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1.
The usefulness of soil phosphorus (P) tests used in routine soil analyses is limited by the fact that a single measurement cannot encompass all P‐related factors potentially affecting plant performance. In this work, we performed micropot (15 mL) experiments to test the hypothesis that the predictive value of two common soil P tests (Olsen P and CaCl2‐P) can be improved by considering properties commonly measured in laboratory analyses. Forty‐nine sets of soils ranging widely in properties were used for this purpose, each set consisting of samples with similar properties but differing in P status. Ryegrass and turnip were grown in a chamber for 30 days in two separate experiments and their yields at harvest recorded. The critical Olsen P and CaCl2‐P levels, which were taken to be those corresponding to 95% asymptotic yield as calculated from data fitted to a Mitscherlich equation, were greater for turnip than for ryegrass, probably as a result of the difference in yield (49 and 160 mg dry matter/micropot on average for ryegrass and turnip, respectively) and hence in P requirements between the two species. Critical Olsen P spanned narrower ranges than critical CaCl2‐P in both crops and is therefore seemingly the more robust of the two tests. Both critical P values exhibited moderate correlations with soil properties. Thus, critical Olsen P was (a) lower in soils with a medium pH – which is consistent with the fact that the bicarbonate solution method tends to overestimate plant‐available P in strongly acid and calcareous soils; (b) positively correlated with pH and carbonate content in calcareous soils; and (c) uncorrelated with soil properties in noncalcareous soils. On the other hand, critical CaCl2‐P in some soil groups was negatively correlated with some properties increasing the P buffering capacity of soil (e.g. Fe oxide content). Taken together, our results suggest that routinely measured soil properties help to predict critical Olsen P better than critical CaCl2‐P.  相似文献   

2.
Abstract

Investigating the relation between concentration or release of phosphorus (P) into soil solution (CaCl2‐P, determined by 0.01 M CaCl2 extraction of soils) and soil test phosphorus (Olsen P, or 0.5 N NaHCO3‐extractable soil phosphorus) for 10 widely ranging and variously managed soils from central Italy, a change point was evident where the slopes of two linear relationships meet. In other words, it was possible to distinguish two sections of the plots of CaCl2‐P against Olsen P, for which increases of CaCl2‐P per unit of soil test P increase were significantly (p<0.05) greater above than below these change points. Values of change point ranged from 14.8 to 253.1 mg kg?1 Olsen P and were very closely correlated (p<0.001) to phosphorus sorption capacity of soils. Similar change points were also previously observed when Olsen P (and also Mehlich 3 P) of surface soils was related to the P concentration of surface runoff and subsurface drainage. Because insufficient data are available relating P in surface soils and amount of P loss by overland, subsurface, or drainage flow, using the CaCl2 extraction of soil can be convenient to determine a change point in soil test P, which may be used in support of agricultural and environmental P management.  相似文献   

3.
The aim of this paper was to compare the concentration of P in soil extracts prepared with water and a ‘soil solution proxy’ (‘SSP’, that is, a salt solution similar in ionic composition and strength to the actual soil solution) with that in 0.01 m CaCl2 extracts, which is usually taken as a measure of soil P intensity. Seventy widely ranging agricultural soils from the Mediterranean part of Spain were used. Soil/solution ratio was 1:10 and extraction time 3 days. For 0.01 m CaCl2, a short extraction time of 30 min was also used as the reference method. CaCl2‐P(3 days) and CaCl2‐P(30 min) were not significantly different for the 40 noncalcareous soils group, but CaCl2‐P(3 days) was significantly larger than CaCl2‐P(30 min) for the 30 calcareous soils group. The Water‐P/CaCl2‐P(30 min) ratio was not significantly related to any soil property, its mean being 6.3 for the noncalcareous and 5.8 for the calcareous soils group. The mean SSP‐P/CaCl2‐P(30 min) ratio was 2.6 for the noncalcareous and 3.1 for the calcareous soils group, and decreased slightly with increasing ionic strength of the soil solution in the noncalcareous soils group. These results are consistent with the promoting influence of the Ca ion and ionic strength on P adsorption by permanent‐charge soils. The fact that extraction with 0.01 m CaCl2 generally results in underestimation of the actual concentration of P in the soil solution should be considered when CaCl2‐P is used as a soil P test.  相似文献   

4.
I. D&#;AZ  J. TORRENT 《土壤圈》2016,26(5):636-642
Maintaining soil phosphorus(P) at adequate levels for plant growth requires assessing how the long-term P balance(viz., the difference between P inputs and outputs) results in changes in soil test P. The hypothesis that routinely measured soil properties can help predict the conversion factor of P balance into Olsen P was tested at 39 sites in agricultural areas of the Mediterranean region in Spain. A set of soil samples from each site was analyzed for Olsen P, inorganic P(P extracted using 0.5 mol L~(-1) H_2SO_4), pseudototal P(P extracted using 0.5 mol L~(-1) H_2SO_4 following ignition at 550℃), and organic P(the difference between pseudototal P and inorganic P). Organic and Olsen P were uncorrelated in most of the 39 soil sets, which suggests that organic P content changed little with P inputs and outputs. The slopes of the regression lines of Olsen P against pseudototal and inorganic P, which were used as two different measures of the conversion factor, ranged widely(from 0.03 to 0.25 approximately), with their average values(about 0.10) being similar to those found in long-term experiments conducted in temperate areas. Neither conversion factor was significantly correlated with any routinely measured soil property; however, the conversion factor for inorganic P was significantly lower for calcareous soils than for noncalcareous soils. Our negative results suggest the need to isolate the influence of soil properties from that of management systems and environmental factors relating to P dynamics in future studies.  相似文献   

5.
Quantifying microbial biomass phosphorus in acid soils   总被引：10，自引：0，他引：10  
 This study aimed to validate the fumigation-extraction method for measuring microbial biomass P in acid soils. Extractions with the Olsen (0.5 M NaHCO3, pH 8.5) and Bray-1 (0.03 M NH4F–0.025 M HCl) extractants at two soil:solution ratios (1 : 20 and 1 : 4, w/v) were compared using eight acid soils (pH 3.6–5.9). The data indicated that the flushes (increases following CHCl3-fumigation) of total P (Pt) and inorganic P (Pi) determined by Olsen extraction provided little useful information for estimating the amount of microbial biomass P in the soils. Using the Bray-1 extractant at a soil:solution ratio of 1 : 4, and analysing Pi instead of Pt, improves the reproducibility (statistical significance and CV) of the P flush in these soils. In all the approaches studied, the Pi flush determined using the Bray-1 extractant at 1 : 4 provided the best estimate of soil microbial biomass P. Furthermore, the recovery of cultured bacterial and fungal biomass P added to the soils and extracted using the Bray-1 extractant at 1 : 4 was relatively constant (24.1–36.7% and 15.7–25.7%, respectively) with only one exception, and showed no relationship with soil pH, indicating that it behaved differently from added Pi (recovery decreased from 86% at pH 4.6 to 13% at pH 3.6). Thus, correcting for the incomplete recovery of biomass P using added Pi is inappropriate for acid soils. Although microbial biomass P in soil is generally estimated using the Pi flush and a conversion factor (k P) of 0.4, more reliable estimates require that k P values are best determined independently for each soil. Received: 3 February 2000  相似文献   

6.
Diffusive gradients in thin‐films (DGT) technology provides an alternative assessment of available phosphorus (P) for a range of crops, suggesting a preliminary examination of the performance of the new DGT‐P test, compared to existing bicarbonate extractable Olsen and Colwell P tests, for pastures is justified. This study utilized historic data from the Australian National Reactive Phosphate Rock (NRPR) study (1992–1994) that included 25 experimental sites representing a wide range of soil types and climates used for pasture production. Stored (~19 yr) soil samples were analysed for DGT‐P, Olsen P and a single point P buffering index (PBI) and re‐analysed for Colwell P. Results showed the traditional bicarbonate extractable Colwell (r2 = 0.45, P < 0.001) and Olsen P (r2 = 0.27, P < 0.001) methods predicted relative pasture P response more accurately, compared to the novel DGT‐P test (r2 = 0.09, P = 0.03) when all 3 yr of data were examined. We hypothesize that the harsher bicarbonate extraction used for the Olsen and Colwell methods more accurately reflects the ability of perennial pasture roots to access less labile forms of P, in contrast to the DGT‐P test, which does not change the soil pH or dilute the soil and appears unable to fully account for a plants ability to solubilize P. Further studies are needed to compare the capacity of DGT‐P to measure P availability in perennial pasture systems and to better understand the soil chemical differences between pasture and cropping systems.  相似文献   

7.
Abstract

Phosphorus fertilizer recommendations were compared by interpretations from P isotherms, Olsen extractable P and the Mitscherlich‐Bray model based on the Olsen method for 15 soils from the Chaouia (dryland) region of Morocco. The P isotherms were fit to straight line and second degree polynomial equations. The P buffer indexes (PBI) derived from the isotherms were not significantly correlated to P buffer capacities as measured by a single P buffer capacity index, but negatively correlated to Olsen P (r = ‐0.63), relative yield (r = ‐0.76) and P uptake (r = ‐0.66). Phosphorus in solution was a quadratic function of P added in 0.01 M CaCl2equilibrium solution. The P fertilizer recommendations to maintain soil solution P concentrations at 0.01, 0.12 and 0.20 mg P L‐1were higher than recommended by direct interpretation of plant response to Olsen extractable P and the quantity based on the Mitscherlich‐Bray model as calculated from Olsen available P values. The P fertilizer recommended to maintain soil solution P of 0.10 mg P L‐1was significantly correlated with Olsen P (r = 0.71) as was that recommended Mitscherlich‐Bray log transformation model (r = 0.81), and nonlinear least square estimation (r = 0.78). Field research will be needed to evaluate if the P fertilizer recommended to maintain this solution P concentration is adequate for maximum economic wheat grain yield under field conditions  相似文献   

8.
《Soil Use and Management》2018,34(3):326-334
Chemical soil phosphorus (P) extraction has been widely used to characterize and understand changes in soil P fractions; however, it does not adequately capture rhizosphere processes. In this study, we used the biologically based phosphorus (BBP ) grading method to evaluate the availability and influencing factors of soil P under four P fertilizer regimes in a typical rice–wheat cropping rotation paddy field. Soil P was assessed after seven rice‐growth seasons at multiple growth stages: the seedling, the booting and the harvest stage. Soil CaCl2‐P, citrate‐P and HC l‐P (inorganic P, Pi) as well as enzyme‐P (organic P, Po) were not significantly different between soil treated with P fertilizer during the wheat season only (PW ) and during the rice season only (PR ) compared with soil treated during both the rice and the wheat seasons (PR +W) at all three rice‐growth stages. No P fertilizer application during either season (Pzero) significantly reduced the concentration of soil citrate‐P and HC l‐P at the rice‐seedling and harvest stages. Significant correlations were observed between the HC l extraction and Olsen‐P (R 2 = 0.823, P  <  0.001), followed by enzyme‐P (R 2 = 0.712, P  <  0.001), citrate‐P (R 2 = 0.591, P  <  0.001) and CaCl2‐P (R 2 = 0.133, P  <  0.05). Further redundancy analysis (RDA ) suggested that soil alkaline phosphatase (S‐ALP ) activity played a role in soil P speciation changes and was significantly correlated with enzyme‐P, citrate‐P and HC l‐P. These results may improve our ability to characterize and understand changes in soil P status while minimizing the overapplication of P fertilizer.  相似文献   

9.
Phosphorus (P) loss from soil can impair surface water quality. Losses from soil are related to soil P concentrations, but agronomic measures such as Olsen P do not in many cases predict the potential for P loss. One possible strategy to decrease P loss is to stop applying P fertilizers. We examined the changes in both agronomic (Olsen P) and environmental [water‐extractable P (WEP) and calcium chloride‐extractable P (CaCl2‐P)] P tests, and the potential implications following a halt to P fertilizer application to four long‐term grassland field trials on different soil types. Exponential decreases in Olsen P and WEP concentration over time were observed in three of the four trials, but only in one trial for CaCl2‐P. The rates of decrease in Olsen P (OP) and WEP concentration were best correlated with initial WEP (WEPi) concentration and the quotient of Olsen Pi/P retention (PR, a measure of Al‐ and Fe‐oxides), respectively. The equation t = 1/(?0.035 × ln OPi/PR ? 0.0455) × (ln WEPt ? ln WEPi) was used to predict the time (t) taken for WEP concentrations at the sites to decrease to 0.02 mg/L (WEPt), which is proposed as a limit for dissolved reactive phosphorus in overland flow, and the result was 23–44 yr. Results from a similar equation for Olsen P predicted a quicker rate of WEP. A significant decline in dry matter (DM) yield was observed at one trial site. For this site, the rate of decline in DM yield was of a similar magnitude to the rate of decline in WEP concentration. This suggests that halting P fertilizer application to decrease P loss as measured by WEP concentration may decrease farm productivity. An alternative, more financially acceptable, strategy is required, such as a negative P balance while maintaining yields with N fertilizer, but further work is required to assess both the agronomic and environmental implications of this strategy.  相似文献   

