暖地の水田作における雑草の生態ならびに防除に関する研究

Abstract

en-abstract=A series of researches on ecology and control of weeds in paddy in the warmer regions of Japan has been performed at Kyushu Agricultural Experiment Station, MAFF for the purpose of obtaining basic information so as to establish the economic and effective technology of weed control in paddy since around 1960.Studies can be generally divided in several subjects. Brief content of each subject would be introduced as follows:1. A study of physiological and ecological characteristics of principal weeds in paddy.Taking up annual principal weeds in paddy, investigation and analysis of emergence pattern of seeds on six weed species, for example, a relation between emergence depth into soils and natures of seeds and/or seedling, and observation and discussion on anatomical and morphological features of leaf-blade of main weeds with reference to control have been made. Further, studies on ecology and control of some specific perennial weeds; Sagittaria pygmaea, Paspalum distichum and so on, have been conducted during the later period of this studies.2. A study of competitive effects and yield losses due to barnyardgrass on rice.Co-existence of barnyardgrass with rice gave yield losses on rice, and then ecological and physiological aspects of yield losses were observed and discussed. For example, a regression of the logarithm of rice yield as percent of weed free rice against barnyardgrass dry weight was expressed by a straight line, that is, a relation between rice yield and barnyardgrass weight can be in formula log Y=a-bx (See Figure 4). Further, it was understood that two critical periods of rice exist when barnyardgrass was allowed to compete with rice until harvest. They are an early stage of growing until maximum tillering and an early ripening stage of rice, as shown in Figure 5.3. Fundamental studies of weed control technology and herbicide properties in paddy.General properties, behaviors into soils and the physiology of several less toxic herbicides to rice have been investigated, as summarized in Table 2. Temperatures and phytotoxicity are particularly interested in Kyushu. The largest phytotoxicity due to high temperatures was found in prometryne and next to MCPCA (MCPA) and PCP. The relation of high temperatures to the phytotoxicity of peometryne on rice was considered as indicated in Figure 6.4. Discussion on future challenge of weed control technology in rice.Future direction of weed control in paddy has been discussed referring to changeable climatic conditions and socio-agronomic situations. A direction of the technology that is effective and economic but without side-effect should be in integrated one.5. Studies of ecology and control of annual winter weeds in drainage lowlands.Four principal weed species in winter were taken up to this studies. Particularly, the ecology of cleaver (Galium aparine) was intensivly investigated compared with other weed species, as shown in Table 4. Further, evaluation tests to obtain effective herbicides to control cleaver were conducted. Effective herbicides could be grouped into five as indicated in Table 5.