Bioavailability of ascorbyl phosphate calcium in hybrid catfish,Clarias macrocephalus (Gunther) × Clarias gariepinus (Burchell) feed

A 10-week feeding experiment was performed in hybrid catfish (Clarias macrocephalus (Gunther) × C. gariepinus (Burchell, 1822) with initial average weight of 1.17 g, in glass aquaria of 200-L capacity. The experiment comprised seven treatments with three replicates each. Ascorbyl phosphate calcium (APCa) was included at 30, 75, 150, 300 and 1000 mg kg⁻¹ feed and compared with one with ascorbyl polyphosphate (APP) at 36 mg kg⁻¹ feed and one without vitamin C supplementation. Fish fed APCa-supplemented feed showed better growth, feed conversion ratio, survival rate and protein utilization compared with those without such supplementation. Ascorbate concentrations in liver and head kidneys were correlated closely with dietary APCa levels. Vertebral collagen and hydroxyproline contents were significantly lower in the fish group without ascorbate supplementation. Red blood cell and white blood cell counts showed no correlation with vitamin C supplementation. Serum protein level was lowest in the group fed feed without vitamin C supplementation and this was lower than those fed feed with APCa and APP supplementation. The fish fed APCa- and APP-supplemented feed showed no difference in serum protein levels. External scorbutic symptoms and histopathological changes of gill tissue were noted in fish fed feed without APCa supplementation. The study indicates that 12.6 mg kg⁻¹ of ascorbic acid molar equivalent supplied as APCa (30 mg kg⁻¹) provided maximum growth and no gross signs as well as histological changes resulting from vitamin C deficiency.     

Phosphorus availability of sewage sludge‐based fertilizers determined by the diffusive gradients in thin films (DGT) technique

The plant‐availability of phosphorus (P) in fertilizers and soil can strongly influence the yield of agricultural crops. However, there are no methods to efficiently and satisfactorily analyze the plant‐availability of P in sewage sludge‐based P fertilizers except by undertaking time‐consuming and complex pot or field experiments. We employed the diffusive gradients in thin films (DGT) technique to quantify the plant P availability of various types of P fertilizers with a novel focus on sewage sludge‐based P fertilizers. Mixtures of fertilizer and soil were incubated for 3 weeks at 60% water holding capacity. DGT devices were deployed at the beginning of the incubation and again after 1, 2, and 3 weeks. Two weeks of incubation were sufficient for the formation of plant‐available P in the fertilizer/soil mixtures. In a pot experiment, the DGT technique predicted maize (Zea mays L.) biomass yield and P uptake significantly more accurately than standard chemical extraction tests for P fertilizers (e.g ., water, citric acid, and neutral ammonium citrate). Therefore, the DGT technique can be recommended as a reliable and robust method to screen the performance of different types of sewage sludge‐based P fertilizers for maize cultivation minimizing the need for time‐consuming and costly pot or field experiments.     

不规则盐度脉冲对许氏平鲉氨氮、磷排泄的影响

在静水系统中,骤然改变水体盐度,形成盐度脉冲;研究许氏平鲉Sebastodes fuscescens(Houttuyn)经历该脉冲后其氨氮、活性磷酸盐排泄的情况。结果表明,盐度改变后,许氏平鲉的氨氮排泄率比正常盐度(30)下呈现出不同程度的升高趋势;当盐度由30降为25和20时,随着体重增加,氨氮排泄率先增大,后又减小;当盐度由30上升为35时,氨氮排泄率随体重增加而呈下降趋势。盐度改变后,许氏平鲉的活性磷酸盐排泄率随体重增大呈先增大后减小的趋势。在同一体重下,盐度由30降至20时,活性磷酸盐的排泄率最大;盐度由30升至35时,磷的排泄率最小。方差分析表明,盐度脉冲对许氏平鲉氨氮排泄率有显著的影响(P<0.05),对活性磷酸盐排泄率的影响不显著(P>0.05)。该研究对于鱼类养殖的水质管理、养殖场的布设等有重要的指导意义。     

Comparative efficiency of phosphate-solubilizing bacteria under greenhouse conditions for promoting growth and aloin-A content of Aloe barbadensis

This study was conducted with Aloe barbadensis in order to investigate the efficacy of four phosphate-solubilizing bacteria (PSB), Pseudomonas synxantha 10223, Burkholderia gladioli 10242, Enterobacter hormaechei 10240 and Serratia marcescens 10241 to solubilize Mussorie rock phosphate (MRP) and to evaluate its effects on growth, soluble P content and P uptake compared with control, i.e. uninoculated plants. Pot experiments were conducted in a greenhouse, in soil supplemented with MRP. Each PSB treatment showed different effects on different plant growth parameters. The maximum increase in leaf length (23.7%), total number of leaves (33.33%) and dry rind weight (69.10%) was observed in plants treated with P. synxantha 10223 compared with control. Whereas, maximum increase in root length (23.43%), fresh leaves weight (79.03%), dry gel weight (113.08%) and total gel volume (112.10%), was observed in plants treated with S. marcescens 10241 compared with uninoculated plants. Maximum increase in aloin-A content [114.92% (per g dry gel weight) and 322.32% (per plant dry gel weight)] was observed in plants treated with P. synxantha 10223 compared with control plants. Root colonization by inoculated PSB as estimated by RAPD technique showed that all PSB were able to survive in the rhizosphere of Aloe plants.     

海水磷酸盐分析方法的优化和试剂稳定性研究

对《海洋调查规范》中测定海水磷酸盐的常规方法进行了优化 ,达到了简化过程 ,缩短分析时间以适应水下现场自动分析的目标。此外 ,实验还对磷酸盐测定所使用的试剂及标准贮备液的稳定性进行了一系列的研究 ,改进试剂保存方法 ,延长试剂使用寿命 ,以满足长期现场测定的要求     

桑树喷施磷酸二氢钾替代春季摘芯效果试验

通过试验得出，春期桑园喷施磷酸二氢钾不仅可以提高桑叶产量和实力利用率，还可以改善桑叶叶质。较春叶摘芯起到更好的效果。本文还提出了该药剂的实用喷施方法。     

Assessment of the effect of time and temperature on the availability of residual phosphate in a glasshouse study of four soils using the Olsen method

Abstract. The Olsen method is an indicator of plant-available phosphorus (P). The effect of time and temperature on residual phosphate in soils was measured using the Olsen method in a pot experiment. Four soils were investigated: two from Pakistan and one each from England (calcareous) and Colombia (acidic). Two levels of residual phosphate were developed in each soil after addition of phosphate by incubation at either 10 °C or 45 °C. The amount of phosphate added was based on the P maximum of each soil, calculated using the Langmuir equation. Ryegrass was used as the test crop. The pooled data for the four soils incubated at 10 °C showed good correlation between Olsen P and dry matter yield or P uptake ( r ²= 0.85 and 0.77, respectively), whereas at 45 °C, each soil had its own relationship and pooled data did not show correlation of Olsen P with dry matter yield or P uptake. When the data at both temperatures were pooled, Olsen P was a good indicator of yield and uptake for the English soil. For the Pakistani soils, Olsen P after 45 °C treatment was an underestimate relative to the 10 °C data and for the Colombian soil it was an overestimate. The reasons for these differences need to be explored further before high temperature incubation can be used to simulate long-term changes in the field.     

磷化氢的生物合成

磷化氢（PH3）是有毒、致癌、无色、有恶臭味的气体，既可由工业化学合成，也可由生物合成。产PH3的微生物一般为兼性厌氧和专性厌氧微生物。借助于气相色谱检测，已发现PH3在自然界中广泛存在。热力学分析，磷酸盐还原成磷化氢是一种吸能反应。目前，磷化氢生物合成的具体机制还不清楚。     

饲喂不同日粮的山羊尿沉渣晶体的化学组成和显微形态

采集饲喂棉饼、玉米粉、麸皮、豆饼四种常见日粮的山羊尿样，应用化学定性分析、Ｘ－射线衍射物相分析、Ｘ－射线能谱分析和扫描电子显微镜观察等手段分别进行尿沉渣晶体的化学组成和显微形态的分析和观察。结果表明，饲喂棉饼日粮和麸皮日粮时山羊尿沉渣晶体的化学组成为磷酸钾镁，显微开矿为斜方柱状；饲喂玉米日粮时为碳酸镁，形态为长方柱状；饲喂豆饼日粮时为碳酸钙（方解石），形态为短方柱状。最后，还对几种尿沉渣晶体的生成     

磷酸二铵作水稻基肥的效果

在水稻上进行不同基肥施用对比试验 ,结果表明 :分别用磷酸二铵 15 0、2 2 5kg/hm2 ,与习惯用碳铵 3 75kg/hm2 +普钙 3 75kg/hm2 作基肥的水稻相比 ,产量分别增加 169.5和 3 15kg/hm2 ,增产 2 .3 %和 4.4% ,达显著水平。用磷酸二铵代替碳铵和普钙作水稻基肥 ,具有省力、增产等优点。