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1.
及时准确掌握农作物种植制度时空分布信息,对于确保国家粮食安全与农业结构合理具有重要意义。随着时序遥感影像质量的不断提高,基于时序遥感数据的农作物种植制度研究备受关注。本文从研究框架、遥感特征参数以及数据产品等角度,分析了基于时序遥感数据的农作物种植制度最新研究进展。研究发现:(1)前农作物种植制度研究框架,主要包括耕地复种指数和农作物制图等相关内容,其问题在于需要高质量耕地分布数据支撑以及易将热带亚热带湿润区撂荒地误判为农作物等;(2)于红边和短波红外的新型多维度光谱指数,有助于更好地揭示农作物生长发育过程,大尺度农作物时序遥感制图取得了系列研究成果,但需要应对不同作物光谱差异细微、同种作物在不同区域和年份存在明显类内异质性的挑战;(3)尺度中高分辨率耕地复种指数产品不断丰富,但其时效性和时空连续性有待加强;(4)欧美少数国家外,目前农作物分布数据产品覆盖的作物类型有限,我国大尺度农作物种植制度数据产品欠缺,特别是复杂多熟制农业区。随着多源遥感数据时空谱分辨率的不断提高以及云计算平台性能的不断发展,我们对以下方面进行了研究展望:(1)新研究框架,建立直接提取耕作区、农作物种植模式的农作...  相似文献   

2.
The Himalayan region is a known hot spot of crop diversity. Traditional varieties (usually called primitive cultivars or landraces), having withstood the rigors of time (including harsh climatic conditions as well as attacks of insects, pests and diseases), can still be found in crop fields in rural parts of Indian Central Himalaya (ICH). These landraces harbor many desired traits from which, for example, varieties that are tolerant/resistant to abiotic/biotic stresses could be developed. In addition to the above benefits, landraces provide a basis for food security and a more varied and interesting diet. Some landraces are also known to be of medicinal value. These, along with some lesser known hill crops, are often referred to by different names such as under exploited crops, crops for marginal lands, poor person crops, and neglected mountain crops. The Himalayan region continues to be a reservoir of a large number of landraces and cultivars whose economic and ecological potential is yet to be fully understood and/or exploited. Indians have had a history of rice cultivation since ancient times. Farmers, including tribals inhabiting the IHR, still cultivate a plethora of landraces of rice and thus directly contribute towardson-farm conservation of valuable germplasm and help in the preservation of crop diversity. The present paper looks at the on-farm conservation of rice germplasm, which is still practised in the Kumaun region of ICH.  相似文献   

3.
The paper scrutinizes that the changes in any sub-system(i.e.agriculture,livestock and forest) have direct impact on biophysical and social processes in village ecosystem of the central Himalayan region.In view of this,we studied the changes in spatial patterns of agricultural land use and dependency of agroecosystem on forest and animal husbandry over a period of two decades.Based on data analysis it was found that the cultivation of some traditional crops has either been abandoned in the area or declined by 25%-85% due to introduction of cash crops viz.,potato,kidney bean and apple farming with acreage increased up to 51%-72% in the last three decades.Livestock population of different categories has declined drastically by 17%-75%,and has resulted shortage of farmyard manure,deterioration of soil quality and fertility which leads to un-sustainability of agriculture system.The changes in agrobiodiversity have led to the dramatic increase in soil loss and runoff from the croplands together with the increase pressure on forests.The economic evaluation of each crop showed higher monetary benefit from cash crops as compared to traditional crops.Among all the evaluated crops,the monetary output/input ratio was found highest(3.04) for kidney bean and lowest(1.26) for paddy.Changes in land use and management have improved household income but at the cost of forest degradation,less productive animal husbandry and loss of agrodiversity in the region.Therefore,there is an urgent need to bring desirable changes in agricultural policy,research,land use and efficient management of the resources for maintaining sustainability in agro and Himalayan forest ecosystem.  相似文献   