10.
The traditional method for quantifying phosphorus (P) in Manitoba soil extracts is the molybdate blue–ascorbic acid colorimetric method. The shift from this traditional method to newer and more sophisticated analytical methods such as inductively coupled plasma (ICP) optical emission spectroscopy for P determination in soil extract could have serious implications on agronomic and environmental P management. Thus, the objectives of this study were to compare P determination by colorimetric and ICP methods in four extractants, namely Olsen, Mehlich 3, CaCl2, and water extraction methods and to evaluate the possibility of developing conversion equations for P determination for the two methods in Manitoba soils. A laboratory experiment was conducted to establish relationships between P determination by colorimetric and ICP methods. Sixty surface soil samples (30 manured and 30 nonmanured) were collected from across Manitoba and extracted with Mehlich 3 reagent, Olsen solution, calcium chloride (CaCl2) solution, and deionized water. Extractable P in the extract was determined by colorimetric (Col-P) and ICP (ICP-P) methods. The concentrations of P measured by the two methods were statistically analyzed. Mean comparison showed that P amounts determined by ICP in Mehlich 3, water, and CaCl2 solutions were significantly greater than those determined by colorimetric method (P < 0.05) in the study. The differences between P determinations by the two analytical methods in the extractants were probably due to the presence of organic P, which was included in ICP determination but not in colorimetric determination. The influence of other factors such as the presence of colloidal particles on the P that was determined by the two methods could not be ruled out. However, Olsen P determined by the colorimetric method was not significantly different from the values determined by ICP (P > 0.05) probably because the alkaline nature of this extractant enhanced the hydrolysis of organic P in the extract, thus including organic P in the colorimetric determination of P. There were significant correlations between the two methods of P determination in the various extracting solutions with correlation coefficients ranging between 0.94 and 1.00. The two methods of P determination were linearly related for all the extracting solutions.  相似文献   

11.
Abstract

Wheat [Triticum aestivum(L.)] is the major cereal crop of the Chaouia (dryland) region of Morocco. Efforts for self‐sufficiency in wheat will require improved fertility management on the calcareous soils of this region. This research was undertaken to evaluate the suitability of five soil P extractors for predicting the need for P fertilization on 15 important soils in this region. The Olsen (0.5MNaHCO3), the Soltanpour (1.0MNH4HCO3+ 0.005MDTPA) and their dilution modifications, and CaCl2solution P method were evaluated in laboratory and greenhouse experiments.

Ten of the 15 soils responded to P fertilization. The five soils for which a significant P response was not measured were from the P plateau of the Chaouia region. The P extractors performed equally to predict the need for P fertilization. The critical levels below which a response would be highly probably and above which no response would be anticipated varied by extractor and method used to interpret the soil test values. A graphic method indicated the critical P values to be: Olsen 10.2, modified Olsen 18.0; Soltanpour 2.0; modified Soltanpour 12.5 and CaCl20.20 mg P kg‐1. A second degree polynomial method indi cated the critical P values to be: Olsen 8.2; modified Olsen 14.0; Soltanpour 1.1; modified Soltanpour 5.1 and CaCl20.12 mg P kg‐1. This limited data will permit the interpretation of soil test values as to whether a response to P fertilization is highly probable for the dominant soils of this wheat region.

Results from this study suggest that any of the five P extractors evaluated could be selected to calibrate P response under field conditions. It might be best to concentrate future research efforts on the Olsen test because most field P calibration data published with similar soils, climate and crops are with this extractor  相似文献   

12.
Accumulation of inorganic and labile organic phosphorus (P) in intensive agricultural systems leads to P loss from soil which can cause serious environmental problems. Soil microbes are important in mobilizing soil non-available P, however, little is known about the role of soil microbes in immobilizing P to reduce P loss. Here, we test whether stimulating microbial biomass to immobilize P could reduce the amount of labile P available for leaching. The distribution characteristics of Olsen P, organic P and microbial biomass P were determined in three intensive agricultural systems. In addition, we conducted a pot experiment with three P and four carbon (C) levels. CaCl2 extractable P was measured and used to indicate the risk of P leaching. We found that there was a positive relationship between soil organic C and microbial biomass P. Carbon addition drove the process of P immobilization and reduced CaCl2 extractable P. Microbial biomass P increased by 64% (p < .05) with the addition of C, and Olsen P and CaCl2 extractable P decreased by 28% and 17%, respectively. Our results show that C addition increased microbial immobilization of P and reduced forms of labile P susceptible to leaching. Stimulating microbes to immobilize P by adding C to soils may have the potential to reduce P loss from intensive agricultural systems, reducing their environmental impact.  相似文献   

13.
We analyzed in soils with contrasting cultivation histories the depletion of P following sequential extractions with soil testing solutions. Soil samples were collected in three experiments in eastern Canada (L’Acadie, Lévis, and Normandin) and P was sequentially extracted 16 times, once daily, using Mehlich-3 (M3) or Olsen (Ol) solution. The cumulative amount of P extracted was 252 mg PM3 kg?1 and 77 mg kg?1 POl for L’Acadie, 212 mg PM3 kg?1 and 66 mg POl kg?1 for Lévis, and 424 mg PM3 kg?1 and 83 mg POl kg?1 for Normandin. The depletion of P was described by a logarithmic function (Y = a ln (N) + b) for PM3, and a power function (Y = αNβ) for POl. The inorganic P pool decreased in the three soils. The organic P pool did not decrease possibly because soil testing solutions did not directly extract P from this pool. This study demonstrated that laboratory soil testing analysis using M3 or Ol solution principally target P from the inorganic pool, suggesting that P fertilizer recommendations to mineral soils relying on these methods do not account for the potential of the organic P pool to contribute to soil P availability.  相似文献   

14.
Abstract

Iron oxide–coated strips (Pi) can serve as a sink to continuously remove phosphorus (P) from solution. In this way, P extraction is analogous to the P absorption by plant roots. The objective of this study was to compare the iron oxide–coated paper strips with other chemical extraction methods to estimate the plant P availability for corn (Zea mays) growing in the greenhouse in some soils of Hamadan province of Iran. Sixteen soil samples with different physicochemical properties were analyzed for available P using Olsen, Colwell, Mehlich‐1, 0.01 M CaCl2, AB‐DTPA, and 0.1 M HCl methods and pi. Furthermore, the effects of two P levels (0 and 200 mg P kg?1) on the plant indices (P uptake, relative yield, and plant responses) were studied in a greenhouse experiment using 10 soil samples. The results showed that the amount of extractable P decreased in the order of 0.01 M CaCl2<AB‐DTPA<pi<Olsen<Colwell<Mehlich‐1<0.1 M HCl. The amount of P extracted by the pi method was significantly correlated with other extractants. The amounts of P extracted by all chemical methods were significantly correlated. The results of a pot experiment showed that the amount of P extracted by the pi method was significantly correlated with the plant P uptake. However, the other methods were not significantly correlated with P uptake. The results of this experiment showed that pi method was able to predict the plant availability of soil P.  相似文献   

15.
Fertilizer phosphorus (P) is generally added to agricultural soils to meet the needs of crop production. In this study, the crop yield and soil Olsen P were measured every year (5–18 years) at 16 winter wheat (Triticum aestivum L.) –maize (Zea mays L.) crop rotation sites in cinnamon soil (Luvisols in FAO system). The mean agronomic critical value of Olsen P for maize was 14.2 mg kg?1 and for winter wheat was 14.4 mg kg?1 when using the Liner-plateau and Mitscherlich models. The change in soil Olsen P was positively linearly correlated with the P budget (P < 0.01), and an increase of 4.70 mg kg?1 in soil Olsen P for each 100 kg ha?1 of P budget in the 0–20 cm soil layer. A model of P fertilizer recommendation rate that integrated values of the change in soil Olsen P in response to P budget and the agronomic critical value of Olsen P was used, in order to adjust current levels of soil Olsen P to the agronomic critical value at the experimental sites over the next 5 years, P fertilizer application rate should be in the range of 0–87.5 kg P ha?1.  相似文献   

