Alternate Wetting And Drying Irrigation Research Articles

Assessment of outcrossing potential between cultivated and weedy rice under alternate wetting and drying irrigation management

AbstractIn recent years, water conservation efforts in rice production have necessitated the use of reduced irrigation input systems such as alternate wetting and drying (AWD) as a substitute to conventional continuous flood‐irrigated systems (FLD), but little is known about the role of AWD in altering outcrossing potentials between cultivated rice and weedy rice (WR). In the United States, rice growers often control WR by cultivating varieties that possess herbicide resistance. However, an ongoing concern with such technology is hybridization or outcrossing between herbicide‐resistant rice cultivars and WR over time. Such outcrossing may result in transferring of herbicide resistance with increased occurrence of herbicide‐resistant WR ecotypes and reduction in the efficacy of herbicide management. This study compared and quantified outcrossing rates between two Clearfield rice varieties (CL142AR and CL261) that are herbicide resistant and two common WR genotypes, strawhull (SH) and blackhull (BH), under FLD and AWD management. Outcrossing was evident in all four genotype combinations (i.e., CL142AR or CL261 cultivated rice and SH or BH weedy rice) in both FLD and AWD; however, outcrossing rates with CL261 averaged about 6.5 times lower than those with CL142AR. Additional analysis revealed that higher outcrossing rates were associated with increased synchrony of flowering times and closer vertical proximity of panicles of WR to CL142AR than with CL261. AWD irrigation reduced outcrossing in SH weedy rice, suggesting that reduced outcrossing of SH weedy rice might be an additional benefit from AWD irrigation management.

Mitigating of waterlogging associated problems by the management practices in the rice ecosystem of the Deltaic zone of Tamil Nadu

Cauvery Delta is the major rice-growing tract of Tamil Nadu. Continuous waterlogging is inevitable in the delta region due to unexpected heavy rain, leading to stunted crop growth and poor soil conditions. The present study aimed to alleviate the waterlogging-associated problems of stunted growth, crop nutrition deficiency, heavy algal growth and poor soil aeration issues in the heavy clayey soils of deltaic region of Tamil Nadu. Field experiments were laid out with the treatments viz., CuSO4,, (5kg/ha) (T1), Gypsum (500 kg/ha) (T2), Conoweeding+Alternate Wetting and Drying Irrigation(AWDI) (T3), microbial consortia (K and Zn solubilising Bacteria 500 ml/ha) (T4) control (T5) and combination of all (T6) except CuSO4 along with control . The results indicated that the T6 recorded higher plant height (110.2 cm), productive tillers/m2 of 332, filled grains of 118.3 and less chaffy grains of 20.3 nos, high nutrient status of 265 kg/ha of available N,35.4 kg/ha of available P,342 kg/ha of available K, 21.1meq/100 g of Ca,8.2 meq/100 g of Mg and root length and volume. The algal population in terms of dry biomass was reduced to 3.1 (g/m2) from the control group of 11.2 (g/m2) at 15 days after imposing treatment. The per cent increase of 26.0 % grain yield was also recorded in the combination treatment over control. From the present research, combined application of gypsum @500 kg/ha +Cono weeding twice +AWDI and microbial consortia of Zn and K solubilising bacteria @500ml/ha could be recommended for better soil environment and rice production in the delta region.

Maximization of Productivity and Water Saving through Alternate Wetting and Drying Irrigation (AWDI) in Rice under Tamil Nadu Irrigated Agriculture Modernization Project (TN IAMP) Aliyar Sub Basin Farmers of Tamil Nadu, India

TN IAMP-II Aliyar sub basin scheme operated by Agricultural College and Research Institute (TNAU), Vazhavachanur, Tiruvannamalai, Tamil Nadu state has conducted large-scale front-line demonstrations on Alternate Wetting and Drying Irrigation (AWDI) practice in transplanted paddy growing in 11 villages of Tiruvannamalai district at 100 farmer’s holdings during kharif season of 2019-20 and 2020-21. The data on productivity, economics and water saving in demonstrated plots were compared with Flood irrigation 1200 mm (Farmer practice). The demonstrated plot yield was 64.2 q / ha compared with farmer practice (51.7 q / ha). The yield increase was 24.3 per cent. The extension gap, technology gap and technology index were 12.6 q ha-1, 5.8 q ha-1 and 8.29 per cent, respectively. The higher gross return (Rs. 128,443 ha-1), higher net return (Rs. 74,319ha-1) and B: C (2.38) was observed in demonstrated plot compared to farmers’ practice plot (Flood irrigation). Higher yield and returns due to reduced cost of cultivation, higher grain yield, net returns and more water saving in AWDI (24.7%).Water depth of 5 cm was maintained in the demo plot (T2) over the farmer’s practice (T1) (Water depth 30.0 cm) and the field water level was measured by Field water Tube. Created awareness and motivated the farmers to adopt AWDI practices in TN IAMP Phase II Aliyar sub basin of Tiruvannamalai district.

Effect of Alternate Wetting and Drying on the Emission of Greenhouse Gases from Rice Fields on the Northern Coast of Peru

The cultivation of rice is one of the main sources of greenhouse gas (GHG) emissions due to continuously flooded irrigation (CF), which demands large volumes of water. As an alternative solution, alternate wetting and drying (AWD) irrigation has been developed as a water-saving strategy. This study was conducted at the Experimental Agricultural Station (EEA) in Vista, Florida, in the Lambayeque region located on the northern coast of Peru. Thus, it was analyzed the effect of AWD irrigation at different depths (5, 10, and less than 20 cm below the surface) compared to CF control on methane (CH4) and nitrous oxide (N2O) emissions and rice grain yield. AWD treatments reduced CH4 emissions by 84% to 99% but increased N2O emissions by 66% to 273%. In terms of Global Warming Potential (GWP), the AWD10 treatment demonstrated a 77% reduction and a Water Use Efficiency (WUE) of 0.96, affecting only a 2% decrease in rice grain yield, which ranged between 11.85 and 14.01 t ha−1. Likewise, this study provides sufficient evidence for the adoption of AWD irrigation as a strategy for the efficient use of water resources and the mitigation of GHG emissions in rice cultivation in the study area, compared to continuous flooded irrigation.

Performance evaluation of alternate wetting and drying irrigation for rice cultivation

An experiment was conducted during the 2009-2010 Boro season at the Shahjalal Science and Technology University campus, Sylhet, Bangladesh, to investigate the impact of alternate wetting and drying irrigation (AWDI) on rice production. Using a randomized complete block design (RCBD), four irrigation treatments were applied to a modern variety (MV) of rice (BRRIdhan 28). One control treatment, T0, maintained a continuous standing water depth of 1-5 cm. Water was irrigated to three AWD treatments, T1, T2, and T3 when the water level dropped 10, 20, and 30 cm below ground level, respectively. In spite of the fact that treatment T0 produced the highest grain yield (4.90 t/ha), its water use efficiency was 38.64 kg/ha/cm. Compared to treatment T1, which produced 4.68 t/ha, treatment T1 had a water use efficiency of 41.86 kg/ha/cm. Treatments T2 and T3 yielded 3.96 t/ha and 3.63 t/ha, respectively. When water levels fall below 10 cm below ground level, treatment T1 may be the best option for rice cultivation in conditions of limited water availability.

Effects of integrated plant nutrition systems with fertilizer deep placement on rice yields and nitrogen use efficiency under different irrigation regimes

Improved fertilizer management, with a combination of organic and inorganic inputs, has the potential to enhance rice yield while maintaining soil health. However, studies on the effects of broadcast prilled urea (PU) and urea deep placement (UDP) applied in combination with organic inputs (poultry litter [PL] and vermicompost [VC]), as integrated plant nutrition systems (IPNSs), on rice yields and nitrogen use efficiency (NUE) under alternate wetting and drying (AWD) irrigation are limited. We conducted field experiments during the dry and wet seasons of 2018, 2019, and 2020 to investigate the effects of fertilizer treatments, including control (no nitrogen), UDP, PU, and IPNSs (PU + VC, PU + PL, and UDP + PL) on rice yield and NUE under two irrigation regimes – AWD and continuous flooding (CF). The results revealed that fertilizer treatment and irrigation regime had significant (p < 0.05) interaction effects on rice yield and the agronomic efficiency of N (AEN) during the dry season. UDP significantly (p < 0.05) boosted rice yield, total dry matter (TDM), and NUE as compared to broadcast PU in both wet and dry seasons. Similarly, the IPNS treatment of UDP with PL significantly (p < 0.05) boosted rice yield, TDM, and NUE in comparison to broadcast PU. Under AWD irrigation, UDP alone produced higher rice yields than other treatments, while UDP, and UDP with PL produced similar yields under CF irrigation. During the dry season, AWD irrigation significantly (p < 0.05) increased rice yield, TDM, and AEN when compared to CF conditions, but during the wet season, AWD irrigation demonstrated a rice yield and NUE equivalent to CF. This research implies that using a UDP alone or in combination with PL as an IPNS could be a good way to boost crop productivity while also maintaining soil fertility.

Development and evaluation of the first automated irrigation system for alternate wetting and drying technique in rice cultivation in Bangladesh

Rice stands as one of the most water-intensive crops in agriculture, demanding a substantial volume of water annually for cultivation in Bangladesh. To address this considerable water requirement, the International Rice Research Institute (IRRI) introduced the alternate wetting and drying (AWD) irrigation method. This approach necessitates consistent manual oversight to maintain the desired water levels in the field. In pursuit of reducing this manual effort, a study was conducted at Bangabandhu Sheikh Mujibur Rahman Agricultural University. The study aimed to develop an automated version of the AWD irrigation system, assess its impact on plant growth and yield-contributing factors, and investigate water use efficiency through using that automated system. The automated AWD system incorporated water level controllers, solenoid valves, and water level detection probes to regulate water levels in the paddy field. The experiment followed a Randomized Complete Block Design (RCBD) with three treatments: T1 (Conventional Irrigation - CI), T2 (AWD), and T3 (Automated Alternate Wetting and Drying - AAWD), each replicated four times. The findings indicated minimal variation in growth and development parameters of the rice plants between the CI and AWD treatments. Likewise, yield components demonstrated no significant differences among the various treatments. Notably, the treatment with automated alternate wetting and drying (AAWD), namely T3, displayed the highest water use efficiency (WUE) at 65.20 kg/ha/cm, while the lowest WUE of 52.56 kg/ha/cm was observed in the conventional irrigation (CI) treatment T1. The results underscore the clear advantage of adopting an automated AWD system, yielding a 20% reduction in irrigation water usage compared to the conventional approach. This transition also minimizes the need for labor-intensive interventions in the paddy fields of Bangladesh, illustrating the potential for more efficient and sustainable rice cultivation practices.

Effects of Water Management and Rice Varieties on Greenhouse Gas Emissions in Central Japan

Greenhouse gas (GHG) emissions from paddy fields depend on water management practices and rice varieties. Lysimeter experiments were conducted to determine the effect of rice varieties (lowland; Koshihikari (KH) and upland; Dourado Precoce (DP)) on GHG emissions under two water management practices: alternate wetting and drying (AWD) and continuous flooding (CF). A repeated cycle of drying and wetting in AWD irrigation was performed by drying the soil to −40 kPa soil matric potential and then rewetting. Consequently, the closed chamber method was used to measure direct emissions of methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2). The result revealed that water management significantly affected CH4 and N2O emissions (p &lt; 0.05), while no significant effect was observed between different rice varieties. Although, AWD irrigation reduced CH4 emissions, it increased N2O emissions compared to CF irrigation, likely due to increased oxygen supply. AWD irrigation decreased GWP by 55.6% and 59.6% in KH and DP, respectively, compared to CF irrigation. Furthermore, CH4 and N2O emissions significantly correlated with soil redox potential and volumetric water content. These results suggest that AWD irrigation might be an effective water management method for mitigating GHG emissions from rice fields in central Japan.

Hydrus-1D Model for Simulating Phosphorus Transport in Paddy Crop Irrigated with Alternate Wetting and Drying Practice

ABSTRACT The alternate wetting and drying (AWD) irrigation practice involves soil moisture stress-based irrigation scheduling which possibly affects the rice field’s phosphorus (P) transport and balance components. The focus of this study was to understand P-transport under AWD irrigation and estimate the associated balance components in rice using a solute transport model, Hydrus-1D. In this study, rice was cultivated in 30 lysimeter plots with three irrigation treatments (no soil water stress/NS, mild soil water stress/400 cm/MS, and severe soil water stress/750 cm/SS) and each treatment was replicated 10 times. The field experimental data were used to simulate P transport with the help of the Hydrus-1D model. The Hydrus-1D model was calibrated and validated for P transport within the soil matrix under AWD irrigation practice. The P distribution was mostly concentrated within the top puddled soil layer (0–20 cm) and did not move to the deeper soil layers. The simulated results indicate that the recommended dose of P with 3–5 cm ponding water depth will increase the P availability for rice and reduce the P leaching loss in AWD irrigation practice. The Hydrus-1D model can be used as a management tool to determine the appropriate P application rate and ponding water depth irrigated with AWD for which the required P nutrients are sufficiently available to rice and the P loss to the environment can be controlled for sustainable rice production.

Mitigation of Nitrous Oxide Emissions from Rice–Wheat Cropping Systems with Sub-Surface Application of Nitrogen Fertilizer and Water-Saving Irrigation

Management of nitrogen (N) fertilizer and irrigation can play a critical role to increase nitrogen use efficiency (NUE). However, the impacts of N application at the root zone via urea briquette deep placement (UDP) and water-saving irrigation alternate wetting and drying (AWD) on N2O emissions are not well-understood. A greenhouse study was conducted to investigate the impacts of UDP on N2O emissions, NUE, and grain yields of rice and wheat compared with broadcast prilled urea (PU). For rice, the effect of UDP was evaluated under continuous flooding (CF) and AWD, while the control (no N) and PU were tested only under CF. In rice, UDP under CF irrigation produced similar emissions to PU-CF, but UDP under AWD irrigation increased emissions by 4.5-fold compared with UDP under CF. UDP under CF irrigation increased (p &lt; 0.05) rice grain yields and N recovery efficiency (RE) by 26% and 124% compared with PU-CF, respectively. In wheat, UDP had no effects (p &gt; 0.05) on emissions compared with PU. However, it produced higher wheat grain yields (9%) and RE (35%) over PU. In conclusion, UDP under CF irrigation increases the RE and grain yields of rice without increasing N2O emissions, but the yield may reduce and N2O emissions may increase under AWD.

Effects of Irrigation Regimes and Rice Varieties on Methane Emissions and Yield of Dry Season Rice in Bangladesh

Adoption of the right rice variety and water-saving irrigation method could reduce greenhouse gas (GHG) emissions in lowland rice cultivation. A study was conducted at the research farm of Bangladesh Agricultural University, Mymensingh, Bangladesh, in 2019 during the Boro (dry) season to determine the impacts of different rice varieties (BRRI dhan29, BRRI dhan47, BRRI dhan69, Binadhan-8, Binadhan-10, and Binadhan-17) on methane (CH4) emissions under two irrigation methods, i.e., alternate wetting and drying (AWD) and continuous flooding (CF). The treatments were laid out in a split-plot design, considering water regime as the main plots and rice variety as the sub-plots. The emission rates of CH4 were determined by collecting air samples using the closed chamber technique and measuring the concentrations using a gas chromatograph. CH4 emission rates varied with the growth and development of the rice varieties. The lowest cumulative CH4 emission rate was observed in Binadhan-17, particularly under AWD irrigation. Across the rice varieties, AWD irrigation significantly reduced the cumulative CH4 emissions by about 35% compared with CF. No significant variation in rice yield was observed between AWD (5.38 t ha−1) and CF (5.16 t ha−1). This study suggests that the cultivation of Binadhan-17 under AWD irrigation could be effective at reducing the carbon footprint of lowland rice fields.

Impact of alternate wetting and drying irrigation and brown manuring on water use, weed control and yield of drum seeded rice

Direct-seeded rice (DSR) is a cost-effective and environmentally friendly method of crop establishment. Weed menaces in DSR considerably reduce the yield potential, which can be addressed by effective irrigation and weed management practices. Information on the impact of various water-saving irrigations and brown manure (BM) on water use, weed studies, and the yield of drum-sown rice is very limited. A field investigation was conducted to determine the effects of alternate wetting and drying irrigation (AWDI) methods (10 cm, 15 cm dropped from FWT and farmers practices) and BM (Sesbania at 15, 20 and 25 kg ha-1, Pretilachlor 0.45 kg ha-1 as PE fbBispyribac Na 25 g ha-1 as PoE + hand weeding (HW) on 45 DAS, HW at 20 and 45 DAS, and weedy check. The results revealed that AWDI at 15 cm depletion of FWT with HW on 20 and 45 DAS increased the water use efficiency (5.3 kg ha mm-1), water productivity (0.53 kg m-3), water saving percentage (35.83%), and reduced the water consumption (770 mm). Continuous submergence with HW at 20 and 45 DAS significantly increased grain (4.4 t ha-1) and straw yield (6.5 t ha-1). At the same time, it reduced the grasses (53.3 and 58.4%) and sedges (76 and 75%), density and dry weight, respectively, over AWDI at 10 cm dropped from FWT. Thus, irrigation at 10 cm below FWT with sesbania BM at 20 kg ha-1 could be recommended for higher productivity of drum-sown rice under sodic soil conditions.

A Low-Cost Wireless Sensor for Real-Time Monitoring of Water Level in Lowland Rice Field under Alternate Wetting and Drying Irrigation

The use of wireless sensors for real-time monitoring of field water level would greatly facilitate the application of alternate wetting and drying (AWD), an irrigation water management technique proven to result to significant water savings and reduced methane emissions in lowland rice production systems. However, most of the commercially available wireless sensors are generally costly. This study developed a low-cost wireless sensor that can perform real-time monitoring of water depth and surface temperature in lowland rice fields under an AWD irrigation regime. The sensor is composed mainly of an ultrasonic depth sensor, a waterproof temperature sensor, a humidity sensor, and a Wi-Fi-enabled microcontroller enclosed in a PVC cap that can be mounted in AWD pipes. The sensor was tested under laboratory, pseudo-field conditions and actual field conditions. Results showed a relatively high degree of agreement between sensor and manual measurements of water depth under all testing conditions, with the error ranging from only 5.2% to 6.6% and RMSE of 5.0 mm to 13.5 mm. The performance of the low-cost sensor also proved to be comparable with that of the high-end sensor, exhibiting practically similar measurement accuracy and higher precision. The wireless sensor developed in this study can provide a low-cost alternative to the high-cost and high-end sensors and other commercially available counterparts for efficient irrigation water management in lowland crop production systems during water-scarce conditions induced by climate change and climate variability.

Effects of mild alternate wetting and drying irrigation and rice straw application on N2O emissions in rice cultivation

Abstract. The shortage of water resources and the decline in soil organic matter (SOM) are critical limiting factors affecting the improvement in rice productivity, while alternate wetting and drying (AWD) irrigation and recycling application of rice straw (S) are considered favorable mitigation measures. However, the impact of such measures on rice yield and greenhouse gas (GHG) emissions, especially nitrous oxide (N2O) emissions, needs to be further clarified to ensure that agronomic practices save water, conserve soil, and reduce GHG emissions. Therefore, we explored the effects of mild AWD irrigation combined with on-site rice straw recycling on N2O emissions and rice yield through rice pot experiments. This experiment included 2 irrigation methods (continuous flooding (CF) irrigation and mild AWD irrigation), 2 nitrogen (N) application levels (0 and 225 kg N ha−1) and 2 rice straw return levels (0 and 9000 kg ha−1), for a total of 10 treatments, and each treatment had 3 replicates. The 15N-urea and 15N-S were added to the soil. The results showed that N2O emissions were primarily affected by urea application and irrigation methods, with urea application being most important. Compared with CF irrigation, mild AWD irrigation increased cumulative N2O emissions, with an average increase of 28.8 %. In addition, adding rice straw to mild AWD irrigation further stimulated N2O emissions by 18.1 %. Under the condition of urea application, compared with CF irrigation, mild AWD irrigation increased the yield-scaled N2O emissions by 17.9 %, and the addition of rice straw further promoted the yield-scaled N2O emissions under mild AWD irrigation by 17.4 % but reduced the global warming potential (GWP) (methane (CH4) + N2O) by 62.9 %. Under the condition of urea application, compared with CF irrigation, mild AWD irrigation reduced the uptake of soil-derived N and aboveground biomass of rice but did not reduce rice yield. Therefore, mild AWD irrigation combined with rice straw return may be a promising agronomic method to maintain rice yield, reduce GHGs, and protect or improve soil fertility.

Arbuscular mycorrhizal fungi inoculation and phosphorus application improve growth, physiological traits, and grain yield of rice under alternate wetting and drying irrigation

Climate change and agricultural malpractices are exacerbating drought in many parts of the world causing a substantial agricultural production loss. The improvement of drought tolerance in rice is crucial for maintaining productivity and ensuring global food security. Alternate wetting and drying (AWD) irrigation along with plant-microbe interaction through arbuscular mycorrhizal fungi (AMF) is a potential approach for enhancing rice production through AMF-induced up-regulation of tolerance and resilience against drought stress. Therefore, the ameliorative role of AMF inoculation and phosphorus (P) application on growth, physiological traits, and grain yield of rice was evaluated under water stress imposed through AWD irrigation. A factorial experiment consisting of four fertilizer treatments where the P percentage varied along with the recommended dose of nitrogen (N) with or without AMF inoculation (P100 as the control, P100 + AMF, P75 + AMF, and P50 + AMF), three soil water potential levels (0, −15, and −30 kPa), and two cultivation methods (wet direct seeding and transplanting) was conducted in a polyhouse. The subscript values of 100, 75, and 50 under P represent 100%, 75%, and 50% of the recommended field application dose. Data were collected on selected growth parameters, physiological traits, levels of mycorrhizal colonization, yield and its components, and water productivity of rice. The results revealed that P100 + AMF inoculated plants had 11%, 14%, 74%, and 54% higher leaf greenness, leaf relative water content, net photosynthetic rate, and grain yield, respectively, for wet direct-seeded plants at reduced soil water potential (−30 kPa) compared with non-inoculated plants (P100). Free proline accumulation gradually enhanced with decreasing soil water potential, and it was maximized by 77% at −30 kPa compared with 0 kPa for P50 + AMF (for transplanted plants). Free proline accumulation was also higher with decreasing soil water potential in AMF-inoculated plants than non-inoculated plants regardless of cultivation methods. Leaf osmotic potential was reduced by −0.5 to −1.2 MPa at −30 kPa compared with 0 kPa under different fertilizer doses. However, AMF inoculation (P100 + AMF and P75 + AMF) improved leaf osmotic potential of plants under severe water stress (−30 kPa) maintained through AWD irrigation resulting in better osmotic adjustment than non-inoculated plants. AMF inoculation improved the response of most of the evaluated physiological traits of rice and enhanced grain yield with higher P availability (even with a 25% reduction in its recommended dose) in the rhizosphere under drought stress. Thus, it can be concluded that AMF inoculation coupled with judicious P management is a promising approach for improving physiological and biochemical traits, grain yield, and water productivity of rice under AWD irrigation regardless of cultivation methods.

