Modeling the Requirements of Agricultural Limestone in Acid Sulfate Soils of Brazil and Colombia     

Enrique Combatt Caballero  Alfredo Jarma Orozco  Manuel Palencia Luna 《Communications in Soil Science and Plant Analysis》2019,50(8):935-947

The aim of this study was to model the determination of the amount of agricultural limestone necessary to correct acidification in acid sulfate soils (ASS). This study used 14 equations and the chemical variables of the soils including pH, soil organic matter (SOM), potential acidity (H+ Al), sum of bases (BS), potential acidity (T), base saturation (V) and exchangeable Al with KCl. The results indicated that in the studied, the lowest requirements for doses of limestone (DL) were described by the equations DL = 2.906((H+ Al) (45-V)/100)°⁸⁰, DL = 0.08 + 1.22Al_KCl, DL = 0.6T – BS, and DL = 1.5Al_KCl, with mean values of 29.5, 30.5, 31.5 and 37.4 t ha^?1. In addition, the models with the best correlation for determining the limestone requirements to obtain 80% of the maximum production of sorghum (dry matter) were DL = ?1.43 + 0.9237 (SOM (6-pH)) and DL = ?0.022 + 2.7425 ((H+ Al) (45-V)/100).  相似文献   

基于文献计量学的《北方园艺》期刊发展特点分析     

左惠凯  闫路娜 《北方园艺》2017,(3)

基于中国知网(CNKI)数据库,对2006—2015年《北方园艺》期刊的发文情况、引文情况、下载及被引情况、核心作者等方面,运用文献计量学方法进行了统计分析。结果表明:《北方园艺》这10年间,基金论文比、各年引文量、篇均引文量、外文引文量、总下载量、篇均下载量和总被引量等指标均呈现快速上升的趋势,其核心作者群已初具规模,刊载论文的质量正逐步提升,学术影响力日益扩大。并通过对园艺类14种期刊比较分析,以期为《北方园艺》的进一步发展提出了几点建议。  相似文献   

Concentrated flow erosion rates as affected by rock fragment cover and initial soil moisture content   总被引：6，自引：0，他引：6  

J. Poesen  E. De Luna  A. Franca  J. Nachtergaele  G. Govers   《CATENA》1999,36(4):294

Concentrated flow experiments using a small hydraulic flume and a constant flow discharge and bed slope have been conducted in order to investigate the effects of rock fragment cover (Rc) on sediment yield for an initially wet and an initially air-dry loamy topsoil. The experimental results indicate that Rc reduces concentrated flow erosion rates (E) in an exponential way (i.e., E=e^−bRc), which is similar to previously reported relations for other water erosion processes such as interrill erosion and sheet-rill erosion measured on runoff plots. The decay rate (b) of this exponential relationship increased throughout the experiments because of scour-hole development and bed armouring. The concentrated flow erosion rates and b-values also depend on the initial moisture content of the topsoil. Depending on Rc, mean concentrated flow erosion rates were 20% to 65% less on initially wet compared to initially air-dry topsoils. The mean value for b was 0.032 for the initially wet, but only 0.017 for the initially air-dry topsoil, indicating that a rock fragment cover is less efficient in reducing concentrated flow erosion rates when the topsoil is initially air-dry than when it is initially wet. The results help explain the data scatter in reported relationships between Rc and interrill–rill erosion rates. They also indicate that a given surface rock fragment cover will offer more protection to wet topsoils than to dry topsoils, which are very common in Mediterranean environments. Event-based water erosion models should incorporate effects of antecedent soil moisture content as well as those of Rc on concentrated flow erosion rates.  相似文献   

Effect of light limitation on the water quality,bacterial counts and performance of Litopenaeus vannamei postlarvae reared with biofloc at low salinity          下载免费PDF全文

Héctor M Esparza‐Leal  Ely S López‐Álvarez  Jesús T Ponce‐Palafox  Josué A Melendrez‐Soto  Marco A Medina‐Astorga  Antonio Luna‐González  Wenceslao Valenzuela‐Quiñónez  Píndaro Álvarez‐Ruiz  Gerardo Rodríguez‐Quiroz 《Aquaculture Research》2017,48(8):4371-4379

The aim of this study was to evaluate the effect of light limitation on the water quality, bacterial counts and performance of Litopenaeus vannamei postlarvae reared with biofloc at low salinity (≈9 g L^?1). Two treatments were designed: T₁ = culture with natural sunlight and T₂ = culture in darkness. After 28 days, in both treatments, the final weight of shrimp was over 0.6 g with a specific growth rate over 7.4% d^?1, and a survival rate over 70%. In both treatments, Vibrio sp. concentration presented low values (culture with natural sunlight = 0.1 to 9.9 × 10² CFU mL^?1, culture in darkness = 0.4 to 11.7 × 10² CFU mL^?1) and Bacillus sp. had high values (culture with natural sunlight = 0.7 to 66.0 × 10⁴ CFU mL^?1, culture in darkness = 0.7 to 65.8 × 10⁴ CFU mL^?1). All water quality parameters remained within the ranges suitable for shrimp culture, except for alkalinity during the first stage of the study. Although in some sampling periods some significant differences were found in bacterial counts and water quality parameters, shrimp productive performance under culture with biofloc at low salinity was not affected significantly by light limitation.  相似文献   

Epidural anaesthesia using lignocaine, bupivacaine or a mixture of lignocaine and bupivacaine in dogs     

M. L. Cruz  S. P. L. Luna  R. M. O. Clark  F. Massone  G. B. Castro 《Veterinary anaesthesia and analgesia》1997,24(1):30-32

The time to loss of interdigital reflex, duration of action, duration of muscle relaxation and cardiorespiratory effects were compared after epidural block using lignocaine, bupivacaine or a combination of lignocaine and bupivacaine in dogs. Dogs were pre-medicated with methotrimeprazine, anaesthesia was induced with thiopentone, in order to facilitate epidural puncture, and a lumbosacral epidural block was performed. Body temperature fell after pre-medication, thiopentone and epidural anaesthesia. Minimal changes were observed in arterial O₂ saturation, end tidal CO₂, respiratory rate, heart rate and mean arterial blood pressure. The combination of bupivacaine with lignocaine produced a shorter time to loss of interdigital reflex than bupivacaine alone, longer analgesia than lignocaine alone and longer muscle relaxation than either lignocaine or bupivacaine. The combination appeared to be the best choice when surgical time is prolonged.  相似文献   

Evaluation of a Biofloc System for Intensive Culture of Fathead Minnows,Pimephales promelas          下载免费PDF全文

Jeonghwan Park  Luke A. Roy  Nilima Renukdas  Trevor Luna 《Journal of the World Aquaculture Society》2017,48(4):592-601

This study was carried out to test the suitability of biofloc technology to improve the productivity of the fathead minnow, Pimephales promelas, a commercially important baitfish in North America. Biofloc growth was induced in treatment tanks by periodic additions of a carbon source (glucose) to maintain a C : N ratio of 12:1. Control tanks (no aeration and no carbon addition) accommodated densities equivalent to 1 million fish/ha, while treatment tanks (biofloc) had densities of 1, 2, 4, and 8 million fish/ha. Fish were fed 4% body weight using a 32% protein commercial diet. There were no significant differences in condition of fish harvested from control and treatment densities (P < 0.05). However, fish growth indicators such as final individual weight, feed conversion efficiency, and specific growth rate were significantly impaired at higher stocking densities. Survival rate was significantly lower in the 8 million/ha treatment (P < 0.05). Results were indicative of possible production efficiencies of twofold higher in biofloc systems stocked at or below 4 million/ha compared with traditional ponds. Although biofloc systems maintained the desired water‐quality parameters, biofloc microbial biomass did not seem to significantly enhance feed conversion and specific growth rates of fathead minnows.  相似文献   

绵羊在澳大利亚的引进和传播     

肖璐娜  张箭 《农业考古》2021,(1)

在欧洲白人到达之前,澳大利亚并没有畜牧业,土著人也没有饲养牲畜。1788年,英国“第一舰队”抵达植物湾,不仅带来了大量农作物,随船还带有羊、牛、猪等若干家畜,这些家畜成为澳大利亚早期畜牧业的基础。后经麦克阿瑟、佩平等优秀养羊者的改良培育,外加优越的放牧条件和科研配种技术的投入,羊毛业有了飞速发展,大量羊毛出口成为促进澳大利亚19世纪经济增长的重要原因,其副业羊肉生产也得益于冷冻技术的应用而有所发展。迄今澳大利亚已发展为现代农牧业最为发达的国家之一,羊群总数及羊毛产量稳居世界第一,特别是澳洲美利奴羊毛,更是享誉世界。故旧大陆绵羊的传入,不仅是家畜的传播,更是新旧大陆农业文明交流的重要结晶,对澳大利亚畜牧业产生了不可估量的重大影响。  相似文献   

Biologic and genetic characteristics of Toxoplasma gondii isolates in free-range chickens from Nicaragua, Central America     

Dubey JP  Sundar N  Pineda N  Kyvsgaard NC  Luna LA  Rimbaud E  Oliveira JB  Kwok OC  Qi Y  Su C 《Veterinary parasitology》2006,142(1-2):47-53

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 98 free-range chickens (Gallus domesticus) from Nicragua was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT), and found in 84 (85.7%) of 98 chickens with titers of 1:5 in 10, 1:10 in eight, 1:20 in seven, 1:40 in nine, 1:80 in 11, 1:160 in one, 1:200 in 27, 1:400 in six, 1:800 four, and 1:3200 in one bird. Hearts and brains of 32 chickens with titers of 1:10 or less were pooled and fed to three T. gondii-free cats. Hearts and brains of 66 chickens with titers of 1:20 or higher were bioassayed in mice. Feces of cats were examined for oocysts. The cat fed tissues from eight chickens with titers of 1:10 shed T. gondii oocysts. The two cats fed tissues of 24 chickens with titers of 1:5 or less did not shed oocysts. T. gondii was isolated by bioassay in mice from 47 chickens with MAT titers of 1:20 or higher. All infected mice from six isolates died of toxoplasmosis. Overall, 41 of 170 (24.1%) mice that became infected after inoculation with chicken tissues died of toxoplasmosis. Genotyping of these 48 isolates (47 from mice and 1 from pooled tissues) using polymorphisms at the loci SAG1, SAG2, SAG3, BTUB and GRA6 revealed eight genotypes. Six isolates had Type I alleles, three isolate had Type II alleles and six isolates had Type III alleles at all loci. Four isolates had mixed infections. Two isolates have a unique allele at SAG1 locus and combination of I and III alleles at other loci. The rest 27 isolates contained the combination of Type I and III alleles and were divided into four genotypes. More than one genotypes were often isolated in chickens from the same household, indicating multiple genotypes were circulating in the same environment. This may explain the high frequency of mixed infections observed. High rate of mixed infection in intermediate hosts such as chickens may facilitate genetic exchange between different parasite lineages in definitive feline hosts. This is the first report of genetic characterization of T. gondii isolates from Nicragua, Central America.  相似文献   

Baby-leaf and multi-leaf of green and red lettuces are suitable raw materials for the fresh-cut industry   总被引：1，自引：0，他引：1  

Ascensión Martínez-SánchezMaría C. Luna  María V. SelmaJuan A. Tudela  Jesús AbadMaría I. Gil 《Postharvest Biology and Technology》2012,63(1):1-10

Consumer demand for softer leaves with variation in taste, shape and colours has encouraged the development of new lettuce products of baby-sized leaves. The objective of this study was the comparison of whole-head lettuce, as the most common raw material for fresh-cut, with baby-leaf and multi-leaf as the newest baby-sized lettuce leaves. Lettuces (Lactuca sativa L.) of the types Green Leaf, Red Leaf and Lollo Rosso were cultivated in the same field with different plant densities, under commercial conditions. Although baby-leaf was subjected to far less wound damage than the shredded lettuce from the whole-head, leaf age could play an important role in increasing respiration rate and determining postharvest quality. After 9-11 d of storage, minimally processed products from the three types of raw material showed good visual quality without differences among them. However, over the 12-d storage period, quality decreased to the limit of marketability mainly due to browning of the cut edge surface of the fresh-cut product from whole-heads and decay due to the soft tissue in the case of baby-leaves. Additionally, with the processing of whole-heads, the increase in cut-damage surfaces and availability of cell nutrients provided conditions that favoured the growth of lactic acid bacteria (LAB) and total coliforms compared to uncut surfaces of baby-sized leaves. The ratio between the oxidized and reduced forms of ascorbate (DHA/AA) increased 2-4 times after 9-11 d of storage. Furthermore, baby-sized leaves had higher phenolic contents than the shredded product from the whole-head which probably contributed to reaching a shelf-life of 11 d. In conclusion, the new green and red baby-sized leaves both at immature and mature stages provided high quality lettuce for the fresh-cut market, meeting specific requirements regarding visual quality, microbial load and high content of phytochemicals.  相似文献   

RADIOGRAPHIC STUDY OF DISTAL RADIAL PHYSEAL CLOSURE IN THOROUGHBRED HORSES     

Luiz C.  Vulcano Maria J.  Mamprim  Lucy M.R.  Muniz  Alankardson F.  MOREIRA  Stelio P.L.  Luna 《Veterinary radiology & ultrasound》1997,38(5):352-354

Monthly radiography was performed to study distal radial physeal closure in ten male and ten female Throughbred horses. The height, thoracic circumference and metacarpus circumference were also measured. Distal radial physeal closure time was sooner in females than males, and took 701 ± 37 and 748 ± 55 days respectively.  相似文献