摘要:

Field experiments were conducted to compare plant residue decomposition and nitrogen (N) dynamics in an alley cropping system (AC) and an annual legume‐based cropping system (NA) in the Piedmont region of Georgia, USA. The hedgerows of the alley cropping system consisted ofAlbizia julibrissin(albizia) established in January 1990. Hedges were four meters apart with a spacing within rows of one‐half meter. A rotation beginning withMucuna deeringiana(velvet bean) followed by a winter annual crop ofTrifolium incarnatumL. (crimson clover), a summer crop ofSorghum bicolor(L.) Moench (grain sorghum) and a winter crop ofTriticum aestivumL. (wheat) was established in the alley cropping system and a control annual cropping system. All crops were grown using no‐tillage systems. Plant residue decomposition and N dynamics were measured using litterbag technologies on crimson clover, albizia, and grain sorghum. Soil and plant total N, decay rate constants (k) for dry matter, soil potentially mineralizable N, and nitrification rates were determined. Decay rate constants for N were best correlated with the lignin content of the plant residues. No residue quality parameter was significantly correlated with decay rate for dry matter. There was no significant difference between AC and NA systems in soil inorganic N and potentially mineralizable N; however, nitrification rates were greater in the AC. Grain sorghum N uptake and biomass production were not different for AC and NA. This was thought to be due to large inputs of organic N prior to the start of the experiment.

ISSN:0010-3624    

DOI:10.1080/00103629409369270

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The influence of soil organic matter on selenite sorption was investigated in the selenite adsorption capacity and the surface particle charge change by ligand exchange reaction using the hydrogen peroxide (H2O2) treatment and the ignition treatment of two Andosols. The removal of organic carbon (C) in soils accelerated selenite sorption, implying that organic matter of soils had negative influence on the selenite adsorption on the soils. Positive charge decrease on soil particles, concomitant proton consumption, and release of silicon (Si), sulfate (SO42‐), and organic C were observed in selenite sorption by the soils. The development of surface particle negative charge with selenite sorption was smaller in the H2O2‐treated soil than in the original soils and was scarcely observed in the ignition‐treated soil. It can be assumed that the increase of negative charge by selenite sorption was attributed to new negative sites borne by released insoluble organic matter and negative charge development directly by selenite sorption was small.

ISSN:0010-3624    

DOI:10.1080/00103629409369271

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The processes involved in the release of silicon (Si) and aluminium (Al) from soils during extraction with 0.01M calcium chloride (CaCl2) were investigated. A considerable amount of Si was released from most soil samples studied during the first hour of extraction which continued steadily until the end of the experiment (144 hrs). Most Si was released from fine grained soils, least from sand. Uncomplexed and complexed Al was initially released rapidly, but after 1 hr net resorption of uncomplexed Al to the soil occurred. Aluminium concentrations appeared to reflect surface characteristics of the soil rather than control by a particular solid phase.

ISSN:0010-3624    

DOI:10.1080/00103629409369272

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Zinc (Zn) deficiency in crops, including rapeseed and mustard, is a widespread nutritional disorder especially in alkaline soils. However, plant analysis diagnostic criteria for interpreting Zn analysis in rapeseed and mustard are scarcely reported in the literature. Use of seeds for diagnosing Zn fertility status of soils has certain advantages over foliar analysis—ease of sampling, processing, and chemical analysis. Despite this, mature seeds of these species were hardly evaluated as an index tissue for this purpose. Our study determined Zn requirement in foliar tissues and also evaluated Zn composition of mature seeds as an index of Zn status of soils and plants. Zinc concentration in mature seeds of the test crops reflected the Zn status of the soil where plants were grown. In fact, the range of Zn concentration in grains was almost comparable with the ranges in foliar plant parts. Critical Zn concentration (mg/kg) in diagnostic plant parts of rapeseed was: whole shoots, 29; leaves, 33; and seeds, 29; while the Zn requirement of mustard was a little higher: whole shoots, 35; leaves, 41; and seeds, 33.

ISSN:0010-3624    

DOI:10.1080/00103629409369273

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A procedure was developed to sample and analyze levels of ammonium and urea as well as pH in the soil within the immediate zone of a single urea fertilizer granule. The method involved sectioning a 2 x 3.6 cm slice of soil (0.9 cm thick) into 45 subsamples, which were analyzed individually. After analysis, the data were presented in graphical format to show the nutrient concentrations in the zone. The method was relatively easy to carry out using equipment that could be easily constructed. The precision of the procedure was high as indicated by the low variability between replicates.

ISSN:0010-3624    

DOI:10.1080/00103629409369274

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103629409369249

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor