华北地下水超采区冬小麦退耕的生态补偿问题探讨

压减冬小麦种植面积是有效减少华北平原地下水用量最为有效的方法。近期,国家和地方政府均出台了土地休耕政策,拟在华北地下水超采区退耕冬小麦,实现“一季休耕、一季雨养”。然而,华北平原已经出现农户主动退耕冬小麦的现象。在此背景下,明确冬小麦退耕的瞄准目标、制订合理适度的补偿标准是土地休耕政策有效实施所面对的核心问题。本文利用农户问卷数据,构建多层次logit模型分析农户种植制度决策的影响因素,并计算冬小麦退耕的机会成本,旨在确定华北平原地下水超采区土地休耕政策的瞄准目标,并为农户补偿标准的制订提供建议。结果表明：① 地块层次的土地质量和灌溉条件是解释农户种植制度差异的关键因素,近70%的四等耕地和90%以上的旱地已退出冬小麦耕作,土地休耕政策应瞄准一、二、三等土地质量的水浇地;② 相似耕作条件的地块种植春、夏玉米的净收益大致相同,土地休耕的机会成本等于种植冬小麦的净收益;③ 仅考虑冬小麦对地下水资源的影响,土地休耕政策初期以地下水回升和地下水环境恢复为主要目标时,建议以350元/亩作为补偿标准参考值,后期目标转为维持地下水资源采补平衡时,可调整至280元/亩左右。

Ecological compensation for winter wheat abandonment in groundwater over-exploited areas in the North China Plain

The North China Plain (NCP) is amongst the global "hotspots" in terms of groundwater over-exploitation, and irrigation for winter wheat is the primary cause. Shrinkage of area sown to winter wheat proves to be a practical strategy to reverse groundwater over-exploitation and to promote groundwater storage. Land retirement policy was introduced by the government to encourage the extension of spring maize single cropping system in groundwater over-exploited areas. In addition, since the 1990s, large areas in the NCP in which winter wheat and summer maize are being replaced by the single cropping system of spring maize, due to the active behaviors of farmers. Not all land parcels grow winter wheat at the moment. Therefore, it is crucial to reveal the targeted land parcels for winter wheat abandonment and to assess reasonable and proper standards for ecological compensation, prior to the implementation of land retirement policy. In this paper, a case study was carried out in Cangxian county of Hebei province. Multi-level logit models were constructed using household survey data, in order to detect the determinants across plot, household and village levels on farmers' cropping system decisions, and the opportunity costs for winter wheat abandonment were calculated using cost-benefit analysis. The aim of this study was to recognize land parcels with winter wheat and to give scientific support on standards for ecological compensation. Results showed that: (1) land quality and irrigation condition at the parcel level are two essential elements influencing farmers' cropping system decisions. Nearly 70% in total area of poor land and more than 90% in total area of unirrigated land has suffered winter wheat abandonment. The targeted land parcels for land retirement policy should be the irrigated ones with land qualities being good, relative good or relative bad. (2) There were no significant differences between the net-profits of spring maize and summer maize under similar farming conditions, and the opportunity cost for land retirement should be equal to the net-profit of winter wheat. (3) When only considering the influence of winter wheat on groundwater resources, the primary purpose of the land retirement policy is to reverse the groundwater table and to induce groundwater recovery and restoration at the preliminary stage, and a high level of 350 yuan/mu was recommended as the subsidies for ecological compensation; at a later stage, the primary purpose of the policy transited to the balance of exploitation and supplement of water resources, and a lower level of 280 yuan/mu was recommended.