摘要:

In order to predict release of nitrogen (N) from controlled‐release fertilizers (CRF) from laboratory experiments, new types of lignin‐coated fertilizers were studied. Laboratory methods were 1) release of urea into water and 2) an extraction procedure using an electroultrafiltration technique (EUF). The results of these two methods were compared to the amount of N released in a vegetation experiment in the greenhouse. The results showed a good relationship between the two laboratory methods. The correlation coefficient between the rate constant K determined in the water extract and each of the N‐fractions was highly significant. The total amount of N released in the vegetation experiment was correlated to parameters of the laboratory methods. The N uptake by the plant was significantly correlated with the first order constant and with the fertilizer's EUF‐NII index. The N leached was also correlated with the EUF‐NI and EUF‐N (I+II) indices.

ISSN:0010-3624    

DOI:10.1080/00103629809370126

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A method is described in which total soil boron (B) was determined by inductively coupled plasma atomic emission spectrometry (ICP‐AES). The method is based on microwave‐assisted digestion of soil samples with nitric acid (HNO3), hydrofluoric acid (HF) and hydrogen peroxide (H2O2). Excess HF was eliminated by adding silicon (IV) oxide (SiO2). The B 208.959 nm line was chosen as the analytical line to avoid the spectral interferences of iron (Fe). A detection limit of 0.0045 mg L‐1was obtained with the selected analytical line under the optimized operating conditions. Four National Institute of Standards and Technology (NIST) standard reference materials (three soils and one river sediment) and four different type of practical soils were analyzed to test the reliability of the method. The total B concentration in selected samples ranged from 19 to 76 mg kg‐1. The excellent recoveries of the spike (98.5–101%) indicate that the proposed procedure is effective and feasible for the determination of total B in soils.

ISSN:0010-3624    

DOI:10.1080/00103629809370127

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Soil samples obtained from basement complex soils which spread across the major soil areas in northern Nigeria were analyzed for both physical and chemical properties. The soils are slightly acid. Acidity decreased with depth. The textural class ranged from sand in the semi‐arid areas to sandy clay loam in the southern part of the sub‐humid zone. Organic carbon content ranged from 0.17 to 1.5%, whereas nitrogen (N) levels ranged from 0.04 to 0.08% in the surface horizon. The soils have high base saturation indicating low Al3+concentration. The levels of available phosphorus (P) were inadequate for satisfactory plant growth, given a critical level of 15 mg kg‐1was established for Nigerian soils. A significant correlation (r=0.63) was observed between pH and P on one hand and with clay content (r=0.47) on the other hand. The low values of the silt:silt + clay ratio, used as a weathering index indicated that the soils must have undergone advanced weathering. The magnitude of calcium:magnesium (Ca:Mg) ratio indicated that more calcium than magnesium was available in the soils. More iron than aluminum was extracted from soils by the dithionite‐citrate method. Soils from the sub‐humid zone had relatively higher levels of organic matter and total N than the semi‐arid areas. In the same vein, marginal higher values for sand and base saturation were found in soils from the semi‐arid areas than the sub‐humid zone.

ISSN:0010-3624    

DOI:10.1080/00103629809370128

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Large areas of salt‐affected soils exists in Syria. Besides, large quantities of phosphogypsum (PG) are stacked in areas close to the fertilizer factories (radioactivity 350 to 400 Bq kg‐1) that may pose a negative impact on the environment. Different rates of PG (0, 0.25, 2.5, 5, and 25%) were mixed with three soils characterized by different level of salinity (ECe5.25, 9.44 and 17.66 dS m‐1) to monitor the effect of mixing PG on the physical and chemical properties of the soils, plant growth and the accumulation of radionuclides in soils and plants. The high PG application rates (2.5, 5, and 25%) were used to monitor the effects of adding the normal application rate of PG (5 T ha‐1) for 10, 20, and 100 consecutive years. Soil‐PG mixtures were put in 8.5 kg pots where trifolium (Trifolium pilulare)and barley(Hordium vulgarevar. Arabi Abyad) were seeded. The results showed that mixing PG increased the saturated hydraulic conductivity, reduced Cl‐1and increased SO2‐4concentrations in the saturated extracts and increased the available phosphorus (P). Mixing PG increased plant height, shoot number and dry weigh of both plants. Barley grain weight increased by 62.0, 49.8, and 39.5% in Ramet‐Leha, Maskane, and Beni‐Taghleb soils, respectively. The radioactivity of barley grains and the vegetative parts of the two plants grown in these mixtures were below the detective level (1.1 Bq kg‐1of dry weight).

ISSN:0010-3624    

DOI:10.1080/00103629809370129

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Most soil testing laboratories require soil samples collected for the pre‐sidedress soil nitrate test (PSNT) to be dried before shipment. Shipment of field‐moist samples would make it easier to use the test. The objective of this study was to measure the effect of bag type on changes in soil nitrate in samples collected for the PSNT. Soil samples were collected from the surface foot of soil when corn (Zea maysL.) plants were 15‐ to 30‐cm tall. Four fields with a history of manure applications were sampled. The bulk sample was subsampled in the field and the subsamples were kept cool during transport to the laboratory and were immediately air dried after arrival at the laboratory. Field‐moist subsamples from each bulk sample were placed into either cloth bags or plastic‐lined paper bags after arrival at the laboratory. Four replications of the subsamples were incubated at 30°C for 1, 2, 3, and 4 days. After removal from the incubator, the subsamples were immediately spread to air dry. The soils incubated in the plastic‐lined paper bags did not significantly increase in nitrate after one day of incubation. There was a significant increase, however, in nitrate each day after the second, third and fourth day of incubation. The soils incubated in the cloth bags did not significantly increase in nitrate until the fourth day of incubation. The average increase in nitrate‐N concentration in the cloth bags between day 3 and day 4 was 1.5 mg kg L‐1soil. The results suggest that cloth bags could be used to ship field‐moist soil samples for the PSNT without significant changes in soil nitrate concentrations.

ISSN:0010-3624    

DOI:10.1080/00103629809370130

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103629809370105

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor