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Agronomic diagnosis of factors limiting upland rice yield in mountainous areas of Northern Vietnam.

机译:越南北部山区限制旱稻产量的因素的农学诊断。

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An experiment was conducted in Bac Kan, Vietnam, to study the interactions between factors and processes, and to identify the major constraints to rice production to develop alternatives to the traditional slash-and-burn systems. Variability between fields in rice yield was explained primarily by slashed forest type (5 classes were identified) and number of years of cultivation. Weed infestation and slope also affect rice growth and yield, especially after a few years of cultivation. Within fields, rice yield variability was largely explained by soil structure (such as porosity, compaction, and bulk density) and partly by soil chemical characteristics in relation to soil biological characteristics. Within fields, rooting depth and weed infestation also partly explain rice growth and yield. All these factors are, at different scales, indicators of soil fertility/degradation status. Forest and soil regeneration is limited by short fallow duration (decreasing in the present context of rapidly increasing population pressure) and by intensive buffalo grazing which leads to soil compaction. Soil degradation is caused by erosion after forests are slashed and burned. As a result, poor soil structure and shallow rooting (limited by physical and chemical soil conditions) leads to very poor water use efficiency, all the more so as frequent dry spells are observed in the area. In addition, weed infestation is a major constraint to upland rice production in these conditions. A synthetic diagram of major factors and interacting processes explains rice growth and yield in the traditional slash-and-burn systems. The main factors limiting upland rice growth and yield in these traditional systems, as conducted in the study area are: poor water use efficiency, due to high run-off, poor soil structure (compaction, and low porosity), and shallow rooting (due to unfavourable physical and chemical soil characteristics); weeds competition. As a consequence, for improvement of (or design of alternatives to) these systems, research priority should be given to the development of techniques or systems that increase water use efficiency and facilitate weed control. Until soils have been rehabilitated and protected, and weeds controlled, "classical" research on topics such as fertilizers or varieties will bring hardly any improvement in the traditional systems.
机译:在越南的巴坎(Bac Kan)进行了一项实验,以研究因素与过程之间的相互作用,并确定水稻生产的主要障碍,以开发出传统的纵火焚烧系统的替代品。稻田产量之间的差异主要通过砍伐的森林类型(确定为5类)和耕种年限来解释。杂草的侵扰和坡度也影响水稻的生长和产量,尤其是在种植数年后。在田间,水稻产量的变异主要由土壤结构(例如孔隙度,压实度和堆积密度)解释,部分由与土壤生物学特征相关的土壤化学特征来解释。在田间,生根深度和杂草侵染也部分解释了水稻的生长和产量。所有这些因素在不同尺度上都是土壤肥力/退化状态的指标。森林和土壤的再生受到休耕时间短(在当前人口压力迅速增加的情况下有所减少)和水牛放牧导致土壤压实的限制。森林砍伐和燃烧后的侵蚀是造成土壤退化的原因。结果,不良的土壤结构和生根浅(受物理和化学土壤条件的限制)导致用水效率非常低,而且在该地区观察到频繁的干旱。此外,在这些条件下,杂草侵扰是陆稻生产的主要制约因素。主要因素和相互作用过程的综合图解释了传统的刀耕火种系统中的水稻生长和产量。在研究区域中,限制这些传统系统中旱稻生长和产量的主要因素是:由于高径流,较差的土壤结构(致密性和低孔隙度)和低生根(应不利的土壤和化学特性);杂草竞争。因此,为了改进(或设计替代方案)这些系统,应优先研究提高水利用效率并促进杂草防治的技术或系统。在对土壤进行修复和保护,并控制杂草之前,有关肥料或品种等主题的“经典”研究几乎不会对传统系统带来任何改善。

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