Alternate Wetting And Drying Research Articles

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 < 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.

Wheat Straw Burial Improves Physiological Traits, Yield and Grain Quality of Rice by Regulating Antioxidant System and Nitrogen Assimilation Enzymes under Alternate Wetting and Drying Irrigation

Wheat straw burial has great potential to sustain rice production under alternate wetting and drying (AWD) irrigation. A field experiment was conducted with three wheat straw burial treatments, including without straw burial (NSB), with light straw burial of 300 kg/hm2 (LSB) and dense straw burial of 800 kg/hm2 (DSB), as well as three AWD regimes: alternate wetting/moderate drying (AWMD), alternate wetting/severe drying (AWSD) and alternate wetting/critical drying (AWCD). The rice growth and grain quality were higher in LSB and NSB than those in NSB under the same AWD regime. The AWMD × DSB treatment resulted in the highest yield, brown rice rate, milled rice rate, amylose content and protein content. Conversely, the AWCD × NSB treatment led to the lowest yield, brown rice rate, milled rice rate, amylose content and protein content. The active absorption area and nitrate reductase activity of roots were higher in the AWMD × DSB treatment than those in the AWCD × NSB treatment, as the former increased organic carbon and nitrogen contents in the rhizosphere, whereas the latter reduced their availability. Total soluble protein content and glutamine synthetase activity were greater in the AWMD × DSB treatment than those in the AWCD × NSB treatment. The activities of superoxide dismutase and catalase were higher in the AWMD × DSB treatment compared with the AWCD × NSB treatment, leading to the amelioration of oxidative cell injury, as shown by a lower malonaldehyde level. This study suggested that farmers should implement AWMD irrigation after leaving the straw residues in the field, followed by deep tillage to improve soil quality and mitigate the drought stress cycles of AWD. This approach can improve rice growth and grain quality and alleviate the problems of disposal of straw residues and water scarcity for sustainable rice production.

A semi-empirical semi-process model of ammonia volatilization from paddy fields under different irrigation modes and urea application regimes

Both empirical models and process-based models of ammonia (NH3) volatilization simulation in paddy field have some disadvantages. This work describes a semi-empirical semi-process model, which combines the simplicity of empirical models with the precision of process-based models, and its combinatorial structure is sufficient for reproducing the characteristic course of NH3 volatilization in paddy fields under different irrigation modes and urea application regimes over time. A dataset consisting of seven rice seasons across three locations was used for model development. Performance indexes showed the model is good (R2 values ranged from 0.67 to 0.94). The influence of air temperature and wind speed on NH3 volatilization was not as great as our conventional understanding, and soil temperature was a more accurate indicator than air temperature for model development. Model performance was better where the less urea splits and the higher urea rate, but there was no significant difference between alternate wetting and drying (AWD) irrigation mode (average values of R2, IA, NSI, and RMSE were 0.82, 0.94, 0.96, and 0.53 kg ha-1 d-1) and flooding irrigation (FI) mode (average values of R2, IA, NSI, and RMSE were 0.86, 0.94, 0.96, and 0.58 kg ha-1 d-1). The ammonium nitrogen (NH4+-N) concentration and pH of surface water and soil water in paddy fields had the greatest impact on NH3 volatilization, and they were mainly related to the amount of urea applied. Splitting the urea application and delaying the first urea application are the fundamental countermeasures to reduce NH3 volatilization. The magnitude of developed model performance varied among rice cropping systems, irrigation modes, urea application regimes, and climatic regions, highlighting the need to understand why measured NH3 volatilization varies among locations. The new model may be a useful tool for predicting fertilizer efficiency of paddy fields applied urea, assessing NH3 volatilization factors, and reducing emission.

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.

