西北干旱灌区不同地膜覆盖利用方式对玉米水分利用的影响

【目的】资源型缺水严重制约干旱灌区的农业生产,传统玉米生产模式地膜投入量大。在极端高温和生态环境污染的挑战日益加剧的情境下,探讨通过免耕地膜重复利用维持较高水分利用的可行性,以期为构建试区地膜减量玉米高效生产技术提供理论支撑。【方法】2017—2018年,在甘肃河西绿洲灌区,设置免耕地膜重复利用(免耕覆膜,NM)、秋免耕春覆膜(少耕覆膜,RM)与传统耕作每年覆盖新膜(传统覆膜,对照,CM)3种地膜覆盖利用方式,研究其对玉米田土壤水分利用的影响,以期为优化试区玉米高产高效栽培管理技术提供理论依据。【结果】NM与RM处理较CM处理提高玉米播种时0—120 cm土层平均土壤重量含水量,分别为7.8%与5.1%,这为玉米播种创造良好的土壤水分环境。玉米播种—拔节期及吐丝—灌浆初期,NM处理较CM处理提高0—120 cm土层平均土壤重量含水量,分别为5.0%与4.7%,弥补了灌浆期玉米植株旺盛生长对土壤水分的大量需求。与CM处理相比,NM处理增加了玉米播种—大喇叭口期的耗水量,降低了玉米吐丝—灌浆初期的耗水量,增大了玉米灌浆初期—收获期的耗水量,有效协调玉米各生育阶段的水分需求关系。虽然NM处理...     

食用菌产前、产中、采后无公害生产技术

分析了发展食用菌无公害生产的优势、特点和重要意义。结合实践经验，并吸收国内外相关技术，提出了食用菌产前、产中、采后无公害生产的措施和技术要点。     

Effects of conservation agriculture on soil quality and productivity in contrasting agro‐ecological environments of Zimbabwe

Experimentation by farmers with conservation agriculture (CA) is increasing in southern Africa, but local longer term data on these new production systems are scarce. This study focuses on CA research at two contrasting on‐farm sites and one on‐station long‐term trial in Zimbabwe. The on‐farm trials were conducted at Chikato village on a sandy soil at Zimuto Communal Area with low rainfall and at Hereford farm near Bindura on a clay‐rich soil in a high rainfall area. The on‐station trial was at Henderson Research Station near Mazowe where more in‐depth soil studies were possible. Results of CA systems from the on‐station site show on average 38 and 65% greater water infiltration on ripline‐seeded (RS) and direct‐seeded CA treatments compared with conventionally ploughed control treatments. Results from on‐farm sites show a 123 and 168% greater aggregate stability at Hereford and 11 and 24% lower dispersion ratio at Chikato on the two CA compared with the conventionally ploughed control treatments. Soil carbon increased by 46% in the first 20 cm on the sandy soils at Chikato in RS and by 104% in direct‐seeded CA treatments in four cropping seasons from 2004 to 2008, while it stayed at low levels on the conventionally tilled control treatment. Yields on CA plots were higher on the sandy soils in dry seasons, but lower in very wet seasons because of waterlogging. Yields on clay soils were less affected by the rainfall season. Crop productivity from CA systems increased at all sites over time owing to better management although significant differences between CA and conventional treatments on the three sites were apparent only after several cropping seasons. Conservation agriculture offers practical solutions to small‐scale farmers threatened by future soil degradation and fertility loss, but its successful use will depend on weed control and adequate application of fertilizers. The results indicate that there is no immediate increase in maize (Zea mays L.) yield when changing from a tilled to a CA system, but there is gradual improvement in some soil quality indicators over time.     

“双亚10号”亚麻离体再生体系的建立

以亚麻的成熟种子为外植体,建立了一种有效的亚麻植株再生体系。研究结果显示,亚麻的发芽培养基为B5;茎尖分化增殖的最佳培养基为MSB＋6-BA1.5 mg.L-1＋IAA0.2 mg.L-1,平均增殖系数达到10.05;生根最适培养基为1/2B5＋NAA0.02 mg.L-1,平均生根数达8条,生根率达到95%。该再生体系的建立为亚麻遗传转化研究奠定了基础。     

Branch thickness in unthinned stands of Sitka spruce (Picea sitchensis (Bong.) Carr.)

Results of branch measurings in unthinned stands of Sitka spruce in Denmark are presented. Three different measures of branch thickness are discussed in relation to visual grading of structural timber. On basis of the average thickest branch 5.0 m above ground it is recommended not to let spacing exceed 1.8x1.8 m‐2.0x2.0 m at establishment. Since Sitka spruce branches react profusely when spacing widens, this is the upper limit, presupposing a no‐thinning regime. With reference to the literature, the same recommendation can be given on basis of machine stress gradings.     

Water repellency and pore clogging at early successional stages of microbiotic crusts on inland dunes,Brandenburg, NE Germany

Biological soil crusts play a key role for hydrological processes in many open landscapes. They seal the topsoil and generate surface run-off. Utilization of the mineral substrate at early stages of microbiotic crusts was investigated using scanning electron microscopy (SEM), water repellency indices were measured using the ethanol/water microinfiltrometer method, and steady state water flow was determined on the dry crusts and after 300, 600, 1200 and 1800 s of wetting, thus allowing to follow pore clogging through swelling of extracellular polymeric substances (EPS). It was found that water repellency increases with initial crust development where filamentous cyanobacteria and filamentous green algae were dominating, but decreases as coccal algae, bryophytes and fungi associated with bryophytes emerged. Swelling of EPS took place immediately after wetting, and its influence on steady state water flow was most pronounced when filamentous cyanobacteria and algae partially filled in the matrix pores and enmeshed sand grains, still leaving micropore channels available for free water infiltration, but prior to appearance of coccal algae, bryophytes and associated fungi which formed a dense cover on the surface. It was concluded that a new phase of crust succession was accompanied by easier wettability but slower infiltration. Transition from hydrophobicity to pore clogging as ruling mechanisms causing water run-off may occur during wetting of individual biological crusts, but also during crust succession over time.     

苹果套袋的回顾反思和展望

苹果套袋栽培是从我国实际情况出发,在特定的历史阶段,生产低残毒苹果,打开国际市场,促进果业生产发展的重要技术措施。为追求市场效益,苹果早采的经营、生产理念,失去原有的品种特性。在市场上的农药可以满足生产国际标准果的条件下,无袋栽培是可行的。从果树生产基地入手,选择应用世界先进的组合农药,是推行无袋栽培的最佳选择。     

边缝式迷宫滴灌带灌水器流道内泥沙沉积影响因素分析

为研究灌水器流道内泥沙颗粒淤积特性的影响因素，进一步降低物理堵塞发生的风险，该研究配置不同浓度（1.8、2.8、3.8 g/L）和不同粒径（0 $\leqslant $ d < 0.054 mm、0.054 mm $\leqslant $ d < 0.075 mm、0.075 mm $\leqslant $ d < 0.1 mm）的含沙水，进行全组合间歇滴灌堵塞试验，对含沙水灌溉下灌水器泥沙沉积特性进行分析并对灌水器内流态进行数值模拟研究。结果表明：灌溉结束后，经由边缝式迷宫灌水器输出的泥沙中，黏粒与砂粒比例下降，粉粒比例上升，即灌水器弯曲流道对小于0.002 mm和大于0.05 mm粒径的泥沙具有明显阻滞作用，流道内堵塞的泥沙集中在0.054～0.1 mm的中大粒径范围内。灌水器流道内部流线在主流区呈波浪状前进，主流区水流流速大于近壁区，中部转角处流速均偏大。沙粒易受上转角和下转角处产生的漩涡影响而沉降集中在漩涡中心及背水面。滞留在漩涡区内的泥沙颗粒是引起灌水器堵塞的主要因素。为减少灌水器堵塞风险，在设计优化时宜考虑减少直角、锐角区域以减少漩涡区的形成。