Relations between soil factors and herbage yields of natural grassland on sandy soils in the south‐eastern Transvaal

Forty systematically‐placed observation points were established in a 1.5‐ha area of floristically unifoim veld in which productivity varied spatially. At each point grass yields were determined by harvesting quadrats at eight‐week intervals during the growing season, and the volumetric water content of the soil was measured weekly. In addition, root mass and root‐N content, and soil variables involving C and N contents, extractable P, K, Ca and Mg, cation exchange capacity and base saturation, pH, clay content and soil depth, were determined. The data were examined using linear correlations between variables, principal components analysis and multiple regression. The major factors associated with variations in yield were, in order of importance, soil water content, the N supply (as expressed by root‐N content or root‐N mass) and the cation supply (as expressed by the topsoil variables, extractable Ca or cation exchange capacity or percentage base saturation). There was a relatively weak positive association between yields and the H⁺ concentration in the subsoil, and a weak negative association between yields and the clay content of the topsoil. A multiple regression function involving all five factors accounted for 77.3% of the variation in dry matter yield.     

COMPUTED TOMOGRAPHY OF NONANESTHETIZED CATS WITH UPPER AIRWAY OBSTRUCTION

Upper airway obstruction is a potentially life‐threatening problem in cats and for which a noninvasive, sensitive method rapid diagnosis is needed. The purposes of this prospective study were to describe a computed tomography (CT) technique for nonanesthetized cats with upper airway obstruction, CT characteristics of obstructive diseases, and comparisons between CT findings and findings from other diagnostic tests. Ten cats with clinical signs of upper airway obstruction were recruited for the study. Four cats with no clinical signs of upper airway obstruction were recruited as controls. All cats underwent computed tomography imaging without sedation or anesthesia, using a 16‐slice helical CT scanner and a previously described transparent positional device. Three‐dimensional (3D) internal volume rendering was performed on all CT image sets and 3D external volume rendering was also performed on cats with evidence of mass lesions. Confirmation of upper airway obstruction was based on visual laryngeal examination, endoscopy, fine‐needle aspirate, biopsy, or necropsy. Seven cats were diagnosed with intramural upper airway masses, two with laryngotracheitis, and one with laryngeal paralysis. The CT and 3D volume‐rendered images identified lesions consistent with upper airway disease in all cats. In cats with mass lesions, CT accurately identified the mass and location. Findings from this study supported the use of CT imaging as an effective technique for diagnosing upper airway obstruction in nonanesthetized cats.     

Sporozoite proteome analysis of Cryptosporidium parvum by one-dimensional SDS-PAGE and liquid chromatography tandem mass spectrometry

Despite the development of new technologies, new challenges still remain for large scale proteomic profiling when dealing with complex biological mixtures. Fractionation prior to liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis is usually the preferred method to reduce the complexity of any biological sample. In this study, a gel LC-MS/MS approach was used to explore the stage specific proteome of Cryptosporidium (C.) parvum. To accomplish this, the sporozoite protein of C. parvum was first fractionated using SDS-PAGE with subsequent LC-MS/MS analysis. A total of 135 protein hits were recorded from 20 gel slices (from same gel lane), with many hits occurring in more than one band. Excluding all non-Cryptosporidium entries and proteins with multiple hits, 33 separate C. parvum entries were identified during the study. The overall goal of this study was to reduce sample complexity by protein fractionation and increase the possibility of detecting proteins present in lower abundance in a complex protein mixture.     

Nitrogen fertilisation of weeping love grass (eragrostis curvula) at Dohne

Three field trials on the nitrogen fertilisation of the Ermelo cultivar of Eragrostis curvula conducted over seven years were collated and reviewed. Dry matter yields in tons obtained from these trials, excluding first year results, were used to derive the regression equation y = 3.9 x — 0.4 x² + 1.3 for the yield response to increments of 100 lb of nitrogen per morgen per annum. This response was nearly linear up to 300 lb of nitrogen, and more than 400 lb of nitrogen was required for maximum dry matter production. The crude protein content of the herbage increased progressively with increasing rates of nitrogen. The recovery of fertiliser nitrogen varied from 51 to 70 per cent ; the latter being achieved by (he application of 300 lb of nitrogen. Ammonium sulphate produced considerably higher dry matter yields than urea or limestone ammonium nitrate when applied in a single dressing in the spring. When the nitrogen was applied in three dressings the yields from urea and LAN were increased and no longer significantly different from those due to ammonium sulphate.     

