Continuous Submergence Research Articles

Post-smolt Atlantic salmon can regulate buoyancy in submerged sea-cages by gulping air bubbles

Salmon lice (Lepeophtheirus salmonis) are the most severe health challenge facing Atlantic salmon (Salmo salar) aquaculture. Infestations threaten farmed and wild salmonids, drive up production costs, and limit industry growth. Submersible sea-cages can reduce infestation pressure by holding salmon below the surface layers where lice larvae are most abundant. However, submergence leads to loss of buoyancy over time, as salmonids must periodically refill their swim bladders by gulping air. Pockets of air held at depth within ‘air domes’ enable salmon to gulp air, but air domes are large and unwieldy structures. A more intuitive solution may be to deliver a stream of air bubbles at depth, as bubbling is commonly used in sea-cages to promote vertical mixing, and salmon interact with these bubbles. Here, we conducted a pilot study to test whether newly sea-transferred salmon would use bubbles for buoyancy regulation. We conducted 3 trials in sequence, each involving 15–19 days of continuous submergence, and recorded buoyancy-related behaviors in 1 cage with full surface access, 1 cage submerged without air, and 2 cages submerged with air bubbling. Bubbling was provided continuously in the first two trials, before being reduced to 90 min day−1 in the third trial. Salmon submerged with bubbling maintained their swim bladder volume and swimming speed at similar levels to the cage with full surface access throughout all trials, indicating that they successfully refilled using bubbles. The same parameters deteriorated in salmon in the cage submerged without air. Acclimation to bubbles took ∼3 days whether at the surface or after submergence, indicating that several days of bubbling before submergence may be beneficial. Some fish accumulated fluid in the swim bladder during submergence (more severe in fish submerged without bubbling). Together, the results suggest that bubbling can improve outcomes for salmon undergoing prolonged submergence. Moreover, bubbling offers an alternative to air domes that is less technically demanding, provides a greater spatial distribution of air, and supports welfare through behavioral enrichment.

Cationic micronutrient fractions in some tropical Alfisols and Inceptisols as affected by organic amendments and simulated moisture regimes: an incubation study

Cultivation of rice is severely jeopardized by the intangible behavior of micronutrients under variable moisture and organics leading to its inconsistent availability. The present study has been conducted to determine the effect of organic amendments and moisture regimes on cationic micronutrients like zinc (Zn), copper (Cu), iron (Fe) and manganese (Mn). Controlled situation incubation study using thrice replicated factorial randomized design with (3 organic amendments × 2 moisture regimes × 2 incubation periods) levels was conducted. Continuous submergence (CS), 50 g kg−1 rice straw and 150 days of incubation (DOI) restored higher soluble and Exchangeable (SE) manganese and iron; while SE-Cu was facilitated under alternate wetting and drying (AWD) condition. SE-Zn was found higher under AWD, no organic administration and 60 DOI. Again AWD, 50 g kg−1 rice straw and 60 DOI recovered higher Mn, Cu, Fe and Zn in organically bound fractions. The adoption of CS, 50 g kg−1 rice straw and 150 DOI recovered higher Mn, Cu, Fe and Zn in manganese and amorphous iron oxide bound fractions; while AWD, no rice straw administration and 60 DOI recovered higher Mn, Cu, Fe and Zn in crystalline iron oxide bound fractions. Substantial change in all the studies fraction resulted into alteration in plant availability of Mn, Cu, Fe and Zn. Under the scenario of global increasing water demands, AWD apart from saving 30-40% moisture improves availability of Cu and Zn which is further accentuated by organic matter, sustaining soil productivity and ensuring food security.

Echinochloa in mid-southern U.S. and California rice: What is known and what are the knowledge gaps?

AbstractSeveral species of Echinochloa P. Beauv., introduced at multiple events, have established themselves as a persistent concern for U.S. rice production. In this review, we highlight the key biological characteristics of economically relevant Echinochloa in U.S. rice production, revisit their historical trajectory, and suggest research directions for their management with special reference to barnyardgrass. Ecologically differentiated Echinochloa species have a distinct association with rice culture methods that have been practiced for the last few decades, barnyardgrass being historically predominant in drill-seeded rice in the mid-South, and early watergrass and late watergrass in water-seeded California rice. However, the emerging evidence challenges the dogma that other Echinochloa species for specific regions are of less importance. Primarily managed by the water-seeding method of rice culture in the early years of the 20th century, Echinochloa species have persisted in the sophisticated U.S. rice culture through the evolution of resistance to herbicides in recent decades. Accumulating knowledge, including those of recent genomic insights, suggests the rapid adaptability of Echinochloa. The last decade has seen a (re)emergence of nonchemical methods as a key component of sustainable management, among which use of harvest weed seed control (HWSC) methods and cover crops in the mid-South and stale-drill seeding in California are being considered as potential methods for managing Echinochloa. In recent years, furrow-irrigated rice has rapidly supplanted a significant proportion of conventionally flooded rice in the mid-South, whereas the propensity for compromised continuous submergence is increasing in California rice. On the cusp of this shift, the question at the forefront is how this will affect Echinochloa interference in rice and how this change will dictate the management efforts. Future research will lead to the development of a clear understanding of the impact of the changing agroecosystems on Echinochloa species and their response to the prospective integrated control interventions.

Microscopy research of the steel surface layer in the splash area of ships and ocean technical facilities

The authors of the article describe research of the surface steel layer for the conditions of continuous submergence into the seawater test solution and for the splash area of ships and ocean technical facilities. Results of microscopic examination indicated a substantial difference in the structure and composition of the surface layer depending on the experimental conditions. Further study of the obtained elemental composition and microscopy images will allow the development of the computer-aided data analysis procedure based on the computer vision system with the application of intellectual frameworks to predict shipbuilding steel potentials at various stages of exposure to seawater with the aim to enhance corrosion protection methods.

Water Savings, Yield, and Economic Benefits of Using SRI Methods with Deficit Irrigation in Water-Scarce Southern Iraq

This study evaluated what intervals of irrigation in conjunction with the use of SRI methods could achieve the greatest economic, as well as agronomic returns when growing irrigated rice under the water-deficit conditions of southern Iraq. A field study at the Al-Mishkhab Rice Research Station in southern Iraq recorded input and output data for three different irrigation regimes: continuous submergence of the rice crop; irrigation at 3-day intervals; and irrigation at 7-day intervals. Benefit–cost analysis showed 3-day intervals with SRI methods, giving the highest net returns and highest internal rate of return, indicating that the continuous irrigation of rice fields is a waste of water, with neither agronomic nor economic benefit. In Iraq, there are large opportunity costs for any unnecessary use of irrigation water. The highest water productivity was achieved with 7-day intervals of irrigation together with SRI methods, but this entails some sacrifice of the yield ha−1, as 13% less grain is produced than with continuous submergence of the crop. With 7-day intervals compared to 3-day intervals, water-saving was 44%, but compared to continuous submergence of the crop, the saving was 72%. This large amount of water could, if redeployed, enable many more farmers to cultivate larger areas of the land, increasing total rice production for Iraq, and some of the water saved could be put to other, high-value uses. It would thus benefit the country and many farmers if, in return for rice farmers’ using irrigation water more productively, those who currently grow rice could be persuaded to accept a grain yield somewhat lower than they could produce with 3-day intervals of irrigation and SRI crop management. The redeployment of water saved by having longer irrigation intervals coupled with SRI methods could raise Iraq’s rice output more than enough to compensate the farmers for forgoing some attainable production by their accepting 7-day irrigation intervals. If no such incentive scheme could be established, there would still be a significant benefit for farmers and for the country by moving to SRI production methods with 3-day intervals rather than continuing the present practice of routinely flooding rice fields and using conventional methods.

Temporal transformation of indium speciation in rice paddy soils and spatial distribution of indium in rice rhizosphere

Indium is a potentially toxic element that could enter human food chains, including soil-rice systems. The submerged environment in rice paddy soil results in temporal and spatial variations in the chemical properties of the rice rhizosphere and bulk soils, expected to cause changes in indium's chemical speciation and consequently affect its bioavailability. Therefore, this study aimed to investigate indium speciation and fractionation in soils at different periods of rice growth under continuous submergence using X-ray absorption spectroscopy and a sequential extraction method. The predominant indium species were identified as indium-associated Fe hydroxide, and indium hydroxide and phosphate precipitates. The reductive dissolution of indium-associated Fe hydroxides led to the release of indium into the soil solution under continuous submergence of soils, and the released indium concentration decreased with time due to re-sorption and re-precipitation. Meanwhile, indium hydroxide was found to be the predominant species in rice rhizosphere using μ-X-ray absorption spectroscopy. The relative depletion of indium-associated Fe hydroxides in the rice rhizosphere was attributed to the low mobility of indium from bulk soil to rice rhizosphere and the root uptake of indium associated with Fe hydroxide around rice roots. Consequently, indium uptake by rice roots was lower during the reproductive and grain-ripening stage of rice growth. Understanding the behavior of indium will help develop a strategy to minimize uptake into crops in indium-contaminated paddy soils.

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.

Productivity, nutrient uptake and profitability of winter season rice (Oryza sativa) varieties as influenced by alternate wetting-drying irrigation and nitrogen management

A field experiment was conducted on clay loam soil at Agricultural Research Institute, Rajendranagar, Hyderabad, Telangana, during the winter (rabi) season of 2016–17 and 2017–18, to identify optimum scheduling of alternate wetting and drying irrigation (AWD) under different nitrogen levels on rice (Oryza sativa L.) varieties. The treatments consisted of 3 irrigation regimes, i.e. recommended submergence of 2 to 5 cm water level, AWD irrigation when water level falls below 3 cm from soil surface in perforated pipe, AWD irrigation when water level falls below 5 cm from soil surface in perforated pipe, as main plot treatments; 3 nitrogen levels (120, 160 and 200 kg N/ha) as subplot treatments; and 2 rice varieties (‘KNM 118’ and ‘JGL 18047’) as sub-subplot treatments laid out in a split-split plot design with 3 replications. There was no significant difference in terms of growth, yield attributes, yield, nutrient uptake and economics between rice varieties ‘KNM 118’ and ‘JGL 18047’ with continuous submergence, and alternate wetting and drying irrigation under different nitrogen levels during the winter (rabi) season. Irrigation maintained at recommended submergence of 2 to 5 cm water level resulted in higher growth parameters, yield attributes, grain yield (7,123 kg/ha), straw yield (8,045 kg/ha), nutrient uptake and net returns (`57,202/ha), which were comparable with AWD irrigation when water level falls below 3 cm from soil surface in perforated pipe. Application of 200 kg N/ha ensued higher growth parameters, yield attributes, grain yield (7,086 kg/ha), straw yield (7,907 kg/ha and net returns (`57,247/ha), which were at par with 160 kg N/ha.

Physiological dissection of submergence tolerance in rice under island ecosystem

Rice cultivation in the islands encounters submergence at various growth stages leading to Substantial yield and quality loss. Continuous and heavy rainfall during a short-span leads to water logging and continuous submergence even up to five days. Developing submergence/flooding tolerant versions of adapted elite rice genotypes helps to reduce the yield loss in these areas. The present study was undertaken to evaluate the physiological response of rice genotypes adapted to island conditions under submergence stress. The outcome of the study will help to identify promising donor for breeding submergence stress tolerance cultivars with the background of popular rice varieties of A&N islands. The tolerant genotypes like Black Burma, IR64 Sub1, revealed that they posses many of the adaptive traits like slower elongation during submergence, chlorophyll retention, higher stem reserves post submergence, higher survival per centage required for the flood-prone island ecosystem.

Prevalence Of Nematode Population In Two Different Rice Cultivation Systems And Its Impact On Crop Growth

An experiment was carried out to study the prevalence of nematode population in two different cultivation systems (SRI and conventional) on rice cv. IET- 4094 (Khitish). Total twenty-eight plots were laid out in paired plot technique. Irrespective of rice cultivation systems, there had been a steady hike in population of Meloidogyne graminicola and Tylenchorhynchus mashhoodi with the maximum being recorded near harvest and a sudden fall during fallow period was observed. The study indicated that SRI cultivation provided comparatively more favourable ecological condition for steady buildup of M. graminicola and T. mashhoodi population than conventional system. Between two systems, SRI method encountered comparatively more population of Hoplolaimus indicus. The spiral nematode, Helicotylenchus dihystera was also found associated with the rice crop but statistical analysis did not reveal any stable result to come into conclusion about their ecological preference. The study revealed that continuous submergence of rice field as in conventional system was detrimental to growth and reproduction of R. reniformis. The rice crop grown under SRI method acquired more vigorous growth as compared to conventional system. Profuse root and shoot growth as evidenced by root length, root biomass yield and straw yield in SRI might have limit the yield reduction in spite of huge infestation of nematodes.

Yield and Economics as Influenced by Irrigation and Weed Management Practices in Rice

An experiment was conducted to study the effect of irrigation and weed management practices weed seed bank at college farm situated in College of Agriculture, PJTSAU, Hyderabad, during kharif 2019 and 2020. The experiment consisted of two main plot treatments and nine subplot treatments laid out in Split plot design replicated thrice. Two irrigation practices (Alternate wetting and drying irrigation and continuous submergence) and nine weed management practices (pretilachloar 50 EC 660 g ha-1(PE) fb mechanical weeding twice, pyrazosulfuron ethyl + pretilachloar 6.15 GR 615 g ha-1 (PE) fb penoxsulam + cyhalofop p butyl 6.12 OD 125 g ha-1 (POE), orthosulfamuron + pretilachloar 6.6 GR 600 g ha-1 (PE) fb mechanical weeding twice, penoxsulam + butachloar 39.77 SE 820 g ha-1 (PE) fb mechanical weeding, flucetosulfuron 10% WG 25 g ha-1(Early PoE) fb mechanical weeding, bispyribac sodium + 2, 4-D sodium salt 56.3 SP 703.75 g ha-1 (PoE) fb mechanical weeding once, florpyrauxifen benzyl + cyhalofop p butyl 12 EC 150 g ha-1 (PoE) fb mechanical weeding once, hand weeding twice and unweeded control). There was no significant difference observed in irrigation practices for grain yield. With respect to weed managements, significantly higher grain yield was recorded in hand weeding and integrated weed management (IWM) involving penoxsulam + butachloar fb mechanical weeding. As an economics aspect is concerned, continuous submergence recorded higher cost of cultivation and higher grass return. Among weed management practices, hand weeding and IWM involving penoxsulam + butachloar fb mechanical weeding recorded higher cost of cultivation and higher gross return. As net return is concerned, IWM involving penoxsulam + butachloar fb mechanical weeding recorded higher, whereas B: C ratio in chemical weed control.

Yield-contributing Factors in Lowland Irrigated Rice as Affected by Variety, Water Management, and Fertilizer Rate in Agusan Soil

Rice grain yields in irrigated areas of Agusan del Norte/Sur provinces ranged at only 3.3–3.8 t/ha in 2010–2019 – hence the need to study the yield potential of varieties, appropriate water management, and optimum fertilizer rates to improve such yields. This study assessed the effects of rice varieties, water management, and fertilizer rates on grain yield and agronomic parameters. It also recommended variety, water management, and fertilizer rate for improving grain yields in Agusan soil. Screenhouse experiment was done using lowland rice soils collected from Remedios T. Romualdez, Agusan del Norte, Philippines. The experiment was laid out in unbalanced randomized complete block design with three factors: [1] PSB Rc 18, NSIC Rc 122, and PSB Rc 82 for the variety factor; [2] continuous submergence (CS) and alternate wetting and drying (AWD) for the water management factor; and [3] PalayCheck (PFR) and farmers’ fertilizer rates (FFR) for the fertilizer rate factor. Three replications each for PSB Rc 18+CS+PFR, PSB Rc 18+CS+FFR, PSB Rc 18+AWD+FFR, NSIC Rc 122+CS+FFR, NSIC Rc 122+AWD+FFR, PSB Rc 82+CS+PFR, PSB Rc 82+CS+FFR, and PSB Rc 82+AWD+FFR plus four replications each for PSB Rc 18+AWD+PFR, NSIC Rc 122+CS+PFR, NSIC Rc 122+AWD+PFR, and PSB Rc 82+AWD+PFR were employed. Data on chlorophyll (chl) levels, plant height, tiller count, and number of healthy and unhealthy leaves were gathered weekly. Yield component data, including panicle lengths and dry weight of all filled grains or grain yields, were determined before and after harvesting. Dry weight of straw and roots were also assessed. Compared with PSB Rc 82, PSB Rc 18 had a significantly higher grain yield by 9% due to enhanced protection of chloroplast structure, leading to longer leaf area duration and higher chl contents across growth stages (GSs). These contributed to an improved “sink” or significantly greater number of grains per panicle by 19% and enhanced “source” or better health status of leaves. Improved “source” increased the grain filling efficiency, resulting in a significantly higher number of filled grains per panicle by 18%, grain weight per panicle by 21%, and harvest index by 6%. In contrast with AWD, CS had a significantly higher grain yield by 7% due to higher soil nitrogen availability leading to better yield-contributing plant traits. These traits include a significantly longer vegetative stage by 3%, greater straw biomass by 9%, higher leaf chl levels, and better health status of leaves from grain filling until harvesting. Moreover, the lower number of small, unproductive tillers in CS allowed more plant resources to be used for improving the health of large, panicle-bearing tillers. Compared with FFR, PFR had a significantly higher grain yield by 18% due to a closer-to- the-optimum fertilizer rate leading to an improved “source.” Improved “source” includes the following statistically significant parameters: [1] higher number of tillers by 7–18%, greater number of healthy leaves, and higher total number of leaves throughout GSs; [2] greater biomass by 15%; [3] higher chl content from booting until grain filling stage; and [4] better health status of leaves from booting until harvesting. The closer-to-the-optimum fertilizer rate also improved the “sink,” which was the significantly higher number of productive panicles by 16% and longer panicles by 2%. The study implies that certain management practices – employing a more adapted variety, CS or PFR in Agusan soil – provides a better genetic or environmental factor, which enhances plant traits and improves grain yields. Management recommendations are as follows: [1] PSB Rc 18 should be selected over PSB Rc 82 because it is more adapted in Agusan soil, [2] CS should be preferred over AWD in a non-zinc-deficient Agusan soil, and [3] the 74-28-43-24 kg N-P2O5-K2O-S/ha PFR should be selected over the 42.0-4.5-10.5-3.8 kg N-P2O5-K2O-S/ha FFR. Variety, water management, and fertilizer rate do not have significant two- and three-way interaction effects on grain yield; hence, no specific combination of the three factors can be recommended.

Why Are Barnacles Common on Intertidal Rocks but Rare in Rock Pools? Effect of Water Temperature, Salinity, and Continuous Submergence on Barnacle Survival in Indian Ocean Rock Pools

Barnacles are less common in rock pools of the rocky intertidal zone than on open rock surfaces adjacent to those pools. Rock pools on the Andaman coastlines of Thailand showed diurnal variations in water temperature, salinity, pH, and dissolved oxygen level, peaking in the afternoon. Multivariate analysis showed that water temperature and salinity (not pH and dissolved oxygen) can affect barnacle abundance in rock pools. The present study tests the hypothesis that a lack of recruitment or pool environmental conditions (continuous submergence, water temperature, and salinity extremes) affect the abundance of barnacles (Chthamalus malayensis and Amphibalanus amphitrite) in rock pools. During the recruitment season, recruits were found in a number of rock pools, but at significantly lower abundances than those in adjacent open rock surfaces. In a laboratory experiment, C. malayensis and A. amphitrite that were continuously submerged had a lower survival (80%) than the controls (simulated tide conditions; >90% survivals). Under different water temperature and salinities treatments, barnacles had low survival (<50%) in the low salinity (0‰) and high temperature treatment (40°C). The present study suggests that C. malayensis and A. amphitrite can recruit into rock pools, and the interplay of continuous submergence, high water temperature and low salinity in rock pools can bring about mortality in barnacles.

Deficit irrigation and organic amendments can reduce dietary arsenic risk from rice: Introducing machine learning-based prediction models from field data

Dietary rice consumption can assume a significant pathway of the carcinogenic arsenic (As) in the human system. In search of a viable mitigation strategy, a field experiment was conducted with rice (cv. IET-4786) at geogenically arsenic-contaminated areas (West Bengal, India) for two consecutive years. The research aimed to explore irrigation management (saturation and alternate wetting and drying), and organic amendments (vermicompost, farmyard manure, and mustard cake) efficiencies in reducing As load in the whole soil-plant system. A thrice replicated strip plot design was employed and As content in the soil, plant parts, and the associated soil physicochemical properties were determined through a standard protocol. Results revealed that the most negligible As accumulation in the edible grains was accomplished by vermicompost amendment along with alternate wetting and drying (0.318 mg kg−1) over farmer’s practice of continuous submergence with no manure situation (0.895 mg kg−1). Interestingly, an increase in the grain yield by 25% was also observed. The risk of dietary exposure to As through rice was assessed by target cancer risk (TCR) and severity adjusted margin of exposure (SAMOE) mediated risk thermometer. The adopted strategy made all the risk factors somewhat benign to ensure a better standard of health. The Machine Learning algorithm revealed that Random Forest performed better in predicting grain As concentration than k-Nearest Neighbour and Generalized Regression Model. Hence, if properly calibrated and validated, the former can represent an effective tool for predicting grain As concentration in rice.

Evaluation of safe alternative wetting & drying and its influence on growth, yield and water use of the efficiency of rice (Orzya sativa l.)

Due to the increase in scarcity of freshwater resources available for irrigated agriculture and escalating demand for food around the world, in the future, it will be necessary to produce more food with less water. Due to inadequate or unevenly-distributed rainfall, irrigation is essential to high rice yields. A field experiment of Alternative Wetting and Drying Irrigation (AWDI) was conducted during kharif season 2014 & 2015 at Soil & Water Management Research Institute, Tamil Nadu Agricultural University, Thanjavur, Tamil Nadu, India. The treatments ranged from delayed irrigations of T1 to T6 (10, 15, 20 cm depletion of water level below the ground level, 15cm depletion of water up to maximum tillering, up to panicle initiation & up to 10 days prior to harvest) and continuous submergence (T7) of field irrigation water denoting the application of 5 cm flooded water condition, when the water level in the perforated PVC pipe fell at 10, 15 and 20 cm below ground level respectively. There was a significant (5% level) consequence of plant height, productive tillers, filled grains, yield and Water Use Efficiency (WUE) due to the influence of AWDI. The highest yield (5981 kg/ha) and WUE (7.56 kg/ha/mm) was recorded in treatment T1. Longer water stress resulted in the loss of grain yield to the tune of 500 to 1000 kg/ha. This study found that in sandy loam soil at 10cm depletion of ponded water produced maximum yield (5809 kg/ha, besides the highest B.C ratio of 2.02) and WUE (7.56 kg/ha mm).

Water Management and Varietal Selection Approach in Mitigation of Arsenic in Inceptisols of West Bengal, India

ABSTRACT Irrigation with contaminated Arsenic (As) water is greatly correlated with increased soil As along with enhanced uptake in plants, which in turn biologically accumulates in different parts of the plant at toxic levels. The current study is aimed at characterization and mitigation of Arsenic contamination through irrigation and varietal selection. Characterization of arsenic was done through staggered random sampling. Experimental plots were laid in highly As contaminated farmer’s field with three rice varieties and three moisture regime in randomized block design keeping summer rice as standing crop. According to the Artificial Neural Network (ANN) study, soil phosphorus, followed by soil pH, Nitrogen, and Potassium have been found to be more sensitive in regulating soil As. The Alternate Wetting Drying (AWD) irrigation regime has significantly less arsenic concentration in rice when compared with Saturation (SAT)<Continuous Submergence (CS). Interestingly, maximum transfer of arsenic from soil to grain has been observed in AWD, with the least use of contaminated irrigation. Transfer factors (TFs) for As was least in cultivar IET-17430 as compared with IR-36> IET-4786.

Soil Organic Carbon Sequestration and Carbon Pools in Rice Based Cropping Systems in Indo-Gangetic Plains: An Overview

Carbon sequestration in the agricultural lands is possible through different soil management strategies and could be substantial with widespread implementation. Sequestration of historic carbon emissions is now essential as mitigation alone is not enough to stabilize our atmosphere. There are numerous management strategies for drawing carbon out of the atmosphere and holding it in the soil. Effectiveness of these strategies vary across different climates, soil types, and geographies. Still, it is a controversy about the durability of sequestration in soil and about the precise conditions that maximize drawdown of carbon emissions. Carbon sequestration in soil is the potential strategy which can reduce or mitigate the impacts of the global warming. The Asian countries are having more than 90% of rice fields, they are being blamed for their contribution in the methane emission and associated climate change. A major part of rice is grown under the continuous submergence condition that may influence the active and passive pools of soil carbon besides methane emission. In this paper we have reviewed the carbon sequestration potential of rice-based soils besides discussion on the mechanisms and strategies that promote accumulation of soil carbon while minimizing carbon emissions. The strategies viz. System of Rice Intensification, Integrated Nutrient Management, promoting mycorrhizal symbiosis in aerobic rice system besides enhancement of phytolith-occluded carbon are some of the key areas facilitating better carbon sequestration in rice ecosystem.

Simulating the Production of Rice Genotypes by Flood Management and End-Season Water Stress Conditions Using AquaCrop Model

ABSTRACT The present study was conducted to assess the ability of AquaCrop model in predicting of grain and biological yield of rice genotypes in water management. A two-year field experiment was conducted at the experimental farm of the Iranian Rice Research Institute in Rasht, Iran from 2016 to 2017. The experiment was established in a split-plot design with two irrigation management (continuous submergence and end season water stress) as the main plot, fourth rice genotypes as the sub-plot and three replications. The goodness-of-fit between observed and simulated grain yield and final biomass was assessed by means of the coefficient of determination (R 2), the absolute and normalized root mean square errors (RMSE). The RMSEn of predicting grain yield at calibration and evaluation stages was in the range of 6–12% and 6–8% for biological yield. The results indicated that AquaCrop model is suitable to predict grain yield and biological yield of rice genotypes in northern Iran. AquaCrop model can be used to determine optimization strategies to improve the water consumption of rice genotypes.

Study on energy consumption of various rice establishment methods and water management practices in tank irrigated command area

Field experiments were conducted at Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai, Tamil Nadu, India, during summer 2019 to find out energy efficient rice establishment methods under irrigation management strategy. Field experiment comprised of four establishment methods in main plot viz., conventional transplanting (M1), machine transplanting under puddled soil (M2), machine transplanting under unpuddled soil (M3) and sowing with seed drill (M4). The sub plot consisted of 4 irrigation management practices viz., farmers’ irrigation practice (continuous submergence of 5 cm throughout the crop period) (I1), Irrigation after formation of hairline crack (I2), irrigation when water level reaches 5 cm below soil surface (I3) and irrigation when water level reaches 10 cm below soil surface (I4). Medium duration fine grain rice variety TKM 13 was used for the study. Result of the study revealed that among the rice establishment methods higher energy output, net energy production, energy ratio and profitability was observed under machine transplanting under unpuddled soil. Among the irrigation management practices, irrigation after formation of hairline crack (I2) observed higher energy output and net energy production; whereas, energy ratio, energy productivity, energy intensity and B:C ratio were higher with irrigation when water level reaches 5 cm below soil surface (I3). This study concluded that machine transplanting under unpuddled soil combined with irrigation when water level reaches 5 cm below soil surface can be recommended as the suitable technology for the farmers of tank irrigated command area to get higher output energy with minimum use of input energy and also to obtain higher profit.

Yield, water use efficiency and water productivity of rice (Oryza sativa L.) relative to irrigation management and crop establishment methods

A field experiment was conducted at Crop Research Centre, RPCAU, Pusa, Bihar during Kharif, 2017. The soil of the experimental plot was sandy loam in texture with low in available N, P2O5 and K2O. The experiment was laid out in split plot design and replicated thrice. A total of twelve treatment combinations were used viz., three irrigation levels (I) in main plots and four crop establishment methods (E) in sub-plots. Irrigation level includes I1 - Continuous submergence throughout crop growth, I2-Saturation maintenance upto PI and (5±2cm) after PI and I3 -Alternate wetting and drying (5 cm irrigation at 3 DADPW) up to PI and (5±2 cm) after PI while the methods of establishment includes E1- Normal transplanting, E2- Direct w.et seeding on puddled soil, E3- Direct dry seeding and E4- Broadcasting on un-puddled soil. Grain as well as straw yield were significantly influenced by different crop establishment methods but not significantly affected by different irrigation levels. Water use efficiency and water productivity were also significantly affected by different crop establishment methods but water productivity was not significantly affected by different irrigation managements.