Assessment of management of direct seeded rice production under different water conditions in Cambodia

Abstract

In order to assess direct seeding of rice technology to cope with future agricultural labor shortage in Cambodia, agronomic experiments were conducted in 2005 and 2006 to compare direct seeding with transplanting under three water conditions (non-flooded, shallow flooded, and deep flooded conditions) with/without weed control by herbicides (bentazone and cyhalofop-butyl) for two Cambodian rice varieties (shorter stature and early maturity Sen Pidao, taller stature and longer maturity Phka Rumduol). Average rice yield in 2 years was lower in direct seeding (341 g m -2 ) than transplanting (404 g m -2 ), but interaction components with year, varieties, water conditions, and weed management were significant, and the attained maximum yield of direct seeding (510 and 464 g m -2 for Phka Rumduol variety in shallow flooded condition with weeding in 2005 and 2006, respectively) was similar to that of transplanting. Plant length and dry weight of rice were reduced in non-flooded and deep flooded conditions compared with shallow flooded condition, and grain yield was the highest in shallow flooded condition. Yield advantage of Phka Rumduol over Sen Pidao increased under direct seeding, particularly under non-flooded conditions in 2005 because weed infestation was more suppressed in Phka Rumduol even without weeding. Increase in 100 g m -2 of weed infestation prior to heading (dry weight basis) reduced about 20% of attainable yield with weed control. This study identified importance of stature and growth duration of rice varieties and presence of standing water as well as the weed control, in order to develop and extend direct seeding in the Cambodia.

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

“…a higher percentage of weed seed emergence compared to rice; Morita & Kabaki (2002)), seedling growth, and resource acquisition (Inamura et al . 2003; Ikeda et al . 2008; Hayashi et al .…”

“…As the soil moisture content decreases from an optimum level in a drought, the comparative advantage for weed growth over rice increases in key processes, such as germination (i.e. a higher percentage of weed seed emergence compared to rice; Morita & Kabaki (2002)), seedling growth, and resource acquisition (Inamura et al 2003;Ikeda et al 2008;Hayashi et al 2009); hence, the produced and scattered weed seeds on soil surfaces for the next season will increase if appropriate weed control measures are not taken. In contrast, the weed growth in the fields in both 2005 and 2006 was not related to the size of the weed seed bank before planting, unlike the observation of several studies in paddy fields (Mineta & Oki 1997), upland cropping fields (Roberts & Neilson 1981), and forestry (Hamada & Kuramoto 1994).…”

“…Weed infestations reduce the grain yield of many Asian rice fields, particularly with direct seeding for crop establishment, a practise that has been increasing in Southeast Asia since the late 1980s (Pandey & Velasco 2002;Ikeda et al 2008;Hayashi et al 2009). Studies have been conducted on weed ecology in paddy fields under different environmental conditions (e.g.…”

Simulating Water Transport and Loss in a Direct-Seeded Paddy Field Using Hydrus-1D

“…直播稻技术凭借省工省力等优点，目前已被众多农民 自发地接受 [1] 。直播稻在田间管理上要做到适墒旱直播， 齐苗 1 叶 1 心后建立薄水层；分蘖期保持浅水，至田间总 苗数达到预期穗数 70-80%时开始搁田，干湿交替；搁田 后抽穗前湿润灌溉，齐穗后干湿交替，前期以湿为主，后 期以干为主 [1][2] 。由于直播稻田在水分管理上与传统移栽稻 田不同，其间产生的水分运移和流失特征也不同，由此可 能直接影响到养分的运移和流失 [2] 。Tuong 等 [3] 认为与传 统移栽水稻相比，旱直播有利于作物更好地利用稻季前期 降水。Cabangon 等 [3] 比较了传统移栽水稻田和直播稻田的 水分管理与作物产量之间的关系。Ikeda 等 [4] 评估了柬埔寨 不同水分管理模式下的直播稻田作物产量。也有研究认 为，直播稻田的土壤特性可能增大了水分的渗漏损失 [5] ， 甚至导致作物产量的下降 [6][7] 。 随着我国太湖地区直播稻田面积的逐年增加，对于直 播稻田的水分管理显得日益重要。掌握稻田水分通过渗漏 等形式流失特征，将有助于稻田的节水灌溉和肥料运筹。 Hydrus-1D 模型主要用来模拟饱和-非饱和带土壤的水分和 溶质的运移规律，其便利的参数率定和边界条件设置使得 其在农田水分、溶质运移模拟方面得到了广泛的应用 [8][9] ， 尤其是在模拟水分渗漏速率和累积渗漏量方面，Hydrus-1D 有更大的优势 [8] 。虎胆等 [10] 利用 Hydrus-1D 模型研究了 新 疆 某 地 土 壤 -秸 秆 水 分 运 动 参 数 。 毕 经 伟 等 [11] …”

High-yielding Crop Management by Enhancing Growth in Reproductive Stage of Direct-Seeded Rainfed Lowland Rice (Oryza sativaL.) in Northeast Thailand

“…The percentage of direct-seeding in Northeast Thailand increased from 4% in 1989 (Pandey et al, 2002) to 36% in 2005(OAE, 2006. Grain yield in direct-seeding was lower than in transplanting under non-flooded and weedy conditions, but was equally high as transplanting under shallow fl ooded and weed-controlled conditions (Ikeda et al, 2008). It would be necessary to classify the target environment by water availability (i.e.…”