Integrated Plant Nutrient Systems Improve Rice Yields without Affecting Greenhouse Gas Emissions from Lowland Rice Cultivation

Efficient management of fertilizers and irrigation could mitigate greenhouse gas (GHG) emissions and increase crop yields. Field experiments were conducted to determine the effects of an integrated plant nutrient system (IPNS) and water regime—alternate wetting and drying (AWD) and continuous flooding (CF)—on GHG emissions and rice yield. Fertilizer treatments included control (no N), prilled urea (PU), urea deep placement (UDP), and IPNS (50% N from poultry litter and 50% N from PU). Gas sampling and analysis were performed using a closed-chamber technique and gas chromatography. IPNS produced significantly (p &lt; 0.05) higher seasonal total methane (CH4) emissions (9–15%) compared to the UDP treatment, but the emissions with IPNS were similar to those of PU. IPNS had an interaction effect with the water regime on nitrogen oxide (N2O) emissions. IPNS produced more emissions than PU under AWD, but their emissions were similar under CF irrigation. IPNS produced a significantly higher total global warming potential (GWP) than UDP but a GWP similar to the PU treatment in both Aus (pre-monsoon) and Aman (wet) seasons. AWD irrigation reduced the total GWP by 8% over CF without yield reductions. IPNS significantly increased rice yields compared to broadcast PU but yields were similar to those of UDP. These findings suggest that both IPNS and UDP could be effective in increasing crop yields without increasing GHG emissions.

Arsenic accumulation in rice: Alternative irrigation regimes produce rice safe from arsenic contamination

The natural occurrence of arsenic (As) in groundwater & soils and its bioaccumulation in rice grains is a major health concern worldwide. To combat the problem, best combination of irrigation management and suitable rice variety altering As content in grains must be ensured. With this aim, a field trial was conducted with two rice varieties and water management including alternate wetting and drying (AWD) and continuous flooding (CF) irrigation regimes with As contaminated groundwater (AsW) and temporarily stored groundwater (TSG) and river water for only CF (as control). Results revealed that As content in different portions of paddy plant was significantly different (P < 0.001) with irrigation practices and rice varieties. AWD irrigation with TSG accumulated lower As in rice grains compared with CF-AsW for both varieties. Data showed that AWD-TSG practice led to 61.37% and 60.34% grain As reduction for BRRI dhan28 and BRRI dhan29, respectively, compared with CF-AsW. For Principle Component Analysis (PCA), first principle component (PC1) explained 91.7% of the variability and irrigation water As, soil total and available As, straw As, root As and husk As were the dominating parameters. With significant (P < 0.05) variation in yields between the genotypes, AWD increased grain yield by 29.25% in BRRI dhan29 Compared with CF. However, translocation factor (TF) and bioconcentration factor (BCF) for both varieties were less than one for all the treatments. The addition of this study to our knowledge base is that, AWD-TSG with BRRI dhan29 can be an As–safe practice without compromising yields.

Alternate Wetting and Drying (AWD) on Rice Irrigation

In Malaysia, numerous methods have been subsequently established subjected to water-saving irrigation aiming to improve the common conventional irrigation system. However, among the most preferred water-saving method, alternate wetting and drying (AWD) irrigation adoption are presently in paddy cultivation yet has very limited information, especially locally. Hence, this study intended to propose two treatments, namely continuously flooded (control) and AWD irrigation, to investigate the feasibility of AWD implementation. The experiment was conducted at the paddy field of Padang Raja Kelantan, Malaysia. From the result, the agronomic performance was evaluated by several attributes under the growth performance evaluation, grain yield performance evaluation, and chlorophyll measurement. Statistical analysis was performed on the obtained data, and both growth, yield performances, and chlorophyll content resulted in no significant difference at p &lt; 0.05, a 95% confidence level.

Rice Growth Performance, Nutrient Use Efficiency and Changes in Soil Properties Influenced by Biochar under Alternate Wetting and Drying Irrigation

Water-saving irrigation occasionally causes an inconsequential yield loss in rice; thereby, biochar incorporation in this context has great scope due to its properties, including the release of nutrients and improving soil physicochemical properties. An experiment was conducted to investigate the effect of biochar combined with fertilizer on physiological response, water and nutrient efficiency of rice and changes in biochemical properties of soil under AWD (alternate wetting and drying) irrigation system. Two types of irrigation practice, such as AWD and CF (continuous flooding), and four types of fertilizer combination, namely T1: 25% Rice husk biochar (RHB) + 75% of recommended fertilizer dose (RFD); T2: 25% oil palm empty fruit bunch biochar (EFBB) + 75% of RFD; T3: 100% RFD; and T0: 0% biochar and fertilizer, were assigned to assess their impacts. The AWD irrigation produced a sharply reduced grain yield (210.58 g pot−1) compared to CF irrigation (218.04 g pot−1), whereas the biochar combination treatments T1 and T2 produced greater yields (260.27 and 252.12 g pot−1, respectively), which were up to 12.5% higher than RFD. Within AWD, irrigation water usage by T1 and T2 (98.50 and 102.37 g L−1, respectively) was profoundly reduced by up to 28.8%, with improved water use efficiency (WUE). The main effect of biochar treatment T1 and T2 also increased photosynthesis rate during vegetative and maturing stage (up to 17.6 and 24.4%, respectively), in addition to boosting agronomic efficiency of nitrogen (N), phosphorous (P) and potassium (K) compared to RFD (T3). Nevertheless, T1 and T2 significantly enhanced the total carbon and nitrogen; dehydrogenase and urease enzyme activities also increased in both irrigation regimes. The results reveal that the integrated application of RHB and EFBB with fertilizer in the AWD regime significantly reduces irrigation water usage and improves nutrient use efficiency, WUE and soil biochemical properties with a minimum yield penalty for rice.

Farmers’ Participatory Alternate Wetting and Drying Irrigation Method Reduces Greenhouse Gas Emission and Improves Water Productivity and Paddy Yield in Bangladesh

In dry season paddy farming, the alternate wetting and drying (AWD) irrigation has the potential to improve water productivity and paddy production and decrease greenhouse gas (GHG), such as methane (CH4) and nitrous oxide (N2O), emissions when compared to continuous flooding (CF). Participatory on-farm trials were conducted from November 2017 to April 2018 in the Feni and Chattogram districts of Bangladesh. Total 62 farmers at Feni and 43 at Chattogram district, each location has 10 hectares of land involved in this study. We compared irrigation water and cost reductions, paddy yield, and CH4 and N2O emissions from paddy fields irrigated under AWD and CF irrigation methods. The mean results of randomly selected 30 farmers from each location showed that relative to the CF irrigation method, the AWD method reduced seasonal CH4 emissions by 47% per hectare and CH4 emission factor by 88% per hectare per day. Moreover, the AWD decreased the overall global warming potential and the intensity of GHG by 41%. At the same time, no noticeable difference in N2O emission between the two methods was observed. On the other hand, AWD method increased paddy productivity by 3% while reducing irrigation water consumption by 27% and associated costs by 24%. Ultimately it improved water productivity by 32% over the CF method.