Determinants in the Adoption of Alternate Wetting and Drying Technique for Rice Production in a Gravity Surface Irrigation System in the Philippines

Alternate Wetting and Drying (AWD) is a well-known low-cost water-saving and climate change adaptation and mitigation technique for irrigated rice. However, its adoption rate has been low despite the decade of dissemination in Asia, especially in the Philippines. Using cross-sectional farm-level survey data, this study empirically explored factors shaping AWD adoption in a gravity surface irrigation system. We used regression-based approaches to examine the factors influencing farmers’ adoption of AWD and its impact on yield. Results showed that the majority of the AWD adopters were farmers who practiced enforced rotational irrigation (RI) scheduling within their irrigators’ association (IA). With the current irrigation management system, the probability of AWD implementation increases when farmers do not interfere with the irrigation schedule (otherwise they opt to go with flooding). Interestingly, the awareness factor did not play a significant role in the farmers’ adoption due to the RI setup. However, the perception of water management as an effective weed control method was positively significant, suggesting that farmers are likely to adopt AWD if weeds are not a major issue in their field. Furthermore, the impact on grain yields did not differ with AWD. Thus, given the RI scheduling already in place within the IA, we recommend fine-tuning this setup following the recommended safe AWD at the IA scale.

Alternate Wetting and Drying (AWD) Mitigates the Decline in Grain Filling of Basmati 370 Due to Low Temperature in Tropical Highlands

In the rice growing area of Kenya’s highlands, the development of a water-saving rice cultivation system is a key strategy because the shortage of irrigation water is a frequently occurring problem. The purpose of this study was to investigate the effect of alternate wetting and drying (AWD) on the growth and yield of rice under the unique cultivation environment of tropical highlands. Field experiments were performed over a period of four years (2014–2017) in a paddy field. Dry matter production of a lowland variety, Basmati 370, was greater under continuous flooding (CF) than under AWD. In years with low minimum temperature (less than 15 °C) during the reproductive and ripening stages, filled grain ratios were significantly higher under AWD than under CF. Accordingly, higher dry matter production under CF did not contribute to grain yield. In the years when rice was not exposed to low minimum temperature during the reproductive and ripening stages, filled grain ratio did not decrease even under CF. Therefore, there was no difference between filled grain ratio under AWD and CF. Our results indicated that AWD could mitigate the decline in grain filling, induced by low minimum temperature during the reproductive and ripening stages in Basmati 370, under the cultivation conditions in tropical highlands. Although AWD may reduce the above-ground biomass, its mitigation effect on grain filling could outweigh this drawback and can still be beneficial to rice farmers in the tropical highlands.

Water-Saving Irrigation and Nitrogen Fertilizer Use Efficiency for Irrigated Rice in the Red River Delta, Vietnam

The objective of this research was to quantify the effects of water-saving regimes and fertilizer application improvement on water productivity, N-use efficiency, and rice yield. The results showed that the tested water treatments did not have significant effects on the growth and development, yield components, and final grain yield, but water productivity was significantly increased from 1.28 kg grain m-3 (W0) water to 1.74 kg grain m-3 water (W1) and 1.94 kg grain m-3 water (W2). In addition, the percentage of total irrigation water saved from W1 and W2 were 25.24-44.52% compared to continuous flooding. Fertilizer deep placement (FDP) combined with organic compost significantly increased the grain yield of the tested hybrid rice variety. Average grain yield increased quickly from 2847 kg ha-1 with 0 kg N ha-1 to 5263 kg ha-1 with 120 kg N ha-1 under the fertilizer deep placement method. The highest total nitrogen uptake, agronomic nitrogen efficiency (ANE), and nitrogen uptake efficiency (NUE) were obtained from alternate wetting and drying at a -20cm water depth and the fertilizer deep placement method (W1N2). In addition, it also gave the highest income in comparison with the other treatments. Therefore, alternate wetting and drying at a -20cm water depth and fertilizer deep placement method should be encouraged for implementation in other regions of Vietnam.

Dimensioning of Wide-Area Alternate Wetting and Drying (AWD) System for IoT-Based Automation

Water, one of the most valuable resources, is underutilized in irrigated rice production. The yield of rice, a staple food across the world, is highly dependent on having proper irrigation systems. Alternate wetting and drying (AWD) is an effective irrigation method mainly used for irrigated rice production. However, unattended, manual, small-scale, and discrete implementations cannot achieve the maximum benefit of AWD. Automation of large-scale (over 1000 acres) implementation of AWD can be carried out using wide-area wireless sensor network (WSN). An automated AWD system requires three different WSNs: one for water level and environmental monitoring, one for monitoring of the irrigation system, and another for controlling the irrigation system. Integration of these three different WSNs requires proper dimensioning of the AWD edge elements (sensor and actuator nodes) to reduce the deployment cost and make it scalable. Besides field-level monitoring, the integration of external control parameters, such as real-time weather forecasts, plant physiological data, and input from farmers, can further enhance the performance of the automated AWD system. Internet of Things (IoT) can be used to interface the WSNs with external data sources. This research focuses on the dimensioning of the AWD system for the multilayer WSN integration and the required algorithms for the closed loop control of the irrigation system using IoT. Implementation of the AWD for 25,000 acres is shown as a possible use case. Plastic pipes are proposed as the means to transport and control proper distribution of water in the field, which significantly helps to reduce conveyance loss. This system utilizes 250 pumps, grouped into 10 clusters, to ensure equal water distribution amongst the users (field owners) in the wide area. The proposed automation algorithm handles the complexity of maintaining proper water pressure throughout the pipe network, scheduling the pump, and controlling the water outlets. Mathematical models are presented for proper dimensioning of the AWD. A low-power and long-range sensor node is developed due to the lack of cellular data coverage in rural areas, and its functionality is tested using an IoT platform for small-scale field trials.

Effect of Alternate Wetting and Drying Irrigation on the Nutritional Qualities of Milled Rice

Alternate wetting and drying (AWD) irrigation has been widely used to save irrigation water during rice production when compared to the traditionally continuous flooding (CF). Although the influence of AWD on water-saving potential and grain yield has been studied before, its detailed effect on grain nutritional quality in milled rice remains relatively unexplored. In this study, AWD could maintain grain yield as compared with CF. Thus, we undertook efforts to compare the nutritional traits of milled rice irrigated with AWD and CF regimes. A targeted metabolome assay on milled rice identified 74 differentially accumulated metabolites (DAMs) with 22 up- and 52 down-accumulated metabolites under AWD vs. CF. Clustering of the metabolite content obtained in this assay suggested that most of the metabolites showing significant changes belonged to “lipids,” “alkaloids,” and “phenolic acids.” In addition, total protein, starch, lipid, and amino acids content were measured to correlate it with the differential accumulation of specific metabolites detected in the metabolome. Overall, the data suggested that AWD may improve the nutritional performance of milled rice by increasing amino acids and phenolic acids and decreasing lipids and alkaloids. Our study provides research proof for the need for the optimization of irrigation to optimize rice nutritional qualities.