氮肥对新疆棉花产量形成期叶片光合特性的调节效应   总被引：25，自引：3，他引：25  

勾玲  闫洁  韩春丽  赵瑞海  张旺锋  杨新军 《植物营养与肥料学报》2004,10(5):488-493

在新疆生态条件下,采用裂区设计研究了氮肥用量对棉花产量形成期叶片光合特性的调节效应。结果表明,适量追施氮肥在一定程度上可以改善叶片光合性能,提高植株生育后期叶片叶绿素含量和硝酸还原酶(NR)活性;维持叶片较高的PSⅡ潜在活性(Fv/Fo)和PSⅡ光化学最大效率(Fv/Fm);提高中下部叶片的光合速率,延缓了叶片衰老,保证了棉花生育后期光合产物的形成,从而使棉花达到高产。这种调节效应因品种和生育时期的不同而异。新陆早6号在盛铃前期叶片叶绿素含量、NR活性、光合速率及Fv/Fo和Fv/Fm随氮肥用量增加而增加,盛铃后期至吐絮期叶绿素含量、Fv/Fo和Fv/Fm、叶片光合速率等指标均以中氮处理(300.kg/hm2)最高,高氮处理易造成植株盛花期生长过旺,群体荫蔽,影响了叶片光合作用;新陆早7号中氮处理与高氮处理之间差异不明显。因此,生产上应根据不同品种和生育时期进行合理施肥,避免因施肥不当造成产量下降和浪费肥料。  相似文献   

Integrating properties of soil map delineations into ordinary kriging   总被引：2，自引：0，他引：2  

BOUCNEAU  VAN MEIRVENNE  THAS  & HOFMAN 《European Journal of Soil Science》1998,49(2):213-229

Stratification of a region based on soil map delineations followed by within-stratum interpolation is sometimes used to combine soil maps and spatial interpolation. However, not all delineations are equally suitable to subdivide an area into precisely located mutually exclusive strata. This paper proposes a flow-path to characterize the nature of soil map delineations and a methodology to integrate the properties of map delineations into ordinary kriging.Four types of delineations were distinguished based on three criteria: the nature of transition (discontinuous or gradual), the mapping accuracy, and the structure of the within-unit spatial variation. For each type of delineation the ordinary kriging algorithm was modified to integrate its properties in the interpolation.As a test case, the sand content of the topsoil in the province of West-Flanders (Belgium) was mapped, using independent test data for validation. Inside the mapping units and at delineations identified as gradual transitions, our procedure, termed ordinary kriging integrating properties of map delineations (OKPD) , performed similarly to stratified ordinary kriging (SOK). However, close to the delineations identified as inaccurately mapped discontinuities the mean square prediction error of OKPD was 0.64 times that of SOK. Moreover, near these delineations, the prediction variance was largely underestimated by SOK (relative variance = 5.1), whereas OKPD produced a more realistic value (relative variance = 1.5).  相似文献   

Charge characteristics in relation to free iron and organic matter of soils from Bambouto Mountains, Western Cameroon   总被引：1，自引：0，他引：1  

VAN RANST  SHAMSHUDDIN  BAERT  & DZWOWA 《European Journal of Soil Science》1998,49(2):243-252

We have examined the charge characteristics, with special emphasis on the role of free Fe and organic matter, of humid tropical soils from Bambouto Mountains, Western Cameroon. The soils, which are formed from tuff, basalt and trachyte, are dominated by kaolinite and sesquioxides. The amounts of Fe oxides in them increase somewhat with depth. Open 2:1 phyllosilicates are present in trace amounts. The point of zero charge of the variable charge components, pH₀, is around 4 in the topsoil (0–20 cm) and around 6 at 100–150 cm depth. In the subsoils, pH₀ exceeds soil pH presumably because of large quantities of Fe oxides. Deferration increases both soil pH and pH₀, but diminishes the anion exchange capacity. Oxides and oxyhydrates of Fe have positive surface charge, so their removal from the soils would result in overall loss of positive charge. Increases in soil pH would bring about an increase in the cation exchange capacity of the soils. Hence, management practices that reduce soil acidity should reduce loss of essential basic cations via leaching.  相似文献   

