摘要:

A model is discussed which relates bulk soil electrical conductivity (ECa) to volumetric water content (θW), electrical conductivity of the soil water (ECW), volumetric content of the solid phase (θS) and average electrical conductivity of the soil particles (ECS). Within the model a distinction is made between the water and dissolved salt present in the “immobile”; (fine pores) and “mobile”; (large pores) phases. The effects of bulk density, particle density and clay content upon ECaare discussed in relation to their influence upon θW, θS, ECSand the proportions of fine and large pores. The practical application of the model to interpret soil salinity requires the estimation of several soil properties in the field and the use of some empirical relations to estimate values of parameters required by the model. These relations and estimates are discussed in terms of their effects on the accuracy of soil salinity appraisal. A brief discussion is given concerning the parameter estimation procedures necessary for the field application of the proposed electrical conductivity model. Evidence is provided to support the utility of the model as an explicit description of electrical conductivity in soil and as a practical field salinity appraisal tool.

ISSN:0010-3624    

DOI:10.1080/00103629009368274

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Principles of electromagnetic induction (EM) and field calibration approaches are discussed as they pertain to the application of EM to soil systems for the purpose of deriving soil electrical conductivity ‐ depth relations. Evidence is provided to support the utility of EM‐derived estimates of ECa‐depth relations. Limitations of using electromagnetic induction to determine ECafor discrete depth intervals through the soil are discussed. Current research designed to increase the accuracy of ECa‐depth determinations by dealing with the spatial variability problem associated with salinity in soil and by mitigating some of the inherent limitations of the calibration approaches is described.

ISSN:0010-3624    

DOI:10.1080/00103629009368275

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The nutrient status (N, P, K, Ca, Mg, K, Fe, Mn, Zn and Cu) of 26 Cox's Orange Pippin and 20 Braeburn apple orchard sites in the Canterbury region of New Zealand was evaluated by soil, leaf and fruit analysis. Concentrations of available nutrients in soils ranged widely but those in leaves and fruit were generally confined to a relatively narrow range. Concentrations of leaf N were high in the study area, as were levels of extractable soil P, and it is suggested that reductions in fertilizer additions of these nutrients would generally be appropriate.

ISSN:0010-3624    

DOI:10.1080/00103629009368276

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Analysis of soil and plant tissue for boron (B) is routine, but more information is needed to clarify the interpretations of test results as a basis for B fertilization of potato (Solarium tuberosumL.). Experiments were conducted in nutrient cultures and in the field to relate the utilization of B by potato plants to visual symptoms of deficiency and toxicity. Without added B the nutrient cultures produced B‐deficient potato plants, but the field plots with 0.3 to 0.4 mg of hot water soluble B/kg of soil did not. Plant shoots from nutrient cultures had a minimum of 13 mg B/kg as compared with plants in field plots with 30 mg B/kg in vines. Concentrations to 50 mg B/kg of dry matter were obtained in plant shoots from nutrient cultures with 1 mg B/L added and in field‐grown plants fertilized with 2.2 kg B/ha. Toxicity to B appeared or was eminent from either adding 3 mg B/L or more to nutrient solutions or 4.5 kg B/ha or more to the field plots. These results suggest the feasibility of developing critical nutrient (sufficiency) ranges for B in plant shoots and vines.

ISSN:0010-3624    

DOI:10.1080/00103629009368277

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A laboratory experiment designed to test the effect of additions of base cations and liming treatments on nutrient availability was carried out using the FH (Oe/Oa) horizon of an Orthic Ferro‐Humic Podzol (Humic Haplorthod) from a sugar maple (Acer saccharumMarsh) stand. Treatment with K2SO4caused a decrease in pH of the leachates from samples incubated for five weeks while liming caused an increase in pH. Application of the base cation‐lime materials caused an increase in Ca, Mg, and K, as would be expected, however these materials also increased NH4and NO3concentrations suggesting that microbial activity and N dynamics were also affected.

ISSN:0010-3624    

DOI:10.1080/00103629009368278

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The determination of total sulfur (S) in soils and plant tissue samples can be accomplished using a combination of sodium bicarbonate/silver oxide, dry ashing and ion chromatography(IC). The proposed method offers high precision and acceptable accuracy for samples with more than 0.02% S. At the same time this procedure makes use of standard analytical equipment used in other phases of soil, water and plant tissue analysis. Soil sample sizes larger than 0.1g or high total S or barite (BaSO4) may not have acceptable S recoveries due to incomplete S oxidation or dissolution of BaSO4. In order to optimize recoveries of total S in these special soil samples, varying (decreasing) sample sizes is required.

ISSN:0010-3624    

DOI:10.1080/00103629009368279

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The effectiveness of a commercially produced prill formulation in enhancing the Se level in a Se deficient grass/clover sward has been assessed. The product which contained 1% Se on a pressure impregnated mineral base was applied in early spring at two levels: 10g Se/ha (the recommended level) and 30g Se/ha. The Se levels in the herbage were subsequently monitored on cut samples taken over a 2 year period. The effect of N fertilisation on the Se status was also investigated.

ISSN:0010-3624    

DOI:10.1080/00103629009368280

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A study was conducted in the north Queensland tobacco producing area to examine the efficiency of use of N, P and K on two tobacco farms in the 1987 growing season. A nutrient balance was calculated from soil and plant analysis plus farmer fertiliser applications to estimate the losses of N, P and K which occur through leaching of these nutrients out of the root zone (0–0.45 m). Losses of 110 to 160, 50 to 80 and 160 kg/ha were found for N, P and K respectively during the grand‐growth period from hilling up to first pick. If 75% of these losses could by prevented, savings of $A5000 on an average 20 hectare crop of tobacco could be achieved.

ISSN:0010-3624    

DOI:10.1080/00103629009368281

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103629009368273

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor