粮食安全的多元维度及其衡量

本文从理论上分析了粮食安全的多元维度,并为每一维度提供了衡量指标。粮食安全是一个动态的不确定性问题,综合其事前和事后维度,粮食安全又可细分为粮食供给、粮食获取、粮食利用和粮食安全稳定性四个维度。四个维度之间既存在着紧密的联系,又有各自的独立性。粮食供给在粮食安全中起着决定性作用,是粮食安全的必要条件。粮食获取是粮食安全的充分条件之一,能否获取足够的粮食取决于获取粮食的经济和物质手段。良好的水源和卫生设施的获取,以及食物处理和储存方式是粮食利用充分程度的重要影响因素。粮食安全稳定性体现在不确定性因素冲击导致粮食不安全的风险。粮食获取和利用的效果又是粮食安全事后维度的体现,食物不足发生率等指标衡量粮食获取结果;五岁以下儿童的人体测量学指标常用来反映粮食利用效果;全球饥饿指数则综合了粮食获取和利用两方面的衡量指标,具有普遍应用意义。

我国粮食安全现状的多维度衡量

文章从粮食供给、粮食获取、粮食利用以及粮食安全的稳定性四个维度较全面地分析了我国粮食安全状况。综合四个维度,我国粮食安全总体状况明显提升,超过发展中国家平均水平,与同为发展中国家的其他人口大国相比也具有一定优势,但与发达国家平均水平相比还有一定差距。我国粮食安全状况在不同维度、不同指标的表现并不均衡:人均粮食产量、膳食能量供应量、自给率等衡量的粮食供给能力明显提升;人均GDP、国内食品价格水平指数、粮食不足发生率等衡量的粮食获取能力持续增强;粮食利用维度中的全球饥饿指数显著降低,清洁饮用水源和良好卫生设施等粮食利用条件明显改善。粮食安全稳定性中的粮食价格波动指数和粮食产量变异指数较高,不利于粮食安全的稳定性。

国家粮食安全政策研究综述

粮食安全事关国运兴衰、经济发展、社会安定和民族独立,是国家安全的重要组成部分。历史上,世界各国对粮食安全问题尤为重视,采取多种措施维护粮食安全。本文首先介绍了粮食安全概念的演变历史,又从粮食供应、粮食获取、粮食利用与粮食稳定四个方面深入剖析了维护粮食安全的政策,旨在为“十四五”时期构建国家粮食安全保障体系提供借鉴参考。

Evaluation for Use Efficiency of Agricultural Resources in Grain Production:A Case Study of Changshu,Taihe and Ansai in China

This paper aims to establish an index system for evaluation of agricultural resources use efficiency(ARUE) in grain production and discuss the causes of low efficiency and high consumption of agricultural resources in Changshu of Jiangsu Province,Taihe of Jiangxi Province and Ansai of Shaanxi Province in China by analyzing the data about meteorology,soil,water consumption and grain production. Agro-ecological Zone(AEZ) method was adopted to calculate the potential productivity,and synthetically multivariate equation was used to evaluate the ARUE of study areas. This paper can be concluded as:1) the agricultural resources in grain production can be classified into five categories,i.e.,climatic resources,water resources,land resources,biological resources and assistant resources,and 15 indexes were selected to evaluate their use efficiency in grain production;2) the values of ARUE in grain production are 0.5868,0.6368 and 0.5390 respectively in Changshu,Taihe and Ansai;and 3) Changshu ranks the highest among the three study areas in terms of the use efficiency of climatic resources and biological resources(evaluation values are 0.0277 and 0.1530) ,but Taihe tops the three in terms of the use efficiency of water resources,land resources and assistant resources(evaluation values are 0.0502,0.2945 and 0.1379 respectively) . However,the ARUE remains always low in Ansai for all the resources. The inefficiencies are caused by poor grain revenue in Changshu,deficient agriculture investments in Taihe and unfavorable natural conditions in Ansai.

Changes and Effecting Factors of Grain Production in China

Based on the data from the Cost-benefit Data of Farm Produce and the China Agricultural Yearbook, this paper aims to examine the spatial and temporal change characteristics of total grain production and its affecting factors. The results show that： 1） During 1980 to 2007, total grain production increased from 3.20 ~ 108 t to 5.02 x 108 t in China, with annual increasing rate of 1.68%. From the regional disparities, most of the regions present increasing trend of total grain production except for several regions with higher level of economic development; 2） Grain sown area decreased from 1.17 × 108 ha in 1980 to 1.06 x 108 ha in 2007, which has negative effect on total grain production; 3） The increase of grain yield per unit area caused by land use intensity changes contributed to the increase of total grain yield greatly. However, as the land use intensity showed that farmers pay more attention to labor-saving input but not yield-increasing input, the less enthusiasm of farmers in grain production may become an important constraint on fu- ture grain production increase in China; 4） Based on the results, this paper proposed different land management poli- cies in different regions, for example, the government should protect cultivated land, promote large scale production. As to the less developed regions, the government should pay more attention to agricultural subsidies to promote farm- ers＇ enthusiasm in grain production.

Soil Degradation and Food Security Coupled with Global Climate Change in Northeastern China

The northeastern China is an important commodity grain region in China,as well as a notable corn belt and major soybean producing area.It thus plays a significant role in the national food security system.However,large-scale land reclamation and non-optimum farming practices give rise to soil degradation in the region.This study analyzed the food security issues coupled with global climate change in the northeastern China during 1980–2000,which is the period of modern agriculture.The results of statistical data show that the arable land area shrank markedly in 1992,and then increased slowly,while food production generally continually increased.The stable grain yield was due to the increase of applied fertilizer and irrigated areas.Soil degradation in the northeastern China includes severe soil erosion,reduced soil nutrients,a thinner black soil layer,and deterioration of soil physical properties.The sustainable development of the northeastern China is influenced by natural-artificial binary disturbance factors which consist of meteorological conditions,climate changes,and terrain factors as well as soil physical and chemical properties.Interactions between the increasing temperature and decreasing precipitation in the region led to reduced accumulation of soil organic matter,which results in poor soil fertility.Human-induced factors,such as large-scale land reclamation and non-optimum farming practices,unsuitable cultivation systems,dredging,road building,illegal land occupation,and extensive use of fertilizers and pesticides,have led to increasingly severe soil erosion and destruction.Solutions to several problems of soil degradation in this region requiring urgent settlement are proposed.A need for clear and systematic recognition and recording of land use changes,land degradation,food production and climate change conditions is suggested,which would provide a reference for food security studies in the northeastern China.

Genotypic Differences in Grain Yield and Physiological Nitrogen Use Efficiency Among Rice Cultivars

Efficient use of N in agricultural practice can increase yield, decrease production costs and reduce the risk of environmental pollution. Effects of N fertilizer application rates on grain yield and physiological N use efficiency (PE) in relation to the accumulation and redistribution of biomass and N in rice (Oryza sativa L.) cultivars were studied at two experimental farms of Nanjing Agricultural University, Nanjing, China in 2004. Three high N use efficiency (NUE) rice cultivars (Wuyunjing 7, Nanguang and 4007) and one low NUE rice cultivar (Elio) with similar growth patterns were studied under seven N rates (0, 60, 120, 180, 240, 300 and 360 kg ha -1 ). Grain yield increased with the N application rate and attained plateau at 180 kg N ha -1 for rice cultivars at each site. Increasing N rate decreased PE for biomass and grain yield. Grain yield and PE of Elio were about 20% and 18% lower than those of high NUE cultivars. Differences in biomass, N accumulation and N redistribution were observed at the post-heading stage among rice cultivars with differing NUEs. The less reproductive tillers of Elio resulted in less demand for C and N during grain filling, thus leading to lower PE of Elio compared with the high NUE rice cultivars.

Economics of Nitrogen Use in Cereal Systems in South and East Asia

A literature survey and focused interviews with experienced agronomists and socio-economists from south, east, and southeast Asian countries were conducted to determine physical and economic relationships of cereal yields and N use, using partial factor productivity （PFP） and nitrogen （N） response functions, while considering the impacts of （N） and crop grain prices. The data were drawn from FAOSTAT, World Bank, and survey results from those countries. Rice has the greatest PFP-N （70 kg grain kg^-1 N）, wheat a moderate （57 kg grain kg^-1 N）, and maize the lowest PFP-N （52 kg grain kg^-1 N） at current application levels. At potential optimal N use rates, estimates for PFP-N were 26 kg grain kg^-1 N for maize, 25 kg for rice and 16 kg for wheat. Assuming a constant average PFP-N （30 kg grain kg^-1 N） for these cereals, it is estimated that 13 Mt N would be needed to meet a projected food demand by 2020 assuming no use of other additional inputs. Assuming a 20% increase in nitrogen use efficiency （NUE） to 36 kg grain kgl N, 10.6 Mt would be needed to meet the food demand, implying an annual growth rate in N use of 1.25%. It is concluded that economically optimal N rates are relatively insensitive to changes in prices of N and cereal grain. Key interventions to improve sustainable food security include increasing N fertilizer use, improving NUE, and reducing environmental impacts.

Investigation and Analysis of Crop Germplasm Resources in Coastal Areas of Shandong Province

This study focused on the investigation of crop germplasm resources in coastal areas of Shandong Province, including 132 villages in 82 towns of 34 counties. The survey collected local varieties and wild resources of grain crops, economic crops, vegetables and fruit trees, and a total of 848 samples were collected, belonging to 54 species of 39 genera in 15 families. In this study, the current situation and growth and decline conditions of crop germplasm resources were investigated, and their botanical classification and utilization importance were analyzed. Furthermore, the conservation, development and utilization of crop germplasrp resources in coastal areas of Shandong Province were also discussed in this paper.

Research on driving forces for rural settlement land changes in China

During the rapid urbanization period, the contradiction between demand for the construction land and the preservation of cultivated land for food security is getting more and more serious in China. With the urbanization the rural settlement land is increasing instead of decreasing; This paper aims at.finding the driving forces for rural settlement land expanston. Based on land use change survey data （1996-2006） by the Ministry of Land and Resources P. R. C., this paper find, that per capita area for rural settlement land is more than per capita area for city; township and industrial land in each province except Tibet. Besides, rural settlement land area and per capita rural settlement land area are increasing while the rural poputation is decreasing in most provinces. The main problems of rural settlement land use are low efficiency, high vacancy rate, chaotic layout and illegal occupancy. Then the driving forces [br rural settlement land expansion, including economic development, family income, family scale, psychological factors, urbanization, transportation, lack of planning, limited circulation of dwelling-house land and imperfect sociat security, ate explored based on above analysis, Finalty, policy recommendations, in view of different influencing factors, are put forward to control the disorder expansion of rural setttement land.

Effects of Ratio of Row Spacing to Intrarow Spacing on Yield and Nitrogen Accumulation and Utilization of Early and Late Rice

[Objective]The aim was to provide a theoretical basis for the rational configuration of ratio of row spacing to intrarow spacing(RS/IS)of double-cropping rice.[Methods]With early rice‘Ganxin 203’and‘Zhongjiazao 17’and late rice‘Ganxin 688’and‘Wufengyou T025’as materials,the effects of RS/IS on yield,nitrogen accumulation and utilization were studied in the same planting density of31.20×104hills/hm2.[Results]The results showed that yield of early rice was higher in RS/IS2.8(30.0 cm×10.7 cm)and RS/IS2.0(25.0 cm×12.8 cm)treatment,and lower in RS/IS5.0(40.0 cm×8.0 cm)and RS/IS1.3(20.0 cm×16.0 cm)treatment,while late rice were higher in RS/IS5.0and RS/IS2.0treatment,and lower in RS/IS2.8and RS/IS1.3treatment.Total nitrogen accumulation and apparent utilization ratio of nitrogen of early rice were higher in RS/IS2.0treatment and lower in RS/IS5.0treatment,while,for late rice were higher in RS/IS2.8treatment and lower in RS/IS5.0treatment.Nitrogen requirement for 100 kg grain production of early rice was higher in RS/IS1.3treatment and lower in RS/IS2.0treatment,while,for late rice were higher in RS/IS2.8treatment,lower in RS/IS5.0treatment.[Conclusion]In sum,4 varieties of early and late rice obtained higher yield in 25.0 cm×12.8 cm and lower yield in 20.0 cm×16.0 cm,and total nitrogen accumulation,nitrogen requirement for 100 kg grain production and apparent utilization ratio of nitrogen were all lower in 40.0 cm×8.0 cm.

Genotypic variations in nitrogen use efficiency of rice cultivars at various levels of nitrogen under subtropical environment

Insufficient N supply is an important constraint to productivity of lowland rice. Studies on N nutrition of rice cultivars with different durations representing the north western part of Indo-Gangetic Plains are scanty. A field experiment was conducted during kharif seasons of 2006 and 2007 at PAU, Ludhiana to assess the differences in grain yield and N utilization of three popular rice cultivars at varying N doses. Significant differences among genotypes were observed in grain yield, N uptake, N use efficiency and N utilization efficiency. The cultivar PAU-201 was found to be superior among all the tested genotypes. Total N uptake and grain N uptake was highest in cultivar PAU-201 followed by cultivars PR-115 and PR-113. On an average, the response to applied N for grain yield was observed upto 90 kg N ha1. Grain yield increased significantly up to 90 kg N hal in cultivars PR-115 and PAU-201 and up to 120 kg N ha1 in PR-113. Apparent recovery efficiency （ARE） and Partial factor productivity （PFPN） of N was significantly reduced at higher level of N （150 kg N hal）. It was concluded that N uptake is predominant factor in grain yield formation and cultivars differ in NUE suggesting that it may be possible to develop cultivars that are efficient at low nutrient level or are capable of using N more efficiently when applied as fertilizer.

Land Suitability Assessment and Landuse Planning： A Prerequisite for Food Security and Climate Change Adaptation

Though Ghana＇s crop yield growth rate was at 17%, 5% of every 1.2 million Ghanaians have insufficient and limited access to nutritious food. Climate change and climate variability have enormously affected the state of agricultural productivity and hence could result in food insecurity. As many ongoing projects use Boolean suitability analysis, land use planning, management recommendations sores, it still remains inadequate to support rural resource poor farmers. This then, is affecting livelihood and agricultural productivity. In this paper, a geostatistical quantitative method to support a geographic information system （GIS） based on multi-criteria decision support system （GMCDSS） for an enhanced land suitability assessment （LSA） and landuse planning （LP） was devised. Project findings indicated that, recommended farm inputs could be estimated and applied accordingly at farm plot levels Soil amendment indicators （e.g., 1.0 t/ha lime ＋ 1.0 t/ha gypsum was estimated for liming） was quantified and currently, farmers can save money in soil fertility management. It has shown that, instead of applying 5.0 t/ha poultry manure （PM） or five bags of N-P-K fertilizer （rate of 15： 15： 15 N-P2O5-K2O/ha） ＋ two bags of sulphate of ammonia （SA）, a farmer may apply 2.0 t/ha PM ＋ two bags 15：15：15 N-P2O5-K2O/ha ＋ one bag of SA. GMCDSS assessment has proved to be fundamental in： （1） urban planning; （2） ensuring food security; （3） poverty reduction and interventions to the effects of climate change and climate variability.