LIGHT INTERCEPTION AND USE EFFICIENCY DIFFER WITH MAIZE PLANT DENSITY IN MAIZE-PEANUT INTERCROPPING     

Qi WANG  Zhanxiang SUN  Wei BAI  Dongsheng ZHANG  Yue ZHANG  Ruonan WANG  Wopke VAN DER WERF  Jochem B. EVERS  Tjeerd-Jan STOMPH  Jianping GUO  Lizhen ZHANG 《农业科学与工程前沿(英文版)》2021,8(3):432-446

• Intercropping intercepted more light than sole peanut but less than sole maize.• Maize light use efficiency (LUE) increased with plant density in the intercropping.• Intercropping did not affect LUE of maize but increased peanut LUE.Intercropping increases crop yields by optimizing light interception and/or use efficiency. Although intercropping combinations and metrics have been reported, the effects of plant density on light use are not well documented. Here, we examined the light interception and use efficiency in maize-peanut intercropping with different maize plant densities in two row configurations in semiarid dryland agriculture over a two-year period. The field experiment comprised four cropping systems, i.e. monocropped maize, monocropped peanut, maize-peanut intercropping with two rows of maize and four rows of peanut, intercropping with four rows of maize and four rows of peanut, and three maize plant densities (3.0, 4.5 and 6.0 plants m⁻¹ row) in both monocropped and intercropping maize. The mean total light interception in intercropping across years and densities was 779 MJ·m⁻², 5.5% higher than in monocropped peanut (737 MJ·m⁻²) and 7.6% lower than in monocropped maize (843 MJ·m⁻²). Increasing maize density increased light interception in monocropped maize but did not affect the total light interception in the intercrops. Across years the LUE of maize was 2.9 g·MJ⁻¹ and was not affected by cropping system but increased with maize plant density. The LUE of peanut was enhanced in intercropping, especially in a wetter year. The yield advantage of maize-peanut intercropping resulted mainly from the LUE of peanut. These results will help to optimize agronomic management and system design and provide evidence for system level light use efficiency in intercropping.  相似文献   

REINTEGRATION OF CROP-LIVESTOCK SYSTEMS IN EUROPE: AN OVERVIEW     

Antonius G. T. SCHUT  Emily C. COOLEDGE  Marc MORAINE  Gerrie W. J. VAN DE VEN  Davey L. JONES  David R. CHADWICK 《农业科学与工程前沿(英文版)》2021,8(1):111-129

• ICLS combines the benefits of specialization with increased resilience of the system.• Clear opportunities but also barriers for ICLS were observed.• ICLS need to be embedded within future environmental legislation.• ICLS systems with a range of intensities are needed to support a biodiverse landscape.Ongoing specialization of crop and livestock systems provides socioeconomic benefits to the farmer but has led to greater externalization of environmental costs when compared to mixed farming systems. Better integration of crop and livestock systems offers great potential to rebalance the economic and environmental trade-offs in both systems. The aims of this study were to analyze changes in farm structure and review and evaluate the potential for reintegrating specialized intensive crop and livestock systems, with specific emphasis on identifying the co-benefits and barriers to reintegration. Historically, animals were essential to recycle nutrients in the farming system but this became less important with the availability of synthetic fertilisers. Although mixed farm systems can be economically attractive, benefits of scale combined with socio-economic factors have resulted in on-farm and regional specialization with negative environmental impacts. Reintegration is therefore needed to reduce nutrient surpluses at farm, regional and national levels, and to improve soil quality in intensive cropping systems. Reintegration offers practical and cost-effective options to widen crop rotations and promotes the use of organic inputs and associated benefits, reducing dependency on synthetic fertilisers, biocides and manure processing costs. Circular agriculture goes beyond manure management and requires adaptation of both food production and consumption patterns, matching local capacity to produce with food demand. Consequently, feed transport, greenhouse gas emissions, nutrient surpluses and nutrient losses to the environment can be reduced. It is concluded that reintegration of specialized farms within a region can provide benefits to farmers but may also lead to further intensification of land use. New approaches within a food system context offer alternatives for reintegration, but require strong policy incentives which show clear, tangible and lasting benefits for farmers, the environment and the wider community.  相似文献   

COMPARISON OF THE ULTRASONOGRAPHIC APPEARANCE OF OSTEOCHONDROSIS LESIONS IN THE CANINE SHOULDER WITH RADIOGRAPHY, ARTHROGRAPHY, AND ARTHROSCOPY     

BARBARA VANDEVELDE  BERNADETTE VAN  RYSSEN  JIMMY H. SAUNDERS  MARTIN KRAMER  HENRI VAN  BREE 《Veterinary radiology & ultrasound》2006,47(2):174-184

Osteochondrosis lesions in 29 shoulder joints (from 20 dogs) were evaluated with ultrasound (US) and the results were compared with survey radiography, arthrography, and arthroscopy. US was performed with a 7-12 MHz linear matrix transducer which was placed in cranio-caudal direction just distally to the acromion while the joint was adducted and maximally endorotated to visualize the caudal aspect of the humeral head. With US, the subchondral defect was completely visible in 21 joints and partially visible in 8 joints. The length of the subchondral defect measured on US was comparable with the length measured on survey radiographs. In two joints, the cartilage flap was mineralized and thus already visible on survey radiographs. The mineralized flap was visible on US as a straight hyperechoic line above the subchondral defect. In the other joints, survey radiographs could not assess the status of the articular cartilage. In 17 joints, the presence of a cartilage flap or cartilage fissuring was suspected based on the presence of a second hyperechoic line at the base of the subchondral defect, and this suspicion was confirmed by arthroscopic examination in 16 joints and also by arthrographic examination in 15 joints. One joint that was suspected of having a cartilage flap on US was normal on arthroscopy and arthrography. When US revealed only focal thickening of the anechoic cartilage layer (5 joints), the joints appeared normal on arthroscopic and arthrographic examination. Of the four joints where the subchondral defect was irregular and covered by heteroechogeneous material on US, arthroseopy revealed the presence of a lesion resembling chondromalacia in two joints, the presence of a small cartilage flap in one joint and the presence of scar tissue underneath the flap at the level of the subchondral defect in one joint. In conclusion, US is a helpful imaging modality in the identification of osteochondritic lesions in the canine shoulder joint. US also appears to be a satisfactory imaging tool for identifying lesions such as joint mice, joint effusion, and distinct new bone formation.  相似文献   

Rabbit model for estimating relative bioavailability, residues and tissue tolerance of intramuscular products: comparison of two ampicillin products     

M. OLLING  K. VAN  TWILLERT  P. WESTER†  A.B.T. BOINK‡  A.G. RAUWS 《Journal of veterinary pharmacology and therapeutics》1995,18(1):34-37

A rabbit model for simultaneous investigation of the bioavailability, tissue residues and tissue tolerance of intramuscularly administered veterinary medicines is described. The bioavailability of ampicillin from two intramuscular products, which had been found to be different in calves, were compared in a two-way crossover design. The ampicillin levels in plasma, ampicillin residues in tissues, the plasma creatine kinase activity and the tissue damage at the injection sites were studied. The absolute bioavailabilities for the products were 100% and 40%. Differences in pharmacokinetics of ampicillin between sexes were observed after intravenous and intramuscular administration. Only slight tissue damage could be detected at the injection sites after intramuscular administration of these products. The results were compared with those obtained previously in calves and were found to be similar. Further investigations with other intramuscular drug products to validate this model are under way.  相似文献   

