Development of lowland weed management and weed succession in Japan

Abstract

Since the introduction of rice production in Japan, lowland areas have been managed for rice production with the purpose of better rice growth, as well as lesser weed infestation. Rice is cropped every year in lowland fields by repeated cultivation of a single crop, with high yields and without soil sickness usually being observed in upland fields.This is probably because the irrigation water supplies various nutrients for healthy rice growth and the drainage washes out and removes harmful factors. However, until recently, the wet or flooded conditions of lowland fields in the Asian monsoon region never have allowed humans to cultivate useful summer crops, except rice or some aquatic plants.Therefore, the management of lowland areas in the Asian monsoon region has been significantly different from European field management, where crop rotation has been the traditional standard practice. Paddy weeds are aquatic plants or hygrophytes that have adapted to lowland fields.Traditionally, tillage and puddling were practiced seasonally in lowland fields on a regular schedule every year. Rice cultivation technology was developed and supported by regional irrigation systems that created stable environments for typical paddy weeds to complete their life cycle. After the introduction of chemical weed control, rice fields became very severe habitats for these paddy weeds, where they could not grow and reproduce without strategies for survival under herbicide exposure. Even so, many of the traditional paddy weeds survived because of their accumulated or uneradicated seed banks, although several aquatic plants were listed as endangered or threatened species.The important weed species changed, sometimes rapidly and sometimes slowly, depending both on their reproductive system and their biological response towards field management and weed control systems.Very recently, the level of perennial weeds, herbicide-resistant weeds, and weedy rice has increased in paddy fields that are highly dependent on herbicide use. In addition, several hygrophyte species have invaded paddy fields. In order to address these issues, the improvement and application of integrated weed management methods are expected to be critical. .x tillage had almost no effect on the final yield of rice even though it was very effective for weed control, based on his study of the physical, chemical, and physiological aspects of the interaction between paddy soil and rice growth. 176 H.Watanabe

Distribution patterns and traits of weed communities along an urban–rural gradient under rapid urbanization in Shanghai, China

“…On the other hand, the distribution and community succession of farmland weeds is closely related to the use of herbicides. As a result of the dif-ferent weed-controlling spectrum of each herbicide, some originally dominant weeds become less dominant due to herbicidal control, but some herbicide-resistant weeds gradually develop from co-occurring weeds into dominant weeds after the long-term use of a particular type of herbicide in a certain area (Watanabe 2011). Therefore, according to the distribution of the weeds, a preliminary judgment can be made about the use of herbicides in the area.…”

Comparison of Weed Seedbanks in Different Rice Planting Systems

“…The risk of grain yield loss due to weeds is greater for DDSR than MTR (Rao et al, 2007). Some weed species infesting upland crops, such as E. indica, D. sanguinalis, Eclipta prostrata, and F. dichotoma, are troublesome in DDSR (Kraehmer et al, 2016;Rao et al, 2007;Watanabe, 2011), and are represented by larger seedbanks. Some principal rice weeds, which are able to produce large numbers of small seeds, become even more problematic in DDSR, such as Cyperus iria (Chauhan and Johnson, 2009), F. miliacea (Chauhan and Johnson, 2009), and Ludwigia prostrata (Li, 1998).…”

“…Although weed community succession in rice fields under different planting systems has been studied in many countries (Kraehmer et al, 2016;Rao et al, 2007;Watanabe, 2011), weed seedbanks under different rice planting systems have seldom been compared. Rice cultivation in Jiangsu Province, China, is a useful model system for understanding weed seedbank composition as a response to different rice planting systems.…”

Life cycle assessment of organic paddy rotation systems using land- and product-based indicators: a case study in Japan

“…in Japan, and rice has been successfully cultivated in succession in a sustainable way, owing to the function of flood irrigation (Watanabe 2011). Then, because of a decrease in rice consumption, the rotation of rice with upland crops has become a common practice throughout the country.…”