Variable-timing,fixed-rate application of cattle biogas effluent to rice using a leaf color chart: microcosm experiments in Vietnam     

Kazunori Minamikawa  Huynh Cong Khanh  Yasukazu Hosen  Tran Sy Nam  Nguyen Huu Chiem 《Soil Science and Plant Nutrition》2020,66(1):225-234

ABSTRACT

Livestock production plays a leading role in agricultural land-use change. Producing biogas from livestock waste and subsequently using the biogas effluent as fertilizer for crops is a promising option to solve environmental problems resulting from expanding livestock production. However, it is difficult to promptly and accurately measure the nitrogen (N) concentration of effluent for farmers in developing countries, making precise N management difficult. The objectives of the current study were (1) to evaluate the feasibility of variable-timing, fixed-rate application of cattle biogas effluent using a leaf color chart (LCC) for rice (Oryza sativa L.) and (2) to determine the optimum LCC threshold for grain yield. We conducted two microcosm experiments in the Mekong Delta of Vietnam in 2018 using eight treatments of N-fertilizer application. In the Zero treatment, we applied no N. In the Estd treatment, we split-applied N as effluent (E) at fixed rate and timing as the standard method. In E2.75, E3.00, E3.25, E3.50, and E3.75, we applied effluent whenever the LCC value went below 2.75, 3.00, 3.25, 3.50, and 3.75, respectively. In U3.25, we applied N as urea (U) whenever the LCC value fell below 3.25. The total effluent-N application rate ranged from 90 to 210 kg N ha^?1 season^?1. Rice growth was normal but there was a substantial yield gap between the two microcosm experiments due to the seasonal difference in solar radiation. Rice yield tended to increase with increasing LCC threshold. There was a positive linear relationship between LCC and chlorophyll content (SPAD) values (R ² = 0.73–0.79). Grain yield was well explained (R ² = 0.70–0.89) by the seasonal mean LCC or SPAD value. Plant total N uptake increased with increasing LCC threshold, but the three calculated indices of N use efficiency (NUE) – apparent N recovery, agronomic NUE, and internal NUE – were not always improved with a higher LCC threshold. Our results showed that the tested variable-timing, fixed-rate strategy for the application of cattle biogas effluent was feasible and the optimum LCC threshold for grain production was 3.75 under the current microcosm conditions.  相似文献   

Unusual soil nematode communities on karst mountain peaks in southwest China     

《Soil biology & biochemistry》2015

On karst mountain peaks in southwest China, soils are very shallow and vegetation cover is very low. Although the subtropical monsoon climate provides abundant rainfall, the soils experience severe dry–wet cycles and extremely high temperatures in summer (wet season). We determined the composition of soil nematode communities along a vegetation succession sere of four common plant communities (i.e., moss crust, moss crust with sparse grasses, sparse grasses, and sparse dwarf shrubs) on karst mountain peaks in the wet and dry seasons. The results showed that the nematode communities were unusual. Specifically, Rhabdolaimus was the most abundant nematode genus. Rhabdolaimus is a common aquatic nematode genus that has been detected in hot springs but has not been previously reported as the dominant genus in relatively arid and semi-arid soils. Therefore, tolerance to extremely high soil temperatures and rapid wet–dry cycles may help explain why Rhabdolaimus dominates the nematode communities in the soils of karst mountain peaks in southwest China.  相似文献   

Observance–Influence Analysis: A Case Study in a Forest Recreation Area     

《Scandinavian Journal of Forest Research》2012,27(5):449-456

Importance–performance (I-P) analysis is a common evaluative measure in forest recreation management. However, concerns with I-P analysis have been raised. In this study, the observance–influence (O-I) analysis technique modified from I-P analysis was adapted for analysing the observance of various use and resource impacts by on-site visitors, and the influence that these impact conditions have on forest recreation area visitor experiences. During the summer and autumn of 2000, 476 Worak-san Forest National Park visitors in Korea were surveyed. The O-I grid generated from the survey data indicated that managers are doing a good job. The grid revealed most impacts clustering in the low priority concern and no concern quadrants. Impacts shown to be of most concern related to utility poles and power lines, poor maintenance of buildings, dead and dying trees, and discourteous behaviour. The O-I grid analysis model has considerable utility for park managers in analysing visitors’ perceptions of park impacts.  相似文献   

Unusual External Adaptations in the Rock Hyrax     

J. B. Sale 《African Zoology》2013,48(1):101-113

Activity in two unrelated genera of mole-rats, Tachyoryetes and Heliophobius, was studied in the field by recording the movements of animals tagged with radioactive wire. Tachyoryetes shows a single marked activity peak and only leaves its nest between 10.00 and 19.00 hour. Heliophobius shows a more dispersed and prolonged activity pattern although peak activity occurs over approximately the same period as in Tachyoryetes. Heliophobius spends over 50 of the day out of its nest, Tachyoryetes, under 25%.

