有机—常规农业中作物产量差距分析

THE CROP YIELD GAP BETWEEN ORGANIC AND CONVENTIONAL AGRICULTURE

关键词:  有机农业 常规农业 产量差异 生产潜力 世界食品安全 农业系统设计

Key words:  organic agriculture  conventional agriculture  yield gap  potential production  world food security  farming system design

摘要:

有机农业能否生产足够的粮食以保障世界粮食安全，是科学家们历来针对有机农业对未来农业贡献争论的焦点，而在这场争论中有机农业与常规农业的产量比较又是讨论的中心点。为此，文章根据已发表研究成果，编制和分析了一个包含362个有机—常规作物产量比较资料的大型数据库。结果表明，单品种有机作物平均产量为常规作物产量的80%，差别是显著的（标准差为21%）。数据库中有机作物产量因作物类型与种植地区的差异而存在显著差别。分析结果为文章的假设提供了一些支持，即当常规作物产量增加时，有机—常规作物产量差距也增大，但这种关系不甚明显。这一假设背后的基本原理是，当常规作物产量很高，且相对接近潜在产量或水分限制产量时，营养胁迫就成为限制产量进一步提升的因子，因为每个潜在产量或水分限制产量的定义中都有低病虫害或病虫害得到良好控制的限定条件，但这些限定条件在有机农业中难以实现。文章通过有机—常规农业方面文献对研究结果进行了讨论，并细致阐述了研究问题以期获取创新性理论观点。文章观点基于作物在田间小环境水平，因有机农业系统在保持养分有效性面临一定挑战，如应用在作物轮作、农场及大区域等更高级系统水平中常规农业与有机农业平均产量差距可能大于20%。值得特别注意的是豆类作物在轮作、农场、大区域等农业系统中的作用，与在农场、大区域水平下有机肥获取的可能性。因此，未来研究工作应集中评估高级系统中（例如农场、大区域及全球系统水平）的两种农业类型的相对产量，并且应特别注意在这种情况下有机与常规农业中养分的有效性。

Abstract:

A key issue in the debate on the contribution of organic agriculture to the future of world agriculture is whether organic agriculture can produce sufficient food to feed the world.Comparisons of organic and conventional yields play a central role in this debate.We therefore compiled and analyzed a meta-dataset of 362 published organic-conventional comparative crop yields.Our results show that organic yields of individual crops are on average 80%of conventional yields，but variation is substantial（standard deviation 21%）.In our dataset，the organic yield gap significantly differed between crop groups and regions.The analysis gave some support to our hypothesis that the organic-conventional yield gap increases as conventional yields increase，but this relationship was only rather weak.The rationale behind this hypothesis is that when conventional yields are high and relatively close to the potential or water-limited level，nutrient stress must，as per definition of the potential or water-limited yield levels，be low and pests and diseases well controlled，which are conditions more difficult to attain in organic agriculture.We discuss our findings in the context of the literature on this subject and address the issue of upscaling our results to higher system levels.Our analysis was at field and crop level.We hypothesize that due to challenges in the maintenance of nutrient availability in organic systems at crop rotation，farm and regional level，the average yield gap between conventional and organic systems may be larger than 20% at higher system levels.This relates in particular to the role of legumes in the rotation and the farming system，and to the availability of（organic）manure at the farm and regional levels.Future research should therefore focus on assessing the relative performance of both types of agriculture at higher system levels，i.e.the farm，regional and global system levels，and should in that context pay particular attention to nutrient availability in both organic and conventional agriculture.