The potential of a herbicide resistant maize technology for Striga control in Africa

Striga is an obligate parasitic weed that attacks cereal crops in sub-Saharan Africa. In Western Kenya, it has been identified by farmers as their major pest problem in maize. A new technology, consisting of coating seed of imidazolinone resistant (IR) maize varieties with the imidazolinone herbicide, imazapyr, has proven to be very effective in controlling Striga on farmer fields. To bring this technology to the farmer, a sustainable delivery system needs to be developed, preferably with substantial participation of the private sector. To help extension agents and seed companies to develop appropriate strategies, the potential for this technology was analyzed by combining different data sources into a Geographic Information System (GIS). Superimposing secondary data, field surveys, agricultural statistics and farmer surveys made it possible to clearly identify the Striga-prone areas in western Kenya. Results found that Striga affected a maize area of 246,000 ha annually, with a population of 6.4 million people and maize production of 580,000 tons, or 81 kg/person. Population density in this area is high at 359 people/km². A survey of 123 farmers revealed that 70% of them have Striga in their fields. A contingent valuation (CV) survey indicated that farmers would, on average, be willing to buy 3.67 kg of the IR-maize seed each at current seed prices, sufficient to sow 44% of their maize area. By extrapolation over the maize area in the zone, total potential demand for IR-maize seed is estimated at 2000–2700 tons annually. Similar calculations, but based on much less precise data and expert opinion rather than farmer surveys or trials, gives an estimate of the potential demand for IR-maize seed in Africa of 153,000 tons.     

不同灌水方式和施肥量对青贮玉米生长和产量的影响

青贮玉米是河北省粮改饲的主要目标作物。为制定合理的水肥管理措施,提高青贮玉米的产量,选取灌水方式和施肥量作为因子进行青贮玉米试验。灌水方式设置畦灌和沟灌两个水平,施肥量设置4个水平,肥料用量在300~750 kg/hm^+2之间。研究结果表明,沟灌与畦灌相比,株高和鲜重分别增加2.2%和3.6%,沟灌有利于青储玉米的生长和产量的提高。施肥量对青储玉米的生长和产量影响显著,施肥量600 kg/hm^+2时青储玉米生长状况和产量最好,与750、450和300 kg/hm^+2施肥量水平相比,株高、叶面积指数、叶绿素和鲜重分别增加0.11%~27.8%、4.01%~10.55%、1.1%~1.8%和3.6%~15.6%。青储玉米鲜重产量介于69.09至81.4 t/hm^+2之间。相关性和回归分析结果表明青储玉米鲜重与株高和叶面积指数之间呈极显著正相关,沟灌、施肥量600 kg/hm^+2的处理组合有助于株高和叶面积生长,因此也有助于获得较高的青储玉米产量。     

基于SWAT模型的沂蒙山水土流失治理区地表水与地下水转化规律研究

为研究沂蒙山水土流失治理区,气候及植被覆盖变化影响下,水资源转化规律,以蒙阴县岸堤水库控制流域为研究对象,采用归一化植被指数(NDVI)为指标,分析植被覆盖的时空变化规律,采用分布式水文模型SWAT研究流域水文要素的时空演变规律,定量分析地表水与地下水转化量.计算结果表明:2000-2016年,流域NDVI呈增大趋势,...     

A comparative analysis of rainfed and irrigated agricultural production in Ethiopia

Ethiopia’s economy is dependent on agriculture which contributes more than 50% to GDP, about 60% to foreign exchange earning and provides livelihood to more than 85% of the population. Ethiopia has a large potential of water resources that could be developed for irrigation. Despite the large water resources, Ethiopia continues to receive food aid to about 10% of the population who are at risk annually, out of a total of more than 67 million. The government of Ethiopia is committed to solving this paradox through an agricultural led development program that includes irrigation development as one of the strategies. This paper compares rainfed and irrigated agricultural production in Ethiopia. Using the stochastic production frontier approach, the study concludes that irrigation development in Ethiopia is a viable development strategy but attention needs to be paid to improving the technology available to farmers under both rainfed and irrigated production.     

河南省烟区灌溉水全盐量和氯含量状况

通过对河南省烟区 135 3个灌溉水样分析表明 ,全省烟区灌溉水全盐量平均为 380 .1m g/ L,氯含量平均为31.98mg/ L。五大植烟区比较 ,全盐含量顺序为 :豫东 >豫中 >豫西 >豫南 >豫西南 ;氯含量顺序为 :豫东 >豫中 >豫南 >豫西南 >豫西。全省约有 80 %烟田灌溉水氯含量比较适宜。     

Regional simulation of maize production in tropical savanna fallow systems as affected by fallow availability

Upscaling of crop models from the field scale to the national or global scale is being used as a widespread method to make large-scale assessments of global change impacts on crop yields and agricultural production. In spite of the fact that soil fertility restoration and crop performance in many developing countries with low-input agriculture rely strongly on fallow duration and management, there are only few approaches which take into account the effect of fallowing on crop yields at the regional scale. The objectives of this study were to evaluate the sensitivity of maize yield simulations with the Environmental Policy Integrated Climate (EPIC) model to fallow availability at the field and regional scale and (2) to present a novel approach to derive a model-based estimate of the average fallow availability within a typical catchment of the sub-humid savanna zone of West Africa. Therefore, the EPIC model has been validated at the field scale and then incorporated into a spatial database covering a typical catchment within the sub-humid savanna zone of West Africa with 121 sub-basins. Maize-fallow rotations have been simulated within 2556 quasi-homogenous spatial units and then aggregated to the 10 districts within the catchment assuming three different scenarios of fallow availability: 100% of the bush-grass savanna area is available and used in fallow-crop rotations (FU100), 50% of the bush-grass savanna area is available and used in fallow-crop rotations (FU50) and 25% of the bush-grass savanna area is available and used in fallow-crop rotations (FU25). A new aggregation procedure has been developed which is based on changes in the frequency of fallow-cropland classes within the sub-basins to render the simulation results in the spatial database sensitive to changes in fallow availability. Comparison of the average simulated grain yield with the mean yield over the catchment shows that the simulations overestimate maize yields by 62%, 44% and 15% for scenario FU100, FU50 and FU25, respectively. The best agreement between simulated and observed crop yields at the district scale was found when using the assumption that 25% of the savanna is available as fallow land under the present cropping patterns, which corresponds to a fallow-cropland ratio of 0.9. Comparison with farm surveys shows that the combination of remote sensing and dynamic crop modelling with yield observations provides realistic estimates of effective fallow use at the regional scale.     

园林绿化技术与养护管理的重要性——浅议中南地区城市居住小区绿化与养护中存在的问题及对策

现代城市居住区绿化关系到居民的生活质量,是城市文明程度和居民文化素质水平的标志,文章指出了中南地区居住小区绿化中存在的问题,提出以人为本,天人合一、充分利用再生绿化空间、强化绿化技术、完善绿地养护管理等措施提高居住小区绿化水平。     

安徽淮北平原井灌几个问题的探讨

安徽淮北平原宜井灌溉面积占总耕地面积近80%。从该区井灌水量平衡分析入手，指出在一般干旱年份（P=75%）淮北平原井灌区的灌溉率（可灌面积/耕地面积）仅为54%左右，即使考虑短期超采，缺水率仍达23%；由于存在两类不均匀系数，井灌的实际可开采程度只有可开采地下水资源量的70%左右，考虑这一因素的影响，对井灌区的地下水资源量进行了校核，结果表明对于一次灌溉而言井灌区的地下水实际可开采量大于灌溉需水量，完全能满足灌溉开采的需求；同时，推荐了该区合理的机井数量、布井方式及井点密度，并就井灌工程建设和地下水的开发利用提出了几点建议。     

基于多源数据的华北平原夏玉米种植区划研究

精准识别农业生产环境信息和农业生产特征,对气象、土壤和作物等多源数据进行综合分类,是提高农业资源利用效率和优化农业种植结构的基础。本研究基于近20年（1998~2017年）气象数据和华北五省的玉米单产统计数据,首先构建了华北平原气候资源和玉米生产时空分布特征数据库,研究区内的降雨量、活动积温、日照时数、太阳辐射和玉米单产均存在显著的时空变化;利用作物精细种植区划方法,将华北平原夏玉米种植区分为极不适宜区、不适宜区、较适宜区、适宜区、极适宜区五大类,各类面积分别占总体的比例约为10%、11%、25%、30%、24%;进一步通过环境类别归属度分析方法,将每一大类分为5小类,概率大于75%的相对稳定区域约占总面积的63%,小于75%的波动区域约占37%;极不适宜区、不适宜区和较适宜区,三类时空分布比较稳定,隶属度为100%分别占各类面积的87.67%、70.41%和84.28%,波动区主要发生在极适宜区和适宜区,以及适宜区和较适宜区之间。本研究构建的华北平原夏玉米精细区划结果,对提高研究区资源利用效率和优化玉米产业布局具有重要的指导意义。     

Rose-scented geranium (Pelargonium capitatum × P. radens) growth and essential oil yield response to different soil water depletion regimes

Effective irrigation management in arid and semi-arid regions, like South Africa, could increase crop yield and thereby improve productivity of scarce fresh water resources. Experiments were conducted at the Hatfield Experimental Farm of the University of Pretoria, South Africa, from 2004 to 2006, to investigate the effect of soil water depletion regimes on rose-scented geranium (Pelargonium capitatum × P. radens cv. Rose) essential oil yield, essential oil composition and water-use efficiency in an open field and a rain shelter. Four maximum allowable soil water depletion levels (MAD), 20, 40, 60 and 80% of the plant available soil water (ASW) in the top 0.8 m root zone, were applied as treatments. Plant roots extracted most soil water from the top 0.4 m soil layer. Increasing the soil water depletion level to 60% and higher resulted in a significant reduction in herbage mass and essential oil yield. Water stress apparently increased the essential oil concentration (percentage oil on fresh herbage mass basis), but its contribution to total essential oil yield (kg/ha oil) was limited. Irrigation treatments did not affect essential oil composition. An increase in maximum allowable depletion level generally resulted in a decrease in leaf area and an increase in leaf to stem fresh mass ratio. Up to 28% of irrigation water could be saved by increasing maximum allowable depletion level of ASW from 20 to 40%, without a significant reduction in essential oil yield.     

小流域时段降雨量空间插值方法研

在作小流域分布式水文模型研究时，首先需要对时段降雨进行空间插值。本文基于时段降雨与年（月）降雨量的不同特点，以桑园流域为例，结合空间信息技术，通过分析小流域时段降雨与经度、纬度、高度等因子的内在关系，提出了一种适用于小流域的时段降雨空间插值方法——回归距离平方反比法（RIDS法），并与距离平方反比法（IDS法）和梯度距离平方反比法(GIDS)作了对比。通过对桑园流域2003年512个时段降雨进行空间插值对比试验，计算结果表明RIDS法的平均相对误差为4.0％，IDS法的平均相对误差为9％，GIDS法的平均相对误差为30.4％，本文提出的RIDS方法的计算结果明显优于IDS法和GIDS法。     

山东省节水灌溉动态变化研究

节水灌溉是解决我国农业干旱缺水的根本性措施,它可以带来显著的经济、社会效益.山东省属水资源缺乏地区,农业用水量约占总用水量的74%,发展节水灌溉势在必行.鉴于此,对1996--2005年山东省有效灌溉面积、节水灌溉面积及二者比例的动态变化进行了分析.结果表明:1996-2005年山东省有效灌溉面积总体有所增加,增幅不大;节水灌溉面积有较大增长,平均每年增加9.314 1万hm2;后者占前者的比例逐年上升,平均每年增长1.903%.而各市有效灌溉面积、节水灌溉面积及二者比例的变化差异性比较明显.山东省整体的节水灌溉效果良好,但发展不够平衡,有些地区仍需加大推广力度.     

Exante assessment of dual-purpose sweet potato in the crop–livestock system of western Kenya: A minimum-data approach

Mixed crop–livestock systems have a crucial role to play in meeting the agricultural production challenges of smallholder farmers in sub-Saharan Africa. Sweet potato is seen as a potential remedial crop for these farmers because of its high productivity and low input requirements, while its usefulness for both food and feed (dual-purpose) make it attractive in areas where land availability is declining. In this paper, we develop and apply a ‘minimum-data’ methodology to assess exante the economic viability of adopting dual-purpose sweet potato in Vihiga district, western Kenya. The methodology uses and integrates available socio-economic and bio-physical data on farmers’ land use allocation, production, and input and output use. Spatially heterogeneous characteristics of the current system regarding resources and productivity are analyzed to assess the profitability of substituting dual-purpose sweet potato for other crops currently grown for food and feed. Results indicate that a substantial number of farmers in the study area could benefit economically from adopting dual-purpose sweet potato. Depending on assumptions made, the adoption rate, expressed as the percentage of the total land under adopting farms, is between 55% and 80%. The analysis shows that the adoption rate is likely to vary positively with the average total yield of dual-purpose sweet potato, the harvest index (the ratio between tuber and fodder yields), the price of milk, and the nutritional value of available fodder. This study demonstrates the usefulness of the minimum-data methodology and provides evidence to support the hypothesis that dissemination of the dual-purpose sweet potato could help improve the livelihoods of smallholder farmers operating in mixed crop–livestock systems in east Africa.     

Modeling soil carbon sequestration in agricultural lands of Mali

Agriculture in sub-Saharan Africa is a low-input low-output system primarily for subsistence. Some of these areas are becoming less able to feed the people because of land degradation and erosion. The aim of this study is to characterize the potential for increasing levels of soil carbon for improving soil quality and carbon sequestration. A combination of high- and low-resolution imagery was used to develop a land use classification for an area of 64 km² near Omarobougou, Mali. Field sizes were generally small (10–50 ha), and the primary cultivation systems are conventional tillage and ridge tillage, where tillage is performed by a combination of hand tools and animal-drawn plows. Based on land use classification, climate variables, soil texture, in situ soil carbon concentrations, and crop growth characteristics, the EPIC-Century model was used to project the amounts of soil carbon sequestered for the region. Under the usual management practices in Mali, mean crop yield reported (1985–2000) for maize is 1.53 T ha⁻¹, cotton is 1.2 T ha⁻¹, millet is 0.95 T ha⁻¹, and for sorghum is 0.95 T ha⁻¹. Year-to-year variations can be attributed to primarily rainfall, the amount of plant available water, and the amount of fertilizer applied. Under continuous conventional cultivation, with minimal fertilization and no residue management, the soil top layer was continuously lost due to erosion, losing between 1.1 and 1.7 Mg C ha⁻¹ over 25 years. The model projections suggest that soil erosion is controlled and that soil carbon sequestration is enhanced with a ridge tillage system, because of increased water infiltration. The combination of modeling with the land use classification was used to calculate that about 54 kg C ha⁻¹ year⁻¹ may be sequestered for the study area with ridge tillage, increased application of fertilizers, and residue management. This is about one-third the proposed rate used in large-scale estimates of carbon sequestration potential in West Africa, because of the mixture of land use practices.     

Salt River Project experience in conversion from agriculture to urban water use

Salt River Project (SRP) was established in 1903 to deliver water to farms on about 250,000 ac (100,000 ha) located in South-Central Arizona. While SRP continues to deliver water to the entire area, today only about 10% of that land is still in agriculture. The remainder has been urbanized. Urbanization of the vast majority of water service area has caused SRP to rethink and adjust every aspect of its business, from daily operation and maintenance to the overarching issues of liability and public involvement. Some of the issues being addressed and lessons learned are addressed in this paper.     

Operational forecasting of South African sugarcane production: Part 1 – System description

Commercial sugarcane crops in South Africa are grown under a wide range of agronomic and socio-economic conditions. These factors, together with climatic variation have resulted in a 17% variation in sugarcane production and there is considerable scope to improve productivity through accurate and timeous forecasts. This paper reports on the development of an operational crop forecasting system based on a simulation model. The country’s entire area of sugar production was subdivided into homogeneous climate zones using a wide range of data and expert opinion. These zones serve as simulation units within the system and model input and area aggregation data were obtained for each climate zone. Irrigation is simulated according to typical, zone specific strategies taking into account water use restrictions. Simulations of crops growing in the current year are completed using 10 historic seasons to substitute the remainder of the season. The selection of these seasons is based on the climate outlook. Reports containing information for national, regional and site specific cane production are generated and distributed to industry stakeholders. To the authors’ knowledge, this is the first national scale model-based operational yield forecasting system for sugarcane. Possible future improvements to the system may include stochastic input variables, more representative irrigation simulations, quantifying forecast uncertainty and providing suitable reference crop yield. The system is evaluated in another paper.     

The Experience of Irrigation Management Transfer in Ghana: A Case Study of Dawhenya Irrigation Scheme

Government disengagement from day-to-daymanagement of irrigation infrastructure hasbecome a widespread strategy in Asia,Africa and Latin America. This paperexamines a case study of managementtransfer of a rice irrigation scheme inGhana. The criteria used relate toagricultural, financial and economicperformance and environmental sustainability.The study showed that whilstboth cropping intensity and cultivated areadecreased after transfer, the relativelyhigh yields were sustained. The averageproduction cost before transfer decreasedby about 7% from $827/ha to $774/haafter transfer. Most importantly, averagenet income increased by more than 100%from $260/ha to $549/ha after transfer.Very high financial self-sufficiency ratioscoupled with low running cost achieved bythe farmers' co-operative led to theconclusion that transfer has resulted inbetter performance so far.     

多旋翼无人机辅助籼粳杂交稻制种授粉研究

水稻是浙江省最主要的粮食作物,而籼粳杂交稻品种已成为浙江省的主要水稻种植品种类型。但籼粳杂交稻制种是一种劳力密集型技术,其中水稻授粉阶段主要依靠人工采用绳索、竹竿或木杆振动父本和自然风力辅助授粉。随着近年来中国农用无人机的发展与研究,为杂交水稻制种辅助授粉机械化提供了可能。以四旋翼无人机为例,通过田间授粉试验、花粉密度观测、结实率测算,考察农用无人机和人工拉绳的授粉效果。结果显示,无人机辅助授粉与人工拉绳相比效果相当,即花粉统计为95个/视野左右,平均结实率为27%左右。但无人机辅助授粉效率是人工的10倍以上,节约50%的人力成本,同时克服种植地形环境等困难,有助于机械化水平的提升。     

带有导流板的蜗形滞流器三维数值模拟

为了在不减少流通面积条件下提高新型改善城市内涝装置的蜗形滞流器节流效率,判断能否将其投入实际应用.采用VOF两相流计算方法对蜗形滞流器外特性进行模拟分析,结果发现:试验曲线与模拟曲线吻合度较好,说明该模拟方法可以较为准确反映蜗形滞流器的流动特性;未设导流板的蜗形滞流器的节流效率为18.2%,在其内部加设导流板后,最终节流效率提高约22.7%;加设导流板的蜗形滞流器节流效果普遍在30.0%以上,并且节流效率与导流板的角度α相关,但并非呈线性关系,在α=15°左右时,其节流效率可达到最高约40.9%.     

Measuring the costs of African animal trypanosomosis,the potential benefits of control and returns to research

This paper addresses issues surrounding measurement of the potential productivity gains from new livestock technologies and the returns to international livestock research. The approach, applicable to many livestock production constraints and technologies, uses geographic information systems (GIS) to spatially link a biophysical herd simulation model with an economic surplus model. The particular problem examined is trypanosomosis in cattle in Africa, and the potential research product is a multi-component vaccine. The results indicate that the potential benefits of improved trypanosomosis control, in terms of meat and milk productivity alone, are $700 million per year in Africa. The disease now costs livestock producers and consumers an estimated $1340 million annually, without including indirect livestock benefits such as manure and traction. Given an adoption period of 12 years, a maximum adoption rate of 30%, a discount rate of 5%, and a 30% probability of the research being successful within 10 years, the net present value of the vaccine research is estimated to be at least $288 million, with an internal rate of return of 33%, and a benefit/cost ratio of 34:1. ©