摘要:

An electronically‐controlled, portable, cone penetrometer was designed, built, and tested. The penetrometer was driven electrically through a linear actuator. Cone position was sensed by a 10‐turn potentiometer, and force was sensed with an electronic load cell. A laptop computer controlled the linear actuator and recorded signals from the sensors through a data logger equipped with a serial interface. The penetrometer was capable of driving the cone at 0.84 cms‐1(±5%) over a load range of 0 to 180 kg. The system allowed force and position excursion limits to be set through software and provided data sets at 1‐cm increments to depths of 45 cm and forcesto2,000 N. The penetrometer demonstrated good repeatability among closely spaced probings when force per unit cone area was plotted against depth.

ISSN:0010-3624    

DOI:10.1080/00103629809370018

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Fifty soil samples (0–20 cm) with corresponding numbers of grain, potatoes, cabbage, and cauliflower crops were collected from soils developed on alum shale materials in Southeastern Norway to investigate the availability of [cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), and manganese (Mn)] in the soil and the uptake of the metals by these crops. Both total (aqua regiasoluble) and extractable [ammonium nitrate (NH4NO3) and DTPA] concentrations of metals in the soils were studied. The total concentration of all the heavy metals in the soils were higher compared to other soils found in this region. Forty‐four percent of the soil samples had higher Cd concentration than the limit for application of sewage sludge, whereas the corresponding values for Ni, Cu, and Zn were 60%, 38%, and 16%, respectively. About 70% the soil samples had a too high concentration of one or more of the heavy metals in relation to the limit for application of sewage sludge. Cadmium was the most soluble of the heavy metals, implying that it is more bioavailable than the other non‐essential metals, Pb and Ni. The total (aqua regiasoluble) concentrations of Cd, Cu, Zn, and Ni and the concentrations of DTPA‐extractable Cd and Ni were significantly higher in the loam soils than in the sandy loam soils. The amount of NH4NCyextractable metals did not differ between the texture classes. The concentrations of DTPA‐extractable metals were positively and significantly correlated with the total concentrations of the same metals. Ammonium nitrate‐extractable metals, on the other hand, were not related to their total concentrations, but they were negatively and significantly correlated to soil pH. The average concentration of Cd (0.1 mg kg‐1d.w.) in the plants was relatively high compared to the concentration previously found in plants grown on the other soils. The concentrations of the other heavy metals Cu, Zn, Mn, Ni, and Pb in the plants were considered to be within the normal range, except for some samples with relatively high concentrations of Ni and Mn (0–11.1 and 3.5 to 167 mg kg‘1d.w., respectively). The concentrations of Cd, Cu, Zn, Ni, and Mn in grain were positively correlated to the concentrations of these respective metals in the soil extracted by NH4NO3. The plant concentrations were negatively correlated to pH. The DTPA‐extractable levels were not correlated with plant concentration and hence DTPA would not be a good extractant for determining plant availability in these soils.

ISSN:0010-3624    

DOI:10.1080/00103629809370019

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Seventy‐one forage samples were analyzed for their macromineral composition and foragein vitroorganic matter digestibility (IVOMD) in three agricultural zones of Benue State, Nigeria. The zones consisted of Northern, Eastern, and Central zones, each of which were made up of four Local Government Areas. In each Local Government Area, grazing animals were monitored and forages corresponding to those consumed were collected during the peak of the wet season (June) and analyzed for their macromineral composition and IVOMD. Fewer number of forage samples were harvested from Northern and Eastern zones due to greater agricultural activities and infra‐structural land use which limited land space for grazing animals. Forage IVOMD ranged from 32% to 78.3% across all classes of forage and from 43.5% to 62.8% in the Local Government Areas. About 18% of total samples, exclusively from the Northern zone, showed forage IVOMD concentrations below 20%, probably resulting from grazing pressures and agricultural activities in the zone. Forages from the Northern zone were deficient in phosphorus (P), potassium (K), and sodium (Na) based on their criteria of adequacy. No deficiency levels were indicated in forage calcium (Ca) or magnesium (Mg). Northern and Eastern zones were in greatest need of mineral supplementation programs.

ISSN:0010-3624    

DOI:10.1080/00103629809370020

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A total of 71 forage samples were analyzed for trace mineral and crude protein concentrations in three Agricultural zones of Benue State, Nigeria. The zones consisted of the Northern, Eastern, and Central zones, each of which was made up of four Local Government Areas. In each Local Government Area, grazing animals were followed and forages corresponding to those consumed were collected during the peak of the wet season (June) and analyzed for the nutrient composition. Deficiencies were observed in copper (Cu) and cobalt (Co) concentrations in all classes of forage, and in forage Cu and zinc (Zn) in all Local Government Areas in the Northern zone. A higher (P<0.05) forage Cu concentration was observed in legumes compared to other classes of forage in the Eastern zone. Concentrations of iron (Fe) and manganese (Mn) were considered adequate and their contents were not affected (P>0.05) by class of forage or Local Government Areas. In the Eastern zone, the contents of selenium (Se) in grass and tree leaf hay were higher compared to leguminous forage, which in turn was higher compared to Se concentrations in crop wastes. Only about 18% of total forage samples showed protein concentrations below the critical value of 7%. Supplementation of Cu, Zn, and Co would seem to be necessary in the Northern zone, and to a lesser extent in the Eastern zone for optimum productivity of grazing animals.

ISSN:0010-3624    

DOI:10.1080/00103629809370021

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A laboratory experiment was conducted at +5°C with undisturbed columns (0.19 m i.d., 0.60 m long) of fine sand, heavy clay, and peat to determine the effect of soil and timing of the rainfall event on the amount of fertilizer nitrogen (N) that might be leached after fertilizer application. The15N‐labeled calcium nitrate [Ca(NO3)2] equal to 120 kg N ha‐1was applied 13 or 1 days before adding a total of 70 mm of water. Drainage water was collected through an inlet attached to the bottom of each column until drainage had ceased nine days later. From the sand columns, 27 and 19% of the fertilizer nitrate‐nitrogen (NO3‐N) applied was leached out when the columns were irrigated 1 and 13 days after fertilizer application, respectively. From the three water‐permeable clay columns containing earth worm burrows, 23 and 53% of the fertilizer NO3applied was leached out when irrigation took place 1 and 13 days later, respectively; the other five clay columns were impermeable. Less than 0.1% of fertilizer NO3was leached out from the peat columns with either incubation treatment. After the experiment, the content of fertilizer N was highest at a depth of 0.12–0.24 m in the peat and clay columns, and at a depth 0.24–0.33 m in the sand columns. In the sand and peat columns, less fertilizer N moved down in the column when soil and fertilizer were incubated before irrigation. It is concluded that in a rainy and cool spring, substantial amounts of fertilizer N can be leached beyond the reach of plant roots and out of the soil profile. The time passing between fertilizer application and rain may reduce the risk of leaching of applied N at low temperatures by diffusion into smaller soil pores rather than by biological immobilization. With the intensity of irrigation applied here, fertilizer N moved down in the sand and clay columns as bypass flow and hydrodynamic dispersion, whereas in peat columns it tended to move more as a front.

ISSN:0010-3624    

DOI:10.1080/00103629809370022

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The aggregate stability of several surface soils from Thessaly plain, Central Greece, was studied using an instability index which classified the soils according to the stability of their aggregates to water. This index was correlated to the basic soil properties influencing aggregate stability. It was found that soil aggregate stability was positively correlated with clay content, total specific surface area, cation exchange capacity, base saturation, and free silicon oxides content. Silt, very fine and fine sand, and the ratio (sand+silt)/clay influenced negatively the aggregate stability. Organic matter content and sesquioxides have no effect on aggregate stability. It was also observed that the fraction of carbonates with silt dimension influenced negatively the aggregate stability. From the results of this study it was concluded that the factors affecting water aggregate stability were specific surface area and cation exchange capacity of the soils.

ISSN:0010-3624    

DOI:10.1080/00103629809370023

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The primary purpose of soil conditioner application is to enhance a soil's resistance to erosion processes by increasing the water stability of aggregates. In this study, a wrist‐action shaker was used to assess the aggregate stability of three Hawaiian soils treated with an anionic surfactant soil conditioner (AGRI‐SC). Aggregates of 2.00 to 4.00 mm in size were treated with Agri‐SC at rates of 1 to 100,000 times the manufacturer‐recommended rate of 0.30 L ha‐1. The manufacturer‐recommended application rate of Agri‐SC was effective for only the most stable soil tested (Kaneloa Oxisol), ineffective for the Lualualei Vertisol, and adversely effective for the Molokai Oxisol. For higher application rates ranging from 10 to 10,000 times recommended, stability of large aggregate fractions increased for the Kaneloa Oxisol. In sharp contrast, the same application rates decreased aggregate stability of the Molokai Oxisol. For the third, least stable soil (Lualualei Vertisol), Agri‐SC was relatively ineffective, except at very high application rates (1, 000 and 10, 000 times recommend). Finally, at the extremely high application rate of 100, 000 times recommended, aggregates for all soils were peptized. These results suggest that careful attention should be given to the application of soil conditioners with anionic surfactants as active ingredients, for aggregate response to various application rates appears to be soil dependent.

ISSN:0010-3624    

DOI:10.1080/00103629809370024

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Shallow‐drained horticultural soils utilized in containers, sporting areas, and landscape sites tend to retain excess water and thereby be poorly aerated as a consequence of capillary retention following irrigation or precipitation. This problem is usually corrected by soil physical amendment with coarse‐textured particulates to add large pores which drain and provide adequate aeration. A variety of materials are used for soil physical amendment. This study examined the water retention of one of the newer amendments used for this purpose, light expanded clay amendment (LECA), relative to its use in shallow‐drained soils. Although LECA is a porous material, its contribution to soil physical properties when used as an amendment were found to be similar to non‐porous amendments such as river sand or gravel because the internal water is not readily available for plant use.

ISSN:0010-3624    

DOI:10.1080/00103629809370025

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The release of carbon and water from soil organic matter (SOM) was determined with a LECO analyzer (RC‐412) and compared to weight loss data obtained by analysis of soils with a normal thermogravimetric method, SOM fractions obtained by wet chemical extractions and SOM subunits of carbon‐13 NMR spectroscopy of bulk soil samples. Four soil horizons were used for the analysis with the LECO analyzer. Wet chemical data as well as NMR spectra show a specific SOM composition of the soil horizons. The thermoanalytical analysis allows a quantitative separation of carbon and water release, and the thermal diagrams confirm the specificity of the SOM in the different soil horizons. The heating rate in the LECO analyzer with a low temperature progression improves the resolution of the carbon release in comparison to the continuous temperature increase (105°C to l,000°C) of at a speed of 70°C min‐1. The thermostability index Rp can be used to characterize the humification level and provides a semiquantitative carbohydrate estimate in the SOM fraction. The obtained C/O and the C/H ratios are perhaps simple parameters to observe changes in carbon (C), oxygen (O), and hydrogen (H) for characterization of turnover processes and humification of organic matter in soil.

ISSN:0010-3624    

DOI:10.1080/00103629809370026

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Soils in the upland areas of Malaysia are mostly weathered (Ultisols and Oxisols), having high aluminum (Al), but calcium (Ca) and/or magnesium (Mg) deficient. Magnesium limestone is available in large quantities in Malaysia and is frequently being used to alleviate acidity in the upland soils. This study aimed at assessing the longevity of the limestone applied to an highly weathered acid soil under conditions prevailing in the tropics. The experiment consisted of two phases; in the first phase the plots were treated with various rates of lime, while in the second phase some plots were left as residual treatments. The results of the study showed that an acid Ultisol of Malaysia can be ameliorated by annual limestone application of 11 ha‐1for maize(Zea maysL.) production. The beneficial effects of liming with ground magnesium limestone (GML) at 41 ha‐1were observed for about eight years. The critical soil pH and exchangeable Al for maize production were found to be 5 and 0.7 cmolcKg‐1soil, respectively. The Ca and Mg from the limestone were mostly found in the topsoils because of the increase in cation exchange capacity (CEC) resulting from the pH increase.

ISSN:0010-3624    

DOI:10.1080/00103629809370027

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor