Proposal of coexistent ecosystems with paddy and water-covered plant for promoting an efficient production of biomass resources

在以水稻为主要种植作物的普通稻田中，尝试提出一种基于多种作物共存的新种植制度，以期减轻环境影响，摆脱单一种植制度。2002-2003年，在相同施肥量条件下，通过3个重复的试验，研究了两种作物共存系统中种植密度对两种作物生长速率、群落结构和产量的影响。我们用水葫芦作为水覆盖的模型作物。水稻种植密度为22.2穴/m^2，水葫芦种植密度分别为22.2、16.7、11.1、5.6和0穴/m^2。结果表明，虽然增加种植密度会对资源利用的竞争和水稻产量产生负面影响，但水覆盖作物的引入有助于单位面积固碳率的提高。最后从固碳的角度估算了水葫芦的最佳种植密度为11.1丘/m^2左右。

In an ordinary paddy field whose cultivated dominant crop is a paddy, we tried to propose a new cropping systems based on coexistence with the plural crops for expecting the mitigation of environmental impact and escape of monoculture systems. In this study, the effect of plant density in coexistent systems on growth rate, structure of community and yield of the two crops were investigated in the 2002-2003 experiments with three repetitions under the same condition of application rate of fertilizer. We used a water hyacinth as the water-covered model crop. Plant densities were 22.2 hills/m^2 for paddy, and 22.2, 16.7, 11.1, 5.6 and 0 hills/m^2 for water hyacinth, respectively. As a result, an introduction of water-covered crop contributed the increment of carbon fixation rate per unit area although some increased plant densities affected the competition of resources utilization and paddy yield negatively. Finally the optimum plant density of water hyacinth was estimated at the neighbor of 11.1 hills/m^2 from the viewpoint of carbon fixation.