STUDY ON LIMITING FACTORS FOR LENGTH OF LONGER SIDE IN LARGE SIZED PADDY FIELD

1.农机作业效率、地面排水和土地平整是大型水田长边长度的主要限制因素。但灌溉淤泥并没有被指出是其中的一个因素。在许多水田中引入无水抛撒，可能会增加地下土层的渗透性。在这种情况下，灌溉入水流量与稻田长边长度之间的关系必须被标记为长边长度的限制因素。2.对两个长边长度为100m的水田进行了试验。一种为透水下垫层，另一种为不透水土层。通过在稻田中浇灌淤泥，以等时间间隔观察推进距离。在有不透水下土层的水稻上，可以根据土壤的气相体积和积水深度来估算推进距离，而在有透水下土层的水稻上，则可以根据上述因素的渗透速率来估算推进距离。从机器系统和田间条件的角度考察了租赁农业的最小规模和最大规模，明确了规模较大的农业系统的农场规模为20-100公顷。4.通过两个大规模农业的案例研究发现，耕作机械决定了一块土地的最小面积，而一块土地的较大面积更有利于机器的操作。

1.Efficiency of farm machine work, surface drainage and land leveling have been indicated as main limiting factors for the length of longer side in a large sized paddy field. But irrigation for puddling has not been pointed out as the factor. Introduction of unponding broadcasting in many paddy fields may increase permeability of subsoil layrs. In this case, the relation between inlet flow rate of irrigation for puddling and length of longer side of paddy plot must be marked as the limiting factor for the longer side.2.Two paddy fields with the longer side of 100m were tested. One had permeable subsoil layr and the other had impermeable one. Through irrigation for puddling in the paddy fields, the advance distances were observed at equal intervals of time. In the paddy with impermeable subsoil layr, the advance distance can be estimated from gaseous phase volume of soil and ponding water depth, and in the paddy with permeable subsoil layr, it can be estimated from percolation rate with the above factors. The relation between inlet flow rate and length of longer side in paddy is one of the limiting factor for large sized paddy fields.3.The minimum and maximum size of a rental farming that was investigated from the viewpoint of machines system and field condition, make cleared that the farm size of larger scale farming system can be 20-100 ha.4.By the case study of two large scale farming it was found that the machines used for farming work decides the minimum side of one plot and larger side of one plot is better for operating machines.