of potassium as K2O were 0, 60, and 120 kg/ha as potassium chloride (KCl). The experimental design was a randomized complete block with 3 replications and a final plant density equivalent to 400,000 plants/ha. A basic application of nitrogen and magnesium fertilizers was made to guarantee the supply of those nutrients. The soybean seeds were inoculated at planting with NITROBAC to ensure nodule formation. Yield results showed a good response to P application and low response to K. The combination of 150 kg P2O5/ha as TSP and 60 kg K2O/ha as KCl produced the maximum soybean grain yields of 2.857 kg/ha at 12% moisture as well as the highest net return of U.S.$393.9/ha. From the results obtained in this experiment as well as ones to be established during the next 3 years, it is expected that there will be an adjustment in the fertilization program followed by the soybean farmers of Mesa de Guanipa as they are now applying higher rates of K and lower rates of P than that applied in this experiment.  相似文献   

4.
Neglected P and K fertilization in organic farming reduces N2 fixation and grain yield in a red clover‐oat rotation N2 fixation is the most important N source in organic farming. An insufficient P, K, and S supply to legumes may reduce their N2 fixation capacity. Consequently, the total yield of plant production may also be reduced. This problem was studied in a pot experiment with red clover followed by oat. Soil was taken from a field where organic farming had been practiced for more than 30 years without applying any mineral fertilizers or buying additional fodder. The soil (luvisol from loess) was characterized by: pH (CaCl2) 5.4; lactate‐soluble (CAL) P 5 mg kg–1 and K 110 mg kg–1. 6 kg dry soil were mixed with 400 mg P applied as (i) triplesuperphosphate (TSP), (ii) rock phosphate (RP) or (iii) compost from organic household residues (BAK). An additional treatment (iv) with TSP received 1000 mg K as K2SO4 (TSP+K) and an additional treatment with RP (v) received only 200 mg P (RP/2). A control treatment received no fertilizer. P application significantly improved the P nutritional status of the plants (P content) and increased the N amount in the shoots of red clover (with 400 mg P per pot by 64 % to 139 % as compared to the control) and the dry matter (DM) yield by 60 % to 130 %. No significant differences between TSP and RP were found. The application of BAK resulted in a significantly higher N yield than the application of RP and TSP. The treatment TSP+K resulted in the highest DM yield (230 %), removal of P was 343 %, of K 228 %, and of N 239 % as compared to the control plants. This indicates a synergistic effect of P, K, and S on N2 fixation, which was also found with BAK. Oat grown after red clover increased its grain yield by 132 % (200 mg P as RP) to 165 % (400 mg P treatments). This was mainly due to a higher P uptake (up to 172 %) and a higher N uptake (up to 172 %) as compared to the control.  相似文献   

5.
In this paper, the effects of arbuscular mycorrhizal (AM) fungi and phosphate amendments on protection of the tropical grass Brachiaria decumbens Stapf. against metal toxicity caused by Zn, Cd, Cu, and Pb were studied in a sterilized soil. Plants inoculated with a mixture of AM fungi (Acaulospora morrowiae, Gigaspora albida, and Glomus clarum) isolated from a heavy-metal-contaminated site or amended with P (added as triple superphosphate) exhibited marked positive growth responses, indicating the ameliorating effects of these two factors. Soil metal concentrations needed to inhibit plant growth by 50% were around twofold higher for AM plants as compared to those for non-inoculated ones. Similarly, phosphate showed ameliorating effects for B. decumbens, but its effects were not related to mycorrhizal conditions. Although mycorrhiza and phosphate act independently, their protecting effects were additive. Metal bioaccumulation factor of B. decumbens is high, especially for Cd; but AM inoculation prevents metal transference from roots to shoots, retaining these metals in the roots. AM fungus and phosphate represent a promising tool for enhancing ground vegetation in heavy-metal-contaminated sites.  相似文献   

6.
Abstract

Land use patterns affect soil nutrient transformation and availability. The study determined the distribution of phosphorus (P) fractions and sorption in five pasture fields composed of Andropogon gayanus, Brachiaria decumbens, Chloris gayana, Digitaria smutsii, and Stylosanthes guianensis. The objectives were to characterize P fractions in improved pastures and to determine the effect of forage species on soil P lability. Total P (Pt) across the pastures was not significantly different. Organic P (Po) accounted, on the average, for 64% of Pt. Resin‐P, considered the plant‐available P, ranged from 4 to 10 mg kg?1, suggesting acute P deficiency in the pastures. The sum of P fractions extracted by 0.5 M NaHCO3, 0.1 M NaOH, and 1.0 M HCl, together with the resin‐P, accounted for less than 35% of Pt. Factor analysis indicated that plant‐available P approximated by resin‐P was furnished by ?HCO3‐Po mineralization and HCl‐P. The highest concentrations of ?HCO3‐Po and ?OH‐Po were maintained by Brachiaria decumbens. Grouping Pi and Po fractions into labile and nonlabile fraction showed that Brachiaria decumbens maintained the greatest concentration of labile P as a proportion of its Pt. The pasture soils sorbed between 31 and 65% of added P from a standard concentration of 50 mmol kg?1. Phosphorus sorbed by soils from the pasture fields was in the order: Digitaria smutsii=Stylosanthes guianensis>Brachiaria decumbens=Chloris gayana>Andropogon gayanus, whereas resin recovery of sorbed P was greater in Brachiaria decumbens than other pastures. Between 82 and 92% of sorbed P was bound irreversibly. It was concluded that the relatively high concentration of labile P maintained by soil under Brachiaria decumbens was probably related to its capacity to sequester more carbon than the other pastures.  相似文献   

7.
The high cost of conventional, water‐soluble phosphorus (P) fertilizers limits their use by resource‐poor farmers in sub‐Saharan Africa. Phosphate rocks are a low‐cost alternative. We evaluated the effectiveness and residual effects of Egyptian phosphate rock (EPR) and Togo phosphate rock (TPR) relative to triple superphosphate (TSP) applied at 0, 20, 40, 80, and 160 kg P ha‐1 to annual Trifolium species grown in a P‐deficient Vertisol. The fertilizers were applied once and their effects were followed on seven consecutive annual clover crops. Clover responded to P at all the rates used. Significant (P<0.05) responses to P at the low 20–40 kg P ha‐1 rates were registered up to the fifth crop after application of P, and responses to higher rates of 80–160 kg P ha‐1 were significant up to the seventh crop. Critical evaluation of residual effects by comparing the response of clover to these fertilizers with response to fresh applications of TSP in the second and third crops confirmed these observations. Over all the seven crops, EPR was 82% as effective as TSP in increasing clover DM and 83% as effective in increasing P uptake. Its substitution rates were 67% for DM yields and 69% for P uptake. For TPR, the relative responses were 54% and 52% for DM yield and P uptake, respectively, and the corresponding substitution rates were 29% and 27%. In separate experiments, the effects of mixing these phosphate rocks with triple superphosphate (TSP) in various proportions (at 60 kg P ha‐1) were also investigated. The highest response of clover was observed with TSP applied alone, but the phosphate rocks applied alone also significantly increased yields compared with the controls without applied P. Mixtures of TPR and TSP increased yields only slightly over pure TPR, and mixtures of EPR and TSP had no effect on yields compared with pure EPR, presumably because EPR is more reactive than TPR. It was concluded that EPR is highly effective in these soils, but the effectiveness of TPR is low. The highly reactive EPR could be used to elevate the P status of the P‐deficient Vertisols and increase feed availability and livestock productivity in the Ethiopian highlands. Mixing of these phosphate rocks with TSP cannot be recommended.  相似文献   

8.
Influence of long-term application of different P-fertilizers on phosphate availability in the rhizosphere of rape The residual P effect was investigated in soils from a 10 years' lasting field trial (North of Hessia, Alfisol-Udalf, pH 5.7) in which different P-fertilizer types had been applied with a rate of 111 kg P2O5 ha?1 a?1. Soil analysis showed that basic slag phosphate had increased the content of CAL-, H2O- and EUF extractable P in the soil to a higher extent than Novaphos (partially acidulated phosphate rock) or Hyperphos (phosphate rock). In the latter treatment the highest content of DL soluble P was found as compared with the other P-fertilizer types. Pot experiments with rye-grass, rape and maize showed that P recovery was highest from the soil with the basic slag treatment and lowest in the treatment with Hyperphos, Novaphos taking an intermediate position. This finding demonstrates that the DL-method does not provide a reliable information on the P-availability of a soil, if treated with rock phosphate. The level of water soluble P in the rhizosphere of rape was investigated with a particular technique (Kuchenbuch and Jungk, 1982). It could be shown that the P level in the rhizosphere of the Hyperphos treatment was only slightly higher than the P level of the P0 treatment (without P fertilizer) while in the Novaphos – and particularly in the basic slag treatment much higher levels of soluble P were found. It thus becomes evident that even in the rhizosphere the solubility of Hyperphos was poor. The levels of water soluble P in the rhizosphere followed a depletion curve. The steepest gradient was found for basic slag, followed by the Novaphos-, Hyperphos- and the P0 treatment.  相似文献   

9.
Abstract

Soil phosphorus (P) deficiency is a constraint to crop production in many regions of sub‐Saharan Africa, which could be overcome through use of either soluble P fertilizer or sufficiently reactive phosphate rock (PR). A field study was conducted with corn (Zea mays L.) for three growing seasons (18 months) on a P‐deficient, acid soil in Kenya to compare a soluble P source (triple superphosphate, TSP) and relatively reactive Minjingu PR from Tanzania. In the 18 months following application of 250 kg P ha‐1, bicarbonate extractable inorganic soil P (Pi) was higher for application of TSP than PR, but Pi extracted with a mixed anion‐cation resin was comparable for TSP and PR. Inorganic P extracted by 0.1M NaOH, without prior extraction of resin and bicarbonate Pi, decreased during the 18 months following TSP application, but increased following PR application. After 18 months, about 7% of the added PR‐P remained as Ca‐bound P that was extracted with 1M HCl. The 1M HCl extractable P., however, underestimated residual PR‐P that gradually dissolved and supplied plant‐available P, as indicated by recovery of <40% of PR‐P added to soil in laboratory incubations even though PR solubility in HCl was >90%. Minjingu PR was an effective source of P for corn. Corn yields were comparable for TSP and PR, and the relative agronomic effectiveness of PR averaged 107% in Season 1 and 79% in Season 3. Anion resin and mixed anion‐cation resin appeared to be superior to bicarbonate and NaOH as a soil P test for use with both TSP‐ and PR‐treated soils.  相似文献   

10.
Phosphate rock (PR) is an alternative fertilizer to increase the P content of P-deficient weathered soils. We evaluated the effects of fertilizer form on indicators of biological cycling of P using an on-farm trial on a Rhodic Kandiudox in western Kenya. Treatment plots were sampled after 13 cropping seasons of P applications as Minjingu phosphate rock (PR) or as triple super phosphate (?TSP) (50 kg P ha?1 season?1), as well as a P-unfertilized control (0 kg P ha?1 season?1). Soils (0–15 and 15–30 cm) were analyzed for microbial biomass P (Pmic), activities of acid phosphomonoesterase, alkaline phosphomonoesterase, and phosphodiesterase, and sequentially extractable P fractions. P additions as Minjingu PR yielded 299% greater Pmic than TSP at 0–15-cm depth despite similar labile P concentrations in the two P fertilization treatments and stimulated activities of acid phosphomonoesterase (+39%). When added in the soluble form of TSP, a greater percentage of total soil P was present in mineral-bound forms (+33% Fe- and Al-associated P). Higher soil pH under Minjingu PR (pH 5.35) versus TSP (pH 5.02) and the P-unfertilized treatment (pH 4.69) at 0–15-cm depth reflected a liming effect of Minjingu PR. The form of P fertilizer can influence biological P cycling in weathered soils, potentially improving P availability under Minjingu PR relative to TSP via enhanced microbial biomass P and enzymatic drivers of P cycling.  相似文献   

11.
To compare the growth performance of Brassica in a phosphorus (P) stress environment and response to added P, six Brassica cultivars were grown in pots for 49 days after sowing, using a soil low in P [sodium bicarbonate (NaHCO3)–extractable P = 3.97 mg kg?1, Mehlich III–extractable P = 6.13 mg kg?1] with (+P = 60 mg P kg?1 soil) or without P addition (0P). Phosphorus‐stress markedly reduced biomass accumulation and P uptake by roots and shoots. However, root–shoot ratio remained unaffected, implying that relative partitioning of biomass into roots and shoots had little role to play in shoot dry matter (SDM) production by cultivars. Biomass correlated significantly (P < 0.01) with total P uptake. Under P stress, the cultivars that produced greater root biomass were able to accumulate more total P content (r = 0.95**), which in turn was related positively to SDM and total biomass (r > 0.89**) and negatively to P‐stress factor (r = ?0.91**). There was no correlation between P efficiency (PE) (relative shoot growth) and plant P, but PE showed a very significant correlation with shoot P content and SDM. Wide differences in growth and better performance of cultivars such as ‘Brown Raya’ and ‘Con‐1’ under P stress encouraged screening of more germplasm, especially in the field, to identify P‐tolerant cultivars.

