摘要:

A possibility of estimating the field capacity (FC), wilting point (WP), total available water (TAW), and readily available water (RAW) of soils was investigated from their saturation percentage (SP). Regression equations were obtained from the data from 166 Nigerian soils with wide variations in texture and other physico‐chemical properties. The results showed a strong linear relationship between saturation percentage and the gravimetric percentage moisture contents at FC (r=0.972, P<0.001), and WP (r=0.949, P<0.001), but a weak linear relationship with TAW (r=0.771, P<0.01) and RAW (r=0.489, P<0.05). The regression equations calculated between these soil moisture constants and SP predicted the FC and WP of 25 independent soils very well, but were not good predictors of TAW and RAW. Reliable and satisfactory estimates of TAW were obtained by subtracting estimated WP from estimated FC, and of RAW by subtracting estimated moisture content at ‐100 kPa matrix potential from estimated FC.

ISSN:0010-3624    

DOI:10.1080/00103629809369995

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Microwave digestion using either only nitric acid or a mixture of nitric acid and hydrogen peroxide is an innovative technique used widely for elemental analysis of soil and plant samples. Only limited information, however, is available on comparisons of digestions with or without hydrogen peroxide. The objective of this study was to investigate the effect of the use of hydrogen peroxide on the analytical results for several metals in soil samples. Three mineral and four organic soil samples were used in this study. The soils were slightly acidic, and the organic carbon ranged from 0.38 to 1.26% for the mineral soils and from 17 to 38% for the organic samples. After microwave digestion, the soil samples were analyzed for aluminum (Al), iron (Fe), magnesium (Mg), zinc (Zn), copper (Cu), lead (Pb), cadmium (Cd), nickel (Ni), chromium (Cr), and manganese (Mn) using inductively coupled plasma spectroscopy. In general, the analytical results obtained with nitric acid alone were not significantly different from those with the nitric acid and hydrogen peroxide mixture regardless of organic carbon content. Since hydrogen peroxide did not promote additional dissolution of these metals in this study, nitric acid alone in microwave digestion is sufficient for determining metal composition of soils.

ISSN:0010-3624    

DOI:10.1080/00103629809369996

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Two lysimeter experiments were conducted on annual leaching losses of calcium (Ca), potassium (K), sodium (Na), chloride (Cl), sulphate‐sulphur (SO4‐S), and magnesium (Mg) (one experiment only) from a sandy soil in central England during 1988–1995 to provide information on typical nutrient losses under arable agriculture below 1.2 m (Experiment 1) or 1.5 m (Experiment 2). Total annual losses, in the absence of manure additions, were highly dependent on the amount of drainage; flow‐weighted average concentrations were similar between years within experiments. Concentrations, averaged over the duration of the experiments were 74 and 78 mg L‐1Ca, 17 and 27 mg L‐1Na, 11 and 8 mg L‐1K, 74 and 77 mg L‐1Cl, and 57 and 38 mg L‐1SO4‐S for the two experiments respectively; Mg concentration was 17 mg L‐1. Applications of chicken litter were madetosome of the lysimeters in the last three years, and all nutrients showed increased leaching as a result. Application rates akin to disposal (rather than for crop fertilization) produced the largest losses. Following a total application of 125 t ha‐1over three years, average concentrations in water draining below 1.5 m in the final year were 57 and 277 mg L‐1Ca, 22 and 75 mg L‐1Cl, 7 and 14 mg L‐1K, 22 and 57 mg L‐1Na, 27, and 125 mg L‐1SO4‐S for the untreated and manured soils, respectively.

ISSN:0010-3624    

DOI:10.1080/00103629809369997

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An investigation was conducted to study the effect of organic matter on nitrogen (N) and phosphorus (P) content in soils derived from loess in Northwest China. The results indicated that available N and total N content were correlated positively with organic matter content significant at the 5% level. Available P content was unaffected, but total P content appeared to increase linearly with increased organic matter content.

