Impact of direct dry seeding on rainfed paddy vegetation in north‐east Thailand

Tomita, Shinsuke; Nawata, Eiji; Kono, Yasuyuki; Inamura, Tatsuya; Nagata, Yasutoshi; Noichana, Chairat; Sributta, Akkadet

doi:10.1046/j.1445-6664.2003.00087.x

Cited by 14 publications

(22 citation statements)

References 5 publications

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“…Our study suggested that higher usage rates apply in the Kamping Puoy Irrigation Rehabilitation Area. As shown in rain‐fed paddy fields in north‐eastern Thailand (Tomita et al . 2003a,b), the rain‐fed fields in higher topographic positions with less water availability (the rain‐fed upslope group) recorded lower percentages of sedges (61% in 2006) and higher percentages of broad‐leaved weeds (39% in 2006).…”

Section: Discussionmentioning

confidence: 61%

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Ecophysiological study on weed seed banks and weeds in Cambodian paddy fields with contrasting water availability

Kamoshita¹,

Ikeda

Yamagishi

et al. 2010

Weed Biology and Management

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Weed infestations are a major cause of yield reduction in rice (Oryza sativa) cultivation, particularly with direct-seeding methods, but the relationship between weed dynamics and water availability in Cambodian paddy fields has not been documented previously.We surveyed the weed abundance and weed seed banks in the soil of paddy fields with inferred differences in their water regime in 22 farm fields in three provinces of Cambodia in the 2005 and 2006 rainy seasons.We studied rain-fed lowland fields in upslope and downslope topographic positions and fields at different distances from the irrigation water source inside an irrigation rehabilitation area.The weed seed banks were estimated by seedling emergence in small containers and weed abundance and vigor were estimated by a simple scoring system.The estimated weed seed bank in the top 5 cm of soil ranged from 52.1 to 167 ¥ 10 3 seeds m -2 (overall mean of 8.5 ¥ 10 3 seeds m -2 ) and contained a high proportion (86%) of sedge species, such as Fimbristylis miliacea L. and Cyperus difformis. Several fields had particularly large seed banks, including one near the reservoir. No clear difference was found in the weed seed banks between the irrigated fields that were located close to (upstream) and distant from (downstream) the water source or between the irrigated and rain-fed lowland fields, but the weed scores were larger in the rain-fed fields and the downstream fields within the irrigated area. A water shortage during the late growing season in 2005 led to a proliferation of weeds in some fields and an associated increase in weed seedbank size in 2006. However, the weed scores in 2006 were more strongly associated with that year's water conditions than with the weed seedbank size.

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Section: Discussionmentioning

confidence: 61%

“…As the number of rain‐fed fields that was surveyed was relatively small, we could not judge whether or not the weed seed banks differed between the fields in the higher (upslope group) and lower (downslope group) topographic positions. Tomita et al . (2003a,b,c) showed that fields in higher topographic positions had more weed vegetation.…”

Section: Discussionmentioning

confidence: 99%

Ecophysiological study on weed seed banks and weeds in Cambodian paddy fields with contrasting water availability

Kamoshita¹,

Ikeda

Yamagishi

et al. 2010

Weed Biology and Management

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show abstract

“…Transformation of the soil seed bank is another important aspect in changes of weed vegetation. Unlike the influence of past cultivating methods on species diversity and productivity (Tomita et al . 2003), species composition was affected by the methods in the previous year.…”

Section: Discussionmentioning

confidence: 99%

“…Our previous work (Tomita et al . 2003) revealed paddy vegetation was largely influenced by disturbance intensity such as land preparation and resource availability.…”

Section: Introductionmentioning

confidence: 99%

Differences in weed vegetation in response to cultivating methods and water conditions in rainfed paddy fields in north‐east Thailand

Tomita

Nawata

Kono

et al. 2003

Weed Biology and Management

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Rainfed paddy cultivation predominates in north‐east Thailand. Direct dry seeding is replacing transplanting rice cultivation to increase the frequency of successful plantings and to save labor. The present study clarified differences in weed vegetation of direct dry‐seeded and transplanted paddy fields under rich, medium and poor water conditions from agricultural and ecological viewpoints. A large number of paddy fields from a wide range of climatic, topographic, soil and hydrological conditions were used. A survey was conducted every three weeks, and data regarding paddy cultivation, weeds and water conditions were collected. Expansion of direct dry seeding may increase species with in‐between water adaptability to hygrophytes and mesophytes, and decrease hydrophytes and mesophytes. This characteristic was remarkable under poor water conditions. Rice cover was similar in either planting method under rich water conditions. However, cover of direct‐seeded rice was significantly smaller than that of transplanted rice under medium and poor water conditions. Species diversity was higher in direct dry‐seeded paddy fields than in transplanted paddy fields under medium and poor water conditions. Impact of direct dry seeding in the fields with rich water conditions on the vegetation is small in the context of maintaining rice production by transplanting and species diversity. However, direct dry seeding is mainly adopted in fields with poor water conditions. Impact of the changes in cultivating methods is large on rice productivity, species composition and species diversity under such conditions. Therefore, how to best use resource‐poor fields may be the key to maintaining rice production and regional‐level species diversity.

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“…alluvial flood plains of several tributaries of the Mekong River and low surfaces of undulating plains, rice is produced in paddy fields, whereas in higher undulating plains, upland field crops, such as cassava, sugarcane and kenaf, are produced. At present, although rapid economic development is accelerating agricultural production changes, including the extension of direct seeding technology in paddy production (Tomita et al, 2003) and expansion of sugarcane producing areas into lowlands, the basic patterns of agricultural land use have not changed significantly. Paddy fields are distributed all over Northeast Thailand, whereas sugarcane fields are mainly distributed in the northwestern (Udon Thani, Khon Kaen and Chayapum Provinces), southwestern (Nakorn Rachasima Province) and the middle eastern parts (Muk Dahan Province) of this area, mainly because of the location of sugar processing factories.…”

Section: Discussionmentioning

confidence: 99%