摘要:

We examined soil potassium (K) supply capacity as related to wheat response to K fertilization, using a cation exchange membrane (CEM) burial technique to measure potential K supply rate. A growth chamber experiment was conducted to determine soil and plant response relationships. Canadian Prairie Spring wheat(Triticum aestivum’Biggar') was grown on three soils of different initial K fertility with three rates of added K. Wheat response to K fertilization was well related to the amount of exchangeable K and K supply rate in the soil. Soils with high initial K supply rate demonstrated an adequate K release rate which was associated with low response to added K fertilizer. A soil K supply rate less than 5 μg cm2hr‐1represented soil K supply power that is less than optimal for wheat nutrition.

ISSN:0010-3624    

DOI:10.1080/00103629809369973

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The present paper deals with the effect of a concentrated, depotassified,Beta vulgarisL. vinasse [desugared beet molasses, 3.5% nitrogen (N),2%sodium (Na)] on germination and growth ofHelianthus annuusL. Compared to other species [Lepidium sativumL.,Sorghum vulgarePers.,Lolium multiflorumLam.,Triticum aestivumL.,Hordeum vulgareL.,Medicago sativaL. and a wildMelilotus segetalis(Brot.) Ser.], sunflower, and ryegrass, had the smallestin vitrogermination indices under both solutions of 0.15 and 0.50% of pure vinasse. However, seedling emergence, plantlet growth, and nutrient content of sunflower grown in pots, in three different soil types, were not negatively affected by the application of a moderate dose of pure vinasse (roughly equivalent to 2–3 t ha‐1) at sowing or 30 days before. In a field experiment, the application of a similar dose of vinasse did not have any detrimental effects on sunflower growth, with the achenes reaching similar oil and fatty acid contents under both vinasse treatments (application at sowing and 30 days before) and control. The application of vinasse at sowing can partially avoid losses of N that can take place if the vinasse is applied too far in advance of sowing.

ISSN:0010-3624    

DOI:10.1080/00103629809369974

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Arsenite sorption was investigated in three Spanish soils. The form of the equilibrium curves of arsenite sorption confirmed that the isotherms of this process pertained to the L class of Giles classification. The curves corresponding to Soils 1 and 3 could be included in the subgroup 1 (monolayer coverage) and the curve of Soil 2 pertained to subgroup 4 (two centers of sorption). The Freundlich equation successfully described As(III) sorption over the entire As(III) concentration range in all the studied soils. Sorption of arsenite increased with increasing temperature; however, this increase was likely caused by an effect on the rate of the diffusion reaction that follows the adsorption process.

ISSN:0010-3624    

DOI:10.1080/00103629809369975

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The parameters obtained from the quantity‐intensity (Q/I) isotherms have been used by several authors as criteria to estimate the immediate availability of labile potassium (K) in a soil. The aim of this work was to study how these parameters have been modified in four agricultural soils in Argentina by the addition of K (0 to 936 kg K2O ha‐1) in an incubation trial simulating K fertilizers application. In two of the soils, the increase in the labile forms of K was proportional to the amount of added K and the recovery percentages were high. In the other soils, a contrasting behavior was found. This difference might be due to different fixing capacity of the soils, which was related to the clay content and mineralogical composition of this fraction. The slopes of the Q/I curves for each soil indicate that the potential buffer capacity (PBC) was similar for the different treatments over the range of K added. The addition of K produced proportional increases in ARe and ?Ko values. This could be attributed to the presence of non saturated planar sites at the highest rates of K applied.

ISSN:0010-3624    

DOI:10.1080/00103629809369976

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This study was conducted to evaluate the effect of vesicular‐arbuscular mycorrhizal (VAM) fungusGlomus etunicatumon growth, absorption, and distribution of calcium (Ca), magnesium (Mg), phosphorus (P), and aluminum (Al) in one Al‐tolerant and one Al‐sensitive barley cultivar. The plants were grown in sand daily irrigated with nutrient solution containing 0 or 600 μM Al at pH 4.8. Significant interaction (P=0.05) among variety, mycorrhiza, and aluminum (VxMxAl) were noted for both shoot and root dry matter (DM); shoot concentration and content of Al, P, Ca, and Mg; root concentration of Al, P, and Mg; and root content of Al, P, Ca, and Mg. With VAM inoculation: i) root colonization degree was about 50% in all treatment, ii) shoot DM yield increased between 30 and 70%, iii) Al concentration and content decrease down to a half both in shoots and roots of sensitive barley, iv) Ca concentration in shoots of sensitive barley showed a high increase at 600 μM Al, and v) P concentration and content in shoots of both varieties increased significantly.

ISSN:0010-3624    

DOI:10.1080/00103629809369977

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The effect of sewage sludge applications on extractability and uptake by chard and lettuce of soil cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), leaf (Pb), and zinc (Zn) was investigated. Ten different treatments (0, 150, 300, and 500 kg N ha‐1) as mineral fertilizer, and 400, 800, and 1,200 kg N ha‐1of aerobically and anaerobically‐digested sewage sludges were applied annually to a sandy‐loam soil since 1984. Seven years after the start of the treatments, higher levels of heavy metals were detected in the soil, depending on the type of metal, depth of sampling, type of sludge used, and, especially, rate of application. Following a sequential extraction procedure incorporating 0.1M CaCl2, 0.5M NaOH, and 0.05M Na2EDTA, most of the heavy metals in soil were detected in the Na2EDTA solution and the residual fractions. Large amounts of Cd appeared to be extracted by CaCl2, whereas substantial amounts of Cu and Ni were isolated by NaOH. The effect of treatments on the percentages of the metals found in each fraction depended on the type of metal, sampling depth, sludge used, and application rate. No significant increases were found in the heavy metal contents of chard and lettuce leaves, but some of the treatments resulted in a significant decrease of Cd and Cr levels in lettuce leaves.

ISSN:0010-3624    

DOI:10.1080/00103629809369978

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The objective of this study was to examine the impact of tillage intensity and crop residue on carbon (C) and nitrogen (N) cycling in a Vertisol. Soil samples (0–10‐ and 10–20‐cm depth) were collected from a Houston Black soil (fine, montmorillonitic, thermic Udic Pellusterts) with three different levels of tillage intensity, varying from no tillage to complete residue burial. The experiment was a split plot design with five replications. The main plots were three crop species [corn (Zea maysL.), grain sorghum (Sorghum bicolor[L.] Moench), and soybean(Glycine max[L.] Merr.)] and the subplots were three levels of tillage intensity (chisel tillage, reduced tillage, and no tillage). Total N, organic C, inorganic N, and C:N ratio were measured on soil samples as well as the potential C mineralization, N mineralization, C turnover, and C:N mineralization ratio during a 7‐ and 30‐d incubation. Chisel tillage reduced total N, C mineralization, and C turnover at the 0–10‐cm depth compared to the other conservation tillage systems. Following corn production, soil organic C increased and C mineralization and C turnover were decreased at the 10–20‐cm depth compared to the other crop species. This data indicates that, in the short term, tillage systems may control soil organic C at the soil surface, while changes in plant rooting may control soil organic C storage at deeper soil depths in Texas Vertisols.

ISSN:0010-3624    

DOI:10.1080/00103629809369979

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Information on the nitrate concentration of soil at the time of sowing crops is useful in estimating the optimal amount of fertilizer nitrogen (N). A field measurement of soil nitrate overcomes the delay and cost of laboratory analysis. The accuracy of Merckoquant test strips used with a hand‐held Nitrachek reflectometer was tested with a wide range of soil samples. We have found that the system gave accurate results provided two precautions were taken. First, samples should be compared with standard solutions analyzed at the same temperature, because the method was found to be temperature dependent. Second, the extractant should be 0.5M K2SO4or water, since the usual soil extractant, KCl, interferes with the analysis. The use of water for extraction reduces the cost of analysis and makes it feasible to analyze kilogram amounts of soil, thereby reducing the error of subsampling. We report a procedure which minimizes the time of extraction and hence the chance of denitrification, by filtering the suspension of soil in water through a 0.8‐mm filter attached to a syringe.

ISSN:0010-3624    

DOI:10.1080/00103629809369980

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A calibrated phosphorus (P) soil test is an important part of an economically and environmentally sound farming program. During the 1956–1958 period, Bray 2 was selected for use at the United States Sugar Corporation as an organic soil P extractant for sugarcane grown in the Everglades Agricultural Area. The purpose of this study was to evaluate and summarize the results of the numerous sugarcane field experiments that have been conducted relating Bray‐extractable soil P with sugar production. Using only years with significant positive responses in sugar production from P fertilizer experiments on Histosols, categories of Bray‐extractable soil P were determined which indicate the relative need for P fertilizer that will be required for optimum sugar production. A maximum applied P rate of 36 kg P ha‐1was found to be sufficient for soils in the very low category of Bray‐extractable P (<14 kg P ha‐1). At fertilizer P rates ≤36 kg P ha‐1, Bray‐extractable P in the zone of application (band application) was increased with the plant cane P application (first crop) and was maintained at or near the same level in succeeding ratoon crops with annual P applications. Several experiments had significant positive sugar production responses only in the ratoon crops, demonstrating the importance of maintaining adequate soil P levels in the fertilizer application zone each year.

ISSN:0010-3624    

DOI:10.1080/00103629809369981

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Highly weathered tropical soils are characterized by having a predominantly variable charge. Many management practices commonly used in the exploitation of these soils (e.g., liming, phosphate application, and manuring) are known to modify their electrical charge and the sorption/desorption behavior of cations and anions. This process is, at least, partially governed by the charges existing in the soil system. Available information on this subject comes mainly from short‐term laboratory and greenhouse experiments. There is a lack of data regarding the cumulative and long‐term effects of those practices used at farm‐scale levels and on the dynamics and availability of nutrients to the plants under field conditions. In the present work, changes in some electrochemical attributes of a variable charge soil (Oxisol) were studied, as influenced by treatments with phosphate + green manure(Cajanus cajan),phosphate + lime, and phosphate + lime + green manure, applied during a six‐year period. In this period, rice, bean, wheat, or corn, were grown in seventeen successive crops. Phosphate (total 334 ppm P) and phosphate + lime (total 5.5 t ha‐1) were shown to increase net electric charge and soil cation exchange capacity (CEC) at the field pH, and not to affect zero point of charge (ZPC), CEC at pH 7.0, or anion exchange capacity (AEC) of the soil at the field pH. The effects of phosphate + lime were more pronounced than those of phosphate alone. Green manure (total 16 t ha‐1dry matter), associated to crop residues and phosphate or phosphate + lime, did not influence electrochemical properties.

ISSN:0010-3624    

DOI:10.1080/00103629809369982

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor