Smallholder Supply Response to Marketing Board Activities in a Dual Channel Marketing System: The Case of Zambia

In recent years, parastatal grain marketing boards have re‐emerged as important elements of grain markets in eastern and southern Africa, yet little is known about how farmers are responding to their scaled up activities. This article develops a conceptual model of farmers’ production decisions in the context of dual output marketing channels (government and private sector) when output prices at harvest time and the availability of one of the marketing channels are unknown at planting time. It then applies the model to the case of Zambia and uses nationally representative household‐level panel survey data to estimate the effects of the Food Reserve Agency (FRA), the government parastatal maize marketing board, on smallholder crop production and fallow land. The FRA buys maize from smallholders at a pan‐territorial price that typically exceeds market prices in major maize producing areas. Results suggest that increases in the farmgate FRA maize price raise farmer maize price expectations, which induces a supply response. Smallholders respond to an increase in the FRA price by extensifying their maize production. On average, a 1% increase in the FRA price is associated with 0.06% increases in smallholders’ maize area planted and quantity harvested. There is also some evidence that farmers reduce the area of land under fallow in response to FRA incentives but there is no evidence of reductions in the area planted to other crops.     

市场化改革背景下我国玉米供给反应实证研究基于2008—2019年东北三省省级面板数据

目的 我国玉米供需形势变化需要国内玉米供给适时作出调整，通过分析玉米供给的影响因素及其背后的农户行为，为国家制定政策并引导农户根据市场需求调整玉米种植决策提出建议。方法 文章利用2008—2019年辽宁、吉林、黑龙江三省省级玉米播种面积和出售价格的面板数据，加入替代作物比较效益和取消玉米临时收储政策虚拟变量，基于Nerlove 模型对玉米供给反应进行实证研究。结果 （1）东北地区玉米短期缺乏价格供给弹性，长期则富有弹性；（2）东北地区玉米播种面积短期内具有一定的刚性；（3）玉米与大豆、水稻的比较效益是影响东北地区农户玉米种植决策的重要因素；（4）取消玉米临时收储政策对东北地区玉米播种面积具有显著的负向影响。结论 短期内仅通过市场价格变化调整玉米供给能力有限，还需要一些配套支持政策及时引导农户调整种植决策；取消玉米临时收储政策后要加快建立优质优价机制，引导农户种植适应市场需求的玉米品种从而增加种粮收入；通过加大“两区”政策支持，将土地、资金、设备等生产要素向优势产区集中，提升优势产区产能。     

Ex post impacts of improved maize varieties on poverty in rural Ethiopia

Public agricultural research has been conducted in Africa for decades. While many studies have examined its aggregate impacts, few have investigated how it affects the poor. This paper helps fill this gap by applying a new procedure to explore the ex post impacts of improved maize varieties on poverty in rural Ethiopia. Plot‐level yield and cost changes due to adoption are first estimated using instrumental variable and marginal treatment effect techniques where possible heterogeneity is carefully accounted for. A backward derivation procedure is then developed to link treatment effect estimates with an economic surplus model to identify the counterfactual household income that would have existed without improved maize varieties. Poverty impacts are finally estimated by exploiting the differences between observed and counterfactual income distributions. Improved maize varieties have led to a 0.8–1.3 percentage drop of poverty headcount ratio and relative reductions of poverty depth and severity. However, poor producers benefit the least from adoption due to the smallness of their land holdings.     

新品种玉米的紫色植株中花色苷色素提取方法研究

研究了从新品种玉米的紫色植株中提取花色苷类色素的方法。通过正交实验确定用乙醇浸提法制备玉米紫色植株色素的最佳条件,以柠檬酸调节酸性条件（pH3）、用80％的乙醇溶液、按料液比1：50,25℃浸提4h提取效果最好,提取率为10％,色价为4．92。利用该原料可以大量生产花色苷类色素。     

Comparing consumer preferences for color and nutritional quality in maize: Application of a semi-double-bound logistic model on urban consumers in Kenya

Consumer preferences for white maize in East and Southern Africa concerns developers of maize biofortified with provitamin A carotenoids, since carotenoids impart a yellow or orange coloration. Urban consumers’ willingness to pay (WTP) for yellow maize was estimated, using a semi-double-bounded logistic model, based on a survey of 600 maize consumers in Nairobi, Kenya, at posho mills, kiosks and supermarkets. Consumers showed a strong preference for white maize. Only a minority would buy yellow maize at the same price as white maize, and fewer consumers in the posho mills (24%) and kiosks (19%) than in the supermarkets (34%) would do so. On average, consumers need a price discount of 37% to accept yellow maize. This discount was less at the posho mills (35%) and kiosks (37%) than in the supermarkets (48%). Most respondents (76%) were aware of the existence of fortified meal and the generally showed an interest. The average premium for fortified maize was much less than the discount for yellow: 5.9% for those aware and 7.4% for those unaware. Consumer preferences were influenced by socioeconomic factors such as gender, education, income and ethnic background. Women have a stronger preference for both white maize and fortified maize than men, and consumers with more education have a stronger preference for white. Income decreases the WTP for yellow maize as well as the price elasticity, but increases the WTP for fortified maize. Consumers originating from Western Kenya have a lower preference for white, while those from Central Kenya had a stronger preference for fortified maize.     

河北省夏玉米需水量变化特征及未来可能趋势

基于1963—2015年近50年间河北省夏玉米主产区8个气象站点气象资料,采用联合国粮食与农业组织(FAO)推荐的Penman-Monteith模型和作物系数法计算夏玉米需水量,再结合《IPCC排放情景特别报告》中的两种排放情景RCP2.6(低排放情景)和RCP8.5(持续排放情景)预估的未来气候情景,探讨气候变化下未来河北省夏玉米需水量的时空演变规律。结果表明:1963—2015年河北省夏玉米需水量呈现下降趋势,在空间上大致以黄骅为高值中心,由东北向西南逐渐递减,并在邢台形成低值中心的分布特征;从未来气候变化情景来看,相对于基准时段(2015年),RCP2.6和RCP8.5情景下,在2020年、2030年、2050年、2070年未来4个典型年份夏玉米的需水量均表现出增加的特征。     

华北平原内陆盐碱区玉米品种资源耐盐性综合评价及分类

目的 华北平原内陆盐碱区是咸水补灌导致盐分积累限制玉米产能提升的典型区域，开展该区代表性玉米品种资源耐盐性评价和分类，为促进华北平原盐碱地以种适地科学利用提供理论和技术支撑。方法 文章选择华北平原内陆盐碱区生产中广泛应用的24个玉米品种，获取发芽势、发芽率、发芽指数、活力指数、胚芽长、胚芽重、胚根长、胚根重8个萌发指标，计算相对发芽率、相对发芽势、萌发指数、相对活力指数、相对胚芽长、相对胚芽重、相对胚根长、相对胚根重和盐害指数9项耐盐指标。并利用主成分分析法、加权隶属函数法和聚类分析法开展玉米品种资源耐盐性综合评价与分类。结果 （1）不同玉米品种对盐胁迫的响应有显著差异，其中萌发指标变异范围是5.11 %～84.33 %，耐盐指标的变异范围为3.7 %～56.3 %；（2）通过主成分分析方法将9个耐盐指标降维获得2个相互独立的玉米耐盐性综合评价指标，指标累计贡献率达到了87.35 %；（3）基于加权隶属函数法的各玉米品种耐盐性综合评价指数（D值）变化范围为3.19～16.22；（4）通过聚类分析，将华北平原内陆盐碱区玉米品种资源分为高耐盐品种、中耐盐品种、低耐盐品种和盐敏感品种等4个类型。结论 华北平原内陆盐碱区玉米品种资源耐盐性存在较大差异，基于主成分分析和加权隶属函数法的耐盐性综合评价指数（D值）是评价该区域玉米耐盐特性的有效指标，研究对于实现耐盐玉米品种与盐渍土壤适生匹配具有指导意义。