16.
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   

17.
Repeated application of phosphorus (P) as superphosphate either alone or in conjunction with cattle manure and fertilizer N may affect the P balance and the forms and distribution of P in soil. During 7 years, we monitored 0.5 M NaHCO3 extractable P (Olsen‐P) and determined the changes in soil inorganic P (Pi) and organic P (Po) caused by a yearly dose of 52 kg P ha—1 as superphosphate and different levels of cattle manure and fertilizer N application in a soybean‐wheat system on Vertisol. In general, the contents of Olsen‐P increased with conjunctive use of cattle manure. However, increasing rate of fertilizer nitrogen (N) reduced the Olsen‐P due to larger P exploitation by crops. The average amount of fertilizer P required to increase Olsen‐P by 1 mg kg—1 was 10.5 kg ha—1 without manure and application of 8 t manure reduced it to 8.3 kg ha—1. Fertilizer P in excess of crop removal accumulated in labile (NaHCO3‐Pi and Po) and moderately labile (NaOH‐Pi and Po) fractions linearly and manure application enhanced accumulation of Po. The P recovered as sum of different fractions varied from 91.5 to 98.7% of total P (acid digested, Pt). Excess fertilizer P application in presence of manure led to increased levels of Olsen‐P in both topsoil and subsoil. In accordance, the recovery of Pt from the 0—15 cm layer was slightly less than the theoretical P (P added + change in soil P — P removed by crops) confirming that some of the topsoil P may have migrated to the subsoil. The P fractions were significantly correlated with apparent P balance and acted as sink for fertilizer P.  相似文献   

18.
Evaluation of five soil phosphorus (P) extractants was done on southwestern Nigerian soils from sedimentary and basement complex parent materials to determine the relationship between the extractants and the most appropriate extractant for the soils. The soils differed in properties. Generally, soils from the basement material had less available P compared with sedimentary material. Olsen extracted the greatest P. Bray 1 measured 67% of Olsen P, Hunter measured 52%, Mehlich measured 42%, and Ambic measured 24%. Positive and significant regression (P < 0.001) existed among Bray 1, Olsen, Mehlich, Hunter, and Ambic extractants. The strongest relationship was found among Olsen, Mehlich, and Ambic P. The relationship between maize P uptake and extracted P was quadratic, whereas the relationship with Mehlich was logarithmic. Bray, Mehlich, and Olsen P were the significant contributors to the maize P uptake and dry-matter yield. Extractants in order of P extraction were Olsen > Bray 1 > Hunter > Mehlich > Ambic.  相似文献   

19.
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20.
Shen  Yan  Duan  Yinghua  McLaughlin  Neil  Huang  Shaomin  Guo  Doudou  Xu  Minggang 《Journal of Soils and Sediments》2019,19(7):2997-3007
Purpose

Calcareous soils are characterized by high pH and phosphorus (P) fixation capacity. Increasing application of P fertilizer recently has significantly improved soil P concentration, especially available P (Olsen-P) and inorganic phosphate (Pi) fractions. However, there are few data available on the ability of soils with different initial Olsen-P levels to continuously supply P (i.e., P desorption capacity) to crops without additional P fertilization and on which Pi fraction exerts the greatest influence on P desorption capacity.

Materials and methods

Five soils with different initial Olsen-P levels (0.5, 14.3, 38.4, 55.4, 72.3 mg kg?1, hereafter refer as OP1, OP2, OP3, OP4, and OP5) but similar other soil properties were selected to evaluate the capacity of P desorption and its relationship with Pi fractions. Soil P was sequentially extracted once daily for 16 consecutive days using Olsen solution.

Results and discussion

The content and proportions of dicalcium phosphate fraction (Ca2-P), octacalcium phosphate fraction (Ca8-P), aluminum phosphorus fraction (Al-P), and iron phosphorus fraction (Fe-P) in Pi increased significantly with the increase of initial Olsen-P (P?<?0.01). Applied P fertilizer was mostly stored as Ca8-P in the soil. Soil P desorbed reached an equilibrium after 16 extractions for all soils, and P desorption capacity (12–358 mg kg?1) showed a significant linear relationship with initial Olsen-P (P?<?0.01), with an increase of 4.2 mg kg?1 desorbed P per 1 mg kg?1 increase of initial Olsen-P. Ca2-P exerted the conclusive effect on P desorption in the first four extractions, but Ca8-P played a more important role in the 16 extractions.

Conclusions

Ca8-P was the greatest potential pool for P desorption after Ca2-P was depleted. P desorption capacity was significantly linearly related to initial Olsen-P (P?<?0.01). Different fertilizer use strategies were developed based on P desorption capacity for soils with different initial Olsen-P levels. The present study provided basic data on how to reduce effectively the application amount of chemical P fertilizer.

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