ISSN:0010-3624    

DOI:10.1080/00103629809369998

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This study was undertaken to assess the mineralization of sulfur (S) in laboratory conditions of three rice soils (Joydebpur, Faridpur, and Thakurgaon), receiving the following treatments: 1) control, 2) rice straw (Oryza sativaL.), and 3) pea vine (Pisum sativumL.). The organic residue (25 mg g‐1) was added and mixed with soil and glass beads (1:1, soil to bead ratio) and placed into a Pyrex leaching tube. The soils were flooded and incubated at 35°C, after which they were leached with deionized water at 1, 2,4, 8, and 12 weeks for analysis of SO4and other chemical properties in the leachates. Potentially mineralizable S (So) and C (Co) pools and first‐order rate constants (Ksfor S and Kcfor C) in soils amended with rice straw and pea vine under flooded conditions were estimated using an exponential equation. The Soand Ksvaried considerably among the soils and types of added organic residues, and their values in rice straw and pea vine ranged from 8.70 to 29.55 and 0.124 to 0.732 mg S kg‐1wk‐1, respectively. Except for the Thakurgaon soil, the Soand Ksvalues in Joydebpur and Faridpur soils were higher in the unamended treatments. Higher Sovalues in the unamended soils were probably due to less microbial activity to mineralize organic S from organic residues. The results indicate that the amount of SO4in flooded soils amended with organic residues are dependent on soil type, nature of organic residues, and time of incubation. The Coand Kcvalues under flooded incubation were higher in residue amended soils than in unamended soils. Pea vine treated soils had higher Coand Kcvalues than the soils treated with rice straw.

ISSN:0010-3624    

DOI:10.1080/00103629809369999

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This study was undertaken to assess the mineralization of nitrogen (N) in rice soils amended with organic residues under flooded condition. A lab incubation study with a 3x3 factorial design (two replications) was conducted with three rice soils (Joydebpur, Faridpur, and Thakurgaon) receiving the following treatments: 1) control, 2) rice straw (Oryza sativaL.), or 3) pea vine (Pisum sativumL.). The organic residue (25 mg straw g‐1soil) was mixed with soil and glass beads (1:1, soil to beads ratio), and transferred into a Pyrex leaching tube, flooded and then incubated at 35°C for up to 12 weeks. The soils in the leaching tubes were leached (while maintaining flooded condition) at 1,2,4, 8, and 12 weeks with deionized water for determination of NH4‐N, NO3‐N, pH, and Eh. Nitrogen mineralization in soils amended with rice straw was somewhat different than that of soils treated with pea vine. Soil treated with rice straw had a higher N mineralization rate than soils treated with pea vine, which was due to a lower carbon (C):N ratio for rice straw. The potentially mineralizable N pool (No) in soils amended with rice straw and pea vine under flooded conditions, estimated using a 1st order exponential equation, were 7 to 15 times, and 3 to 9 times greater for rice straw Novalues and pea vine, respectively, than the control. The KNvalues for unamended soils ranged from 0.35 to 0.52 mg N kg‐1wk‐1and rice straw and pea vine treated soils were from 0.75 to 1.22 and 0.46 to 0.58 mgN kg‐1wk‐1. The lower Noand KNvalues in pea vine treatments suggested there was greater immobilization of N than in rice straw treatments.

