MATHEMATICAL MODEL OF WEED SEED DYNAMICS

研究成果由三部分组成。在第一部分中，杂草生活史模型被发展为一个以地表种子数和埋种数为状态参数的动力系统。这种模式涉及除草、耕作和收获。在第二部分中，对建立的模型进行了修正，使之更符合田间栽培的实际情况。状态参数从2个扩展到8个。从模型的参数统计来看，每年改变耕作深度是降低农田种子势能的可能方法。第三部分，对发芽、生长和播种过程进行了数学模拟。通过田间试验确定了各过程的函数表达式。利用该模型，从种子生产的角度对除草调度进行了优化。

The research results consists of 3 parts. On the 1st part, weed life history model was developped as a dynamical system where surface and buried seeds number are state parameters. The model deals weeding, tillage, and harvesting. With the model, 2 strategies were developed.On the 2nd part, the dynamical model developed was modified to fit actual field cultivations. The number of state prameters were expanded from 2 to 8. From parameter staties with themodefied model, changing the tillage depth in each year is a possible method to reduce a seed potensial of agricultural fields.On the third part, germination, growth, and seeding process were modelled mathematicaly. The functions express each processes were determined by field experiments. With the model, optimization of weeding scheduling in terms of seed productions was conducted.