Focus expansion of bean rust in cultivar mixtures   总被引：1，自引：0，他引：1  

HABTU ASSEFA  F VAN DEN  BOSCH† J. C. ZADOKS 《Plant pathology》1995,44(3):503-509

Radial expansion of foci in mixtures of susceptible and resistant bean cultivars was studied at two sites in Ethiopia. The foci expanded in a wave-like fashion. At Ambo (1990), radial expansion velocity ranged from 6 cm per day in mixtures with 20% susceptible plants to 15 cm per day in plots with the susceptible plants only. At Debre Zeit, the velocity ranged from 3 cm per day in a mixture with 20% susceptible plants to 16 cm per day in plots with 100% susceptible plants. At both sites the radial expansion velocity of foci correlated linearly with the logarithm of the fraction of susceptible plants in the mixture. Velocities of focus expansion at Ambo and Debre Zeit were approximately equal in plots consisting of susceptible plants only. At lower proportions of susceptible plants the velocities at Debre Zeit were lower than at Ambo. Indications were given as to the environmental factors responsible for the observed difference between sites. At each site, the variation between plots showed a clear spatial pattern, probably due to environmental factors.  相似文献   

Effect of gonadal hormones on the plasma clearance and metabolite formation of antipyrine in the dwarf goat   总被引：1，自引：0，他引：1  

R. F. WITKAMP  S. M. NIJMEIJER  H.J. KOLKER  J. NOORDHOEK  A.S.J.P. A. M. VAN MIERT 《Journal of veterinary pharmacology and therapeutics》1993,16(2):164-173

The effect of gonadal hormones on the plasma elimination and urinary metabolite profile of antipyrine was studied in dwarf goats. Female goats were treated with testosterone and male goats were treated with 17β-oestradiol. Castrated males were treated with either testosterone or 17β-oestradiol. Antipyrine (25 mg/kg, i.v.) was given both before and after the hormonal treatments. The effects of the hormonal status on the plasma elimination of the parent compound were not consistent. This was possibly due to the fact that formation of the main metabolite of antipyrine in the goat, 4-hydroxy antipyrine (OHA), was not affected by sex or hormonal treatment. On the other hand, there were clear effects of hormonal status on urinary excretion of the three other metabolites. In females and castrated males testosterone suppressed the formation of norantipyrine (NORA), 3-hydroxymethylantipyrine (HMA) and 4,4'-dihydroxyantipyrine (DOHA). Intact males produced smaller amounts of these metabolites than females. It is concluded that distinct xenobiotic metabolizing pathways exist in the dwarf goat, which are influenced in their activity by gonadal hormones. This confirms previous findings in rats and mice. The possibility that sex hormones influence drug metabolism in food-producing animals could have consequences for veterinary therapeutics and public health. This study also demonstrates that, when using the antipyrine test for the assessment of hepatic drug metabolism, it is very important to include the determination of metabolites.  相似文献   

Regulation of bronchomotor tone in conscious calves     

P. GUSTIN  A. R. DHEM  P. LEKEUX  F. LOMBA  F. J. LANDSER  K. P. VAN DE WOESTIJNE 《Journal of veterinary pharmacology and therapeutics》1989,12(1):58-64

The purpose of this study was to investigate the effects of some a and β sympathomimetic and sympatholytic drugs on respiratory impedance in healthy conscious calves. Ten Friesian calves were investigated in this study. The forced oscillation technique was used to measure the resistance ( R _rs) and the reactance ( X _rs) of the respiratory system at frequencies ranging from 4 to 26 Hz. Isoprenaline (1 μg/kg i.v.), propranolol (3 μg/kg i.v.), noradrenaline (2 μg/kg i.v.), xylazine (20 μg/kg i.v.) and yohimbine (0.25 mg/kg i.v.) were administered. Isoprenaline induced a significant decrease of R _rs. An increase of R _rs after administration of propranolol was observed but without any change of the frequency dependence of R _rs. A small increase in the resonant frequency was also recorded. A decrease of R _rs was recorded after yohimbine injection. Noradrenaline and xylazine administration increased the resistances and the resonant frequency and induced a negative frequency dependence of R _rs. These results suggest that (1) the major effects of β adrenergic drugs are on the central airways, (2) the a adrenergic system may play a role on the regulation of bronchomotor tone in calves, (3) the effects of a adrenergic drugs are on both central and peripheral airways and (4) the forced oscillation technique allows the differentiation of calibre changes occurring in small and large airways.  相似文献