Improvement and testing of ORYZA model water balance modules for alternate wetting and drying irrigation

While the ORYZA crop model has been widely used in the simulation of rice growth, its computation ability is limited in terms of simulating the water balance components (WBCs) of paddy fields under water-saving irrigation conditions, such as alternate wetting and drying (AWD) regimes. In this study, a new water balance simulation framework (WBSF) reflecting the characteristics of AWD is integrated into the original ORYZA2000 (v2.13) model to simulate the WBC of paddy fields. In addition, algorithms for dynamically simulating the root length growing rate are added to the original ORYZA. Algorithms quantifying water stress are also modified. The improved model is further applied to paddy fields in Yongkang and Tuanlin, which are two typical rice growing areas in China. The results show that the improved model performs well at simulating WBCs. The Nash-Sutcliffe efficiency (NSE) of daily ponded water depth ranged from 0.82 to 0.94 across experiments under continuous flooding and AWD at the two sites, showing an increase in NSE of at least 0.23 compared to ORYZA (v3) levels. The absolute value of relative errors (A RE) between simulated and measured values for total irrigation and drainage amount was mostly no more than 10% and showed a reduction of at least 11%. The improved model also showed better performance in terms of evapotranspiration, percolation and root length simulation compared to ORYZA (v3). The yield predictive accuracy of the improved model is slightly better than that of ORYZA2000 (v2.13) but worse than that of ORYZA (v3), which might be due to the poor performance of nitrogen balance modules in the improved model. In general, given the results achieved, it is possible to state that the WBSF of the improved ORYZA2000 showed an enhanced capability to simulate WBCs, which are recommended for use in water balance simulations of paddy fields.

Increased rice yield and reduced greenhouse gas emissions through alternate wetting and drying in a triple-cropped rice field in the Mekong Delta

For sustainable food production in the Mekong Delta, greenhouse gas (GHG) emissions from rice cropping activities need to be reduced without sacrificing rice productivity. Each year, a substantial amount of straw is incorporated into paddy soils through triple rice cropping, which is characterized by a short cropping period and nearly year-round flooding, such that a large amount of methane is emitted. Exposing these soils to oxidative conditions by altering the cropping-period water regime might have the potential to reduce GHG emissions with increased rice yield. To test this potential, a split-plot experiment was conducted in a typical triple-cropped alluvial farmer's paddy in a central delta area over five years and 15 consecutive cropping seasons.The emissions observed from the continuously inundated paddies were 1.1–2.7 times greater than the reported emission factors for Vietnamese continuously inundated paddies. A significantly higher emission peak was detected at the beginning of the rice cropping and flooding fallow periods in continuously flooded (CF) paddies than in alternate wetting and drying (AWD) paddies, although the differences in field water level and soil moisture among the paddies were negligible. AWD reduced annual methane emissions (−51 %) and increased rice yield (+9 %), presumably through enhanced translocation of carbohydrates from leaves to panicles. The amount of GHGs emitted from straw use also decreased (11 %) under AWD management because the straw production rate was significantly lowered (9 %) by enhanced nutrient translocation. These results indicate that GHG emission reduction potentials in the Mekong Delta have been underestimated by previous studies, corroborate the necessity of additional long-term observations of triple rice cropping systems and demonstrate the need for a robust methodology for monitoring the permanence of AWD effects after policies promoting its widespread dissemination take effect.

Combined Use of Biochar with 15Nitrogen Labelled Urea Increases Rice Yield, N Use Efficiency and Fertilizer N Recovery under Water-Saving Irrigation

Biochar is a potential carbon-rich soil amendment that improves the physicochemical properties of soil, besides acting as a controlled release fertilizer. An experiment was conducted to investigate the effect of biochars on rice yield, fertilizer use efficiency and recovery under water-saving irrigation by 15N isotopic tracer study. Two types of irrigation as alternate wetting and drying (AWD) and continuous flooding (CF), and four types of biochar treatments such as rice husk biochar (RHB) with 15N urea, oil palm empty fruit bunch biochar (EFBB) with 15N urea, 15N urea alone and control, were applied to assess their impact on rice. About 4% reduced grain yield with 18% improved water productivity was achieved by the AWD regime over the CF, whereas RHB and EFBB significantly increased rice yield compared to unamended soil. RHB and EFBB enhanced the water productivity up to 25.3%. The fertilizer N uptake and recovery were boosted by RHB and EFBB up to 18.8% and 24.5%, respectively. RHB and EFBB accelerated the agronomic use efficiency and partial factor productivity of N (up to 21% and 8%, respectively). RHB and EFBB profoundly enhanced the pH, the total C and N and the available N (NH4+ and NO3−) of the post-harvest soil. This study suggests that adding RHB and EFBB with urea improves fertilizer N utilization and soil N retention, and their combination with AWD could enhance rice yield with better water productivity due to their porous structure and controlled N release capacity.

Effect of potassium fertilizer and alternate wetting and drying (AWD) irrigation system for Boro rice cultivation in Faridpur region

Effect of potassium fertilizer and alternate wetting and drying (AWD) irrigation system for Boro rice cultivation in Faridpur region

Improving Nitrogen Use Efficiency in Aerobic Rice Based on Insights Into the Ecophysiology of Archaeal and Bacterial Ammonia Oxidizers.

The abundance and structural composition of nitrogen (N) transformation-related microbial communities under certain environmental conditions provide sufficient information about N cycle under different soil conditions. This study aims to explore the major challenge of low N use efficiency (NUE) and N dynamics in aerobic rice systems and reveal the agronomic-adjustive measures to increase NUE through insights into the ecophysiology of ammonia oxidizers. Water-saving practices, like alternate wetting and drying (AWD), dry direct seeded rice (DDSR), wet direct seeding, and saturated soil culture (SSC), have been evaluated in lowland rice; however, only few studies have been conducted on N dynamics in aerobic rice systems. Biological ammonia oxidation is majorly conducted by two types of microorganisms, ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). This review focuses on how diversified are ammonia oxidizers (AOA and AOB), whose factors affect their activities and abundance under different soil conditions. It summarizes findings on pathways of N cycle, rationalize recent research on ammonia oxidizers in N-cycle, and thereby suggests adjustive agronomic measures to reduce N losses. This review also suggests that variations in soil properties significantly impact the structural composition and abundance of ammonia oxidizers. Nitrification inhibitors (NIs) especially nitrapyrin, reduce the nitrification rate and inhibit the abundance of bacterial amoA without impacting archaeal amoA. In contrast, some NIs confine the hydrolysis of synthetic N and, therefore, keep low NH4+-N concentrations that exhibit no or very slight impact on ammonia oxidizers. Variations in soil properties are more influential in the community structure and abundance of ammonia oxidizers than application of synthetic N fertilizers and NIs. Biological nitrification inhibitors (BNIs) are natural bioactive compounds released from roots of certain plant species, such as sorghum, and could be commercialized to suppress the capacity of nitrifying soil microbes. Mixed application of synthetic and organic N fertilizers enhances NUE and plant N-uptake by reducing ammonia N losses. High salt concentration promotes community abundance while limiting the diversity of AOB and vice versa for AOA, whereas AOA have lower rate for potential nitrification than AOB, and denitrification accounts for higher N2 production. Archaeal abundance, diversity, and structural composition change along an elevation gradient and mainly depend on various soil factors, such as soil saturation, availability of NH4+, and organic matter contents. Microbial abundance and structural analyses revealed that the structural composition of AOA was not highly responsive to changes in soil conditions or N amendment. Further studies are suggested to cultivate AOA and AOB in controlled-environment experiments to understand the mechanisms of AOA and AOB under different conditions. Together, this evaluation will better facilitate the projections and interpretations of ammonia oxidizer community structural composition with provision of a strong basis to establish robust testable hypotheses on the competitiveness between AOB and AOA. Moreover, after this evaluation, managing soils agronomically for potential utilization of metabolic functions of ammonia oxidizers would be easier.

