Development of technologies for sustainable agricultural use of tropical peats with a premise to maintain wetland conditions

为实现湿地条件下热带泥炭的可持续农业利用，通过田间试验研究了施肥对西米的改良效果，以及西米种植对土壤肥力、水环境养分释放和温室气体（CH_4和CO_2）排放的影响。通过模型实验揭示了泥炭土中微量元素的行为。在与油棕标准施用量相同的水平上连续施用各种宏微量营养素组合，对叶片中元素浓度、株高和叶片数均无显著影响。虽然施用10倍的宏观营养物使总生物量增加，但这是由于吸盘生物量的增加。因此，控制与母株竞争的吸盘可能是取得积极施肥效果的最重要因素。根系生物量在30 cm深度内最高，但施肥对其生长无积极影响。泥炭土有机氮的总矿化率与反映腐殖质中易分解有机质相对丰度的烷基C/ o -烷基C比值有关。土柱试验结果表明，无论在何种氧化还原条件下，土壤中98% ~ 94%的Cu和Fe主要被腐殖质吸收而无法利用。西米种植的连续利用、施肥种类和施肥量对土壤CH_4和CO_2排放率、土壤和流域水体养分和重金属浓度以及土壤理化性质没有影响，表明西米种植在土壤肥力和环境负荷方面具有可持续性。

In order to sustainable agricultural use of tropical peat under wetland conditions, improvement of sago perm by fertilizer application, and influence of sago plantation on the soil fertil ity, release of nutrients to water environment, and emission of greenhouse gasses (CH_4 and CO_2) were examined in field experiments. Model experiments were also performed to reveal the behavior of trace elements in a peat soil. No significant effects on the element concentrations in leaves, plant height, and number of leaves were observed when various combinations of macro and micro nutrients were applied continuously at the same level as standard application rates for oil palm. Although a 10-times application of macro nutrients increased the total biomass, it was due to the increase in the biomass of sucker. Hence, the control of sucker that competes with mother plant could be most important to result in positive effect of fertilizer application. Root biomass was found to be highest within 30 cm depth, although no positive effect on its growth was observed by fertilizer application. Gross mineralization rate of organic N in peat soils was suggested to be related to the alkyl C/O-alkyl C ratio as an index of the relative abundance of readily-decomposable organic matter in total humus. Soil column experiment indicated that 98% and >94% of the applied Cu and Fe were not available due mainly to absorption to humus irrespective of the oxidative and reductive conditions. The emission rates of CH_4 and CO_2, the concentrations of nutrients and heavy metals in soil and drainage waters, as well as physico-chemical properties of soils did not vary due to continuous use for sago plantation and to kinds and rates of fertilizers applied, suggesting sustainability in terms of soil fertility and load to environments.