Yield and growth characteristics for cotton under various irrigation regimes on sandy soil

Over-watering cotton wastes a valuable and scarce resource; it can also lead to rank growth, nutrient leaching, and contaminated groundwater. Since under-watering can decrease yields, the question becomes one of finding the optimum application regime. An irrigation experiment was set up to apply water at six different application rates, ranging from 33% to 144% of normal, with hopes of identifying the regime that produces maximum yield. Two cultivars, Acala Maxxa and Acala PhytoGen-72 (Gossypium hirsutum L.), were planted on sandy soil and irrigated daily with a highly efficient subsurface drip irrigation system for four seasons. The results showed that on the average there was no significant difference in the yield of the two cultivars and there was no significant difference in the yield for the three wettest treatments. The driest of the three wettest treatments, treatment 4, was a critical point on the water production function curve. It represented the least amount of water applied that still produced essentially maximum yield, and it had the highest water use efficiency. This critical level of water application during mid-season was found to be, on the average, 95% of Class A pan evaporation; it corresponded to a total seasonal application of 654 mm of water. Any application less than this critical level decreased yields. Reducing the water application by 5% below the critical level caused about a 4.6% reduction in yield. The critical level produced a soil moisture level that remained nearly constant throughout the season. The final plant height was closely related to the depth of water applied, with the wettest treatment producing plant heights of 2.0 m, and the driest treatment producing plant heights of 0.6 m. At the extremes of the water application rates there were some small differences in the early-season growth rate of the plants, but the main cause of differences in final plant height was the date of cutout (cessation of main stem node production). The length of season for the driest treatment was about 4 weeks shorter than for the wettest treatment on both cultivars. Results showed that deficit irrigation of cotton on sandy soil can greatly reduce yield, and the practice should probably be avoided.     

Impact of fish feed on airlift pumps in aquaculture systems

Airlift pumps are commonly used in aquaculture systems to circulate water and maintain critical gas levels. In production marine reuse systems, a significant decrease in airlift pump flowrate was visually observed immediately after feeding. In experimental systems without fish, it was found that feed additions of less than 10 mg/L decreased water flow by as much as 78% for diffuser injectors but only 10% for pumps with direct air injection. For both injector types, feed impact diminished over several hours but persisted longer in seawater than in freshwater. Video footage revealed increasing bubble coalescence with the addition of feed. The decrease in pump flow is likely attributed to water property changes due to compounds leaching out of the feed. This decrease in pumping rate has the potential to negatively impact water quality, system performance, and fish health.     

近40 a黄河乌兰布和沙漠段河道演变特征

基于Landsat系列卫星遥感数据,利用目视解译法提取黄河乌兰布和沙漠段近40 a夏季河道演变特征值,对比分析两岸河道演变特征并分析其变化原因.结果表明:①以乌海水利枢纽为起点,1973-2015年黄河乌兰布和沙漠段左岸堆积面积最大的河段分布在11.5 ～36.7 km处,右岸堆积面积最大的河段分布在61.5～73.1 km处;②1973-2015年黄河乌兰布和沙漠段堆积与侵蚀总面积分别为82.73 km2和5.28 km2,其中1973-1989、1989-2000、2000-2005、2005-2008、2008-2010年和2010-2015年各时期的堆积速率分别为1.52 km2·a-1、2.36kim2·a-1、3.70km2 ·a-1、2.45 km2 ·a-1、1.22 km2·a-1和0.84 km2·a-1.黄河乌兰布和沙漠段整体呈现淤积状态,河道萎缩并向右迁移;③随着石嘴山水文站年均径流量的增大,河岸堆积速率呈逐渐降低趋势,而侵蚀速率变化趋势则正好相反.该研究有利于了解黄河上游沙漠宽谷河段的河道演变特征,为沙漠地区植被恢复及当地环境的治理提供理论依据.     

Comprehensive Effects of Temperature and Relative Humidity on Rebar Corrosion in Concrete

The corrosion rate of steel in concrete is highly dependent on the heterogeneous structure of the concrete and the environmental exposure conditions. Temperature and relative humidity are two important environmental factors that simultaneously influence the corrosion process and cannot be separated or isolated from each other. The interaction of temperature and relative humidity for characterizing the corrosion rate has been sufficiently studied. The resules show that the higher the temperature is, the greater the relative humidity is when rebar corrosion rate reaches the max, and as to different relative humidity, the increasing extent of rebar corrosion rate with rise in temperature is different.     

长崎齿瓢虫属Afissula Kapur1955种类及地理分布的研究

长崎齿瓢虫属Afissula Kapur自1955年建立以来,近30年经各国学者不断地发现,有的重新组合到这个属,迄今该属共有13个种。本文从生物学、生态学及区系学的角度研究了这13个种的形态、食性及其分布特点,从此可以看出该类群发源于喜马拉雅地区并向该地区的东北、东南方向扩展。本研究对食植瓢虫亚科的演化增添了新的内容。     

An Approach for Estimating the Final Ultimate-bearing Capacity of Driven Pile In Soft Clay

The prefabricated pile,driven in soft clay,can squeeze the soil laterally in a certain scope around the pile,and the void ratio is reduced significantly;consequently,the shear bearing capacity is raised.But the soil parameter,which is used to estimate the capacity of pile,is reduced according to the soil state before the pile was driven.Then,a certain difference appears when the pile is working.The calculation result usually is partial to conservative.This paper analyzes the squeezing mechanism of the pile using the theory of cylindrical cavities expansion.And a formula,which is used to estimate the increment of shear bearing capacity of soil around the pile when excess pore water pressure from pile driving distributes completely,is presented based on the unique relation between the shear bearing capacity and the density of the soil.This formula can be used to estimate the final ultimate-bearing capacity of the pile.The calculated results by the proposed formula are in good agreement with those of the site measurement.     

Influence of Neutral Principal Stress on the Elastic-Plastic Solution of Expansion of Cylinder Cavities

In the elastic-plastic solution of expansion of cylinder cavities based on Tresca strength criterion and Mohr-Coulomb strength criterion, the influence of neutral principal stress is not considered. In this paper the influence of neutral principal stress on elastic-plastic solution of expansion of cylinder cavities is considered. The calculation shows that the radius and displacement of plastic zone will reduce when the neutral principal stress is considered. The conclusions are of practical significance for geotechnical engineering.     

桉树速丰林鸡粪施用效应分析

采用随机区组设计开展桉树施用鸡粪的试验研究,对不同施肥处理的林分生长量、林相特征以及经济效益进行分析,结果表明,穴施0.5kg以上近似绝干的鸡粪作基肥,其施用优势明显,能显著提高林分生产力,叶片浓绿、宽大、肥厚,叶绿素含量较高,树势强壮,而且经济效益较好,2年生林分平均树高、胸径、材积和蓄积分别达8.0～8.5m、7.0～7.4cm、0.015 6～0.018 6m3和21.5～26.3m3·hm-2,比穴施钙镁磷肥0.5kg为基肥的分别提高9.5% ～15.8%、9.6% ～15.7%、31.1% ～56.3%和32.8% ～62.7%,其中尤以穴施0.75kg鸡粪的经济效益最好,投入产出比高达14.91.     

设施蔬菜土传病害的综合调控及防治进展

简述了设施蔬菜土传病害日益严重的原因。在防治上可综合运用抗病品种、轮作倒茬、增施有机肥、栽培防病、土壤消毒等农业措施,结合生物防治或高效低毒杀菌剂进行综合调控。利用电处理技术是防治土传病害的一种新思路,并对生物土壤添加剂防病的前景进行了展望。