Labile organic matter fractions as early‐season nitrogen supply indicators in manure‐amended soils

Soil test indicators are needed to predict the contribution of soil organic N to crop N requirements. Labile organic matter (OM) fractions containing C and N are readily metabolized by soil microorganisms, which leads to N mineralization and contributes to the soil N supply to crops. The objective of this study was to identify labile OM fractions that could be indicators of the soil N supply by evaluating the relationship between the soil N supply, the C and N concentrations, and C/N ratios of water extractable OM, hot‐water extractable OM, particulate OM, microbial biomass, and salt extractable OM. Labile OM fractions were measured before planting spring wheat (Triticum aestivum L.) in fertilized soils and the soil N supply was determined from the wheat N uptake and soil mineral N concentration after 6 weeks. Prior to the study, fertilized sandy loam and silty clay soils received three annual applications of 90 kg available N (ha · y)^?1 from mineral fertilizer, liquid dairy cattle manure, liquid swine manure or solid poultry litter, and there was a zero‐N control. Water extractable organic N was the only labile OM fraction to be affected by fertilization in both soil types (P < 0.01). Across both test soils, the soil N supply was significantly correlated with the particulate OM N (r = 0.87, P < 0.001), the particulate OM C (r = 0.83, P < 0.001), and hot‐water extractable organic N (r = 0.81, P < 0.001). We conclude that pre‐planting concentrations of particulate OM and hot‐water extractable organic N could be early season indicators of the soil N supply in fertilized soils of the Saint Lawrence River Lowlands in Quebec, Canada. The suitability of these pre‐planting indicators to predict the soil N supply under field conditions and in fertilized soils from other regions remains to be determined.     

保水剂特性测定及其在农业中的应用

高分子化学材料的保水剂,具有高倍吸水和保水能力,种类较多。该研究测定了钠类保水剂主要化学特性改土保土效应。通过田间试验,分析其对作物产量和肥料利用率的影响。研究表明,保水剂溶液钠离子和电导度随其浓度增加而增加,但增幅较小,对pH值影响不大。钙、镁等二价离子对聚丙稀酸钠保水剂的吸水力拮抗作用明显,与尿素混用无不良效果。土壤加入保水剂后,其保水能力增加,改善结构,沙壤土较重壤土更显著。当土壤中保水剂含量在0.005%～0.01%范围时,土壤团聚体增加量明显。在-0.5MPa土壤水势压内,含保水剂0.5%的土壤中90%水分可为植物根系利用。研究认为,保水剂保水作用主要表现4方面:自身保水、改良土壤结构增加土壤保水、促进植物生长提高肥料利用率、缓慢释水减少蒸发。田间试验发现,穴施15kg/hm²的保水剂的玉米和马铃薯分别增产22%和16%,投产比为1∶3.5和1∶4.2。保水剂与尿素或尿素磷肥混合使用于玉米,可分别提高尿素和磷肥利用效率18.72%和27.06%。     

渭北黄土台塬灌区雨水资源化的途径

渭北黄土台塬,地处渭河北岸的黄土高原边缘区,年均降水量仅为400mm,而且时空分布不均。汛期时雨水集中且多暴雨,易造成洪涝灾害,雨水资源大部分被流失掉。冬春季节,干燥少雨,造成灌区用水肾张。该地区雨水资源化的途径主要有雨水汇流集蓄和坡田改造等工程措施,以此充分利用雨水资源,加强雨水资源的季节调控,对缓解灌区用水危机具有十分重要的意义。     

维生素E缺乏对雏鸡淋巴细胞膜脂质和通透性的影响

维生素E是机体内具有广泛生理功能的重要脂溶性维生素和营养性抗氧化剂,广泛存在于体内储脂器官和生物膜上,具有免疫调节、阻止自由基对组织攻击和维持膜结构的稳定等重要作用[1].     

Circulation of prions within dust on a scrapie affected farm

Prion diseases are fatal neurological disorders that affect humans and animals. Scrapie of sheep/goats and Chronic Wasting Disease (CWD) of deer/elk are contagious prion diseases where environmental reservoirs have a direct link to the transmission of disease. Using protein misfolding cyclic amplification we demonstrate that scrapie PrP^Sc can be detected within circulating dusts that are present on a farm that is naturally contaminated with sheep scrapie. The presence of infectious scrapie within airborne dusts may represent a possible route of infection and illustrates the difficulties that may be associated with the effective decontamination of such scrapie affected premises.     

金银花品种“九丰1号”引种栽培研究初报

金银花为常用中药材,以花蕾入药,主产区为山东、河南。研究引种山东产区的金银花品种"九丰1号"在云南栽培,调查分析金银花的生长开花习性和花蕾产量品质。研究结果表明:引种栽培金银花生长正常,1年开三茬花,大白期花蕾千蕾鲜重228g,千蕾干重44g;二白期千蕾鲜重216g,千蕾干重35g,花蕾绿原酸含量5.30%;第一、二茬二白期单株花蕾产量分别达到692.36g和443.26g。     

利用Minirhizotron技术监测火炬松新根生长动态

利用Minirhizotron技术 ,研究了位于美国路易斯安那州的 19年生的火炬松新根生长动态。结果表明 ,火炬松新根的根量密度随时间呈增长趋势 ,在生长季末的 1、2月份达到最大。经过林地土壤干旱处理 (通过建立穿透雨隔离系统 ,阻止雨水到达地面 )的树木的根量密度自 9.3cm处 ,随土壤深度增加呈下降趋势 ,未经干旱处理的树木在离土表 80　 10 0cm深处仍有较高的根量密度 ,达 3.4 8　5 .12条·m- 1,是经干旱处理树木对应土壤层次中根量密度的 10多倍。火炬松从 3月份开始发生新根 ,随后迅速增加 ,至 6月份发生最多 ,然后缓慢减少 ,5　 7月的新根发生数占总量的 4 1.8% ,大部分新根发生在离土表 30cm以内的土壤中。 11个月的干旱处理显著地降低火炬松的根量密度 (1 1条·m- 1,未经干旱处理的为 3 2 7条·m- 1)和新根发生数 (5 7条·株- 1,未经干旱处理的为 15 6条·株 - 1) ,干旱处理还可导致新根推迟 1 0　 1.5个月发生。 5a前在土表撒施化肥似乎对新根的发生和生长没有明显影响