Integrated Management of Weeds in Direct-Seeded Rice in Cambodia

Joel Janiya,Chariya Korn,Sokunroth Chhun,Ratha Rien,Robert Martin,Sophea Yous,Bunna Som

doi:10.3390/agronomy10101557

Joel Janiya, Chariya Korn + Show 5 more

Open Access

https://doi.org/10.3390/agronomy10101557

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Abstract

The objective of this work was to determine the value of improved establishment methods and herbicide applications as alternatives to high seeding rates to improve weed suppression in rice. Field experiments were carried out in 2010 and 2011 to determine optimal seeding rates and seeding methods with and without weed competition in wet-seeded rice. Under wet seeding conditions, drum seeding at 80 kg ha−1 was the most profitable treatment for both weed-free and unweeded rice. Although pre-emergence herbicides are beginning to be adopted in wet-seeded rice, they are seldom used in dry direct-seeded rice in Cambodia. Experiments were carried out in 2018 and 2019 to test crop tolerance and the efficacy of butachlor, oxadiazon, pendimethalin and pretilachlor applied post-sowing and pre-emergence to dry direct-seeded rice. Oxadiazon and butachlor, with the option for a post-emergence herbicide, provided effective weed control and a high grain yield in dry direct-seeded rice. Pretilachlor did not effectively control weeds under dry seeding conditions. Although pendimethalin exhibited good weed control, crop damage was a risk in poorly prepared seedbeds which typify Cambodian rice systems. With an effective integrated weed management strategy, it might be possible to safely reduce seeding rates below 80 kg ha−1 using drum or drill seeding machines.

Highlights

Agriculture accounts for 22% of Cambodia’s Gross Domestic Product (GDP) [1], and rice is by far the most important commodity, making up around half of the agricultural GDP
After a marginal analysis of costs and returns, this study found that all broadcast seeding rates were dominated both with and without weeds and that the drum seeder at 80 kg ha−1 was the most cost-effective treatment with and without weeds in a wet-seeded direct seeding situation
This study suggests that increasing the seeding rate alone is not a cost-effective method to reduce paddy yield losses from weeds and that an integrated approach to weed management should be adopted [19]

Summary

Introduction

Agriculture accounts for 22% of Cambodia’s Gross Domestic Product (GDP) [1], and rice is by far the most important commodity, making up around half of the agricultural GDP. The total area of agricultural production in Cambodia was 4 million ha in 2016 [2] and of this there was 3 million ha (75%) of rice. Cambodia produced 10.7 million tonnes of paddy in 2018 [3] and a domestic surplus of. The climate of North-West Cambodia is affected by the South-East Asia Monsoon, characterised by distinct wet and dry seasons [4]. The hottest month is April with an average maximum temperature of 36.1 ◦ C. January is the coolest month with an average minimum temperature of 19.3 ◦ C

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