Effects of Land Management Practices on Labile Organic Carbon Fractions in Rice Cultivation

A research trial with four land management practices, i.e., traditional tillage-fallow (TTF), traditional tillage-wheat (TTW), conservation tillage-fallow (CTF) and conservation tillage-wheat (CTW), was sampled in the 15th year after its establishment to assess the effects of different management practices on labile organic carbon fractions (LOCFs), such as easily oxidizable organic carbon (EOC), dissolved organic carbon (DOC), particulate organic carbon (POC) and microbial biomass carbon (MBC) in a typical paddy soil, Chongqing, Southwest China. The results indicated that LOCFs were significantly influenced by the combination of no-tillage, ridge culture and crop rotation. And, different combination patterns showed different effectiveness on soil LOCFs. The effects of no-tillage, ridge culture and wheat cultivation on EOC, DOC, POC and MBC mainly happened at 0-10cm. At this depth, soil under CTW had higher EOC, DOC, POC and MBC contents, compared to TTF, TTW and CTF, respectively. Moreover, the contents of LOCFs for different practices generally decreased when the soil depth increased. Our findings suggest that the paddy soil in Southwest China could be managed to concentrate greater quantities of EOC, DOC, POC and MBC.

Classification and Gradation of Cultivated Land Quality in Bishan County of Chongqing, China

The conflicts among food security, economic development and ecological protection are the “sticking point” of undeveloped southwestern mountainous areas of China. The objectives of this study are to identify appropriate inte- grated indicators influencing the classification and gradation of cultivated land quality in the southwestern mountainous area of China based on semi-structure interview, and to promote the monitoring of cultivated land quality in this region. Taking Bishan County of Chongqing as a study case, the integrated indicators involve the productivity, protection, ac- ceptability, and stability of cultivated land. The integrated indicators accord with the characteristics of land resources and human preference in southwestern mountainous area of China. In different agricultural zones, we emphasize different indicators, such as emphasizing productivity, stabilization and acceptability in low hilly and plain agricultural integrative zone (LHP-AIZ), protection, productivity and stability in low mountain and hill agro-forestry ecological zone (LMH-AEZ), and acceptability in plain outskirts integrative agricultural zone (PO-IAZ), respectively. The pronounced difference of classification and gradation of cultivated land, regardless of inter-region or intra-region, is observed, with the reducible rank from PO-IAZ, LHP-AIZ to LMH-AEZ. Research results accord with the characteristics of assets management and intensive utilization of cultivated land resources in the southwestern mountainous area of China. Semi-structure interview adequately presents the principal agent of farmers in agricultural land use and rural land market. This method is very effective and feasible to obtain data of the quality of cultivated land in the southwestern mountainous area of China.

山区合适耕地经营规模确定的实证研究——以重庆市为例

在地形起伏、地块破碎、分布半径较远等约束下,山区多大的经营规模是合适的?这是目前必须弄清的科学问题之一。使用480份有效调查问卷,以投入农业的劳动力为测算单位,以劳均纯收入为评价指标,分作物类型和地块分布半径,构建计量经济模型,测算不同条件下合适的耕地经营,结果表明:(1)在现有社会经济条件下,样本村农业土地适度规模经营面积为24~32亩,适度规模下的劳均纯收入远高于当前农村人均纯收入,且与城镇居民的差距明显缩小。(2)作物类型对适度规模影响不大,但对农民纯收入产生较大作用。经济作物和粮食作物的适度规模分别为24.33亩、24.63亩,差异不显著,但种植经济作物和粮食作物在适度规模下的劳均纯收入相差3638元,巨大的差距将促使经济作物种植面积不断扩大。(3)距离对适度规模影响较大,但对劳均纯收入影响不大。0.5 km内、0.5~1 km的适度规模分别为28.62亩、31.83亩,单位劳动力的适度规模相差3亩,这表明距离是目前从事农业生产时劳动力投入时须考虑的重要因素。但是,对应的劳均纯收入相差较小,又说明伴随耕作距离的增加,更多的投入主要依靠机械来完成,从而带动适度规模的扩大。1 km外的建模未通过检验,也进一步说明未实现规模经营、没有进行机械化耕作、离家远的土地收支严重不平衡,撂荒严重,规模化经营、机械化耕作是解决距离问题的有效途径。本文得出的土地适度规模是可行的,也验证了推进土地适度规模经营的可行性和必要性。

重庆市煤矿临时建设用地复垦现状、问题及模式与对策研究

【目的】分析重庆市煤矿临时建设用地的复垦利用现状特征及存在的问题并提出相应的对策与建议,以期为重庆市煤矿临时建设用地的复垦利用工作提供参考。【方法】通过对重庆市25个存在临时建设用地煤矿的重点调查、对4个煤矿的临时建设用地土壤的重金属含量检测和查阅国内外相关文献资料,得出重庆市煤矿临时建设用地复垦利用的现状、存在的问题、可供借鉴的先进经验以及相应的对策与建议。【结果】1)重庆市煤矿临时建设用地具有分布分散、规模大而单块面积小、以压占损毁为主、损毁程度不等、土地负荷大、硬化度高等特征,主要包括主工业广场、堆矸场、炸药库、矿区道路、风井场地、瓦斯抽放泵站等占用地,分别占比约59.14%,27.36%,2.08%,0.98%,10.17%和0.27%;2)采样区土壤中Cr,Ni,Cu,Zn,Cd,Pb,As和Hg共8种重金属元素均未超过国家土壤环境质量三级标准,但在与渝西地区土壤环境背景值对比时,却存在重金属元素超标现象,且差异较大;3)重庆市煤矿临时建设用地复垦取得一定成效,已备案煤矿区复垦项目477个,但仍存在约43%的煤矿临时建设用地处于闲置状态;4)重庆市已复垦的煤矿临时建设用地利用类型以耕地、林地、草地和园地为主,分别占到总面积的44.64%,43.99%,5.22%和4.84%。5)重庆市煤矿临时建设用地复垦利用存在分散、单块面积小复垦难度大、底数不清、污染状况不明、复垦利用技术标准缺失、复垦利用方向确定随意等问题。【结论】重庆市煤矿临时建设用地分布零散、底数不清、污染状况不明,急需开展相关调查与复垦研究,编制复垦技术规范指导重庆市煤矿临时建设用地复垦利用工作。