4.
It is of paramount importance to have sustainable agriculture since agriculture is the backbone of many nations’ economic development. Majority of agricultural professionals rarely capture the cropping patterns necessary to promote Good Agricultural Practises.Objective of this research is to explore the potential of mapping cropping patterns occurring on different field parcels on small-scale farmlands in Zimbabwe. The first study location under investigation are the International Maize and Wheat Improvement Center(CIMMYT) research station and a few neighboring fields, the second is Middle Sabi Estate. Fourier time series modeling was implemented to determine the trends befalling on the two study sites. Results reveal that Sentinel-1 synthetic aperture radar(SAR) time series allow detection of subtle changes that occur to the crops and fields respectively, hence can be utilized to detect cropping patterns on small-scale farmlands. Discrimination of the main crops(maize and soybean) grown at CIMMYT was possible, and crop rotation was synthesized where sowing starts in November. A single cropping of early and late crops was observed, there were no winter crops planted during the investigation period. At Middle Sabi Estate, single cropping on perennial sugarcane fields and triple cropping of fields growing leafy vegetables, tomatoes and onions were observed. Classification of stacked images was used to derive the crop rotation maps representing what is practised at the farming lands. Random forest classification of the multi-temporal image stacks achieved overall accuracies of 99% and 95% on the respective study sites. In conclusion, Sentinel-1 time series can be implemented effectively to map the cropping patterns and crop rotations occurring on small-scale farming land. We recommend the use of Sentinel-1 SAR multi-temporal data to spatially explicitly map cropping patterns of single-, double-and triple-cropping systems on both small-scale and large-scale farming areas to ensure food security.  相似文献   

5.
Shifting cultivation is a traditional farming system practiced in the tropical mountainous areas. Although it has been widely perceived as an economically inefficient and environmentally harmful agricultural production system, recent science reviews, however, indicate that the deleterious impacts of shifting cultivation on environment may have been overestimated. Despite the pressures of agricultural intensification in areas where shifting cultivation occurs, farmers across the tropics still maintain this traditional farming system. The objective of this study was to explore existing traditional shifting cultivation practices and their various modifications including the innovative farming techniques developed by farmers in the Chittagong Hill Tracts (CHTs), the mountainous region of Bangladesh, and examine their importance with respect to recent socio-economic and environmental changes. The study revealed that shifting cultivation still exists as the most dominant farming method which supports livelihoods and culture of the hill ethnic people. However, demand for more food and household income to meet livelihood needs of an increasing population combined with a rapid deterioration of soil and water quality over decades contributed to development of innovative farming practices through fallow land farming, crop substitution, agroforestry and homestead gardening in the CHTs. Through these farming techniques farmers maintain a strong relationship with traditional knowledge system embedded in the age-old shifting cultivation practices. Today state policies and market forces act in favor of replacement of traditional farming with intensive cash crop agriculture. It seems that disappearance of traditional farming practices from the hills may threaten local biodiversity and food security. It may be recommended that shifting cultivation should be encouraged in areas where they have potential for contributing to preservation of native biodiversity and ecosystem services, and protection of local peoples’ food security and cultural identity.  相似文献   

6.
叶面积指数Leaf Area Index(LAI)作为植被生物量指标之一,耕作区LAI不仅能反映作物的长势动态,且与农业生态、作物产量密切相关.本文通过对2001-2017年中国农田区域的MODIS-LAI长时序数据进行重建,利用Mann-Kendall检验、变异系数、重心迁移模型等方法分析了中国耕作区LAI的时空变化...  相似文献   

7.
Various kinds of human disturbances on cropland are the main reasons for soil erosion and land degradation. Farming practices in mountainous areas vary greatly among cropland plots because of the heterogeneity of biophysical conditions and differences in farmers’ management behavior. The main purpose of this paper is to develop a composite index of cropland physical disturbance intensity (CLDI) to reflect the plot-scale discrepancy of potential soil erosion in mountainous areas. The study was based on both plot survey and household interview data, collected from six typical catchments in mountainous areas of southwestern China. Four kinds of physical disturbance practices and two kinds of conservation practices during one crop rotation period were synthesized to develop the CLDI index. The rough set theory was referenced to avoid subjectivity during weight allocation. The results show that conventional tillage, deep fertilization, and manual weeding are the main causes of cropland soil erosion, whereas manure application in combination with seasonal fallow reduces soil erosion. Different crop types as well as cropland location factors determine the spatial pattern of CLDI. Crop rotation modes with major crops of tobacco and maize resulted in a maximal CLDI, and cropland plots with a distance radius of 150 meters away from households received the most intensive physical disturbance. These results are critical to help better protect rural environments in mountainous areas. Based on the results, methods to reduce cropland soil erosion are suggested.  相似文献   

8.
More than 30 ethnic groups are now living in northern mountainous regions, Vietnam, mainly relying on shifting cultivation with the fallow period being shortened from time to time. Naturally, soil fertility reduces from cycle to cycle, entailing the reduction of productivity. Large areas of moderately sloping lands suitable for upland agriculture have become bare after many cultivation-fallow cycles. The soils there have been severely degraded with more toxicity, low porosity, low water retention capacity and poor floral diversity. Normally, these lands cannot be used for food crop cultivation. So farmers in uplands have to rely on slash-and-burn practices for their livelihood. As there is no more forest with good soil in medium slopes, farmers go to cut forests in watershed, high slope lands and old forests up to the mountains‘ top. There are ecologically and environmentally very sensitive areas, so their destruction will inevitably cause hazardous consequences in the whole basin. Meanwhile,cultivation in these areas has low economic efficiency and sustainability because the crop yield may decrease very fast due to severe erosion as the higher the slope, the more serious erosion. Consequently living standards of highland farmers remain low and unstable. Sustainable farming on these lands in the perspective of a seriously deteriorated ecology and environmental is not an easy task. There have been many projects trying to help mountainous farmers get out of their vicious circle. However, due to different reasons, the results gained are low, and in some cases,things ceased to move after the projects phased out. During past few years, based on the farmer experiences, the Vietnam Agricultural Science Institute has cooperated with local and international partners to implement different projects in order to solve the problems by developing simple, easy and cheap cultivation technologies, which can be accepted and applied by local poor farmers for sustainable agricultural production. The first results of our activities offered good opportunities for sustain food production, improve soil health, recharge of aquifers,and enhanced household income for better rural lively hoods in the upland eco-regions of northern Vietnam.  相似文献   

9.
This study examines the technical efficiency (TE) differences among typical cropping systems of smallholder farmers in the purple-soiled hilly region of southwestern China. Household-, plot-, and crop- level data and community surveys were conducted to explore TE levels and determinants of typical cropping systems by using a translog stochastic frontier production function. Results indicate significant difference in TE and its determinants among cropping systems. The mean TEs of the rice cropping system (R), the rice-rape cropping system (RR), the rice-rape-potato cropping system (RRP), and the oil cropping system (O) are 0.86, 0.90, 0.84, and 0.85, respectively, which are over 1.17 times higher than those of the maize-sweet potato-other crop cropping system (MSO) and the maize-sweet potato-wheat cropping system (MSW) at 0.78 and 0.69, respectively. Moreover, Technical inefficiency (TIE) of different cropping systems is significantly affected by characteristics of the household as well as plot. However, the impact of land quality, mechanical cultivation conditions, crop structure, farming system, farm radius, household type, cultivated land area per capita, and annual household income per capital on TIE vary by cropping system. Additionally, output elasticity of land, labor, and capital, as a group, is greater than the one of agricultural machinery and irrigation. Finally, when household-owned effective agricultural labor is at full farming capacity, optimal plot sizes for the R, RR, RRP, MSO, MSW, and O cropping systems are 1.12 hm2, 0.35 hm2, 0.25 hm2, 2.82 hm2, 1.87 hm2, and 1.17 hm2, respectively.  相似文献   

10.
GlObalwa-rmingisoneoftheseriousenvironmentproblemswhichattractattentionsofscientistsandgove~entsofvariouscountries.TheglobalatmOSpherecomponentschangebecauseofhtirnanactivitiesandthedevelopmentofindustry.Theincreaseofgreenhouseeffectleadstoglobalw~ng.Basedonthepredictionofgeneralcirculationmodel(GCM),bythemiddleofnextcentury,theconcentrationofopwillbedoubledandtheglobaltemperaturewillinCreasebyZt(Han,1993;She~,1983).WestudiedthelawofvegetationalterationunderthisconditioninnortheastChinain…  相似文献   

11.
Agricultural practices are the main stay of the people of Uttranchal. Out of the total population,more than 75% people are engaged either with the main occupation of agriculture or its allied practices,dominated by traditional subsistence cereal farming.Among them, the main crops are rice, wheat, millet,barley, all types of pulses, all types of oilseeds and almost all types of fruits. The crops, vegetables and fruits of all varieties are grown in the different climatic zones such as tropical, temperate, and cold because, the region is characterized by the different altitudinal zones elevated from 200 m to more than 8000m. As a result, different climates are found from hot tropical to sub temperate and chilly cold. Pulses varieties are grown extensively. Among vegetables,potato, onion, carrot, all types of green leaf vegetables,brinzal, pumpkin, ladyfinger, pea, gram, radish,ginger, garlic, etc, are grown widely. All fruit varieties are grown in the different altitudinal zones. The mainfruits are orange, malta (a big size of orange),elephant citrus, lemon and all other types of citrus,apple, stone fruits including peach and pears, manykinds of nuts, and the fruits which are grown in the low lying areas. In spite of feasible climatic conditions,agricultural dominant society, and availability of all types of crops, the production and productivity of these crops are very low, even they are unable to meet the grain-need of the people in Uttaranchal. Agricultural crops are grown almost in all the altitudinal zones -- from the low-lying areas, which are called ‘Ga. ngarh‘, to the highly elevated region,where the legendary term is given as ‘Danda‘. The growing seasons vary according to the heights. The present paper aims to discuss the agricultural practices including cropping season, cropping pattern,land use, production of cropsagricultural system in thisand ecological aspect of Himalayan state and suggest some measures for developing farming system,which could lead the sustainability, in terms of meeting the food grain needs of the people on the one hand and restoring the ecological balance on the other.  相似文献   

12.
Agricultural systems in Thailand’s northeastern mountains are described in terms of their type of crops, marketing channels, and labor requirements. Five distinctive systems are identified: The Field crop system, Fruit tree system, Industrial tree plantation system, Specialty crop system and Agro-tourism system. The different systems are compared with each other in order to identify their respective strengths and weaknesses as development models. The Field crop system covers the largest area of agricultural land and is found in all mountainous villages but it generates very low net profits per hectare. The Specialty crop system and Agro-tourism system generate very high net profits per hectare but cover only a small land area and have a restricted spatial distribution. Expansion of these high value systems may be limited because they are capital and labor intensive and require highly skilled farmers to manage them successfully. If these constraints can be overcome, they may offer a useful model for mountain agricultural development.  相似文献   

13.
Double-and triple-cropping in a year have played a very important role in meeting the rising need for food in China.However,the intensified agricultural practices have significantly altered biogeochemical cycles and soil quality.Understanding and mapping cropping intensity in China′s agricultural systems are therefore necessary to better estimate carbon,nitrogen and water fluxes within agro-ecosystems on the national scale.In this study,we investigated the spatial pattern of crop calendar and multiple cropping rotations in China using phenological records from 394 agro-meteorological stations(AMSs)across China.The results from the analysis of in situ field observations were used to develop a new algorithm that identifies the spatial distribution of multiple cropping in China from moderate resolution imaging spectroradiometer(MODIS)time series data with a 500 m spatial resolution and an 8-day temporal resolution.According to the MODIS-derived multiple cropping distribution in 2002,the proportion of cropland cultivated with multiple crops reached 34%in China.Double-cropping accounted for approximately 94.6%and triple-cropping for 5.4%.The results demonstrat that MODIS EVI(Enhanced Vegetation Index)time series data have the capability and potential to delineate the dynamics of double-and triple-cropping practices.The resultant multiple cropping map could be used to evaluate the impacts of agricultural intensification on biogeochemical cycles.  相似文献   

14.
黑河流域中游地区作物种植结构的遥感提取   总被引：1，自引：0，他引：1  
及时、准确地获取农作物种植结构对区域水资源管理与作物产量估测等具有重要意义。随着对通过遥感手段获得作物种植结构的深入研究,如何优选遥感数据和分类器成为需要重点考虑的关键问题。针对黑河流域中游地区的作物分布与种植特点,提出一种基于多时相遥感影像与多分类器组合的作物种植结构提取方法。利用2018年18景16 m分辨率的GF-1 WFV影像,构建NDVI时间序列。根据NDVI时间序列表征的作物季相节律和物候变化规律特点,采用分层的策略,首先解译一级土地覆被类型,再解译二级土地覆被类型。一级土地覆被类型解译中,使用决策树分类方法先将NDVI特殊且易提取的水体进行解译,再使用面向对象分类方法通过分区将需借助NDVI纹理信息提取的建设用地进行解译,最后使用随机森林分类方法解译耕地、林地、草地、裸地和湿地。在对耕地的进一步分类中,使用决策树分类方法首先将具有特殊物候规律且易于区分的苜蓿类别解译出来,再将与其他类别物候差异较大的小麦解译,最后将物候相似的玉米、蔬菜及其他解译。黑河流域中游研究区内一级土地覆被分类总体精度为97.24%,卡帕系数为0.96;作物种植结构解译总体精度为86.58%,卡帕系数为0.80。此外,还分析了影响黑河流域中游研究区解译精度的4个因素：对土地覆被类别的定义、混合像元、影像分割时基础影像的选择以及分类方法的选择。通过对不同分类方法的比较发现,与仅使用最大似然分类方法、支持向量机分类方法或随机森林分类方法相比,本文提出方法的解译结果更好,解译精度更高。  相似文献   

15.
Daily and ten-day Normalized Difference Vegetation Index(NDVI) of crops were retrieved from meteorological statellite NOAA AVHRR images ,The temporal variations of the NDVI were analyzed during the whole growing season,and thus the principle of the interaction between NDIV profile and the growing status of crops was discussed,As a case in point,the relationship between integral NDVI and winter wheat yield of Henan Province in 1999 had been analyzed.By putting integral NDVI values of 60 sample counties into the winter wheat yield-integral NDVI coordination,scattering map was plotted. It demonstrated that integral NDVI had a close relation with winter wheat yield.These relation could be described with linear,cubic polynomial ,and exponential regression,and the cubic polynomial regression was the best way,In general ,NDVI reflects growing status of green vegetation ,so crop monitoring and crop yield estimation could be realized by using remote sensing technique on the basis of time serial NDVI data together with agriculture calendars.  相似文献   

16.
 近20年以来,随着我国经济结构的调整和农村劳动力的转移,部分地区冬闲田的面积呈明显增长态势。为了科学、合理及高效地利用冬闲田资源,本研究以长江中下游农业区为实验区,利用长时间序列NDVI数据,结合研究区耕地空间分布和农作物在出苗期和成熟期NDVI变化特征,构建了NDVI动态阈值法的冬闲田遥感监测方法,进而对研究区2007至2008年冬闲田的空间分布和闲置时间进行了提取分析。研究发现,2007至2008年,我国长江中下游农业区冬闲田总面积为20.55万km2,占耕地总面积的45.49%。冬闲田集中分布于研究区北部和西北部的江苏、安徽、河南、湖北、湖南和江西的西北部地区,其中,湖北、湖南和江苏是冬闲田分布面积最多的省份,3省冬闲田面积占了研究区冬闲田总面积的53.41%。  相似文献   

17.
Himalayan mountain system is distinguished globally for a rich biodiversity and for its role in regulating the climate of the South Asia.Traditional crop-livestock mixed farming in the Himalaya is highly dependent on forests for fodder and manure prepared from forest leaf litter and livestock excreta. Apart from sustaining farm production, forests provide a variety of other tangible and intangible benefits, which are critical for sustainable livelihood of not only 115 million mountain people, but also many more people living in the adjoining plains. Extension of agricultural landuse coupled with replacement of traditional staple food crops by cash crops and of multipurpose agroforestry trees by fruit trees are widespread changes. Cultivation of Fagopyrum esculentum,Fagopyrum tataricum, Panicum miliaceum, Setaria italica and Pisum arvense has been almost abandoned. Increasing stress on cash crops is driven by a socio-cultural change from subsistence to market economy facilitated by improvement in accessibility and supply of staple food grains at subsidized price by the government. Farmers have gained substantial economic benefits from cash crops. However, loss of agrobiodiversity implies more risks to local livelihood in the events of downfall in market price/demand of cash crops, termination of supply of staple food grains at subsidized price, pest outbreaks in a cash crop dominated homogeneous landscape and abnormal climate years. Indigenous innovations enabling improvement in farm economy by conserving and/enhancing agrobiodiversity do exist, but are highly localized. The changes in agrobiodiversity are such that soil loss and run-off from the croplands have dramatically increased together with increase in local pressure on forests. As farm productivity is maintained with forest-based inputs, continued depletion of forest resources will result in poor economic returns from agriculture to local people,apart from loss of global benefits from Himalayan forests. Interventions including improvement in traditional manure and management of on-farm trees,participatory development of agroforestry in degraded forest lands and policies favoring economic benefits to local people from non-timber forest products could reduce the risks of decline in agricultural biodiversity and associated threats to livelihoods and Himalayan ecosystems.  相似文献   