Ontogeny of Themeda triandra tillers in the false thornveld of the eastern cape

Abstract

Marked populations of Themeda triandra tillers were sequentially sampled at fortnightly intervals under normal conditions and without moisture stress respectively, covering a period from tiller initiation through to senescence after flowering. Parameters recorded were height of shoot apex, tiller mass, leaf area, leaf number, secondary tiller development and premature tiller mortality. Tillers of irrigated plants had a significantly higher mass, more elevated shoot apices, and produced a greater total number of leaves than those of non‐irrigated plants. Fewer unstressed tillers senesced prematurely than those experiencing moisture stress.     

Motivating rice farmers in the Mekong Delta to modify pest management and related practices through mass media

A participatory planning process was applied to develop a media campaign to motivate rice farmers in the Mekong Delta to modify pest management practices together with seed and fertilizer inputs. Locally named ‘Ba Giam Ba Tang’ or ‘Three Reductions, Three Gains’, campaigns were launched in two provinces, Can Tho and Tien Giang. In both provinces, farmers' practices changed significantly. Their insecticide sprays reduced by 13–33% while their seed rates dropped ～10% and nitrogen rates, ～7% and proportion of farmers using insecticides declined by ～11%. These practices were supported by modifications in belief attitudes that favored high inputs. Farmers who reported significant reductions in the three inputs also changed their perception of yield loss. The campaigns in Can Tho and Tien Giang had significant multiplier effects. They stimulated several provincial governments as well as the Ministry of Agriculture and Rural Development to provide additional resources to reproduce the materials and campaign process for local use which eventually reached more than 3 million farmers in south and central Vietnam.     

Root Growth and Soil Water Dynamics in Relation to Inorganic and Organic Fertilization in Maize–Wheat

Agricultural productivity is increasingly becoming dependent upon soil fertility, which is generally thought to be supplemented through the application of nutrients mainly through inorganic fertilizers. The present study aims to characterize the soil physical environment in relation to long-term application of farmyard manure (FYM) and inorganic fertilizers in a maize–wheat cropping system. The treatments in both the maize and wheat systems included a control (without any fertilizer or FYM), FYM (farmyard manure at 20 t ha^?1), N₁₀₀ (nitrogen at 100 kg ha^?1), N₁₀₀P₅₀ (nitrogen and phosphorus at 100 and 50 kg ha^?1), and N₁₀₀P₅₀K₅₀ (nitrogen, phosphorus, and potash at 100, 50, and 50 kg ha^?1). The treatments were replicated four times in a randomized complete block design in sandy loam soil. The root mass density in surface layers of both the crops was lower in FYM and higher in inorganic fertilizer plots. The root length density was found to be highest in FYM-treated plots and lowest in control plots. The periodic soil matric suction during wheat following maize remained highest in FYM plots followed by that in N₁₀₀ plots in all the layers. The soil water storage of wheat at harvest (rice–wheat) was highest (21.1 cm) in control and lowest (17.8 cm) in FYM-treated plots. The soil water status, root growth, and crop performance improved with balanced fertilization.     

注射器内分散固相萃取-超高效液相色谱-串联质谱法快速测定茶叶中24种农药残留

基于茶叶基质特点,开发了注射器内分散固相萃取快速前处理技术,建立了茶叶中24种农药残留超高效液相色谱-串联质谱检测方法。茶叶样品经乙腈提取,无水MgSO₄盐析,在设计的注射器装置内以N-丙基乙二胺键合硅胶和石墨化炭黑作为分散吸附剂进行净化,超高效液相色谱-串联质谱法进行检测。在3个添加水平（0.01、0.05、0.5βmg·kg^-1）下,红茶和绿茶中24种农药的平均回收率为61.7%~98.8%,相对标准偏差为0.4%~5.5%,准确度和精密度良好。24种农药的红茶和绿茶基质标准工作液线性关系良好,相关系数（R²）均大于0.995,检出限（LOD）和定量限（LOQ）分别为0.05~5.36βμg·kg^-1和0.18~17.86βμg·kg^-1,该方法具有良好的灵敏度。本方法具有简便快捷、所需仪器少、省时等优势,适用于茶叶中多农药残留的定量检测。     

Coupling Mass Spectral and Genomic Information to Improve Bacterial Natural Product Discovery Workflows

Bacterial natural products possess potent bioactivities and high structural diversity and are typically encoded in biosynthetic gene clusters. Traditional natural product discovery approaches rely on UV- and bioassay-guided fractionation and are limited in terms of dereplication. Recent advances in mass spectrometry, sequencing and bioinformatics have led to large-scale accumulation of genomic and mass spectral data that is increasingly used for signature-based or correlation-based mass spectrometry genome mining approaches that enable rapid linking of metabolomic and genomic information to accelerate and rationalize natural product discovery. In this mini-review, these approaches are presented, and discovery examples provided. Finally, future opportunities and challenges for paired omics-based natural products discovery workflows are discussed.