耕地复种差研究进展

Cropping intensity gap：a review

关键词:  复种  复种指数  种植频率  土地利用  土地潜力  土地集约化

Key words:  multi-cropping  multi-cropping index  cropping frequency  land use  land productivity potential  land intensification

摘要:

目的 一个区域的粮食总产受作物单产、耕地面积与复种3方面因素影响，通过缩小实际复种与潜力复种之间的差值（即复种差）来提高粮食生产能力是可行的。方法 文章从复种的理论基础出发，以“复种差概念—实际复种研究—潜力复种研究—复种差研究”为主线，系统梳理当前复种差研究的进展与问题。结果 研究发现，当前研究大多利用复种指数描述复种情况，且认为“复种差=潜力复种指数-实际复种指数”。复种指数体现的是区域的平均情况而非地块的特定情况，因此，基于复种指数估算复种差，无法针对特定地块提出具体的复种差利用策略。实际上，地块尺度复种差与（区域）生育期长度（LGP）、（作物）成熟天数（DTM）以及种植方式等因素有关。文章进而从LGP利用的视角提出了一个地块复种差研究的可行模式，认为“复种差=（LGP-现实作物DTM）/潜在作物DTM”。结论 地块尺度复种差研究能为优化资源利用方式，提高耕地集约化利用程度，提升粮食生产能力提供新的理论与方法支撑。

Abstract:

Purpose Food production is determined by three fundamental factors：crop yield，cropland area，and cropping frequency. Facing the global pressures that crop yield increase is stagnating and fertile cropland areas are constantly shrinking，food production could be enhanced by the third measurement，i.e. closing the cropping frequency gap between the actual multi-cropping and the multi-cropping potential.Method This paper we reviewed the current research activities that are relevant to multi-cropping，multi-cropping potential and cropping frequency gap.Results We found that most of the existing researches used multi-cropping index（MCI）-measured by harvested area divides cropland area in a region-for the proxy of multi-cropping，and estimated the cropping intensity gap by subtracting the MCI by the PMCI（potential multi-cropping index）. Both MCI and PMCI are the regional level measurements which ignore the field level details，suggesting that the existing estimations on cropping intensity gap are hardly able to inform intensification solutions for specific fields. In respect of the basic definitions of multi-cropping，the field level cropping intensity gap should be comprehensively determined by the Length of Growing Period（LGP）for the given region，the Date to Maturity（DTM）of individual crops，and the specific cropping approaches applied（or would be applied）. However，none of the existing researches have paid attention to these aspects. Subsequently，an innovating framework is conceptualized to re-examine the cropping frequency gap，intensification options and production impact at a field level，by considering the interaction between LGP，DTM and LGP-remained. Computationally，the new framework measures the cropping intensity gap as：GAP=（LGP-actual DTM）/potential DTM，instead of the traditional measurement：GAP=PMCI-MCI.Conclusion Our new framework provides new perspectives for relevant researches in both terms of theory and methodology，and the research outcomes are supposed to update understandings on food production and cropland use intensification.