These differences can be attributed to a different function of the nest in the two genera (Tachyoryetes has a multipurpose nest; Heliophobius uses its nest solely for rest), and also to the fact that Tachyoryetes has light-sensitive eyes whereas Heliophobius appears unable to appreciate light; Tachyoryetes periodically comes to the surface to forage and this exposure to light may trigger the 24-hour activity cycle.  相似文献   

Life Histories of Frogs in the Namib Desert     

A. Channing 《African Zoology》2013,48(2):299-312

Four anuran taxa inhabit the central Namib: Xenopus laevis, Tomopterna delalandei cryptotis, Phrynomerus annectens and Bufo vertebrate hoeschi. Xenopus is confined to permanent pools in the Kuiseb river canyon. Tomopterna extends further into the Namib, but is restricted to the Kuiseb river bed. The Kuiseb is normally dry, receiving water only briefly (as floods) during the rainy season. These floods are responsible for moving adults and larvae. Phrynomerus and Bufo occur on granite inselbergs. The inselbergs provide shelter mainly in the form of cracks under granite exfoliations. Large runoff surfaces collect the low rainfall (25 mm per year) in depressions in which the frogs breed. Phrynomerus is only active at night; males are aggressive towards one another; oviposition takes place in deep pools and development takes at least eight weeks. Bufo is active during the heat of the day; oviposition takes place in warm shallow pools; development takes about three weeks.  相似文献   

A note on the diet and feeding selectivity of juvenile riverbream,Acanthopagrus berda (Forskal, 1775), in a subtropical mangrove creek     

T.D. Harrison 《African Zoology》2013,48(1):36-42

The diet and food selectivity of juvenile (< 100 mm S.L.) Acanthopagrus berda were investigated in Beachwood creek, north of Durban. Fish and benthic samples were taken from November 1986 to September 1987. The diet of juvenile A. berda was varied but crustaceans, mainly amphipods, were the dominant prey item. Ivlev's (1961) electivity index revealed a positive selection for amphipods, tanaids and fish scales.  相似文献   

Establishment of a microbiologically acceptable daily intake of antimicrobial drug residues     

C. J. van Nie 《The Veterinary quarterly》2013,33(3):152-160

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Formation of carbon–carbon composite using wood as a precursor     

《Wood material science & engineering》2013,8(2):152-158

Abstract

The use of wood as structure-giving material may be an effective approach to reduce some barriers for producing high temperature ceramic especially carbon composites. The objective of this study was to develop a simple process for producing carbon–carbon (C–C) composite through porous template result from pyrolysing of wood. Walnut, known to be relatively permeable, was being heat treated under controlled atmosphere. The carbon-template formed was infiltrated with coal tar pitch. Morphological characterization of the resulting composite was carried out by scanning electron microscopy morphology and physical properties of sample were evaluated with determination of bulk density and open porosity. In addition mechanical properties of products were analysed with three-point bending test and Vickers micro hardness. Results showed that bulk density had an uprising trend with increasing the number of densification cycles and subsequently open porosity decreased. Moreover, from mechanical property's point of view, results had a good compatibility with increase in the densification cycles.  相似文献   

Development of site index curves for Pinus kesiya in the Philippines     

《Southern Forests》2013,75(2):115-120

This study was conducted to develop a height–age growth model and site index curves for site quality evaluation of old secondary-growth stands of Pinus kesiya in the northern Philippines. The Chapman-Richards growth function was used in the guide curve method to generate anamorphic site index curves for this species. In order to evaluate the developed model, coefficient of determination (R ² ), root mean square error (RMSE), bias (ē), absolute mean difference (AMD) and mean percent bias (MPB) were used as statistical criteria. The Chapman-Richards model explained about 96.84% of the total variation of the dominant height. The value of ē was ?0.004 m, AMD was 2.566 m, MPB was 3.88% and RMSE was 3.331. The site index curves developed as a result of this study are significant for forest managers in predicting the growth patterns and classification of site productivities for Pinus kesiya stands.  相似文献   

Immediate and subsequent effects of drying and rewetting on microbial biomass in a paddy soil     

Kozue Sawada  Shinya Funakawa  Takashi Kosaki 《Soil Science and Plant Nutrition》2019,65(1):28-35

Many surface soils in Japan may experience more frequent and intense drying–rewetting (DRW) events due to future climate changes. Such DRW events negatively and positively affect microbial biomass carbon (MBC) through microbial stress and substrate supply mechanisms, respectively. To assess the MBC immediately after DRW and during the incubation with repeated DRW cycles, two laboratory experiments were conducted for a paddy soil. In the first experiment, we exposed the soil to different drying treatments and examined the MBC and hourly respiration rates immediately after the rewetting to evaluate the microbial stress. In the second experiment, we compared microbial growth rates during the incubation of the partially sterilized soil with a continuously moist condition and repeated DRW cycles to evaluate the contribution of the substrate supply from non-biomass soil organic C on MBC. First, all drying treatments caused a reduction in MBC immediately after the rewetting, and higher drying intensities induced higher reduction rates in MBC. A reduction of more than 20% in MBC induced the C-saturated conditions for surviving microbes because sufficient concentrations of labile substrate C were released from the dead MBC. Second, repeated DRW cycles caused increases in the microbial growth rates because substrate C was supplied from non-biomass organic C. In conclusion, MBC decreased immediately after DRW due to microbial stress, whereas MBC increased during repeated DRW cycles due to substrate C supplied from non-biomass organic C.  相似文献