摘要:

The need for reliable recommendations for phosphorus (P) application on cropland has become increasingly important in recent years with the need to optimize economic inputs and minimize adverse water quality impacts. We used results from a series of recent laboratory and field experiments with Vermont and New York soils, combined with those of earlier work, to revise state recommendations for P application on field crops. Based on results of field and greenhouse studies, we established a critical value of 4 mg kg‐1(optimum range of 4.0 to 7.0) using modified Morgan extractant [1.25 M ammonium acetate (NH4OAc), pH 4.8] as a measure of plant‐available P. Aluminum (Al) in the same extractant ("reactive”; Al) correlated well with the amount of added P needed to increase soil test P. Consequently, P rate recommended for soils below 4 mg kg‐1is based on a combination of extractable P and Al. Within the “Optimum”; range only a low rate of P is recommended. Modified Morgan P also correlated well with P desorbed into water or calcium chloride (CaCl2) solution, suggesting it is a good indicator of the potential for a soil to release P into runoff. These research results support use of modified Morgan‐extractable P and Al for P fertilizer recommendations for crop production and water quality purposes in the New York‐New England region of the United States.

ISSN:0010-3624    

DOI:10.1080/00103629809370064

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Phosphorus (P) fertilizer recommendations can be improved if the amount of P required to raise the soil test to a desired value is known. The objective of this study was to determine the increase in soil test P per unit of applied P, the P buffer coefficient, in the laboratory by various means and to compare those values with P buffer coefficients from field data. Phosphorus was applied to soils with predominately kaolinitic mineralogy. The mixtures were then incubated for either 180 and 120 d with numerous drying cycles, or for 7 d and 16 h with either one drying cycle or maintained moist. The samples were extracted with the Mehlich‐3 solution and the change in extractable P per unit of applied P was calculated and termed the Mehlich‐3 P buffer coefficient (M3PBC). The M3PBC varied widely among soils, but was linear within the range of 0 to 300μgP cm‐3applied for each. The M3PBC decreased with an increase in time, markedly between 16 h and 7 d, then more slowly from 7 d to 180 d. Drying also reduced the M3PBC, especially on the coarser textured soils. Mehlich‐3 P buffer coefficients from ten field studies were related to the laboratory M3PBC values from dried samples. The prediction of Field M3PBC from the 180‐d M3PBC was linear, while those for the 7‐d and 16‐h M3PBC were quadratic. As time is critical in routine analysis, the 16‐h, dried method was selected as most practical. A prediction equation was calculated to estimate the Field M3PBC from the results of the 16‐h, dried method.

ISSN:0010-3624    

DOI:10.1080/00103629809370065

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Phosphorus (P) sources were evaluated for their usefulness as P fertilizers in four acid Arkansas soils. Soils were amended with acidulated rock phosphorous, Florida rock phosphate, liquid ammonium phosphate, North Carolina rock phosphate, and triple superphosphorous, at 50 mg P kg‐1. After application, the soils were incubated for two years at 33 kPa soil moisture potential, with samples taken periodically. At each sampling Mehlich III (M‐III) and Bray‐Kurtz PI (BK1) extractants were used to measure available P levels. Acidulated rock phosphate was consistently the best P source for all soils, although P levels were significantly raised above the check by all P sources. Mehlich III extracted significantly more P than did BK1 for all soils. Phosphorus release varied among amendments during the incubation period. Acidulated rock phosphate, liquid ammonium phosphate, and triple superphosphate exhibited rapid initial release. The Florida and North Carolina rock phosphates did not achieve their maximum P release until one year of incubation. The correlation between extractants for P was M‐III = 1.2 + 1.06 (BK1) with r2= 0.94.

ISSN:0010-3624    

DOI:10.1080/00103629809370066

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Phosphorus (P) extraction by anion exchange resin membranes (AEM, IONICS) was studied in two Andisols from a greenhouse experiment with corn(Zea maysL.). Membranes were sequentially eluted with sodium chloride (NaCl) and sodium bicarbonate (NaHCO3). More P was extracted in the later. Resin eluents were fractionated for P and the different P fractions were correlated with crop yield. In the NaCl eluents, iron (Fe) and silicon (Si) were detected. In addition, aluminum (Al) and organic carbon (OC) were found in the bicarbonate eluents. Strong correlations were observed between P, Al, and OC in the resin eluents corresponding to the different P treatments. Phosphorus increased with OC and Al, suggesting that added inorganic P had reacted with complexes of the type: humus‐Al‐OH (to humus‐Al‐P), and that soil adherence to membranes were not aleatory.

ISSN:0010-3624    

DOI:10.1080/00103629809370067

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

For many years and in most agricultural production systems, phosphorus (P) has been identified as the most frequently occurring essential element deficiency limiting crop yields, and it is still an element that continues to receive considerable research attention. However, little has been researched or written about the effects of high P on plants other than that associated mainly with zinc (Zn) nutrition, and iron (Fe) to some degree, as high P levels are known to interfere with their normal metabolism. Also, P is known to promote manganese (Mn) uptake. At what levels P would be considered toxic has not been clearly defined for most crops. The author has observed the occurrence of nutritional stress in tomato plants when the P level in leaves exceeds 1.00% of its dry matter, mainly occurring for container‐grown plants and those being grown hydroponically. This and other data will be presented that suggests that 1.00% P may indeed be the critical level between sufficiency and toxicity for tomato plants. Visual symptoms of P toxicity will also be described.

ISSN:0010-3624    

DOI:10.1080/00103629809370068

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Neutral normal ammonium acetate (NH4C2H3O2) is the extractant predominately used to determine exchangeable cations in agricultural soils. On calcareous soils containing calcium carbonate (CaCO3), this method over estimates exchangeable calcium (Ca). A study was conducted to evaluate five method variables: extractant pH, extraction ratio (soil to extractant), shaking time, shaking vessel, and extractant volume. Modifying these variables, soils formerly utilized in the Western States Proficiency Testing Program were extracted and analyzed for Ca, sodium (Na), magnesium (Mg), and potassium (K). Results indicate that the extraction ratio significantly increased the amount of extractable Ca in soils containing more than 0.5% CaCO3. As the soil:extractant ratio decreased, the amount of measurable Ca increased. The concentration of Ca in noncalcareous soils remained constant in extraction ratios greater than 1:5. Additionally, the pH of the NH4C2H3O2significantly altered the Ca concentration of the calcareous soils. As pH increased from the prescribed value of 7.0 to 9.0, extractable Ca decreased significantly. Increased extractant pH had little effect on exchangeable K, Mg, and Na for the soils tested. Further analyses with 30 soils indicate an NH4C2H3O2extractant of pH 8.5 extracted equivalent amounts of K, Mg, and Na independent of the CaCO3content.

ISSN:0010-3624    

DOI:10.1080/00103629809370069

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Results of a field survey in northern Germany and Denmark strengthened the importance of a balanced sodium (Na) and potassium (K) supply for sugar beet. Compensation of K by Na is obvious in the range of moderate K deficiency but maximum yields required a minimum concentration of 35 mg K g‐1in foliar dry matter and a minimum of 6 mg Na g‐1at the same time. Field studies were carried out in order to quantify the effect of Na applications on yield and quality of sugar beet in relation to soil type. Sodium fertilization decreased K contents in sugar beet leaves significantly in favor of higher Na and chlorine (Cl) uptake which also induced higher water contents in the leaves of sugar beet during the main growing period. Additional Na supply resulted in yield increases of up to 87 dt ha‐1.

ISSN:0010-3624    

DOI:10.1080/00103629809370070

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Earlier reports in the literature indicated that responses to phosphate (P) fertilization of apple and pear trees were rare. Yet more recently in orchard soils low in available P or in leaves with low P concentrations, greenhouse and orchard trials showed a marked response to applications of monoammonium phosphate (MAP) fertilization. Trees receiving MAP fertilizer frequently resulted in improved tree vigor, fruit production, and in some cases fruit quality. Our experimental trials indicated that apple and pear trees responded to soil‐surface applications of MAP fertilizer rates, but excessive usage may result in low soil pH or a high incidence of bitter pit in apples or cork spot in ‘d'Anjou’ pears.

ISSN:0010-3624    

DOI:10.1080/00103629809370071

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Soils with variable surface charge are reported to have high affinities for the adsorption of anions and also to selectively retain cations. A laboratory study was conducted to determine the influence of sulfate (SO42‐) anion on phosphate (PO43‐) sorption/desorption from tropical soils. Duplicate 1.0 g soil samples were shaken with 10 mL portions of varying concentrations of calcium sulfate (CaSO4lb2H2O) (0.0 to 1.5 x 10‐2M). Subsequently, the samples were equilibrated with increasing concentrations of monocalcium phosphate [Ca(H2PO4)2#lbH2O] in 0.01M calcium chloride (CaCl2) to measure PO4sorption and afterwards with 0.01M CaCl2for PO4desorption. Results showed that PO4sorption maxima increased as concentrations of SO4in solution increased. In the most acidic soil, SO4adsorption from the 0.015M CaSO4#lb2H2O solution increased PO4sorption by 93%. There was a decrease in pH in the SO4extracts; this would indicate that calcium (Ca) from the SO4salt applied to the soils before P addition was specifically adsorbed by the exchange complex and originated new sites for binding PO4. On the average, about 20% of the sorbed PO4was removed with the CaCl2treatment, suggesting that PO4was specifically adsorbed by the variable charge soils.

ISSN:0010-3624    

DOI:10.1080/00103629809370072

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Samples of 22 soils of the State of São Paulo, Brazil were collected from the 0–20 cm layer, dried, sieved, and analyzed for sulfur (S) utilizing the following extracting solutions: (a) calcium phosphate [Ca(H2PO4)2], 500 mg P L‐1in 2.0 mol acetic acid (HOAc) L‐1, (b) 1 mol ammonium chloide (NH4C1) L‐1, (c) 0.5 mol ammonium acetate (NH4OAC) L‐1in 0.25 mol HOAc L‐1, (d) ion exchange resin ‐ Resin 1 ‐ (2.5 cm3of soil + 2.5 cm3of resin in water and further extraction with 50 mL 0.8 mol NH4Cl L‐1in 0.2 mol hydrochloric acid (HCl) L‐1), (e) ion exchange resin ‐ Resin 2 ‐ (5.0 cm3of soil + 5.0 cm3of resin and 25 mL 0.8 mol NH4Cl L‐1in 0.2 mol HCl L‐1), (f) ion exchange resin ‐ Resin 3 ‐ (5.0 cm3of soil + 2.5 cm3resin and 25 mL 0.8 mol NH4Cl L‐1in 0.2 mol HCl L‐1). Amounts of 2 kg of each soil, in four replicates were limed in order to reach a base saturation of 70% of the cation exchange capacity (CEC). After a period of incubation of 30 days all nutrients, except S, were added to the soil and corn seeds were planted. Plant tops were removed after 70 days, dried at 50°C, weighed, and analyzed for S determination. The correlation between the bioavailable S in the soil and the yield of dry matter or S uptake was best represented by the linear or the √X models. The coefficient of determination varied from 0.56 (Resin 1) to 0.82 (NH4OAc). Resins 2 and 3 methods showed good efficiency (R2from 0.63 to 0.79), and can be utilized in the evaluation of S bioavailability in soils.

ISSN:0010-3624    

DOI:10.1080/00103629809370073

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor