Identification of Critical Water Levels in Flooded Rice Fields

A mathematical model was developed to simulate the transient hydrology of a flooded rice field. With the model, users can determine the critical interlevee areas in which to monitor the water levels so that the irrigation well can be turned on at the critical low water level, and turned off at the critical high water level, in order to maximize water application efficiency. Sensitivity analysis performed with the model showed that it will be necessary to calibrate the model for each specific field. A calibration procedure has been developed

Benthic macroinvertebrates and degradation of phytomass as indicators of ecosystem functions in flooded rice cropping.

The objective of this work was to evaluate the ecosystem functions of a natural wetland and of artificially flooded rice areas, managed under organic and conventional systems, by phytomass degradation and by the colonization of this material by benthic macroinvertebrates. The experiment was carried out in a natural wetland area, and in two flooded rice areas managed under organic and conventional systems. Twenty-five decomposition bags filled with 10 g of dry vegetation were installed in each site. At 14, 28, 42, 56, and 70 days after the beginning of the experiment, five bags from each site were collected. Macroinvertebrates were identified and classified by functional trophic group. The number of species of benthic macroinvertebrates increased: natural wetland > organic system > conventional system. The Chironomidae group was present in all areas, confirming its food plasticity and adaptability to different substrates and environmental stress situations. The Amphipoda group was present only in the artificially flooded rice area, and the Acari, only in the natural wetland. The diversity of species in the natural wetland area was higher than in the artificially flooded rice area. Nutrient cycling, provided by phytomass decomposition, is affected by the management system, and the delay in this process causes a reduction of the ecosystem functions in the conventional system.Título em português: Macroinvertebrados betônicos e degradação da fitomassa como indicadores de funções ecossistêmicas em arroz irrigado por inundação

Could biochar and green manure be a substitute for synthetic nitrogen fertilization to guarantee rice grain yield and decrease greenhouse gas emissions?

The objective of this study was to find a feasible alternative to the use of nitrogen fertilizers for smallholders and commercial farming in tropical flooded rice systems

Integrating fish into seasonally flooded rice fields: on-farm trials in Assam, India

In the State of Assam, floodplains cover 2.6 million ha of area that is traditionally rice growing. The ecosystem in the rice-growing areas has undergone major changes as a result of various developmental activities and adoption of modern farming technology. Rice fields were once the major source of fish for the rural farmers. There has been a sharp decline in fish population in rice field leading to a chronic shortage of fish in the State and a deterioration of the rice ecosystem. This paper describes two on-farm experiments for integrating rice cultivation and fish production with the intent of contributing to the understanding of how raising fish can improve rice yields, riceecosystems and farm incomes

Performance of flooded rice grown in succession to winter cover crops

Mean grain yield of flooded rice in southern Brazil has increased in recent years due to the use of high-yield cultivars and improvement of crop management practices. Nevertheless, stagnation in grain yields has been observed in some riceproducing regions. Adoption of conservation tillage systems based on cover crops may be a strategy to increase rice grain yield potential. The objective of the present study was to evaluate the effect of winter cover crops on initial establishment, development, and grain yield of flooded rice (Oryza sativa L.) grown under different fertilization levels and no-tillage. A field experiment was carried out for three consecutive years (2010/11, 2011/12, and 2012/13) in Cachoeirinha, Rio Grande do Sul, South Brazil. Treatments included three winter cover crops [ryegrass (Lolium multiflorum Lam.), native serradella (Ornithopus micranthus Benth.), and a ryegrass-serradella mixture] and fallow, and three fertilization levels for rice grown in succession. More than 3 Mg ha-1 of serradella aboveground residue or 4 Mg ha-1 of ryegrass residue limited rice emergence in the first year when rainfall in the sowing-emergence period was higher than in the second and third years In contrast, a large amount of residue (serradella >2 Mg ha-1; ryegrass >3 Mg ha-1) was beneficial to rice emergence when rainfall was low in the sowing-emergence period of the second and third years. The serradella cover crop increased rice aboveground biomass at anthesis by 22 % compared to the ryegrass cover crop. Furthermore, rice grain yield was 15 % higher in succession to serradella than to ryegrass in the third year. Continuous cultivation of flooded rice in succession to ryegrass over three years reduced grain yield by around 1.4 Mg ha-1, regardless of fertilization level. Fertilization for very high production expectations increased rice grain yield in all years, especially in the second year, when solar radiation was higher than normal. The use of winter cover crops affected plant emergence, aboveground biomass, and grain yield of flooded rice. Rice grain yield increased with increases in fertilization level, and this response was not affected by the previous cover crop

Management of the Rice Tungro Virus Vector \u3ci\u3eNephotettix virescens\u3c/i\u3e (Homoptera: Cicadellidae) with Controlled-Release Formulations of Carbofuran

Field trials were conducted in lowland flooded rice in the Philippines to evaluate a number of carbofuran controlled-release formulations in comparison with commercial formulations. The test formulations were based on a biodegradable matrix of pine kraft lignin and were used as granules of different sizes and also in the form of small strips. The release rates were assessed under field conditions by bioassaying rice plants in the field, using adult rice green leafhopper, Nephotettix virescens Distant. The lignin formulations with a high level of active ingredient (15–45% by weight) gave as good or better control than the commercial 3% granules in tests based on three application techniques: broadcast into the floodwater, soil incorporation, and root zone injection. The improvements in control levels of green leafhoppers were most marked with soil incorporation and root zone application. The best lignin-based formulation reduced levels of tungro virus infection from 23% for a conventional flowable carbofuran formulation to 1.0% at an application rate of 0.5 kg (AI)/ha. At the same rate, the grain yield was increased from 3.56 t/ha to 5.5 t/ha, using the controlled-released formulation

RED EUGLENOID BLOOMS: A BIOMARKER OF ENVIRONMENTAL IMPACT IN FLOODED RICE FIELDS

The nutrient load introduced into flooded rice fields is one of the main factorsthat impact this type of ecosystem, contributing to the development of bloomsof pigmented euglenoids. This study was carried out to investigate thebehavior of red euglenas, a group of pigmented euglenoids, forming blooms inthis type of environment. Sedimented spores in the soil after water drainage,as well as water samples from vegetative cells in living blooms were collected.The collected material was inoculated into a culturing medium for microalgaeand incubated for three weeks. The cultures grown in nutrient medium wereused for morphometric analysis to identify the species. In order to characterizethe water environment, chemical and physical parameters were alsomonitored "in situ". The results indicated Euglena sanguinea Ehr. as thebloom-forming species and nitrogen as a key element in the behavior of thisspecies in this type of ecosystem. It was suggested, however, that more studiesare needed to indicate the use of red euglenas as biomarkers of nitrogenoverload in flooded rice fields

Water Balance of Flooded Rice in the Tropics

Department of Agriculture and Food, WA staff member authored Water Balance of Flooded Rice in the Tropics in the publication Irrigation and Drainage - Sustainable Strategies and Systems’, edited by Muhammad Salik Javaid, published by INTECH, May 2015 Chapter Summary: Excess groundwater recharge rates under irrigated agriculture may lead to problems such as rising watertable, waterlogging and salinity. In irrigated areas, growers may need to manage this water and hence, understanding what leakage is attributed to what crops will become more important. In this study, evaporation, transpiration, and deep percolation losses were estimated for ponded rice culture, using a set of three lysimeters and lockup bay tests. The average deep percolation losses were estimated to be less than 0.97 mm/day or approximately 1 ML/ha for the crop cycle. At this rate, deep percolation under ponded rice culture in Cununurra clay soils is within accepted leakage rates and the rates should not unduly affect growers or environmental managers in terms of rising groundwater levels, waterlogging and salinity.https://researchlibrary.agric.wa.gov.au/books/1000/thumbnail.jp

Direct Nitrous Oxide Emissions From Tropical And Sub-Tropical Agricultural Systems : A Review and Modelling of Emission Factors

We acknowledge the financial support from the CGIAR Research Programs on Climate Change, Agriculture and Food Security (CCAFS). Grant ref. n. P25.Peer reviewedPublisher PD

Influence of Rice Production on the Quality of Water in Tailwater Collection Reservoirs

Since maintaining high water quality standards in the state remains a high priority, monitoring for pesticides in water sources must continue. Determining the type, concentration, and characteristics of any pesticides present in water supplies are essential to the overall assessment of water quality. Five independent locations, implementing contained water management systems and recyclable water, were monitored in 1995 and 1996. Irrigation, runoff, and pond water samples were collected every 10 to 14 days between permanent flood establishment and draining. Water samples were transported to the laboratory and extracted for 16 pesticides using solid phase extraction (SPE) techniques. Quantification and confirmation of pesticide residues were obta1ned by HPLC and GC/MS analysis. The lower limit of quantitation for all pesticides was between 1.0 -1.3 pg L-1 in water. Pesticides selected for monitoring were determined after assessing state recommendations and our analytical capabilities. Pesticides included: benomyl, bensulfuron methyl, carbaryl, carbofuran, 2,4-D, fenoxaprop ethyl, propiconazole, malathion, MCPA, methyl parathion, molinate, pendimethalin, propanil, iprodione, quinclorac, triclopyr, and thiobencarb. Since each field location was independently managed, individual results are site specific. 2,4-D, benomyl, molinate, propanil, quinclorac, thiobencarb, and pendimethalin were the pesticides actually applied during the seasons. These pesticides were detected, usually at trace levels, in tailwaters shortly after application but did not appear to buildup in the reservoirs. Quinclorac residues in the tailwaters were more persistent (up to 8 weeks) than the other detected compounds (less than 2 weeks)