18.
在生长季早期获取作物的种植情况,对于农业水资源管理,尤其是缺水地区的水量分配等具有重大的意义。本文利用改进型时空自适应融合模型（ESTARFM）,将作物生长早期3—6月的Sentinel 2影像与MOD09GQ数据计算得到的NDVI数据进行融合,建立NDVI时间序列,并利用随机森林分类方法对2019年黑河流域中游地区作物种植结构进行早期识别。利用3-6月Sentinel-2 NDVI与时空融合NDVI相结合建立的时间序列,作物分类精度达到91.42%,kappa系数为0.85,相比仅使用Sentinel-2 NDVI时间序列的作物分类精度提高1.05%,kappa系数提高0.02。与使用整个作物生长期（3—10月）Sentinel-2 NDVI时间序列的作物分类结果相比,精度仅低1.53%,kappa系数仅低0.03。利用Gini系数对利用Sentinel-2 NDVI与时空融合NDVI相结合建立的时间序列进行特征重要性评估,发现Gini系数得分高于平均值的10期NDVI影像中,有6期为时空融合影像,说明时空融合获取的NDVI数据利于提高分类精度的有效性。对比使用不同长度NDVI时间序列对作物种植结构进行早期识别的精度发现,最早可在4月中旬与4月下旬分别实现对苜蓿和玉米的早期识别;玉米的分类精度受NDVI时间序列长度的影响较大,可在5月下旬实现对玉米的早期识别。  相似文献   

19.
宁夏自治区具有土地、光能、引黄灌溉等优势,为宁夏特色农作物（硒砂瓜、枸杞、大枣）的生长提供了先天条件。快速准确地获取特色农作物的种植信息不仅是宁夏特色农作物监测、估产和灾害评估的重要依据,同时也是分析特色农作物结构分布变化和评价区域特色农业生产影响的重要凭证。近年来,随着航天技术和卫星传感器的不断发展,越来越多的学者将遥感技术运用到农作物种植信息的提取研究中。但是传统的遥感调查模型都是基于中低分辨遥感数据建立的,对于新的高分数据没有完备的信息提取模型。此外,基于GF-1遥感影像对类似宁夏特色农作物（硒砂瓜、枸杞、大枣）的信息提取研究相对较少,决策条件和分类模型的选择也难以满足高分农业的需求。基于此,本文利用国产GF-1 PMS遥感影像,在分析3类特色农作物光谱特征和纹理特征的基础上,建立了面向对象的支持向量机（SVM）分类模型,总体分类精度达到94.94%,Kappa系数为0.9174。同时将分类结果与传统的SVM分类结果相比较,研究发现面向对象的SVM模型的精度更高,效果最好,纹理信息的引入使光谱特征差异较小的枸杞和大枣更容易区分,有效降低了模型错分和漏分误差,改善了模型分类结果。研究结果为实现宁夏特色农作物的快速自动化提取提供了有效途径,也为开展农作物承保和受灾定损评估体系建设提供技术支撑。  相似文献   

20.
Rapid economic growth in China has brought about great economic-social changes in rural areas, having considerable impact on the society in economy and environment. With a per capita possession of about 0.08 ha of cropland, Chinese farmers in rural areas adopt various ways in response to these changes in a bit to maintain their livelihood, wherein the agricultural system is facing one more options possible. To understand how rural communities have used different mechanisms to adapt to the economic and natural changes, we joined a survey in dry valleys of the Min upriver area under Maoxian county of western Sichuan province, southwestern China and visited the local people. Changes in the main crop cultivation have shown up an important means to keep up their household income. Farm households start seeking economic growth through diversified cultivating of cereal and economic crops in five lines, namely cereal, apple monoculture, apple and vegetables, plum and vegetables, mixed fruits and vegetables. These new lines mirror farmers’ flexibility to cope with today’s economic-social and climatic changes. The farming operation has changed all the more from a subsistence on grain to special agricultural products. Economic reforms in the early 1980 s motivated theprogress first in conversion of production from grain to fruits, and the desire to increase family income turned out to be an impetus for the subsequent events. At present, more farmers moving out of the rural areas, uneasy availability of labor force, increased opportunity cost of labors and their wages, increased farm size, and the urgent demand for the agricultural labor force, all these combine into the trend of the agricultural system of China on facing further economic-social reforms and reconstruction of the countryside across China.  相似文献   

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