Abstract
Incorporation of dry-season crops in the lowland production systems of the Lower Mekong Basin (LMB) may provide local smallholder farmers the opportunity to increase household cash income through diversification. However, water availability and lowland rice-growing soil characteristics often limit the yield potential of dry-season crops in rotation with wet-season rice. This work studied the effects of three frequencies of irrigation on the crop performance of dry-season furrow-irrigated maize (Zea mays Linnaeus) and peanut (Arachis hypogaea Linnaeus) grown on lowland rice-growing soils in terms of biomass, yield and water productivity (WP). In addition, the response of maize to two fertiliser rates was evaluated. The study was carried out in sites with typical lowland rice-growing soils located in Cambodia and Laos. Soil matric potential (Ψm) was monitored during the season at the centre of the beds and percentage of canopy cover, aboveground biomass (AGB), yield and WP were determined. The results showed that within the first weeks of furrow irrigation (~two weeks after emergence), Ψm dropped considerably (<−200 kPa) after all treatments at both sites, suggesting that water movement from the furrows to the centre of the beds was limited. Shorter frequency of irrigation led to significantly (p < 0.05) higher AGB and yield in maize but not in peanut. Fertiliser rates did not have a significant effect on maize. WP ranged from 0.84 kg m−3 to 1.42 kg m−3 for maize and from 0.27 kg m−3 to 0.49 kg m−3 for peanut with no significant differences among treatments. This work provides evidence of a lateral water movement limitation that is not well documented for the establishment of furrow-irrigated dry-season crop production in the lowlands of the LMB. Further research on methodologies that could help to overcome this limitation in these soils, such as the application of soil amendments or implementation of alternative irrigation systems, would be of great value.
Highlights
The Lower Mekong Basin (LMB) consists of four nations, Thailand, Laos, Cambodia and Vietnam, and is home to approximately 60 million people
The objectives of this study were to determine: (1) whether on typical lowland rice-growing soils, soil moisture monitoring at the centre of the bed could be a useful method for scheduling irrigation in two of the major non-rice cultivars grown in Cambodia and Laos [4], being maize (Zea mays Linnaeus) and peanut (Arachis hypogaea Linnaeus); (2) the effect of frequency of irrigation on maize and peanut performance in terms of percentage of canopy cover, aboveground biomass (AGB) and yield, and; (3) the water productivity (WP) of these two crops on lowland rice-growing soils of the LMB
The lack of lateral soil water movement was evidenced at both sites by the low soil matric potential values recorded in the centre of the beds soon after furrow irrigation commenced
Summary
The Lower Mekong Basin (LMB) consists of four nations, Thailand, Laos, Cambodia and Vietnam, and is home to approximately 60 million people. ~33% of the population lives below the poverty line and ~32% of people are undernourished [2]. The main agricultural activity is smallholder production of wet-season rice, which is grown mostly in the lowlands and generally as a monoculture without crop rotation [5]. These lowland systems occupy approximately 80% of the total rice production area, which, in 2016, equated to a harvested lowland area of ~0.78 million ha and 2.3 million ha in Laos and Cambodia, respectively [4]
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