Alternate wetting–drying enhances soil nitrogen availability by altering organic nitrogen partitioning in rice-microbe system

Alternate wetting and drying (AWD) irrigation influences soil nutrient cycling and the functioning of soil microorganisms. However, the effects of AWD on organic nitrogen (ON) partitioning in rice-microbe ecosystems and soil microbial communities are poorly understood. A root-box microcosm experiment with two rice varieties (Nipponbare, Nip; Yangdao 6, YD6), two irrigation regimes (conventional flood irrigation (CF); AWD) and three N application levels (zero N, N0; medium N, N1; high N, N2) was performed based on the 13C,15N-labelled glycine and 13C-phospholipid fatty acids (PLFA) techniques. Compared to CF, AWD increased soil dissolved oxygen, microbial growth and the enzymes related to N transformation, thus enhancing rice growth and the N utilization index (NUI). Approximately 4.9–10.3% and 7.7–13.6% of the exogenous glycine was directly utilized by Nip and YD6 seedlings, respectively, and its ratio increased with increasing N levels, whereas 4.4–11.2% and 4.6–10.3% were incorporated into soil microbes. It seems that rice has an appreciable capacity to utilize organic N despite fierce competition with soil microbes. The 13C:15N ratio showed that 12.5–37.5% and 11.0–41.0% of the added glycine was taken up intact by soil microorganisms in the rhizospheres of Nip and YD6. At the N1 and N2 levels, AWD increased rice 15N-glycine uptake but decreased microbial 15N-glycine uptake. Rice intact glycine uptake and soil inorganic N contents were positively correlated with rice biomass and NUI, indicating that the enhanced inorganic N under AWD is beneficial for soil ON availability and rice growth. Gram-negative and general bacteria were the dominant competitors with rice for soil ON. AWD increased the contents of gram-negative bacteria and fungi and the ratio of fungi:bacteria in rhizosphere soils. Collectively, AWD creates a good rhizosphere oxygen environment for rice and microbial growth. ON partitioning in the rice-microbe system and the adaptive adjustment of the microbial community play important roles in modulating soil nutrients for optimal rice growth.

Sustainable groundwater use in the Eastern Gangetic Plains requires region-specific solutions

This study aimed to examine whether conservation agriculture can be applied across the Eastern Gangetic Plains (EGP) as a strategy to ensure that groundwater use for irrigation remains sustainable as demands increase. The study analysed the groundwater balance in the EGP at sub-region, district and field scales using MODFLOW, a water balance model, and the APSIM model, respectively and evaluated the current state of groundwater development aiming to address sustainability concerns. Long-term groundwater use and aquifer reserves reveal the significant influence of groundwater extraction on the current state of the water balance. In the Indian and northwest Bangladesh sub-regions, accelerated extraction may result in groundwater mining in areas where potential maximum recharge has already been achieved or exceeded, while further development of groundwater may be possible in areas where actual recharge is still less than potential recharge. At district level, the water supply versus demand situation shows a large annual surplus in the East but a deficit in the West. Conservation Agriculture (CA) and Alternate Wetting and Drying (AWD) irrigation practice exert varying impacts on water demand; crop transpiration (Ep) is generally higher in CA compared to Conventional Tillage (CT), while soil evaporation (Es) is similar in both practices. Net evapotranspiration, although very similar in both practices, is generally greater in CA. AWD has a limited effect on Es but reduces the percolation rate and therefore irrigation requirement of Boro rice. In conclusion, the cause–effect associations between irrigation water use and groundwater sustainability are not spatially uniform across the EGP, nor will they likely be so under further agricultural development associated with increased water demands. The study suggests that the cause–effect interactions between irrigation water use and groundwater sustainability cannot be generalized across the EGP and, therefore, CA or AWD should not be applied uniformly across the region.

Performance evaluation of a water level sensor under various turbidity levels in lowland crop production systems

The practice of alternate wetting and drying (AWD), a water-saving technology in lowland crop production systems, can be greatly facilitated using wireless water level sensors. However, these sensors generally work under clear water conditions. The sensitivity of these sensors to turbidity is important for accurate water level measurement and appropriate irrigation scheduling. This study evaluated the performance of a high-end water level sensor of the submersible pressure transducer type under various turbidity levels. The performance tests were performed in the laboratory using water samples collected from a typical lowland rice production system under various levels of turbidity replicated three times with clear water as control. The readings of the sensors were compared with manual readings for each turbidity level in all replications. Results showed that the measured water level depth generally increases with increasing turbidity for each voltage level. The linear regression or calibration equation developed for each turbidity level proved to be adequate as evidenced by a relatively low RMSE of less than 1 mV. Results of ANOVA suggest that turbidity significantly affects the accuracy of the water level sensor (p <.001). A unified calibration equation (R2=0.9985 and RMSE=1.971 mV) was developed to account for the effect of turbidity up to 4300 FAU on the water level measurements. Results of this study can be used to improve the accuracy of water level monitoring in irrigated lowland crop production systems employing alternate wetting and drying technology to further increase irrigation efficiencies and augment water savings particularly during the dry season or under water-scarce conditions for a more sustainable crop production.

Nutrient Dynamics of Rice Cultivars under Different Irrigation Regimes and Systems of Cultivation

ABSTRACT This study investigated the performance of rice cultivars under the best method of irrigation and system of cultivation on clay loam soils of Indian Institute of Rice Research, Rajendranagar, Hyderabad, Telangana, during the kharif seasons of 2017 and 2018. Thetreatment consisted of two irrigation regimes, viz. alternate wetting and drying (AWD) and saturation as main plot treatments; three establishment methods, viz. system of rice intensification (SRI), drum seeding (DS), and normal transplanting (NT) as subplot treatments; and four cultivars, namely DRR Dhan 42, DRR Dhan 43, MTU-1010, and NLR-34449 as sub-sub plot treatments summing up to 24 treatment combinations laid out in split–split plot design with three replications. Among the irrigation regimes, AWD noticed significantly superior nitrogen, phosphorus, and potassium uptake at 60, 90 DAS/DAT, and at harvest during 2017 and 2018 as compared to saturation. Between irrigation regimes, AWD recorded significantly superior N, P, and K use efficiency as compared to saturation. At 60, 90 DAS/DAT, and at harvest, SRI method recorded significantly superior N, P, and K uptake as compared to NT and DS during both the years. Higher NUE of nitrogen, phosphorus, and potassium was observed with SRI than DS and NT methods. N, P, and K uptake was significantly superior with DRR Dhan 43 at 60, 90 DAS, and harvest during both the years of study followed by MTU-1010. Among the rice cultivars, higher N, P, and K use efficiency was recorded in DRR Dhan 43 over other rice cultivars.

Physicochemical Variables Better Explain Changes in Microbial Community Structure and Abundance under Alternate Wetting and Drying Events

Soil microbial communities play an important role in nutrient cycling; however, their response under repeated long-term fertilization has attracted little attention and needs further appraisal. A 14-day incubation study compared the relative abundance, diversity, and composition of bacterial and fungal microbial communities in soils treated with long-term applications of chemical fertilizer (CF), pig manure plus chemical fertilizer (PMCF), and rice straw plus chemical fertilizer (SRCF) in a paddy field. A high-throughput sequencing approach was applied to assess the diversity and composition of microbial community. Results revealed the Shannon index of the bacterial community decreased with fertilizer addition but increased in case of fungal community. The abundance of the Actinobacteria was higher in the PMCF, while Proteobacteria were higher in the CF and SRCF treatments than those in the unamended control under alternate wetting and drying (AWD) and permanent flooding (PF). In addition, chemical fertilizer history increased the abundance of Firmicutes under AWD. Initially, Nitrospira were found higher in the unamended control than in the amended treatments, but an increase was observed with time in fertilized treatments. Among all genera, Proteobacteria were the most abundant bacterial genus. The main properties that markedly affected the bacterial communities were SOC (R2 = 0.4037, p &lt; 0.02), available P (R2 = 0.3273, p &lt; 0.05), and NO3− (R2 = 0.3096, p &lt; 0.08). Soil physicochemical factors and biogenic factors explained a variation of 46.27% and 29.35%, respectively. At the same time, 4.59% was the combined effect of physicochemical and biogenic factors. Our results suggested that the physicochemical properties had a more significant impact on bacterial activities than water regime by increasing N and organic matter concentrations in the soils.