In another study, potential relative agronomic effectiveness (RAE) of sparingly soluble P sources was investigated by growing two contrasting cultivars. The P sources incorporated into soil at 0, 10, 25, 50, and 100 mg P Kg?1 were (i) powdered Jordan rock P (RP), (ii) triple superphosphate (TSP), (iii) powdered low‐grade TSP [TSP(PLG)], (iv) a mixture of RP + TSP compacted into pellets at 50:50 P ratio [RP + TSP(PelC)], and (v) a mixture of powdered RP + TSP at 50:50 P ratio [RP + TSP(PM)]. The RP was low in RAE and only 5 and 29% as effective as TSP in producing dry matter (DM) of P‐sensitive ‘B.S.A.’ and P‐tolerant ‘Brown Raya’ cultivars, respectively. There were no significant differences between TSP and RP + TSP(PelC) in DM yield of ‘Brown Raya,’ whereas, in the case of ‘B.S.A.’ RP + TSP(PM) was significantly less effective than RP + TSP(PelC) compared with TSP. Combined utilization of superior genome and P sources [such as TSP(PLG) and RP + TSP(PelC)] produced from low‐grade RP (that cannot be used either for direct application or acidulated P fertilizers) can be used as an alternative strategy for sustainable crop production, especially in resource‐poor environments. Further field trials at the level of cropping systems are needed.  相似文献   

12.
Abstract

The amount of phosphorus (P) dissolved in a closed‐incubation system, in soils receiving Christmas Island grade‐A phosphate rock (CIPR), Gafsa phosphate rock (GPR), and triple superphosphate (TSP), as measured by extraction with 0.5M NaHCO3 (APb) or 0.5M NaOH (AP) and expressed as ?Pb/?P*100 (PDP) was compared to P uptake (?Ps) by Setaria in a glasshouse experiment. There was no direct relationship between APs and PDP for CIPR, GPR, and TSP added at 50 and 150 mgP/kg soil to three Malaysian soils (Bungor, Kundor, and Segamat) during a 10‐month period. Averaged across soils, rate of addition, and P sources, ?Ps was 17% higher than PDP. Overestimation of PDP by ?Ps could be due to the ability of the roots of Setaria to use more of the P which is dissolved from the three P sources and then chemisorbed, than can be extracted by the NaHCO3 reagent. The chemisorbed P pool is extractable using 0.5M NaOH. There was a close relationship between ?Ps and ?P, with a correlation coefficient of 0.85**. Residual P, determined by Pb method after each harvest, successfully predicted Ps by Setaria in the subsequent harvest with correlation coefficients varying between 0.74* and 0.99** for CIPR, GPR, and TSP in five soils (Bungor, Durian, Kundor, Segamat, and Tok Yong). The critical Pb values ranged from 5 for Durian to 10 mgP/kg soil for Kundor.  相似文献   

13.
Abstract

The majority of soils in Africa are phosphorus (P) deficient, but the high cost of water‐soluble P fertilizers limits their use by resource‐poor farmers. A low‐cost alternative is to use phosphate rocks. We evaluated the effectiveness of Egyptian phosphate rock (EPR) relative to triple superphosphate (TSP) applied at 0, 15, 30, 45, and 60 kg P ha‐1 to annual Trifolium species grown on a P‐deficient Vertisol. The fertilizers were applied once and their effects were followed on seven consecutive annual clover crops. Clover responded to P at all the rates used. Significant (P<0.05) P effects on clover P content and DM yields were observed up to the fourth crop. Over all the seven crops, EPR was 89% as effective as TSP in increasing herbage DM and 93% as effective in increasing herbage P content. Its substitution rates were 79% for DM yield and 86% for clover P content. Therefore, EPR was highly reactive and its use could elevate the P status of the P‐deficient Vertisols and increase feed and livestock productivity in the Ethiopian highlands.  相似文献   

14.
Acid sulfate soils (ASS) are characterized by low pH, aluminum (Al), and iron (Fe) toxicity and are typically deficient in phosphate (PO4). The application of phosphorus (P) fertilizer could help reduce the level of exchangeable Al and Fe, thereby improving the rice growth and yield. Five levels of P (0, 20, 40, 60 and 80 kg phosphorus pentoxide (P2O5)/ha) were tested with rice varieties MTL560 in the wet season and MTL480 in the dry season. The optimum rate of P was 60 kg P2O5/ha for rice in the dry season and 80 kg P2O5/ha in the wet season. Soil testing showed at the start of the season that there was sufficient P in the soil. At the end of the season there was a reduction in soil Al and Fe in plots that had P rates above 40 kg P2O5/ha. It is therefore likely that P application reduced Al and Fe toxicity through precipitation and formation of Al-P and Fe-P compounds, which boasted yield, rather amending a soil P deficiency.  相似文献   

15.
The geochemical reactivity of single superphosphate (SSP), triple superphosphate (TSP), phosphate rock (PR), partially acidulated phosphate rock (PAPR) and potassium dihydrogen phosphate (KH2PO4) was evaluated in an incubation trial. The soil was Anthrosols, Ap horizon (Sandy loam). Solubility equilibrium of phosphates was calculated by phosphate (PPot = logH2PO4 – pH) and calcium (CaPot = logCa + 2pH) potentials. Next, activity ratio (AR°) and Woodruff potential (ΔF) were considered for estimating phosphate dynamics in the soil. Data showed that phosphate potentials stressed on significant solubility process and varied accordingly to the rates of the fertilizers: ?5.50, ?4.81, ?4.47 and ?4.09 for 0, 50, 100 and 150 kg P ha?1. The values of the Woodruff potential (ΔF) varied widely from ?1929 to 8573 cal mol?1, i.e., from marginal supplying power in the case of the control treatment to very high supplying power for the TSP (Triple superphosphate). These findings are of practical value for the following reasons: TSP and KH2PO4 are recommended for quick and high P supply to plants; SSP and PAPR for moderate supply and finally PR for slow and low supply. Phosphorus efficiency should be treated with priority particularly for areas with intensive cropping and susceptibility to runoffs.  相似文献   

16.
With the increase in phosphate fertilizer prices, there is a need to find lower-cost alternatives that are as efficient as soluble sources such as single (SSP) and triple superphosphate (TSP). In Brazil’s northern and northeastern regions, there are reserves of igneous rocks with low solubility containing high concentrations of total phosphorus (P) that can be used to produce fertilizers, such as thermalphosphates. To assess the efficiency of sources of P and two types of lime on soybean yield, a field experiment was carried out in an area with dystrophic Red Latosol (Oxisol) in a Cerrado region in the southern part of Maranhão State. The experimental design was randomized blocks in a 2 × 3 × 4 factorial scheme, with four replicates. The treatments were two types of lime [calcitic (CL) (<5 dag kg?1 of MgO) and dolomitic (DL) (>13 dag kg?1 of MgO)], three phosphate fertilizer sources [triple superphosphate (TSP), “Yoorin” thermalphosphate (YT), and experimental thermalphosphate (ET)], and four rates of phosphorus pentoxide (P2O5; 0, 100, 200, and 300 kg ha?1). After 2 years of cultivation, the application of DL resulted in greater soybean yields than the application of CL. The two lime types influenced the pH, carbon (C), calcium (Ca), and magnesium (Mg) concentrations as well as the Ca/Mg, Ca/K, and Mg/K ratios in the soil. With respect to sources of P, the YT applied in the soil with DL produced an agronomic efficiency index (AEI) similar to that of TSP, whereas in the soil with CL, the TSP, YT, and ET were similar, with maximum technical efficiency (MTE) under both conditions starting at 230 kg ha?1 of P2O5. The critical concentration of available phosphorus (P) in the soil (Mehlich-1 extractant) for cultivation of soybean under the climate and soil conditions studied was between 5.0 and 6.0 mg kg?1.  相似文献   

17.
Abstract

The effect of liming on the agronomic effectiveness of three phosphate rocks (PRs) Pesca and Huila from Colombia and Sechura from Peru as compared with TSP was evaluated in a greenhouse experiment for an Al‐tolerant soybean cultivar grown on an acid Ultisol. On both unlimed (pH 4.4) and limed (pH 5.0) soils, the agronomic effectiveness of P sources in terms of increasing seed yield followed the order of TSP > Sechura PR > Huila PR > Pesca PR > check, an order similar to that of solubility of P sources. Liming slightly decreased the effectiveness of Pesca PR, whereas liming had no effect on Huila PR. A significant increase in agronomic effectiveness was observed upon liming for Sechura PR and TSP. Soil‐available P as extracted by the Pi method was closely related to the amount of N fixed by soybean crop that, in turn, was related to the soybean seed yield. Values of relative agronomic effectiveness (RAE) of PRs with respect to TSP were calculated by assuming the check = 0% and TSP = 100%. On unlimed soil, the RAE values of PRs were: Pesca PR = 31%, Huila PR = 42%, Sechura PR = 84%. On the limed soil, the RAE values were: Pesca PR = 8%, Huila PR = 24%, Sechura PR = 66%. It can be concluded that the use of PR with respect to that of TSP for soybean crop is more favorable in the unlimed soil than in the limed soil, provided that the soybean plant is relatively Al‐tolerant.  相似文献   

18.
《Journal of plant nutrition》2013,36(12):2149-2158
Abstract

The effects of different commercial phosphate fertilizers [Triple superphosphate (TSP), Tricalcium phosphate (TCP), and ARAD rock phosphate) and soil aluminum (Al) saturation (86, 29, and 0%) on the mineral composition and dry mass production of corn (Zea mays) plants were studied. As soil Al saturation values decreased, pH, calcium (Ca), and magnesium (Mg) levels in the soil increased. High Ca values in the shoot resulted in the reduction in potassium (K) concentrations. The high values of P availability in the soil for the ARAD source of P did not correspond to the high values of dry mass production of corn plants. The high values of corn mass production were noticed for the TSP phosphate source, and the mass productions values were reduced as the soil Al saturation values increased.  相似文献   

19.
Abstract

The agronomic effectiveness of Mussoorie phosphate rock (MPR) from India and a 2:1 mixture of MPR and single superphosphate (SSP) was compared against SSP as phosphate fertilizers for crops. The experiment was conducted for three seasons and was designed to study the response of crops to current application as well as residual effects of the various P fertilizers. Three crops were grown in sequence: finger millet (Eleusine coracana), maize (Zea mays L.), and blackgram (Phaseolus mungo) on a calcareous soil under irrigated conditions. The phosphate fertilizers were applied to finger millet and/or maize but not to the blackgram. Soil samples were collected at intervals and analysed for Olsen bicarbonate‐extractable P. The agronomic effectiveness of fertilizers relative to SSP (RAE) were calculated from the fertilizer substitution ratios. When used on finger millet, the RAE of MPR, calculated at a yield which corresponded to 90% of calculated maximum yield on applying SSP, was 42%. For the mixture of MPR and SSP the RAE was 68%. On maize, yield in MPR treatment plateaued at too low a level (about 80% of calculated maximum yield for SSP) to calculate RAE but for MPR/SSP the RAE was 80%. The residual effectiveness of fertilizers on the second crop, compared against freshly applied SSP was 41% for SSP, 49% for MPR, and 73% for MPR/SSP. Olsen bicarbonate‐extractable P values determined one month after fertilizer application increased over control by about 55% in MPR and 86% in MPR/SSP treatments relative to SSP. Economic calculations indicated that, application of MPR is of equal value to SSP for the cropping sequence whereas MPR/SSP for the cropping sequence as well as for individual crops.  相似文献   

20.
Abstract

Urea phosphate (17–44–0) (UP) was injected in surface placed drip irrigation lines, subsurface placed drip irrigation lines (15 cm below soil surface), or band under furrow irrigation on a calcareous soil. In drip irrigation, UP was split in two applications, two weeks apart, to give a total rate of 50 kg P2O5/ha. The furrow rate was 100 kg P2O5/ha in a single application. Soil analysis one month after the first injection of UP showed high levels of available P (NaHCO3 extractable) around the drip emitters. Considerable P mobility in the soil was detected within 20 cm from the emitters. Banding UP under the furrow did not leave any measurable levels of available P by the end of the experiment. Soil NO3‐N levels were comparable in all fertilized irrigation treatments, and were higher than the levels under an unfertilized furrow. Soil pH was reduced by 0.5 units around the drip emitters, but no change was measurable under furrow irrigation. Soluble salts (ECe) were concentrated in the top 10 cm of the soil surface in all the fertilized irrigation methods. Split application of UP in subsurface drip irrigation provided the longest residual and best distribution of available P in a calcareous soil.  相似文献   

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