Sustainable cassava production on sloping lands in Vietnam
Sustainable cassava production on sloping lands in Vietnam
复制标题
越南坡地上的可持续木薯生产
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
T. Phien
中科院分区：
文献类型：
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作者：
R. Howeler;T. Phien
越南的木薯产量很低，部分原因是木薯主要种植在土壤被侵蚀和养分枯竭的坡地上，而且很少或不适当地投入化肥和/或肥料。此外，许多农民在收获根的同时还收获茎、叶甚至落叶，导致大量N、K、Ca和Mg的去除，土壤养分供应迅速枯竭。尽管研究表明，收获木薯根茎并不比收获其他作物去除更多的养分(K可能除外)，但当木薯茎叶也从田间移走时，养分去除，特别是N、Ca和Mg的去除，与只收获根部相比增加了一倍以上。如果种植在山坡上，木薯种植可能会导致严重的侵蚀，因为种植的植物间距很大，而且作物最初的生长速度很慢。这会导致树冠形成缓慢，使土壤暴露在降雨飞溅和侵蚀之下。侵蚀不仅会导致土壤及其相关的有机质、养分和微生物的流失，而且还会优先损失粘土、有机质和一些养分，导致剩余土壤的贫化。大量养分在侵蚀土壤(主要是N和K)和径流(主要是K)中流失。根据收获的木薯产品的养分吸收和有机肥和化肥的养分添加计算越南木薯种植区的养分平衡，发现6个地区中有3个地区的N、K平衡均为负，1个地区的P平衡为负。在大多数地区，农民没有施加足够的K和N，而在一些地区，他们以有机肥和SSP的形式增加了太多的P。这些磷的过量使用不仅是对资源的浪费，而且可能会造成下游水道和湖泊的污染和富营养化。通过将植物顶端和落叶归还土壤，以及防止径流和侵蚀，可以减少土壤养分的消耗。去除的养分应通过施用有机肥和无机肥料，或通过绿肥、间作或间作来替代，在这种情况下，修剪或间作残留物将重新并入土壤。后者可能导致N的适度增加，以及P和K在系统内的循环。可以通过主要在高投入的平地种植木薯来防止侵蚀，以获得高产量。当种植在斜坡上时，作物应该以最少的耕作和相当紧密的种植间距种植，或者与花生等间作作物结合种植。使用优质的种植材料、繁茂的品种和适量的化肥或有机肥，将促进植物的生长和形成土壤覆盖。等高垄沟、等高树篱的种植，以及秸秆覆盖的应用，将进一步减少径流和侵蚀。农民不太可能采取土壤保持措施，除非这些措施在建立和维护方面不太昂贵或劳动密集型，并在增加产量或有用产品方面提供立竿见影的好处。制定和传播更可持续的生产做法最好是在农民直接参与的情况下进行，以确保建议的做法适合当地条件，在成本和预期收益方面是可以接受的。在越南，木薯是种植面积仅次于水稻、玉米、蔬菜和甘薯的第五大粮食作物。1998年1CIAT亚洲木薯研究协调办公室，系。农业部，差图猜，曼谷10900，泰国。2越南河内土莲国家土壤肥料研究所。
Cassava yields in Vietnam are low partially because the crop is grown mainly on sloping land with eroded and nutrient depleted soils, and with little or inappropriate inputs of fertilizers and/or manures. Moreover, many farmers harvest the stems, leaves and even the fallen leaves in addition to the roots, resulting in the removal of large amounts of N, K, Ca and Mg and a rapid depletion of the soil’s nutrient supply. Although research has shown that the harvest of cassava roots does not remove more nutrients than the harvest of other crops (with the possible exception of K), when cassava stems and leaves are also removed from the field, nutrient removal, especially that of N, Ca and Mg, more than doubles compared with harvesting only the roots. When grown on slopes, cassava cultivation can result in serious erosion due to the wide plant spacing used and the crop’s slow initial growth. This leads to slow canopy formation, exposing the soil to rainfall splash and erosion. Erosion not only leads to loss of soil, with associated organic matter, nutrients and micro-organisms, but also a preferential loss of clay, organic matter and some nutrients, resulting in empoverishment of the remaining soil. Substantial amounts of nutrients are lost in eroded soil (mainly N and K) and runoff (mainly K). Calculating the nutrient balance in cassava growing regions in Vietnam from the nutrient off-take in harvested cassava products and the nutrient additions in manure and chemical fertilizers, it was found that the N and K balances were both negative in three of the six regions, while the P balance was negative in one. In most areas farmers do not apply enough K and N, while in some areas they apply too much P, in the form of manure and SSP. These excessive applications of P are not only a waste of resources but may also cause pollution and eutrophication of waterways and lakes down stream. Soil nutrient depletion can be reduced by returning plant tops and fallen leaves to the soil and by preventing runoff and erosion. Nutrients that are removed should be replaced through application of organic and inorganic fertilizers, or by green manuring, alley cropping, or intercropping, in which case the prunings or intercrop residues are reincorporated into the soil. The latter may lead to modest additions of N, and to recycling of P and K within the system. Erosion can be prevented by planting cassava mainly on flat lands with high inputs to obtain high yields. When planted on slopes, the crop should be planted with minimum tillage and at rather close plant spacing, or in combination with intercrops like peanut. The use of good quality planting material, vigorous varieties and adequate applications of fertilizers or manures will enhance plant growth and formation of soil cover. Contour ridging, the planting of contour hedgerows, as well as application of straw mulch, will further reduce runoff and erosion. Farmers are not likely to adopt soil conservation measures unless they are not too expensive or labor intensive in establishment and maintenance, and provide immediate benefits in terms of increased yields or useful products. The development and dissemination of more sustainable production practices can best be done with direct participation of farmers to ensure that the recommended practices are suitable for the local conditions and are acceptable in terms of costs and expected benefits. INTRODUCTION In Vietnam cassava (Manihot esculenta Crantz) is the fifth most important food crop in terms of area planted, after rice, maize, vegetables and sweetpotato. In 1998 1 CIAT Office for Coordination of Cassava Research in Asia, of Dept. of Agriculture, Chatuchak, Bangkok 10900, Thailand. 2 National Institute for Soils and Fertilizers, Tu Liem, Hanoi, Vietnam.