Mitigating the accumulation of arsenic and cadmium in rice grain: A quantitative review of the role of water management

Arsenic exposure through rice consumption is a growing concern. Compared to Continuous Flooding (CF), irrigation practices that dry the soil at least once during the growing season [referred to here as Alternate Wetting and Drying (AWD)] can decrease As accumulation in grain; however, this can simultaneously increase grain Cd to potentially unsafe levels. We modelled grain As and Cd from field studies comparing AWD and CF to identify optimal AWD practices to minimize the accumulation of As and Cd in grain. The severity of soil drying during AWD drying event(s), quantified as soil water potential (SWP), was the main factor leading to a reduction in grain total As and inorganic As, compared to CF. However, lower SWP levels were necessary to decrease grain inorganic As, compared to total As. Therefore, if the goal is to decrease grain inorganic As, the soil needs to be dried further than it would for decreasing total As alone. The main factor driving grain Cd accumulation was when AWD was practiced during the season. Higher grain Cd levels were observed when AWD occurred during the early reproductive stage. Further, higher Cd levels were observed when AWD spanned multiple rice growth stages, compared to one stage. If Cd levels are concerning, the minimum trade-off between total As and Cd accumulation in rice grain occurred when AWD was implemented at a SWP of −47 kPa during one stage other than the early reproductive. While these results are not meant to be comprehensive of all the interactions affecting the As and Cd dynamics in rice systems, they can be used as a first guide for implementing AWD practices with the goal of minimizing the accumulation of As and Cd in rice grain.

Evaluating the Suitability of System of Rice Intensification Practices for Enhancing Rice and Water Productivity in Semi-Arid Environment, Tamil Nadu, India

&#x0D; In the world of rapid change in climate, irregular rainfall pattern tends to pose serious impact on water availability for agriculture. Rice is one of the important food crops to get affected by the low water availability because of its high water requirement. Various techniques were used in the past to mitigate low water availability and increase productivity but most techniques will improve one aspect at the expense of the other. System of Rice Intensification (SRI) is being tried by many countries with several modifications based on their priorities, with the aim of enhancing productivity besides reducing the water demand for rice cultivation. It is essential to have more insight into the individual and compounding effect of multiple components of SRI on yield, and water productivity of rice for identifying the potential and suitable SRI practices. Investigating the influence of different practices of SRI viz., planting of young and single seedlings per hill in wider spacing, water saving irrigation like Alternate Wetting and Drying (AWD), and weed control using cono-weeders on rice using the data obtained from the field experiment carried out during 2021 in Tamil Nadu Agricultural University, Coimbatore, India. Water productivity of rice plants under SRI were compared with conventional practices. The results revealed that plants grown with complete SRI practices had increased water productivity by 0.25 kg grain/m3 of water which is almost twice that of conventional cultivation system. The yield obtained in SRI treatments was higher about 39% than conventional treatments. The total water savings were 20 % higher in AWD treatments than continuous flooding treatments.&#x0D; &#x0D;

Unravelling the Growth Potential of Rice under Modified Rice Cultivation System in Tamil Nadu, India

There is a need for increasing rice productivity to cope up with increasing population and water shortages, especially in Tamil Nadu, India. Efforts were made in the past, mainly to increase the genetic potential of the crop, by developing high yielding varieties. However, adoption of improved agronomic practices and production technologies could further increase the productivity besides saving water. System of Rice Intensification (SRI) comprises the various altered agronomic practices and is proved to be an effective cultivation method by enhancing the rice growth and productivity. It is important to understand influence of individual practices and their combinations on rice growth and productivity for deriving the maximum growth and yield advantages of SRI features. A field experiment was conducted at Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu to study the growth responses of rice to different practices of SRI viz., 14 days old seedling with single seedling per hill, square planting pattern with wider spacing, Alternate Wetting and Drying (AWD) method of irrigation and, use of cono-weeders to control weeds. It was found that planting younger seedlings with single seedling per hill greatly increased dry matter assimilation in rice plants and the use of cono-weeders encouraged the tiller production in rice. The treatments with complete SRI practices produced 3 times higher number of tillers and panicles per hill and 38.9 percent more dry matter content than conventional practices. SRI practices could be adopted by the farmers to boost the growth attributes of rice and to achieve higher rice productivity in Tamil Nadu.