897 resultados para Agricultural Irrigation.
New considerations of ecological risk assessment for heavy metal contamination of agricultural soils
Resumo:
实行西部经济大开发 ,水资源是制约的首要因素。要改善西部农业生产条件 ,加快生态环境建设 ,促进国民经济的发展 ,就必须在分析水资源利用现状的基础上 ,研究提出西部旱作农业抗旱节水的调控技术与途径 :加强水资源管理 ,建设节水型农业 ,从水资源时空调节角度出发 ,通过工程调水实现区域调节 ,建设库窑实行年季调节 ,拦蓄径流集雨补灌 ,充分利用自然降水 ,防止水土流失 ,增加覆盖防止蒸发 ,合理耕作促进根系深扎 ,最大限度地提高旱农区的水分利用率和利用效率 ,是西部旱作农业的根本出路。
Resumo:
旱地作物需水量预报决策辅助系统是利用人工智能技术 ,在 Penman公式的基础上结合现有西北旱区的农学知识、模型以及经验进行系统集成而建立的智能化计算机软件系统 ,该系统是西北地区节水农业专家系统的一个子系统。在生产实践中可为陕西关中地区的冬小麦、夏玉米的栽培作出灌溉方案的决策咨询。
Resumo:
China's cultivated land has been undergoing dramatic changes along with its rapidly growing economy and population. The impacts of land use transformation on food production at the national scale, however, have been poorly understood due to the lack of detailed spatially explicit agricultural productivity information on cropland change and crop productivity. This study evaluates the effect of the cropland transformation on agricultural productivity by combining the land use data of China for the period of 1990-2000 from TM images and a satellite-based NPP (net primary production) model driven with NOAH/AVHRR data. The cropland area of China has a net increase of 2.79 Mha in the study period, which causes a slightly increased agricultural productivity (6.96 Mt C) at the national level. Although the newly cultivated lands compensated for the loss from urban expansion, but the contribution to production is insignificant because of the low productivity. The decrease in crop production resulting from urban expansion is about twice of that from abandonment of arable lands to forests and grasslands. The productivity of arable lands occupied by urban expansion was 80% higher than that of the newly cultivated lands in the regions with unfavorable natural conditions. Significance of cropland transformation impacts is spatially diverse with the differences in land use change intensity and land productivity across China. The increase in arable land area and yet decline in land quality may reduce the production potential and sustainability of China's agro-ecosystems. (C) 2008 Elsevier B.V. All rights reserved.