Grain Production Driven by Variations in Farmland Use in China:An Analysis of Security Patterns

自从1978年改革开放以来,随着经济的迅速发展,中国的耕地利用格局发生了很大的变化。耕地数量和质量的变化直接导致粮食生产的变动。本文利用来自政府部门的农业统计数据,分析了1978-2004年间中国耕地利用水平的时空动态格局,并通过构建"粮耕弹性系数"来反映耕地利用变化与粮食生产的互动关系。研究结果表明:耕地投入的增加和质量的提升在一定程度上缓解了1978年以来我国耕地资源严重流失给粮食生产安全带来的压力;自改革开放以来,中国耕地利用水平呈现由经济快速发展带来的普遍性提升局面,并随着经济发展程度由东南沿海向内陆递减,耕地利用水平的提升速率也呈现由东南沿海向内陆梯级递减态势。然而,耕地集约利用程度的不断提升,并不一定会带来粮食产量的持续稳定增长。耕地集约利用增长的边际效用递减特性,使得中国粮食生产安全的保障已逐步由耕地集约利用水平的提升转向了耕地面积的保护,由此导致耕地资源的数量成为了左右粮食生产安全的关键,这也为当今中国制定严格的耕地保护目标和战略提供了现实的科学依据。

Improving Yield and Nitrogen Use Efficiency Simultaneously for Maize and Wheat in China： A Review

Achieving both high yield and high nitrogen use efficiency （NUE） simultaneously has become a major challenge with increased global demand for food, depletion of natural resources, and deterioration of environment. As the greatest consumers of N fertilizer in the world, Chinese farmers have overused N, and there has been poor synchrony between crop N demand and N supply because of limited understanding of the N uptake-yield relationship. To address this problem, this study evaluated the total and dynamic N requirement for different yield ranges of two major crops （maize and wheat）, and suggested improvements to N management strategies. Whole-plant N aboveground uptake requirement per grain yield （Nreq） initially deceased with grain yield improvement and then stagnated, and yet most farmers still believed that more fertilizer and higher grain yield were synonymous. When maize yield increased from 〈 7.5 to 〉 12.0 Mg ha-I, Nreq decreased from 19.8 to 17.0 kg Mg-1 grain. For wheat, it decreased from 27.1 kg Mg-1 grain for grain yield 〈 4.5 Mg ha-1 to 22.7 kg Mg-1 grain for yield 〉 9.0 Mg ha-1. Meanwhile, the percentage of dry matter and N accumulation in the middle-late growing season increased significantly with grain yield, which indicated that N fertilization should be concentrated in the middle-late stage to match crop demand while farmers often applied the majority of N fertilizer either before sowing or during early growth stages. We accordingly developed an integrated soil-crop system management strategy that simultaneously increases both grain yield and NUE.

A Review and Implication of Land Fallow System Research

Land fallow is of great significance for undertaking land reclamation, safeguarding national food security, promoting environmental improvements and ensuring the sustainable use of land resources. This paper reviews the important achievements in three areas of research on the land fallow system. It reviews and compares the land fallow system in different countries and regions of the world; it examines the response of farmers to the land fallow system and ecological environment; and it looks at the economic effects of the land fallow system. Based on Chi- na＇s rotation system for cultivated land, some relevant policy implications are put forward. Based on the different degrees of land damage, the evaluation system and the subsidy accounting standard for fallow land are formulated, and the compulsory fallow and voluntary participation of the niche fallow are targeting. The land fallow system should improve both the regulatory and the restraint mechanisms, improve the environmental awareness and en- vironmental protection skills of farmers, change the production behaviors of farmers, and encourage farmers to change to high coverage crops to protect the land. In view of the negative effects produced by implementation of the fallow system should take corresponding management and compensation measures.