ISSN:0010-3624    

DOI:10.1080/00103629809370000

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This study was undertaken to assess the effect of residue carbon:sulfur (C:S) ratio on the mineralization of S in rice soils under aerobic‐flooding cycles. A lab incubation study with a 3x2x2 factorial design (two replications) was carried out for 12 weeks. The treatments were two rice soils, Faridpur and Joydebpur; three levels of wheat straw (Triticum aestivumL.) added to soils as 1) control, 2) straw C:S ratio (400:1), or 3) straw C:S ratio (100:1); and two moisture levels of 1) two weeks aerobic‐flooding cycles or 2) four weeks aerobic‐flooding cycles. The organic residues (25 mg straw g‐1soil) were mixed with 30 g soil and an equal amount of glass bead mixtures (1:1) and transferred into a leaching tube. Soils in leaching tubes were leached with deionized water and analyzed for sulfate‐sulfur (SO4‐S) and other chemical properties at two week intervals up to 12 weeks. Cumulative SO4‐S in all soils amended with a narrow C:S ratio (100:1) of the straw had a significantly higher accumulation of SO4‐S over the control or the wider C:S ratio (400:1). The first‐order rate constants (Ks) in soils amended with wheat straw under aerobic‐flooding cycles ranged from 0.112 to 0.160 mg S kg‐1wk‐1and the Kg values ranged from 0.030 to 0.149 mg S kg‐1wk‐1for unamended and straw amended soils, respectively. Among the two straw C:S ratio treatments, the narrow C:S ratio residue treatment had the highest Ksvalues, indicating greater rates of microbial S mineralization and potential to provide more plant‐available S. The cumulative amount of C mineralized was linearly related to time of incubation and corresponded to S mineralization.

ISSN:0010-3624    

DOI:10.1080/00103629809370001

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Little attention has been devoted to calibrating plant tissue tests for phosphorus (P) in the field for upland rice in West Africa, although information is needed for improving crop production through efficient P nutrition. A field experiment was conducted under rainfed conditions in the 1994 season to establish the relationships between plant P content and grain yield of upland rice grown on an Ultisol, having a range in extractable P, in the humid forest zone of Ivory Coast. The critical limit of P content in the whole rice plant tops at the tillering stage, at 90% relative grain yield, was found to be 2 g kg‐1P for the four upland rice cultivars tested. Total P uptake in the biomass was significantly correlated with rice grain (r=0.81, n=20) and straw (r=0.79) yields of the cultivars.

ISSN:0010-3624    

DOI:10.1080/00103629809370002

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A possible artefact ofin situmeasurements of nitrogen (N) net mineralization may result from the inclusion of abscised fine roots in incubated soil. Fine roots usually have a relatively wide carbon (C)/N ratio and if fine root carbon is available to micro‐organisms they will immobilize N. In this study nitrogen and carbon in microbial biomass were compared between incubated soil and surrounding soil at the end of field incubation periods. It was hypothesized that immobilization of N would result in higher microbial N in incubated soil when compared to the surrounding soil. Incubations were carried out in steel tubes at sites of different fine root density. No net immobilization of N occurred during incubations. There were no significant increases of microbial N in incubated soil suggesting that immobilization of N in microbial biomass did not occur. A comparison of K2SO4‐extractable organic N concentrations between incubated and surrounding soil also indicated that immobilization of N into extractable metabolites was unlikely. However, under herbaceous vegetation significantly lower microbial N concentrations were measured in incubated soil compared to the surrounding soils. This may suggest a decrease in microbial biomass during incubations due to cessation of C input from fine roots. If the reduction in microbial biomass leads to the mineralization of microbial tissue, net N mineralization using thein situincubation technique may be overestimated.

ISSN:0010-3624    

DOI:10.1080/00103629809370003

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Soil and plant samples were collected from 12 different rural areas of Beijing, China. Metals [calcium (Ca), iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn)] in the soils were partitioned by the Tessier's and BCR's sequential extraction procedures. The results obtained showed significant correlation between the metals extracted in the three steps of the BCR's procedure and that extracted in the corresponding steps of the Tessier's method. The correlations were identical whether using the Tessier's or BCR's procedure in evaluating plant availability of soil metals. Correlation analysis indicated that the Zn and Mn contents in the plant were positively correlated to Zn and Mn bound to Fe‐Mn oxides in the soil. However, the Ca content in the plant was negatively correlated to Ca bound to carbonates in the soil. The Fe and Cu content in different parts of corn were not significantly correlated to the different metal forms in the soil. The “best”; regression equations were obtained by stepwise multiple regression analysis to predict the metal absorption by corn.

ISSN:0010-3624    

DOI:10.1080/00103629809370004

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor