摘要:

In Western Australia soil samples to measure soil‐test phosphorus (P) are collected November to March when soils are usually dry. Most of the soils are hard‐setting when dry and it is difficult to penetrate and collect soil samples to 10 cm using the traditional sampler, which is a 2.5 cm diameter tube that is pushed into the soil by foot. Farmers collect too few soil samples at shallow depths to measure soil‐test P. In Part 1 of this paper, it was shown that soil‐test P can vary markedly for individual soil samples collected from uniform areas in paddocks. Consequently, an adequate number of soil samples needs to be collected and bulked from defined areas to measure soil‐test P. Phopshorus accumulates near the top of the soil of (i) pastures since P fertilisers are applied to the surface of pastures, and (ii) crops sown by minimum (conservation) tillage. Crops are increasingly being sown using conservation tillage methods. Collecting too few soil samples to a shallow depth can result in large errors when estimating the current P status of soils and determining optimum fertiliser application levels. A new rotating blade method of collecting soil samples to the standard 10 cm depth for measuring soil‐test P was compared with the traditional sampler. The new sampler successfully penetrated hard‐setting soils to the standard depth and the soil samples it collected produced similar soil‐test P as the traditional sampler. Consequently, the same soil‐test P calibrations determined using the traditional sampler can also be used for the new sampler. The new sampler is, therefore, recommended for collecting soil samples to measure soil‐test P. It should have application wherever hard‐setting soils pose a problem for soil P testing.

ISSN:0010-3624    

DOI:10.1080/00103629409369195

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

When soils are extracted with sodium bicarbonate to measure soil test phosphorus (P) by the standard Colwell procedure, the concentration of P in the extract solution is measured using the Murphy and Riley procedure. This measures P as orthophosphate (PO4) and most of the organic P extracted is not measured. The total (inorganic plus organic) P extracted can be measured by digesting an aliquot of the extract solution with perchloric acid to convert all the extracted P to PO4before measuring the P concentration by the Murphy and Riley procedure. This is called total Colwell P. Data from one crop and two pasture field experiments in Western Australia are presented in which soil test P measured in 1991 and 1992 by the standard and total Colwell procedures were compared. Fertiliser P residues, including organic P, accumulate in the topsoil because, (i) the fertiliser is applied to the surface of pastures, and (ii) crops are being increasingly sown by minimum (conservation) tillage when P is concentrated in the top approximate 5 cm of the soil compared with about 10 cm when crops are sown conventionally. Consequently, to measure soil test P in the present study, soil samples were collected in February 1991 to either 5 or 10 cm depth. For the two Colwell procedures and both sampling depths, soil test P was related to: (i) the level of P applied in previous years and to (ii) plant yield measured later on that year (the soil test P calibration). Soil test P was larger for the total Colwell procedure and for soil samples collected to 5 cm depth. Total Colwell P as the dependent variable was closely correlated with standard Colwell P as the independent variable. The relationship between soil test P and the level of P applied, and the calibration relating yield to soil test P, were different for standard and total Colwell P. Neither method can be claimed to be significantly better than the other. It is concluded that use of the total Colwell procedure instead of the standard procedure is not warranted. Likewise, there was no evidence that collecting soil samples to 5 cm to measure soil test P provided better estimates of the current P status of soils than collecting soils to the standard 10 cm depth. There is therefore no need to change the sampling depth.

ISSN:0010-3624    

DOI:10.1080/00103629409369196

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Incineration reduces sewage sludge volume, but management of the resulting ash is an important environmental concern. A laboratory incubation study and greenhouse pot experiments with lettuce(Lactuca sativaL.) and corn (Zea maysL.) were conducted to examine the potential for recycling elements in sewage sludge incinerator ash in agricultural systems. Ash rates in both the laboratory and greenhouse were 0, 0.95, 3.8, 15.2, and 61.0 g/kg soil (Typic Hapludoll). Ash was also compared to equivalent rates of citrate soluble P from superphosphate fertilizer in a soil‐less growth medium. During soil: ash incubation, Olsen P and DTPA extractable copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) increased with incubation time at the higher ash rates. Release rates diminished rapidly, however, and the limited release of these elements after 280 days was associated with decreasing pH. In the greenhouse, ash amendment increased extractable soil P, plant tissue P, and the growth of lettuce and corn. Ash was a less effective P source than superphosphate fertilizer in the soil‐less growth medium and Olsen P levels were more consistent with these differences than Bray P. Ash increased extractable soil levels and plant tissue concentrations of calcium (Ca), magnesium (Mg), sodium (Na), Cu, and Zn, but extractable soil manganese (Mn) and plant tissue Mn decreased. Ash increased soil pH and extractable SO4‐S. DTPA extractable Cd and Pb increased, but chromium (Cr) and nickel (Ni) decreased. Lettuce accumulated higher amounts of these trace metals than corn, but tissue concentrations were at control levels or below detection limits in both crops.

ISSN:0010-3624    

DOI:10.1080/00103629409369197

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Log yard residues (LYR) a bark and soil waste material produced during log handling, could find use as a growth medium for plants. In this study, log yard fines (LYF), a screened fraction of the LYR (<1.3 cm), were either not amended or amended with a N‐S fertilizer mixture (LYF + F) or with cow manure (LYF + M) and then composted outdoors in insulated, aerated tanks for 18–22 weeks. The resulting substrates were then evaluated as growth media for ‘Chief crimson clover (Trifolium incarnatumL.) and ‘Streaker’ red top (Agrostis albaL.). Plants were fertilized (0 or 78 kg N/ha) and grown in a growth chamber.

ISSN:0010-3624    

DOI:10.1080/00103629409369198

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A representative grassland soil of the lowland areas of the Flooding Pampa (Argentina) was sampled to study the dynamics of the non‐exchangeable ammonium under waterlogging conditions. Most of the external factors determining fixed ammonium release and fixation were considered. There was no net release of ammonium from the clay fixing‐sites to the soil solution, when this soil was flooded under laboratory conditions. We conclude that the non‐exchangeable ammonium fraction in this soil is very stable and with little importance as a nitrogen source for plants.

ISSN:0010-3624    

DOI:10.1080/00103629409369199

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A study was conducted to calibrate and evaluate five buffers for the lime requirement (LR) determination of tropical peat soil. The buffers tested were the Shoemaker‐McLean‐Pratt (SMP); Mehlich; 0.1M ammonium acetate (NH4OAc); 0.1M barium acetate [(Ba(OAc)2]; and 0.1M calcium acetate [Ca(OAc)2]. Calibration was done by comparing the precision of linear regression equations adjusted to the relationships between the LR rates required to achieve pH 5.0 measured in a 1: 4 (soiltwater) ratio as determined by incubation and soil‐buffer pH values. Incubation LR using calcium carbonate (CaCO3) to achieve pH 5.0 by peat soil was utilized to calibrate each buffer. Evaluation was carried out by assessing the LR from the calibrated buffers which estimate the LR nearest to the target pH of 5.0. The calibration study showed that the SMP and Mehlich buffers were less precise than the Ba(OAc)2, NH4OAc, and Ca(OAc)2buffers. The evaluation study indicated that the Ba(OAc)2buffer is the most accurate, followed by NH4OAc and Ca(OAc)2buffers. The Ba(OAc)2buffer method is recommended for LR determination of tropical peat soil and NEUOAc or Ca(OAc)2as an alternative method.

ISSN:0010-3624    

DOI:10.1080/00103629409369200

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The relationship between nutrient concentration and yield of plant forms the basis of using plant analysis to assess nutrient status of plants. This study determined critical levels of phosphorus (P) in diagnostic plant parts of four grain crops. The crops were grown in greenhouse using a P‐deficient Typic Ustochrept fertilized with 0, 10, 30, 90, and 270 mg P/kg soil. Crop sensitivity to P deficiency was: sorghum > maize > sunflower > mungbean. Fertilizer requirements (mg P/kg soil) for near‐maximum grain yield were: sunflower, 89; and maize and mungbean, 74. Fertilizer requirement of sorghum was much greater than the other species. Critical P concentrations in whole shoots (≤30 cm tall) were: mungbean, 0.30%; sunflower, 0.29%; and maize, 0. 24%. Equivalent values for diagnostic leaves were: mungbean, 0.33%; sunflower, 0.31%; and maize, 0.26%. Critical P concentrations in mature seeds were: mungbean, 0.34%; maize, 0.29%; and sunflower, 0.20%.

ISSN:0010-3624    

DOI:10.1080/00103629409369201

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effects of triple superphosphate (TS) and liming on macronutrient accumulation and root growth of Pioneer 3072 and Cargill 505 corn hybrids were studied. Corn plants were grown up to 30 days in pots with 7 L of a dark red Latosol sandy loam (Haplortox). Lime was applied to raise base saturation to 30, 50, and 70%, in two levels of phosphorus (P) fertilization with TS (0 and 200 ppm P). There was an increase in root surface due to lime only in pots without TS, with no effects on plant growth or nutrition. Both corn hybrids responded to P fertilization, but Pioneer yielded more dry matter than Cargill. The roots of Cargill were thicker and, when in TS presence, were longer and had a larger surface than Pioneer. There was an increase in macronutrient uptake in the P fertilized pots. Pioneer required more nutrients and showed a higher efficiency in acquiring and utilizing the nutrients from the soil. A higher response of Pioneer in dry matter and nutrient acquisition was more related to the physiological efficiency than to root morphology.

ISSN:0010-3624    

DOI:10.1080/00103629409369202

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Snap beans (Phaseolus vulgaris)were grown using conventional tillage (CT) and no‐tillage (NT) soil management following either hairy vetch (Vicia villosaRoth) or rye (Secale cerealeL.) in 1992 and 1993 in the mountain regions of Georgia near Blairsville. Soil bulk density and inorganic nitrogen content as well as crop dry matter production and yield were monitored. Soil bulk density of the surface (0 to 10 cm) layer under NT exceeded that under CT at planting by as much as 0.33 Mg/m3. However, growth‐limiting bulk densities (values>1.45 Mg/m3) did not occur under either tillage regime. Inorganic soil nitrogen to a depth of 30 cm at planting and at five weeks after planting was similar for the two tillage systems. However, soil nitrogen (N) tended to be greater following hairy vetch than following rye. There were no significant effects of tillage or cover crop on plant stand or plant dry weight. Total yields were generally similar regardless of tillage or cover crop. A notable exception was that early yield in 1992 was 62% greater using NT. These results indicate great potential for use of conservation tillage and cover crops in the production of snap beans in the mountain regions of the southeastern United States.

ISSN:0010-3624    

DOI:10.1080/00103629409369203

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This study examined the effects of organic manure and chemical fertilizer on soil microflora, soil respiration, number of inorganic phosphate solubilizing bacteria, and organic phosphorus (P) mineralizing bacteria. The inorganic phosphate solubilizing rate, organic P mineralizing rate, and selected enzyme activities in a blue purple paddy soil were also studied. The results showed that organic manure significantly increased the total number of fungi, actinomyces, bacteria, P solubilizing bacteria, organic P mineralizing bacteria, P solubilizing rate and organic P mineralizing rate, soil respiration rate, and selected enzyme activities, whereas chemical fertilizer resulted in a smaller effect, and bacteria were affected more than fungi and actinomyces by organic manure. The enhancement of biological activities caused by organic manure might be due to the introduction of a large amount of living microorganisms and readily‐utilizable carbon source on which microorganisms live. This study showed that the augment of inorganic phosphate solubilizing bacteria and organic P mineralizing bacteria was one of the reasons that organic manure increased the avilability of P in a blue purple paddy soil.

ISSN:0010-3624    

DOI:10.1080/00103629409369204

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor