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Nutrient leaching is a common issue in sandy soils. The use of hydrogel polymers can mitigate this problem by enhancing soil water retention. This study aims to assess the effect of hydrogel polymer application on nutrient leaching in sugarcane-cultivated soil and its impact on plant growth over a 196-day cycle. Parameters examined include soil water retention (%), nutrient leaching (N, P, K, Ca, Mg, and S) analyzed through the water collected after natural drainage, as well as various plant growth parameters such as stem height and diameter, and fresh and dry stem and leaf mass. The highest soil water retention was observed in treatments with 1.5 and 2.0 g kg-1 of hydrogel polymer. Regarding nutrient leaching, the treatments with 1.5 and 2.0 g kg-1 of hydrogel polymer exhibited the lowest values, resulting in reductions of over 85% for all accumulated nutrients leached by the end of the crop cycle. The application of hydrogel, especially at higher doses, also enhanced sugarcane growth, notably increasing fresh stem mass. These results suggest that hydrogel polymers could serve as a sustainable solution for controlling nutrient leaching in sugarcane cultivation, contributing to the sustainable development of agriculture and environmental preservation.

Cotton is the most ubiquitous and profitable fiber with diverse industrial and domestic applications. Grown in over 100 countries, it has a global market value of about USD\begin{document}${\$} $\end{document}40 billion and employs over 350 million people from fields to textile mills, contributing about 7% of total labor-force recruitment in developing economies. Cotton has an indeterminate growth habit and an extensive tap root system affected by soil physicochemical and environmental conditions. There is a consensus among experts that conventional cotton cultivation still has a long way to go to attain sustainability, which is essential if cotton is to maintain its competitive edge over other natural and synthetic fibers like hemp, polyesters, and rayon. Despite several efforts already committed to growing cotton sustainably, sustainability has eluded cotton cultivation globally because of the intense farm input needs (freshwater, pesticides, and heavy-duty equipment), especially in developing economies. Some of the technological advancements towards achieving the goal of sustainable cotton cultivation include the development of new varieties, improved irrigation and mulching and precision agriculture techniques, application of remote sensing and Unmanned Aerial Systems (UAS) combined with image processing, and the introduction of autonomous and multi-purpose robotic platforms for growing and harvesting cotton. This review attempts to evaluate the successes already achieved by stakeholders in moving cotton towards sustainable production and identify areas where efforts are still needed to reach sustainable production and improved profitability goals for cotton with projections for future research directions.

ABSTRACT The application of silicon (Si) in plants benefits the performance of several species. However, the dynamics of the element, mainly in non-accumulating species such as tomatoes, are rarely analyzed. This study investigated the dynamics of Si in tomato plants cultivated under different forms of application and water conditions. The experiment was carried out in a completely randomized design with four replications, using a factorial scheme 2 x 4: two water conditions (60 and 100% of the evapotranspiration of the crop - ETc), and four forms of silicon application (without application, full dose applied at soil, split dose applied at soil, and foliar application). Si content in the soil and in the different plant organs were analyzed. Si content in the soil increased after the crop cycle depending on the application form (full or split doses). The dynamics of Si accumulation and extraction by tomato are influenced by the application form (higher in soil application) and water management, with fruits and leaves having the higher values. Si application, mainly in the soil, increased the rate of Si accumulation and extraction by tomatoes cultivated in different water conditions.

Growing conditions such as water supply and soil fertility influence oregano morphological development and physiological responses. Our study aimed to analyse the physiological responses of oregano plants grown under different water conditions and bokashi application rates. The experiment was carried out in a greenhouse under a randomized block design and a 3 x 4 factorial scheme. Treatments encompassed three water replacement levels (60, 80, and 100% crop evapotranspiration - ETc) and four bokashi rates (0, 100, 200, and 300 g m-2), with five replications each. Oregano seedlings were transplanted and grown in a spacing of 0.3 m between plants and 1 m between bed rows. After 60 days, treatments were evaluated for photosynthetic rate (A), stomatal conductance (Gs), internal CO2 rate (Ci), transpiration (E), and water-use efficiency (WUE). Data underwent variance analysis by F-teste, multivariate analysis, and Pearson's linear correlation. Oregano physiological responses were significantly influenced by water replacement level and the application rate of fermented bokashi compost. The multivariate analysis allowed us to analyse the interaction effect between water replacement level and bokashi rate on photosynthesis, stomatal conductance, internal CO2, and transpiration.

Context: Riverine systems consist of distinct habitats along a landscape gradient and characterising the composition and structure of vegetation in these habitats can support environmental water-management decisions. However, in many regions, including northern Australia, there is a paucity of hydro-ecological data. Aims: We aimed to characterise the species composition and the structure of riparian and floodplain woody vegetation of the lower Fitzroy River. Methods: We surveyed woody vegetation in different habitats within the riparian zone and floodplain. Multivariate analysis was used to assess differences in the composition of riparian woody species among the four habitat types and univariate analysis was used to compare vegetation structure, recruitment, and environmental variables among habitats. Key results: The composition and the physical structure of woody species differed among habitat types of the lower Fitzroy River, indicating a zonation of riparian and floodplain vegetation in response to fluvial processes and water availability. The floodplain was characterised by sparsely distributed Eucalyptus microtheca and a sparse (∼30%) canopy cover. In contrast, the riverbank habitat type had very large trees (mean basal area = 0.26 m2), with a dense canopy cover (∼80%) and was dominated by Melaleuca argentea , M. leucadendra and Barringtonia acutangula. Both the top of bank and off-channel wetlands represent a more intermediary environment, characterised by greater species richness and greater seedling recruitment. Conclusions: Identifying these habitat types and characterising their physical and biological properties, such as the relationship between flooding and the composition of woody species, provides a framework to assist the management of large floodplain river systems. Characterising the composition and structure of riparian and floodplain woody vegetation is an important step in making informed water-management decisions. In the large river system of the lower Fitzroy River, Western Australia, vegetation reflects different habitat types, related to fluvial processes. Water managers are encouraged to consider how changes to the flow regime may affect landscape units differentially to help protect riparian and floodplain vegetation across the river and floodplain landscape. [ABSTRACT FROM AUTHOR]

Fish kills are very visible, with high levels of public scrutiny and major effects on populations. In 2018–19, extensive fish kills in the lower Darling River, south-eastern Australia, resulted in the deaths of millions of fish, including threatened and popular, iconic angling and important cultural species. This distressed local communities and the broader Australian society, who questioned the competence of fish and water management. Fish kills are increasing in frequency and severity, exacerbated by climate change. This paper reports on eight major fish-kill case studies across the Murray–Darling Basin that were examined to assess management adequacy. Field assessments and reporting have been poor, not documenting all species or numbers affected. Few values of fishes (cultural, conservation, recreational, social, ecological, economic) have been assessed and replacement or management costs not determined. There is a need to philosophically change our approach to take fish kills more seriously. More comprehensive approaches to assessment, evaluation and management are needed. Responsibilities for fish kills should be clarified and include water and habitat management agencies. Post-kill recovery plans that include the replacement of lost ecological assets should be published and enacted. This paper provides a fresh perspective on fish kills, with 15 key recommendations applicable to improve future management worldwide. Fish kills are increasing and need greater attention. This paper provides 15 recommendations to improve their assessment, evaluation, reporting and future management. [ABSTRACT FROM AUTHOR]

In the summer of 2018–19 mass fish kills occurred in the Lower Darling (Baaka) River in south-eastern Australia. The fish kills received national and international attention and have been the focus of numerous government agency and independent assessments. Although fish kills have previously been recorded in the Lower Darling region, the size and rapid succession of the 2018–19 'Menindee' fish kills made them unprecedented in the Murray–Darling Basin, placing significant pressure on the native fish community. Although the deaths of millions of fish were documented, the significant negative effect that the fish kills had on local communities, particularly the traditional Baakandji people, was largely ignored. The social and cultural aspects of such events can have major non-economic effects on local communities. In this paper we document heart-felt feelings conveyed by local community members. Their sense of loss, despair and helplessness is compounded by frustration regarding water management and policy decision making in the Murray–Darling Basin. However, these tragic events have increased understanding of traditional Baakandji connection to the river and its fish and, together with local recovery efforts, now provide prospects for enhanced community and agency cooperation to improve the health of the lower Darling Baaka River and restore its native fish populations. During 2018 and 2019, major fish kill events occurred throughout the drought-stricken Murray–Darling Basin in Australia. However, although large fish kills often receive substantial media attention, the significant negative effects that the fish kills have on local communities, particularly Indigenous groups, are rarely documented. We explore the social and cultural aspects of a series of major fish kills on the lower Darling Baaka River in Australia. [ABSTRACT FROM AUTHOR]

ABSTRACT Arrowroot is a plant originated in Latin America that has aroused interest in the food industry due to its high starch content, with differentiated characteristics and high commercial value. However, information on the management of arrowroot are scarce, precluding its commercial competition with other similar species, being necessary further studies with the crop. Thus, the objective of the present study was to characterize extracted starch from arrowroot grown under different agronomic management. Three agronomic factors were studied: planting systems (PS), forms of water management (WM) and planting density (PD). The experimental analyses were performed in a completely randomized design (CRD) with three replicates, being evaluated the extraction yield, percent composition, quantity of starch, pH, titratable acidity, swelling power, solubility and electron microscopy analysis. In general, the analyzed extracted starches deriving from different agronomic treatments have low crude fiber, besides typical characteristics of arrowroot extracted starch such as texture, color, shape and size of granules, without any other apparent particle than the starch itself, indicating extraction efficiency. However, the planting density may have contributed to influence some parameters of the chemical composition of the extracted starch, such as the content of starch, ash, ether extract, protein and carbohydrate fraction.

The plant fruiting process requires more energy and availability of soil water. Consequently, identifying the appropriate time for additional water supplying for cultivation of mango is an important part of successful crop handling for production of fruit with high quality. Therefore, we studied effects of additional water supplied by irrigation on chlorophyll fluorescence parameters in a field experiment during phenological stages of Mangifera indica L. cv. Ubá. Our results showed that the irrigation at specific periods of plant development improved fluorescence parameters (resulting in high values of the performance index), preventing damage of the photosynthetic apparatus, which positively influenced the supply of photoassimilates to fruit load. Furthermore, the results suggest that the additional water supply by irrigation in rainfed mango trees is recommended for maintaining high photosynthetic performance just during fruit development and fruit maturation.

Fluvial marine plains harbor environments with reduced declivity, but with different environmental attributes that may be relevant ecosystem services in their watersheds, which can be transformed into opportunities for the development of environmental services payments. This study digitally spatialized part of the ecosystem services related to water availability in the microbasins of the Guandu Basin Hydrographic Basin, the main source of water supply for the metropolitan region of Rio de Janeiro, based on geo-environmental factors and the effects of transposition of watersheds, in order to facilitate the formulation of public policies regarding environmental services. The excerpts with the highest potential for producing environmental services from subsurface water flows, Topographic Wetness Index-ITU (ITU > 11), flat formation and low altimetry (< 40 m), are close to the old silted thalwegs, which can be potentialized by the effects of transposition, notably in the APA Guandu conservation unit. These areas should be prioritized in public and private water systems’ preservation programs. The areas near the transposition canals feature environmental services that depend directly on the transposition, and may be subject to management, as found in Guandu conservation unit. Flat areas with (7

Worldwide, riverine fish are the target of environmental water because populations have declined in lotic river habitats following river regulation. Murray cod is an endangered Australian riverine fish with remaining populations associated with lotic river reaches with instream habitat, including some creeks operated as part of irrigation systems. Our objectives were to develop a life history model, apply the building block method of environmental flows to enhance the abundance of juvenile Murray cod and promote population recovery. From 2008 to 2018 we evaluated changes to Murray cod juvenile abundance before and after implementation of a perennial environmental flow regime that began in 2013. During the first year of the environmental flow, larvae were collected as evidence of spawning. Murray cod abundance can be enhanced with environmental flows that target: (1) an annual spring spawning or recruitment flow with no rapid water level drops; (2) maximising hydrodynamic complexity (i.e. flowing habitats that are longitudinally continuous and hydrodynamically complex); and (3) an annual base winter connection flow. Recognition that incorporating hydraulics (water level and velocity) at fine and coarse time scales, over spatial scales that reflect life histories, provides broader opportunities to expand the scope of environmental flows to help restore imperilled fish species in regulated ecosystems. Murray cod are the target of environmental water because populations have declined. We developed a life history model and applied environmental flows from 2008 to 2018. Fish abundance increased after the perennial environmental flows which also included no rapid water level drops, maximised hydrodynamic complexity and an annual base winter flow. Incorporating hydraulics into environmental flows helped restore an imperilled fish species. [ABSTRACT FROM AUTHOR]

Studies focused on limnology and quality of water bodies are essential to produce data that support the planning and management, diagnose the current situation and propose measures to minimize the possible negative impacts on water resources. The Tereza Botas creek drains the town of Poconé-MT, situated in the Pantanal border. In this sense, the objective of this study was to verify the variations in limnological characteristics along the longitudinal gradient and evaluate the water quality of the Tereza Botas watershed, identifying the impacts from anthropogenic activities of this important Pantanal watershed. Four sampling points along the longitudinal gradient of the water stream have been defined, and physical, chemical and microbiological variables were analyzed. The results indicated that the changes in limnological and water quality derive from the riparian vegetation removal, erosion and discharge of sewage in natura. In addition, high density of E. coli was observed in most of the sampled points, demonstrating that the lack of proper sanitation as well as the presence of rudimentary cesspit are negatively affecting water quality in the headwaters region.

Two experiments were performed to evaluate the effect of ash (40, 80, and 120 g per plant), castor cake (140 and 280 g per plant) and water depth (135, 165, 191, and 213 mm) on the growth and production of organic tomato cultivated in pots in a greenhouse. The experimental design was randomized blocks, and the irrigation was managed using an automatic irrigation device. The following variables were evaluated: plant heights, numbers of leaves, bunches, flowers and fruits, total mass of fruits, mass of marketable fruits, mass of fruits with blossom-end rot, total diameter of fruits, and diameter of marketable fruits. Most of the growth variables showed gains with the application of 140 g of ash and 280 g of cake. The dose of 280 g of castor cake was responsible for the greatest mass of marketable fruits (1.78 kg per plant), regardless of the ash dose. The water deficit reduced values of most of the variables of growth and production. The irrigation depth of 213 mm was responsible for the greatest mass of marketable fruits (4.04 kg per plant). The highest water use efficiencies, 37.00 and 37.93 kg m-3, were observed at irrigation depths of 191 and 213 mm, respectively.

This work aims at comparing irrigation strategies on the basis of deficit irrigation and soil spatial variability assessed through electrical resistivity mapping (ERM) conducted by an automatic resistivity profiler on-the-go sensor. Profiles chosen along a range of soil electrical resistivity showed different soil properties linked to water holding capacity within a field, with total available water (TAW) values of the coarser-textured zone corresponding to about 50% of TAW in the finertextured zone within the field. Multi-year weather data were obtained on a daily basis and scenarios were developed for climatic demand conditions representing dry average and wet years. The ISAREG water balance and irrigation scheduling model was afterwards applied to the different soil profiles and with different strategies for full and deficit irrigation, to compute water and irrigation requirements as well as related yield impacts of deficit irrigation for artichokes and dry beans. Deficit irrigation allowed calculated water savings up to about 50% for the winter crop and 33% for the summer crop with yield losses lower than 10%. Irrigation requirements within irrigation strategy were 10 to 44% different between profiles, and this indicates that soil visualization techniques such as ERM can be used for the identification of zones for site-specific irrigation management.

This paper introduces a new approach to water management that is ‘Safe & SuRe’. This includes presenting a conceptual framework to link the emerging threats of climate change and variability, rapid urbanization and population growth, energy constraint and tightening environmental regulation through to their consequences on social, economic and environmental recipients. The framework allows identification of the role and need for mitigation, adaptation and coping strategies. The paper proposes definitions and discusses what engineering, organizational and/or social options can potentially develop the degree of resilience and sustainability needed to deal with these 21st century threats. The paper goes on to propose how these approaches might be objectively assessed and identifies gaps in our knowledge that require further research. [ABSTRACT FROM AUTHOR]

Midseason aeration (MSA) is an effective way to reduce the combined global warming potential (GWP) of methane (CH4) and nitrous oxide (N2O) emissions [GWP (CH4 + N2O)] during the rice (Oryza SativaL.) growing season. Altering timing of MSA would affect CH4and N2O emissions from rice cultivation. To evaluate the mitigation of net GWP (CH4 + N2O) from double rice (Oryza SativaIndica) cultivation by adjusting the time to start MSA, a two-year (2009 ∼ 2010) field experiment was conducted in Yingtan, Jiangxi Province, China. Four treatments, i.e. continuous flooding, early aeration, normal aeration (local practice) and late aeration, were adopted in the experiment. Results showed that compared with continuous flooding, midseason aeration significantly reduced seasonal CH4emission and net 100-year GWP (CH4 + N2O) from double rice cultivation without significant changes in grain yield. In the early rice season, the reductions in CH4emission and net 100-year GWP (CH4 + N2O) due to midseason aeration varied from 37% to 51% and from 36% to 50%, respectively, being lowest in early aeration and highest in normal aeration. In the late rice season, the reduction in CH4emission and net 100-year GWP (CH4 + N2O) due to midseason aeration varied between 49% and 57%, being lowest in late aeration and highest in early aeration. The GWP from N2O emission was negligible compared to that from CH4emission. The findings indicated that the GWP in the late rice season could be effectively reduced by advancing suitably the time to start MSA. [ABSTRACT FROM PUBLISHER]

The article presents a study on the development of a resource selection model for the propagation of Wood Stork during the 2006 breeding season in the southern Everglades, Florida using proportional hazards regression model (PHRM). The study determined the suitable foraging environment for the broad-winged bird based on geographical and hydrological characteristics and developed maps that locate areas identified by the foraging habitat selection model to have the highest probability of use.

Exploitation of scarce water resources, particularly in areas of high demand, inevitably produces conflict among disparate stakeholders, each of whom may have their own set of priorities. In order to arrive at a socially acceptable compromise, the decision-makers should seek an optimal trade-off between conflicting objectives that reflect the priorities of the various stakeholders. In this study, game theory was applied to a multiobjective conflict problem for the Alto Rio Lerma Irrigation District, located in the state of Guanajuato in Mexico, where economic benefits from agricultural production should be balanced with associated negative environmental impacts. The short period of rainfall in this area, combined with high groundwater withdrawals from irrigation wells, has produced severe aquifer overdraft. In addition, current agricultural practices of applying high loads of fertilizers and pesticides have contaminated regions of the aquifer. The net economic benefit to this agricultural region in the short-term lies with increasing crop yields, which requires large pumping extractions for irrigation as well as high chemical loading. In the longer term, this can produce economic loss due to higher pumping costs (i.e., higher lift requirements), or even loss of the aquifer as a viable source of water. Negative environmental impacts include continued diminishment of groundwater quality, and declining groundwater levels in the basin, which can damage surface water systems that support environmental habitats. The two primary stakeholders or players, the farmers in the irrigation district and the community at large, must find an optimal balance between positive economic benefits and negative environmental impacts. In this paper, game theory was applied to find the optimal solution between the two conflicting objectives among 12 alternative groundwater extraction scenarios. Different attributes were used to quantify the benefits and costs of the two objectives, and, following generation of the Pareto frontier or trade-off curve, four conflict resolution methods were then applied. [Copyright &y& Elsevier]

A concept of co-evolution is argued to complement Integrated Water Resource Management's gap in administrative integration. Co-evolution's complement to Integrated Water Resource Management is explored through issues surrounding joint water management arrangements between the Israelis and Palestinians in the late 1990s and early 21st century. How co-evolution contributes to such a water management approach highlights how we might think about what it means to encourage innovation. Conclusions of the article suggest co-evolution provides the language and description for the changing interactions and political environment and therefore provides a sharper conceptualization for administrative integration. [ABSTRACT FROM AUTHOR]

A simple model of rainfall redistribution within a terraced sandy grassland landscape has been developed. The model assumes that rainfall redistribution is driven by rainfall impulses and is controlled by characteristic field capacity of soils. When the rainfall intensity is large enough to render soil water content greater than its characteristic field capacity, the excessive soil water can drain very quickly by means of large amounts of non-capillary pores of sandy soils or by means of surface runoff. Exponential distribution of rainfall impulses was assumed and tested with measured daily rainfall at two meteorological stations in the sandy grassland area of north China. The model was solved to give the equivalent rainfall at each terrace in the landscape. [ABSTRACT FROM AUTHOR]

Factors that constitute resilience can themselves change over time in social-ecological systems. This poses a major challenge for understanding resilience and suggests greater investigation is needed of how social-ecological systems evolve through time and how to manage along more resilient pathways given continuous change. Resilient pathways account for the changing context of social-ecological systems, such as changing management discourses and their societal inclusiveness, changing system boundaries and external connections, and lingering consequences of past management actions. In this paper I use two well-known conceptual frameworks to explore change in social-ecological systems and associated resilience in the case of water management in South Africa, which is undergoing a major transformation: (1) the conceptual framework of the Millennium Ecosystem Assessment (MA) and (2) the adaptive cycle described by Holling and others. Both frameworks, with minor adaptations, illustrate the system's shift from a centralized command-and-control style bureaucracy to a decentralized system guided by new legislation and a vision to balance efficiency, equity, and sustainability. During the former era, water managers attempted to maintain system stability and productivity through institutional and technical means that favored certain sectors of society, but resilience of the water management system declined as a result of increasingly unpopular policies and loss of ecosystem services. In using both frameworks, it becomes clear that the water management system contains two distinct social subsystems, representing South Africa's previously advantaged and disadvantaged populations, and that these do not progress through the phases of the MA framework and adaptive cycle uniformly. This implies particular challenges for achieving the water management vision: (1) the potential for management discourses to be manipulated by powerful groups, (2) equity issues that reflect new system boundaries that extend beyond South Africa's borders, and (3) past overallocation and poor management of water that make the previous level of privileges unattainable today. The South African water sector is a compelling case because of its dramatic transformation with as-yet unknown outcomes, but it presents challenges that are common among many large-scale social-ecological systems. With great international interest in operationalizing resilience definitions and frameworks, this exercise suggests the need to revisit definitions, continue applying these frameworks, and adapting them to capture variations in social-ecological systems.

We examined the vegetation of the Southeast Saline Everglades (SESE), where water management and sea level rise have been important ecological forces during the last 50 years. Marshes within the SESE were arranged in well-defined compositional zones parallel to the coast, with mangrove-dominated shrub communities near the coast giving way to graminoid-mangrove mixtures, and then Cladium marsh. The compositional gradient was accompanied by an interiorward decrease in total aboveground biomass, and increases in leaf area index and periphyton biomass. Since the mid-1940s, the boundary of the mixed graminoid-mangroveand Cladium communities shifted inland by 3.3 km. The interior boundary of a low-productivity zone appearing white on both black-and-white and CIR photos moved inland by 1.5 km on average. A smaller shift in this `white zone' was observed in an area receiving fresh water overflow through gaps in one of the SESE canals, while greater change occurred in areas cut off from upstream water sources by roads or levees. These large-scale vegetation dynamics are apparently the combined result of sea level rise - ca. 10 cm since 1940 - and water management practices in the SESE. [ABSTRACT FROM AUTHOR]

Total amounts of CH4 emission from a Sumatra rice field were in the ranges 2975-4872 and 4370-6476 g CH4 m-2 season-1 for the plots with chemical fertilizer (CF-plot) and those with rice straw application (RS-plot), respectively. Nearly the same amounts of CH4 were emitted in the first and second half of the growth period, irrespective of rice straw application. The increase in the amounts of CH4 emission by ricestraw application were from 173 to 176 times. There was no significant difference in the mean CH4 emission rates between rainyand dry seasons. Rain-fed conditions decreased the CH4 emission by 27-37% compared with continuously flooded conditions. Totalamounts of CH4 emission from a rice field growing eight popular modern rice varieties in Indonesia were in the ranges 3276-4177 and 5173-6476 g CH4 m-2 season-1 for CF- and RS-plots, respectively. Total amounts of CH4 emission from four Sumatra rice fields with different soil types (a Typic Paleudult, a Typic Sulfaquent, a Typic Tropohumult and a Typic Tropopsament) were in the range 2271 (a Typic Sulfaquent) to 5374 (a Typic Tropohumult) g CH4 m-2 season-1 for CF-plots and from 2677 (a Typic Sulfaquent) to 7272 (a Typic Tropohumult) g CH4 m-2 season-1 for RS-plots. CH4 emission rates from Bali rice fields with soils of volcanic ash origin were very low; 375-777 and 573-1473 g CH4 m-2 season-1 for CF- and RS-plots, respectively. Respective rice fields showed the specific productivity of grain production, and CH4 emission rates for 1 kg grain production were scattered widely from 8-11 and 11724 g CH4 kg-1 grain for rice fields of volcanic ash origin to 83 and 121 g CH4 kg-1 grain for a Sumatra rice field for C [ABSTRACT FROM AUTHOR]