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1.
Abstract

Zinc of index corn leaves samples from 91 Minnesota sites on numerous soil types was correlated with soil Zn extracted by four routine procedures. The EDTA?(NH4)2CO3 ‐ extractable soil Zn was more closely correlated with leaf Zn than soil zinc extracted by 0.1N HCl, EDTA‐NH4OAc, or by NH4OAc ‐ dithizone. Soil pH, CaCO3 equivalent, extractable P, and organic matter of both acid and calcareous soils were negatively correlated with leaf Zn. When EDTA ? (NH4)2CO3 ‐ extractable Zn was included with routine soil tests, a prediction equation for corn leaf Zn was formulated and compared with analytical values. However, the use of 1.4 ppm EDTA ? (NH3)2CO3, ‐ extractable soil Zn alone as a critical value was equally effective in predicting leaf Zn.  相似文献   

2.
Abstract

Field experiments were conducted at 60 sites in central and north‐central Alberta to determine the yield response of barley (Hordeum vulgare L.) to phosphorus (P) fertilizer and economics of P application on soils with different concentrations of extractable P in the 0–15 cm soil layer. On the unfertilized plots, barley yield increased with increasing concentration of extractable P in the soil up to 22 mg P kg‐1, but the yield response to applied P decreased. The net present value (NPV) of returns from P fertilization increased with increasing rate of P up to approximately 51 kg P2O5 ha‐1. The NPV of applied P decreased with increasing concentration of extractable P in soil. On soils with extractable P more than 22 mg P kg‐1, P application did not result in positive NPV.  相似文献   

3.
Abstract

Soil solution P level is believed to be important in determining P uptake rates from soil. The objective of this research was to investigate the relation between initial P concentration in the soil solution and P flux into the root. Millet (Panicum milaceum) was grown on five soils each of which was adjusted to six Cli levels by addition of P. Millet was also grown in solution culture and P influx vs. P concentration in solution measured. There was a curvilinear relation between P influx and relative yield of the Cli levels on each soil (R2=0.74). A P influx of at least 16 pmoles cm‐1 sec‐1 was needed to obtain 90% of maximum yield. However, yield response was not correlated with Cli, indicating Cli was not a suitable indicator of P availability on these soils. Influx of P on soils with Cli less than 6 μM was greater than occurred at similar P concentrations in solution culture indicating P influx was increased by the effect of the root on the soil.  相似文献   

4.
Abstract

Knowledge of the change in soil extractable phosphorus (P) as a consequence of soil P fertilization could be useful in discriminating soils with a potential for soil P release to runoff or movement of P along the soil profile. In this research, soils with low to medium P retention capacity were equilibrated for 90 days with soluble P (KH2PO4) at rate of 100 mg P kg‐1 soil. After this period, soil samples both with and without the P addition were analyzed using six conventional methods: 1) Olsen, 2) Bray 1,3) Mehlich3,4) Egner, 5) Houba, dilute CaCl2 solution, and 6) distilled water, and three “innovative”; P‐sink methodologies: 1) Fe oxide‐coated paper strip, 2) anion exchange resin membrane, and 3) cation‐anion exchange resin membrane. The soils without P addition had low levels of extracted P as determined by all nine procedures. Net increases in the amount of P extracted from the soils with added P ranged from 4.2 mg kg‐1 (CaCl2 extraction) to 57.6 mg kg‐1 (cation‐anion resin membrane extraction). Relationships between change in extracted P and i) physical and chemical characteristics, and ii) soil P sorption properties are also presented and discussed.  相似文献   

5.
Abstract

The rates of applied phosphorus required for 90% maximum yield of Desmodiim intortum cv. Greenleaf were calculated from pot experiments using 24 fertilized and unfertilized soils from the Atherton Tableland, Queensland, Australia.

Phosphorus required was highly correlated (r2 = 0.94) with the phosphorus sorbed (P sorbed) by the soils at a supernatant solution P concentration of 0.08 ppm. P sorbed was found to be a function of phosphorus buffer capacity at 0.08 ppm ("PBC") and phosphorus extractable by acid (0.005 M H2S04) or bicarbonate (0.5 M NaHCO3). PBC was highly correlated (r2 = O.84) with a phosphorus sorption index ("PSI") derived from one addition of 500 μg P g‐1 soil.

Combining PSI with acid or bicarbonate extractable P in a multiple regression equation allowed the estimation of phosphorus required with multiple correlation coefficients of R2 = 0.80 and R2 = 0.83 respectively.  相似文献   

6.
Abstract

Soil and vegetative samples of ley and cereals were collected four times during the growing season from field and pot trials with different phosphorus (P) fertilisation levels. The soil samples, dried and of field moisture condition, respectively, were extracted by 0.01M calcium chloride (CaCl2) at two different soil:extractant ratios (1:2 and 1:10), and analysed by inductively coupled plasma emission spectrometry (ICP) for content of P. The plant samples were digested in concentrated nitric acid (HNO3) and the P content determined by ICP. Calcium chloride‐extractable P content was lowest in the middle of the growing season, while plant P was highest in the beginning of the season. Phosphorus extracted by CaCl2 solution was higher at a soil:extractant ratio of 1:10 than at 1:2, and also when drying the soil before extraction. A soil:extractant ratio of 1:2 minimizes the risk of coming too near the limit of determination. However, if organic soils are also to be included, a ratio of 1:10 has to be used in order not to have all the solution absorbed by some types of soils. The solution of ammonium lactate/acetic acid (AL) extracted nearly two powers of ten more P than CaCl2 solution. There was a good relationship between the methods. If calcareous or very acid soils had been included, a less good relation would have been expected. Plant P content varied more in straw than in grain between different treatments. Measuring CaCl2‐extractable P with ICP might be able to predict plant uptake of P by plants. This would be a great advantage when using 0.01M CaCl2 as a universal extradant.  相似文献   

7.
Abstract

Surface horizons from Podzolic and Gleysolic soils were collected in various parts of the province of Quebec, Canada, and equilibrated with various amounts of KH2PO4 in 0.01 M CaCl2 for 48 hours. P sorption data conformed to the linear form of the Langmuir and Freundlich equations. P solubility isotherms showed evidence of hydroxyapatite formation in most samples studied, whereas equilibration solutions of only few samples were saturated with respect to either dicalcium phoshate dihydrate or octocalcium phosphate. These reaction products were associated to soil pH and levels of added phosphate. The average values of the Langmuir sorption maximum for these studied Gleysolic and Podzolic samples were 763 and 1096 μg/g respectively. These values were higher than those obtained by the segmented and modified Freundlich models.

Relationships between the soil characteristics and P sorption parameters were evaluated by regression analysis. Among all variables, oxalate‐extractable Fe plus Al content of the Podzolic samples and the ratio of oxalate—extractable Al to clay of the Gleysolic samples gave the best significant correlation coefficients. Furthermore, soil pH and various ratios such as pyrophosphate‐extractable Fe and Al, oxalate‐extractable Fe and organic matter to clay were found to be significantly correlated only with the P sorption parameters of the Gleysolic samples.  相似文献   

8.
Abstract

Changes in agronomic and environmental soil phosphorus (P) availability parameters, i.e., Mehlich‐ and Olsen‐extractable P, reversibly‐adsorbed P, soil‐solution P, and equilibrium‐P concentration were determined following equilibration of 13 Italian soils with five rates of P application (0, 12.5, 25, 50, and 100 mg P kg‐1 soil). Soil P availability as determined by each parameter increased with added P. The relative change in soil P availability with added P was a function of soil sorption index silicon (SI), according to the equation DP=(Padded)a*exp(b+g*SI). This equation accounted for 94 to 98% of the variance in soil‐P availability. The inclusion of SI in a soil testing program may increase the reliability in assessing both soil‐P fertilizer requirements and the vulnerability of a soil to P loss in runoff following land application of fertilizer or manure P.  相似文献   

9.
Abstract

Twelve soils with low‐medium phosphorus (P) retention capacities were equilibrated for 3 months with soluble phosphate at a rate of 100 mg P kg‐1 soil. The P sorption properties of these soils both with and without added P were studied, including equilibrium P concentration (EPCo), standard P requirement (SPR), soil P sorption capacity (b), maximum buffer capacity (MBC), and P sorption index (P‐SI). In general, the soils with no added P showed low values of all the above parameters. Oxalate extractable aluminum appeared to be the major responsible element for the control of P sorption in these soils. The addition of P to these soils had a considerable effect on their P sorption properties. The changes in EPCo were well correlated with P sorption index (r=0.80; p≤0.01 ). The EPCo values of the soils with and without added P were closely correlated to bicarbonate extractable P (P0lsen) and calcium chloride extractable P (PCaC12), with r=0.80, and r=0.99 (p≤0.001), respectively. Ninety percent of the variability in EPCo was explained by the corresponding variability in POlsen when a curvilinear relationship was adopted. The P sorption properties examined appear to be useful parameters to assess the environmental impact of soil P on the quality of surface waters.  相似文献   

10.
Abstract

Rhodes grass (Chloris gayana Kunth ) plants were grown on various soil types In order to study the relationships between the available and hardly available soil P fractions. Results indicate that when plants are grown intensively in soils for long periods without additional P fertilization, recharge rate of the available fraction of soil P becomes a limiting factor. An approach to determine the recharge rate, using data on plant uptake and changes in sodium bicarbonate extractable soil P content are suggested.  相似文献   

11.
Abstract

A new soil extractant (H3A) with the ability to extract NH4, NO3, and P from soil was developed and tested against 32 soils, which varied greatly in clay content, organic carbon (C), and soil pH. The extractant (H3A) eliminates the need for separate phosphorus (P) extractants for acid and calcareous soils and maintains the extract pH, on average, within one unit of the soil pH. The extractant is composed of organic root exudates, lithium citrate, and two synthetic chelators (DTPA, EDTA). The new soil extractant was tested against Mehlich 3, Olsen, and water for extractable P, and 1 M KCl and water‐extractable NH4 and NO2/NO3. The pH of the extractant after adding soil, shaking, and filtration was measured for each soil sample (5 extractants×2 reps×32 soils=320 samples) and was shown to be highly influential on extractable P but has no effect on extractable NH4 or NO2/NO3. H3A was highly correlated with soil‐extractable inorganic N (NH4, NO2/NO3) from both water (r=0.98) and 1 M KCl (r=0.97), as well as being significantly correlated with water (r=0.71), Mehlich 3 (r=0.83), and Olsen (r=0.84) for extractable P.  相似文献   

12.
Abstract

Two methods of measuring phosphate (P) adsorption were assessed as a means of predicting soil and plant responses to P fertigation for four British Columbia (B.C.) orchard soils. In Method 1, soils at 0.1 bar moisture tension were incubated for 1, 7, 14, 28, 56, or 84 days with solutions of H3PO4 supplied as a single or eight weekly doses. In Method 2, soils were equilibrated with P solutions at 1:10 soil:solution ratio for one day. Langmuir adsorption maxima calculated from the latter data ranged from 99 to 372 mg/kg. Solution P concentrations after one day for single dose incubations and 1:10 soil:solution equilibrations were highly correlated. Solution P concentrations remained elevated for 12 weeks after both single and weekly doses in incubated soils. Four availability indices were derived from the adsorption studies:solution P after one day equilibration for both methods and the fraction of the P adsorbing surface covered by added P at either one or fifty‐six days.

Peach seedlings (Prunus persica L. Batsch) were grown for 12 weeks in the greenhouse in a randomised complete block experiment with five levels of P (0, 15.5, 31, 62, and 124 mg P/kg) supplied as H3PO4 on the same schedule as for the incubated soils. Top dry matter increased in response to the first level of added P for three soils but was not correlated with any of four P availability indices measured. Initial soil solution P concentration was a better indicator of response to P fertilizer than Kelowna‐extractable (0.25 M HCl + 0.015 M NH4F) P. Estimated critical values of soil solution P for the two adsorption methods were 0.85 μg/mL (Method 1) and 0.42 μg/mL (Method 2).  相似文献   

13.
Abstract

Labor and laboratory expense could be reduce if soil extractable nitrate (NO3) was extracted simultaneously with other routinely used soil extractants. This study was conducted to compare 1M potassium chloride (KCl), saturated calcium oxide (CaO), and Bray and Kurtz P1‐extractable soil NO3, the proposed new method to 2M KCl. Nitrate was extracted from 140 selected soils with 1M KCl, saturated CaO, Bray and Kurtz P1, and 2M KCl extractants and analysed by cadmium reduction with a flow injection analyser. Nitrate extracted with 2M KCl was used as the standard. When 1M KCl, saturated CaO, and Bray and Kurtz P1 was regressed against 2M KCl, the slopes were equal to 1.0 and the intercepts were equal to 0.0 with r2>0.99. No detectable differences in extractable NO3 were measured between 1M KCl, saturated CaO, Bray and Kurtz Pl, and 2M KCl extraction procedures. Bray and Kurtz P1 can be used to simultaneously extract phosphorus (P) and NO3.  相似文献   

14.

Background

Organic farmers frequently report sufficient yield levels despite low or even very low soil phosphorous (P) contents questioning the applicability of widely used laboratory methods for soil P testing for organic farming.

Aims

The aim of this study was to compare the validity of a broad range of different soil extraction methods on soils under organic management from South West Germany and to test the correlation of the measured soil P concentration with plant offtake.

Methods

Twenty-two soil samples of eight different organic farms were extracted with different solutions: (1) water, (2) CAL, (3) Olsen, (4) Mehlich 3, (5) Bray P1, (6) Bray P2, (7) NaOH+Na2EDTA, and (8) total P. The results were then correlated with above ground plant P.

Results

Spearman's rank correlation coefficient (rs) of correlations between above ground plant P and extractable soil P (Water-P, CAL-P, and Olsen-P [+active charcoal {+AC}]) determined with ICP-OES were strong (0.94, 0.90, and 0.93, respectively). Among the tested methods, above ground plant P showed a strong correlation with CAL-P as detected by ICP-OES (rs = 0.90) and colorimetry (rs = 0.91). The comparison of CAL-P data provided by farmers and CAL-P analyzed during this research showed discrepancies between the results.

Conclusions

The results of this study indicate that the CAL method can be used in organic farming despite a low extraction of organic P (Porg). Furthermore, it is recommended for farmers to take soil samples for analyses regularly and interpret changes in P in the long-term instead of interpreting individual samples.  相似文献   

15.
Abstract

Few studies have utilized a statistical approach for the evaluation and comparison of breakthrough profiles obtained from soil column investigations. Our objective was to investigate the use of nonlinear estimation techniques to identify the phosphorus (P) breakthrough point and other parameters endemic to breakthrough data. Four soils exhibiting a range in physical and chemical properties were leached under saturated‐flow conditions with a 10 mg P/L solution for 34 d. Leachate P concentrations were analyzed by flow injection colorimetric analysis. A four‐parameter segmented exponential model provided a good fit for the breakthrough data in each soil tested. In addition to identifying the breakthrough point, the model parameters provided estimates of other identifiable aspects of a breakthrough profile including background P concentration, equilibrium P concentration, and the rate of concentration change once breakthrough is attained. Estimation of these parameters also facilitated statistical comparison of breakthrough profiles from different soils. Single and joint hypothesis tests showed that significant differences existed among the breakthrough profiles, the breakthrough points, and the rates of concentration change. Additionally, simulation was used to examine the correlation structure between the estimated breakthrough point and 17 soil properties. The simulation showed that 6 soil properties— ammonium oxalate extractable aluminum (Al) and iron (Fe), citrate dithionite extractable Al, CaCl2 and acetate extractable P, and P sorption capacity— were strongly correlated with P breakthrough.  相似文献   

16.
An Indiana silt loam soil was equilibrated with various amounts of Ca(H2PO4)2 H2O and a 0.01 M CaCl2 solution to construct its phosphorus sorption isotherms. Using the isotherms, the P buffering capacity of the soil was calculated and amounts of fertilizer P necessary to give several levels of P in the soil solution, for experiments conducted over a 2 year period, were determined. Twenty‐four day old tomato seedlings were grown and measured for leaf area, root length, dry weights and P concentrations in leaf, petiole, stem and root.

Phosphorus concentration in soil solution increased slowly with the first increment of P added to the soil. Subsequent P additions increased the P concentrations in solution exponentially. The maximum P absorption by the soil was 324 μg P/g soil and the constant related to P binding energy was 1.37. In addition, the soil buffering capacity decreased with an increase in the amount of P in the soil solution.

Plant shoot dry weight increased linearly with P increase in the concentration range 0.65 to 6.5 μM P in soil solution. However, beyond this level the response was low. The leaf area rate of increase in the 0.65 to 6.5 μM P solution concentration range was 75 times that in the 6.5 to 84 μM P. The root length: shoot dry weight ratio decreased with increasing P supply in the soil solution. P uptake by the plants increased with increased P concentration in soil solution. At soil solution concentrations above 6.5 μMP the rate of P uptake in the shoot was 20 times less than the rate for concentrations below 6.5 μM P. Of the P taken up by tomato seedlings about 65% was in the leaf, 13% in the stem, 13% in the petiole and 9% in the root.  相似文献   


17.
Limiting the use of phosphorous (P) in intensive agriculture is necessary to decrease losses to surface waters. Balanced fertilizer application (P supply equals P offtake by the crop) is a first step to limit the use of P. However, it is questioned whether this balance approach is sufficient to maintain soil fertility. A long‐term field experiment (17 yr), on grazed grassland, has been conducted on sandy soil, marine clay soil and peat soil to obtain insight into the effects of balanced P fertilizer application on soil test P values and to explain the results by changes in P pools in the soil. The balance approach led to a gradual decline in plant available P, measured as P‐AL, in the topsoil (<0.10 m deep). This decline was accompanied by a decline in oxalate extractable P, dithionite extractable P and inorganic P (0.5 m H2SO4). The decline in these mineral P pools in the topsoil was (partly) compensated by an increase in the amount of organic P. There was evidence for the accumulation of P in an occluded form, especially at one of sites which received P as Gafsa rock phosphate [Ca3(PO4)2].  相似文献   

18.
Abstract

Standardization of the P soil test procedures is desirable; however, both NaOAc and NaHCO3 are currently used to extract P from soils in the Pacific Northwest region of the USA. The purpose of this study was to determine the relationship between NaOAc and NaHCO3 extractable P in soils and to evaluate the effect of plant material on this relationship in a northern Idaho soil. The Ap horizon of a Latahco silt loam was used and alfalfa (Medicago sativa), pea (Pisum sativum) and wheat (Triticum aestivum) plant materials were added as amendments at rates of 0%, 1%, 5% and 10% (w/w). The soils were incubated for 20 weeks under controlled conditions. In addition, other parameters studied included soil water potential (‐0.05, ‐0.15 and ‐0.40 MPa), incubation temperature (10, 20 and 30°C and incubation period. P in samples was extracted by NaOAc and NaHCO3 extractants. A statistically significant linear relationship between NaOAc and NaHCO3 extractable P was observed (r2 = 0.96). In addition, the types of plant residues added to soil differently affected P extraction by the two extractants. The difference between NaOAc and NaHCO3 extractable P was greatest in the wheat material treatment while alfalfa material resulted in the smallest effect. Sodium acetate extractable P values increased faster than NaHCO3 extractable P with increasing amendment rate.

A simple regression relationship will allow conversion between NaOAc and NaHCO3 extractable P in the Latahco soil. Additions of less than 5 mt/ha plant material will have a minimal impact on this relationship.  相似文献   

19.
A major challenge in sustainable crop management is to ensure adequate P supply for crops, while minimizing losses of P that could negatively impact water quality. The objective of the present study was to investigate the effects of long‐term applications of different levels of mineral fertilizers and farmyard manure on (1) the availability of P, (2) the relationship between soil C, N, and P, and (3) the distribution of inorganic and organic P in size fractions obtained by wet sieving. Soil samples were taken from the top 20 cm of a long‐term (29 y) fertilization trial on a sandy Cambisol near Darmstadt, SW Germany. Plant‐available P, determined with the CAL method, was little affected by fertilization treatment (p < 0.05) and was low to optimal. The concentration of inorganic and organic P extracted with a NaOH‐EDTA solution (PNaOH‐EDTA) averaged about 350 mg (kg dry soil)–1, with 42% being in the organic form (Po). Manure application tended to increase soil C, N, and Po concentrations by 8%, 9%, and 5.6%, respectively. Across all treatments, the C : N : Po ratio was 100 : 9.5 : 2 and was not significantly affected by the fertilization treatments. Aggregate formation was weak due to the low clay and organic‐matter content of the soil, and the fractions > 53 μm consisted predominantly of sand grains. The different fertilization treatments had little effect on the distribution of size fractions and their C, N, and P contents. In the fractions > 53 μm, PNaOH‐EDTA ranged between 200 and 300 mg kg–1, while it reached 1260 mg kg–1 in the fraction < 53 μm. Less than one third of PNaOH‐EDTA was present as Po in the fractions > 53 μm, while Po accounted for 70% of PNaOH‐EDTA in the smallest fraction (< 53 μm). Therefore, 16% and 28% of PNaOH‐EDTA and Po, respectively, were associated with the smallest fraction, even though this fraction accounted for < 5% of the soil mass. Therefore, runoff may cause higher P losses than the soil P content suggests in this sandy soil with a weak aggregate formation. Overall, the results indicate that manure and mineral fertilizer had similar effects on soil P fractions.  相似文献   

20.
Abstract

All mineral phosphates in soil dissolve more completely when HCl is mixed with H2SO4 than with the HCl alone. It was hypothesized that a new extracting solution of H2SO4 alone with the same ionic strength or the same acidity as the Mehlich P1 extractant would extract similar amounts of soil phosphorus (P) as the Mehlich P1 soil test. Thirty six acid soils from Alabama, Georgia, North Carolina, South Carolina, and Colorado were used in this study. These acid soils reflect wide ranges in parent materials, texture, pH, organic matter, and available soil P. They were analyzed for available soil P with the Mehlich P1 soil test and with the two H2SO4 methods: Method A has an extracting solution of same ionic strength (0.0875M) as the Mehlich P1 extractant, and Method B was an extracting solution of the same acidity (0.0375M) as the Mehlich P1 extractant. Correlations between the results of Mehlich P1 with Method A and Method B were 0.994 and 0.997, respectively. The measured test precision was <3.5% for all three methods. The new H2SO4 methods are simple and faster to conduct under routine operations than the original Mehlich P1 extractant, and because of the high correlations, the H2SO4 methods should predict crop response to P as well as the original Mehlich P1 extractant for acid soils.  相似文献   

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