摘要:

Determination of soil texture, particularly the clay (<2 μm) fraction, is an important measurement in most soil investigations. In this study a modified method for mechanical analysis was evaluated that eliminated the need for bulky laboratory equipment and long settling times associated with standard pipette and hydrometer methods. Termed a “micro‐pipette”; method, the modified procedure uses 2 to 4 g soil with 40 mL of dilute dispersant, shaken overnight in 50 mL centrifuge tubes. Clay is determined by sampling 2.5 mL using an adjustable volume pipettor from a depth of 2.5 cm after approximately 2 h of settling, as calculated from Stokes’ law. The dried suspension weight is used to compute clay content after correction for salt content of the dispersant. Sand can be determined by sieving at 50 μm after clay analysis, with silt calculated by difference. Using 12 soils with a range of particle sizes, the proposed method was found to give textural values nearly identical to those found with the standard pipette method. Variability between replicates was higher for clay content with the use of 2 g in the micro‐pipette method, but was not different from the standard pipette when 4 g were used. Variability was also higher in the micro‐pipette sand determination with both soil weights, although was still within acceptable limits (coefficient of variation < 4%). The major advantage of the method is that one person can run analyses on 50 soils per day (including duplicates) in limited laboratory space with standard laboratory equipment. The method is also useful for determining water‐dispersible clay in soils, and for measuring sediments in runoff and natural waters.

ISSN:0010-3624    

DOI:10.1080/00103628709367799

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Seasonal variation of N, P, K, Ca, Mg, S, Fe, Mn, Cu, Zn, B were determined in leaves ofPrunus aviumL., cv Napoleon. An equation for each element relating sampling date and content is given.

ISSN:0010-3624    

DOI:10.1080/00103628709367800

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The dynamics of eleven essential elements were studied in “Golden Japan”; plum trees. Throughout the vegetative period the leaf concentrations of N, P and Zn fell. There was an accumulation et Ca, Mg, S, Fe, Mn and Cu, but there was no clearly defined tendency for K or B. The concentration of each element was time‐related and correctly defined by a polynomial equation.

ISSN:0010-3624    

DOI:10.1080/00103628709367801

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Available carbon (C) is defined as soil organic C that heterotrophic microorganisms can readily utilize as an energy and C source. Several techniques for assessing available C have been described in the literature, but none has become standard. Four of these methods, (i) mlneralizable C (Min‐C), (ii) cold water soluble C (CWS‐C), (iii) boiling water extractable C (BWE‐C), (iv) and total C (Tot‐C), were compared to each other and to a denitrification potential (DP) bioassay of C availability. These comparisons were made across selected forest soils which exhibited wide ranges of textural composition and organic C content and which ranged in acidity from pH 3.1 to 5.4. Carbon mineralized to CO2during a 7 day aerobic incubation of field‐moist soil (Min‐C) provided the best prediction of DP. Min‐C also appeared to distinguish between available C and refractory C in a soil with high Tot‐C.

ISSN:0010-3624    

DOI:10.1080/00103628709367802

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Salt damage to plants may be caused by competition in uptake between salt ions and nutritional ions. The effect of sodium chloride (NaCl) on nitrate (NO3), o‐phosphate (P), and potassium (K) uptake by cotton (Gossypium hirsutumL.) was measured. Plants were grown in nutrient cultures with added 0–450 mM NaCl for 41 days. Uptake of NO3, P, and K was measured according to their depletion in the solution with time, and measured root surface area. Net‐influx Inin low external concentrations was assumed to obey the Hill equation: In=Imax.Cn/(Kan+Cn), where C is concentration, Imaxthe value of Inwhen C is infinite, Kais the apparent Michaelis‐Menten coefficient, and n is the cooperativity index.

ISSN:0010-3624    

DOI:10.1080/00103628709367803

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

In this review, an attempt is made to summarize the information on transformations of iron oxides in the soils under wetland rice‐based cropping systems and to understand whether these transformations influence soil properties and eventually nitrogen transformations. The effects of iron oxides and their transformations on soil properties such as pH, redox potential, cation exchange capacity, and structure are apparent. Limited available information tends to suggest that nitrogen reactions such as sorption‐desorption of ammonium, ammonification, denitrification, and ammonia volatilization may be influenced by the transformations of iron oxides. However, more work is needed to confirm the effects.

ISSN:0010-3624    

DOI:10.1080/00103628709367804

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A field experiment was conducted on a clayey, kaolinitic Typic Tropudult of Panama to study the dynamics of soil pH, exchangeable Ca and Al following lime application and their subsequent effects on plant growth and yield of cassava(Manihot esculentaCrantz, cv. Brazilena). Increasing rates of CaCO3were applied to reduce percent Al saturation below 65, 60, 50, 30 and 0.

ISSN:0010-3624    

DOI:10.1080/00103628709367805

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Inductively coupled plasma spectrometry (ICPS) was used for the simultaneous determination of P, K, S, Ca, Mg, Na, Al, Cu, Zn, Mn, Fe, Co, Mo and B in the nitric acid soluble portion of a variety of plant materials. Conditions for pre‐digestion, digestion and the requirement to grind cereal grain were investigated.

ISSN:0010-3624    

DOI:10.1080/00103628709367806

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103628709367798

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor