An international collaborative network for agricultural systems applications (ICASA)

In the 1970s and 1980s much progress has been made in studying agricultural production systems by using simulation modelling of agronomic processes. The International Benchwork Sites Network for Agrotechnology Transfer (IBSNAT) group in the USA and the group around Professor Kees De Wit in Wageningen were active in this new area of research which created an important ‘niche’ within the agricultural sciences because of its integrative, interdisciplinary character and its focus on quantitative, process-based approaches. A first joint scientific meeting of the two groups was held in Bangkok in 1991 (SAAD1 conference: Systems Analysis for Agricultural Development). At the SAAD2 conference at IRRI in 1995, in which also other groups took part, notably the Agricultural Production Systems Research Unit (APSRU) group from Australia, the International Consortium for Agricultural Systems Applications (ICASA) was established as a forum for researchers engaged in the study of agricultural systems at different spatial scales ranging from fields, farms to regions and beyond. The ICASA is an informal network with a focus on three major activities: (1) sharing experiences and joint development of compatible software allowing more widespread use of models having been developed by various member groups; (2) organization of joint courses on different aspects of dynamic modelling of agricultural production systems. There is an increasing interest in such courses, also in developing countries, and local researchers increasingly take an active part in them; and (3) joint research on projects dealing with dynamic characterization of agronomic production systems at different spatial scales. ICASA researchers take part in eco-regional methodology development, through projects that are funded by the Dutch and Swiss governments, with ISNAR acting as the administrative agency. ICASA intends to be an effective platform on which researchers, stakeholders and policy makers can interact.     

小造纸厂蒸煮废液治理技术研究

采用混凝－厌氧－SBR法处理草浆碱法造纸厂黑液及中段水、工艺路线可靠,COD总去除率达95％以上,处理后出水可以达到《造纸工业水污染排放标准》中的二级标准。     

Nitrate-N loadings through subsurface environment to agricultural drainage ditches in two flat Midwestern (USA) watersheds

A study was conducted to understand the contributions of tile flow and baseflow to total nitrate-N (NO₃-N) loadings in two subsurface (tile)-drained watersheds, namely the Big Ditch (BD) and the Upper Embarras River (UER) watersheds in Illinois. Two stream sections were selected in the watersheds and rectangular cutthroat flumes were installed at the upstream and downstream ends of the stream sections to calculate the flow mass balance for separating baseflow. The stream section at BD site had two tile outlets draining into it. The stream section at UER watershed did not have any tile drain. Tile flow was also measured along with stream flow. Water samples were collected not only from the stream sections using auto-samplers but also manually from the tile drains. Average baseflow rates per unit lengths of the stream sections at BD and UER sites were 3.5 × 10⁻⁰⁴ and 9.4 × 10⁻⁰⁵ m² s⁻¹, respectively. At BD site, for six study periods, the percentages of baseflow and tile flow contributions of NO₃-N loads within the stream section were 90 and 10%, respectively. Annual NO₃-N contributions by the upstream subwatersheds for BD and UER stream sections were 61,819 and 16,155 kg, respectively. Annual NO₃-N loss from these two subwatersheds within BD and UER watersheds was 42.9 and 7.0 kg ha⁻¹, respectively. For the stream section at BD site, baseflow seemed to play a more important role than tile flow in raising the NO₃-N concentration level in the stream water. Land use seemed to play a major role in the significant difference in NO₃-N concentrations at the two subwatersheds upstream from the project sites. Nitrate-N loadings primarily depended on precipitation, antecedent moisture condition (AMC), fertilizer application time, and evapotranspiration (ET).     

A model for the design of drainage in flat agricultural lands

A model is presented that can be used to determine drainage measures and their costs. It has been elaborated for a wet tropical climate, for situations with open field drains, shallow groundwater table and a homogenous soil underlain by an impervious layer. The land is flat and the proposed agricultural use requires control of the groundwater table.A basic element of the model is a scheme to compute the water balance per day for a drainage parcel. Discharge, evapotranspiration, groundwater level and soil moisture storage are estimated as functions of rainfall, potential evapotranspiration, vegetation and soil characteristics and of an assumed drainage intensity. The water balance computation is performed for periods of 5–40 years of daily rainfall data, for a series of drainage intensities. The results can be subjected to a drainage criterion, from which a design drainage intensity and a corresponding drain spacing can be derived.Finally the layout of canals for a block of 4 × 1 km² is determined and excavation and a series of canal characteristics are computed.A summary of some applications is included.     

Optimal sampling density of hydraulic conductivity for subsurface drainage in the Nile delta

The density of hydraulic conductivity measurements is of primary importance for the design of large-scale subsurface drainage projects. This study was conducted to investigate the effect of sampling density on hydraulic conductivity estimation, and to determine the optimal sampling density using results of 3488 hydraulic conductivity tests from a 33 500 ha subsurface drainage project in the Nile Delta of Egypt. Kriging was used to obtain hydraulic conductivity point and block estimates based on the original 300 m sampling grid and on reduced sampling grids with spacings of 600, 900, and 1200 m. Kriged estimates from the complete grid were compared to those from reduced grids. The correlation coefficient between kriged estimates of block hydraulic conductivity based of the 300 m versus the 600 m measurement grid was larger than 0.90, which indicates that the optimal sampling grid spacing is in the order of 600 m. Slopes of the estimation standard deviation versus sampling density showed that the optimal sampling grid spacing was between 400 and 600 m, and could be determined from sampling grids with a spacing of 900 m or less. It appears that, for the Nile Delta, the optimal sampling density of hydraulic conductivity can be determined from a preliminary survey with a grid spacing of 900 m.     

Evaluation of surface water drainage systems for cropping in the Central Highlands of Ethiopia

In Ethiopia vertisols cover about 10% of the total land area and is the fourth most important soil used for crop production, accounting for nearly 23% of the total arable land used for crop production. More than half of the vertisols are found in the Central Highlands of Ethiopia, with an altitude of more than 1500 m above mean sea level. The unique physical and chemical properties of these soils and the high rainfall during the main cropping season create severe surface waterlogging problems which hinder crop production activities. Severe surface waterlogging affects the growth of plants by impeding nutrient uptake and creating oxygen deficiency around the root zone. To address this crop production problem, three surface water drainage methods, namely broad bed and furrow (BBF), ditch, and flat (traditional) methods were evaluated using the water balance of the plant root zone and wheat as a test crop. The experiment was conducted at the Ginchi Research Station in the central highlands of Ethiopia over two consecutive seasons (2000 and 2001). The results showed that both the BBF and the ditch drainage methods gave about 33% and 22% more grain yield than the flat treatment, respectively. However, there were no significant differences between BBF and ditch for both grain and biomass yield during both experimental seasons. During both seasons the total water balance (ΔW_r) at the root zone especially, in the months of June, July and August on all the treatments was higher than the crop water requirement (ETc) and showed no significant difference between the treatments. Thus, the results of this study indicated that the soil water in the root zone was not significantly altered by surface drainage systems and therefore implies the need of further improvement of the different surface drainage methods regarding improving the waterlogging condition and hence the productivity of the vertisols in the Central Highlands of Ethiopia.     

Cover crop effects on nitrogen load in tile drainage from Walnut Creek Iowa using root zone water quality (RZWQ) model

Studies quantifying winter annual cover crop effects on water quality are mostly limited to short-term studies at the plot scale. Long-term studies scaling-up water quality effects of cover crops to the watershed scale provide more integrated spatial responses from the landscape. The objective of this research was to quantify N loads from artificial subsurface drainage (tile drains) in a subbasin of the Walnut Creek, Iowa (Story county) watershed using the hybrid RZWQ-DSSAT model for a maize (Zea mays L.)-soybean [Glycine max (L.) Merr.] and maize-maize-soybean rotations in all phases with and without a winter wheat (Triticum aestivum L.) cover crop during a 25-year period from 1981 to 2005. Simulated cover crop dry matter (DM) and N uptake averaged 1854 and 36 kg ha⁻¹ in the spring in the maize-soybean phase of the 2-year rotation and 1895 and 36 kg ha⁻¹ in the soybean-maize phase during 1981-2005. In the 3-year rotation, cover crop DM and N uptake averaged 2047 and 44 kg ha⁻¹ in the maize-maize-soybean phase, 2039 and 43 kg ha⁻¹ in the soybean-maize-maize phase, and 1963 and 43 kg ha⁻¹ in the maize-soybean-maize phase during the same period. Annual N loads to tile drains averaged 29 kg ha⁻¹ in the maize-soybean phase and 25 kg ha⁻¹ in the soybean-maize phase compared to 21 and 20 kg ha⁻¹ in the same phases with a cover crop. In the 3-year rotation, annual N loads averaged 46, 43, and 45 kg ha⁻¹ in each phase of the rotation without a cover crop and 37, 35, and 35 kg ha⁻¹ with a cover crop. These results indicate using a winter annual cover crop can reduce annual N loads to tile drains 20-28% in the 2-year rotation and 19-22% in the 3-year rotation at the watershed subbasin scale over a 25-year period.     

Subsurface drainage results for over-wetted soils of the Latvian S.S.R.

In the Latvian S.S.R. experiments on hydrological drainage action have been carried out for some 16–17 years on 200 drainage fields. It is found that the average annual removal of excess water is 150–250 mm and, in particularly moist years, 400–500 mm and more. Drainage results in a considerable reduction of the duration of over-wetting and over-flooding of the active soil layer. The importance of drainage in the control of the soil water regime is the greatest in the winter and spring periods. The most effective draining and the best economic indices have been achieved by applying deep systematic drainage. For sandy and loamy soils, a 1.3–1.5 m deep drainage installation and use of larger diameter drain pipes are recommended. It is expedient to determine the drain spacing by combining the hydromechanical and the empirical methods, making the most of the data of many years of observations of the action of drainage systems.     

Historical water storage for irrigation in the Fayum depression (Egypt)

Investigations into the much-discussed question of a historical manmade water storage lake within the Fayum depression were carried out in spring 1988. The results of the research into the dam between Itsa and Shidmuh indicate that there existed an artificial lake in the south-east of the Fayum as early as the 3rd Cent. B.C. The findings are in agreement with the reports of the classical writers. There is no reason not to identify this lake in the El-Mala'a basin with the lake the ancient (post-Ptolemaic) historians and geographers referred to as Lake Moeris. The question as to whether Herodotus in the 5th Cent. B.C. described the same lake or whether he saw the water level of the Birket el-Qarun at 19 to 21 m must, at present, remain unanswered.     

引江大型灌区的治理规划与灌排调度

1　灌排区基本情况1.1　地理概貌江汉平原由于长江、汉水的冲积成土过程的影响 ,地势从西北向东南倾斜 ,地面高程在 5 0～ 2 5ｍ(吴淞基面 ,下同 )以下。平原内部受网状水系的泥砂沉积过程中的水力泥砂的分选作用 ,以及地形局部差异的影响 ,形成了相对高差数米至十余米的沿江高地和河间湖洼地相分布的地貌特点。四湖地区位于江汉平原腹地 ,因区内有长湖、三湖、白露湖和洪湖四大湖而得名。区域面积 115 47ｋｍ2 ,行政区划有荆州市、荆门市、潜江市等 8个县 (市 )、区 ,耕地约 42 .6 7万ｈｍ2 ( 6 40万亩 )。四湖地区的西北部的丘陵地区是漳…     

第二讲现代地面灌溉机械设备(二)

3平地机械 土地是否平整,可显著影响灌溉水的利用率,一般进入田间的灌水量有1/3由于深层渗漏、积水、跑水等原因而浪费掉,即田间水利用系数只有0.6～0.7,其主要原因就是土地不平整.所以,平整土地是实施地面灌溉的先决条件.     

第二讲 现代地面灌溉机械设备(五)

6 田间灌水设备与机械 6.1 新型灌水管 用于直接将水送至灌水沟、畦的管道,均在地表面上使用. 6.1.1 聚乙烯薄膜管(LDPE或改性LLDPE俗称"小白龙") 折径300～400 mm(折径即管子扁平时的直径),直径×厚度为192×0.23 mm,256×0.45 mm,过流量可达40～80 m3/h(在地坡为2‰,工作水头0.2～1 m时),每卷长约50 m,使用时长150～250 m,中间卡环箍联接(有内外锥度的双环塑料套件),需要时还可热合塑膜管三通.     

第二讲现代地面灌溉机械设备(六)

6.3 波涌灌溉设备 波涌灌又称涌流灌或间歇灌.是地面灌溉的重大发展,20世纪70年代源于美国,80年代传入我国,实践证明它是值得大面积推广的一种先进技术.     

实用节水灌溉机械(设备)讲座第二讲现代地面灌溉机械设备(四)

5 低压输水管道 以管道替代土渠进行输水是世界各国认同的发展趋势.低压管道输水可以采用各种管材、管径的管道将水从水泵一直输送到田间进行地面灌溉,输水管道几乎全埋在地下.它所具有的优点主要是水的有效利用率高(约95%,比土渠提高30%～40%);工作压力低(≤0.02～0.2MPa,可节能20%～25%);节约土地(1%～3%);省工(40%);运行费用低;受外界干扰少(如气候、地形、经营体制、作物分区、灌水时间等);灌水快(管内流速快,流量集中),灌水周期短,节省农时;技术简单易学等.缺点主要是投资较大,但目前随着新管材、新工艺的出现,投资在日益下降.     

第二讲现代地面灌溉机械设备(三)

4 开沟(渠)机与防渗渠道成型、施工机 要提高地面灌溉水的有效利用率,输水渠道是关键.据统计,土渠输配水的损失占用水总损失的60%～80%,也就是说,我国灌溉水的有效利用率低(只有0.4左右)的原因,主要是从水源到田间的输水损失.因此,要节水就要把握住输水损失.国内外经验证明,提高地面灌溉的水利用率的主要措施是管道输水和渠道防渗,管道输水由于投资高等原因,目前推广缓慢,所以,把握输水损失主要是靠土渠输水的渠道规范化及其防渗技术.     

试从国际法视角看中日钓鱼岛之争

本文介绍了钓鱼岛名称的由来、钓鱼岛争端的实质及钓鱼岛争端中"美国因素"的考量,分析这一区域对中日两国重要的政治、经济、军事意义以及美国在钓鱼岛争端中所扮演得的角色.提出"搁置钓鱼岛主权争议,共同开发东海海洋资源"等可行的解决方案.     

A database program for enhancing irrigation district management in the Ebro Valley (Spain)

In the last decade irrigation districts in the Ebro Valley of Spain have started to use database applications to enhance their management operations. Such applications often put more emphasis on administrative issues than on water management issues. A new irrigation district management software called “Ador” is presented in this paper. This database application has been designed to overcome limitations identified in an analysis of the software used in the study area. Ador can be used in irrigation districts independently of the type of irrigation system (surface, sprinkler or trickle) and the type of irrigation distribution network (open channel or pressurised). It can even be used in irrigation districts combining different types of irrigation systems and different types of irrigation distribution networks. The software can be used with minimum district information. The goals are to manage detailed information about district water management and to promote better on-farm irrigation practices. Ador is currently used to enhance management of 62 irrigation districts accounting for some 173,000 hectares in the Ebro Valley.     

浅谈小型机械制造自动化可以有效抑制人才流失状况

本文在分析当前机械制造领域中的民营中小型企业面临人才严重流失的困境下,通过调查某典型企业应用机械制造自动化前后人才流失数据,进行分析研究表明,企业应用机械制造自动化使得企业培养定向专门人才成为可能,能有效的地抑制人才流失,降低了培训员工的培训成本。     

地理信息系统和地质统计学在昆虫生态学中的应用

该文较系统地论述了地理信息系统和地质统计学在昆虫生态学领域的应用前景,并对其未来的应用领域进行了展望。地理信息系统在昆虫生态学中主要运用时空分析和叠置分析来查明害虫发生的适宜生境及影响因子;地质统计学主要集中在害虫空间格局分布、空间插值和估计、种群时空动态以及爆发情况。