California Rice Fields Research Articles

Partitioning of Penoxsulam, a New Sulfonamide Herbicide

Penoxsulam (trade name Granite) is a new acetolactate synthase (ALS) inhibitor herbicide for postemergence control of annual grasses, sedges, and broadleaf weeds in rice culture. This study was done to understand the equilibrium phase partitioning of penoxsulam to soil and air under conditions simulating California rice field conditions. Partitioning of penoxsulam was determined between soil and water (Kd) by the batch equilibrium method and between air and water (K(H)) by the gas-purge method. In four representative soils from the Sacramento Valley, the Kd values ranged from 0.14 to 5.05 and displayed a modest increase with soil pH. In soil amended with manure compost, soil sorption increased 4-fold with increasing soil organic matter content, but was still low with a Kd of 0.4 in samples with high organic carbon contents of 15%. Penoxsulam was confirmed to be extremely nonvolatile and did not partition into air at any measurable rate at 20 or 40 degrees C. K(H) (pH 7) was estimated at 4.6 x 10(-15) Pa x L x mol(-1) on the basis of available water solubility and vapor pressure data. The results imply that soil and air partitioning of penoxsulam do not significantly affect its potential for degradation or offsite movement in water.

Crayfish effects on seeds and seedlings: identification and quantification of damage

Summary1. The red‐swamp crayfish (Procambarus clarkii) is an invasive species and an important pest of wet‐seeded rice fields (Oryza sativa) in California (U.S.A.) and in Portugal. Our work quantifies rice consumption and non‐consumptive destruction and identifies the types of direct damage inflicted by crayfish.2. The following fractions were quantified in the presence and absence of crayfish and at 3 and 6 days of rice development: (1) non‐germinated seeds, (2) damaged seeds, (3) seeds not recovered, (4) intact rooted seedlings, (5) rooted damaged seedlings, (6) uprooted intact seedlings, (7) uprooted damaged seedlings.3. Coarse particulate organic matter (CPOM) fragments produced during the feeding process were <2% of the material removed by crayfish.4. Damage occurred with or without uprooting of the plants, but the incidence of uprooting without consumption was low (1.4%).5. Consumption of recently developed parts of the rice plant was the main cause of damage and the observed effect was stronger on 6‐day‐old than on 3‐day‐old seedlings. Seedlings were more affected by crayfish than were seeds.6. Crayfish affected the majority of seeds and seedlings available although consumption was low: 0.015 g dry weight (DW) rice g−1 wet weight (WW) crayfish per 12 h at 3 days and 0.063 g DW rice g−1 WW crayfish per 12 h at 6 days.7. Our results are important for the mitigation of crayfish related problems in rice fields and for understanding the mechanisms of crayfish‐macrophyte interactions.

Influence of organic carbon on reductive dechlorination of thiobencarb in California rice field soils

The herbicide thiobencarb is suspected of causing delayed phytotoxicity syndrome (DPS) in rice plants. While the ultimate agent appears to be its dechlorinated product (deschlorothiobencarb), the influence of organic carbon on the formation of deschlorothiobencarb in California rice field soils has not been investigated. Thus, two different soils were compared for their ability to reductively dechlorinate thiobencarb with carbon augmentation: one from the eastern Sacramento Valley, which has historically displayed DPS, and one from the western Sacramento Valley, which has not. Rice straw was homogenized into samples of each soil to produce 0, 0.33 or 2% organic carbon augmentation. During 90-days of anoxic incubation, substantial deschlorothiobencarb production was measured in both soil types. However, only the thiobencarb degradation rate in the eastern valley soil was positively correlated with carbon content. Thus, other characteristics of DPS-resistant soils may limit deschlorothiobencarb formation.

Factors Underlying Yield Variability in Two California Rice Fields

Modern technologies associated with precision agriculture provide the opportunity to more precisely measure yield variability and the ecological processes underlying this variability. Effective analysis of data from these measurements requires statistical methods different from those traditionally employed on data from controlled agronomic experiments. Our objective was to develop and test multivariate statistical methods appropriate for use in analyzing precision agriculture data. We analyzed a data set taken from two commercial California rice fields and consisting of yield spatial trends together with soil core data from a grid of sample points. We used cluster analysis to discern spatiotemporal patterns in grain yield. We applied a Monte Carlo randomization process to the generation of clusters to analyze cluster stability. We then used classification and regression trees (CART) to determine the factors underlying cluster distribution. The clustering procedure successfully identified stable, physically meaningful clusters with recognizable spatial and temporal structure. Thus, the randomization procedure may present an attractive alternative to fuzzy clustering. The CART analysis identified some but not all of the factors underlying the cluster patterns. The number of available data values may have been too small to take advantage of the CART partitioning capabilities.

Characterization of California rice field soils susceptible to delayed phytotoxicity syndrome.

Characterization of California rice field soils susceptible to delayed phytotoxicity syndrome.

Herbicide-resistant late watergrass (Echinochloa phyllopogon): similarity in morphological and amplified fragment length polymorphism traits

Abstract Late watergrass is a serious weed of California rice that has evolved resistance to molinate, thiobencarb, fenoxaprop-ethyl, and bispyribac-sodium. To obtain an insight into the origin and spread of resistant (R) late watergrass in California rice fields, we evaluated similarities in morphological traits and amplified fragment length polymorphism (AFLP) fingerprints among 15 R strains compared with susceptible (S) strains. All strains were derived by inbreeding from accessions collected in rice fields of the Sacramento Valley, CA. In the field, R plants were shorter than S plants; they also had narrower and shorter flag leaves and thinner culms. Spikelets also appeared smaller and more slender in R plants. There was greater morphological similarity among the 15 R strains than among the eight S strains. The mean coefficients of variation for morphological traits were much smaller among R strains, which in a cluster analysis (Ward's method) were grouped morphologically apart at early clustering sta...

NIR and DRIFT-MIR spectrometry of soils for predicting soil and crop parameters in a flooded field

The increasing popularity of site-specific management (SSM) calls for fast, inexpensive, simultaneous analyses of large numbers of soil variables. The objective of this study was to assess the potential of near infrared (NIR) and diffuse reflectance Fourier transformed in the mid-infrared range (DRIFT-MIR) spectrometry for predicting crop and soil parameters in a flooded California rice field. Two transects of 400 m each were left unfertilized, and 100 sample locations were established. Soil samples were taken in spring, and crop and weed samples at harvest. IR spectra were linked to total soil C and N, mineralizable N, P Olsen, effective cation exchange capacity (eCEC) and exchangeable cations (Ca, Mg, Na and K), as well as yield, N uptake, biomass and weed biomass using partial least squares regression (PLSr). The PLSr models were calibrated using 50 random observations, and validated using the remaining 50 observations. For soil, predictions for eCEC, Ca and Mg were the most accurate, with r 2 values of 0.83, 0.80 and 0.90 for NIR and 0.56, 0.60 and 0.61 for DRIFT-MIR. Correlations for P Olsen were 0.71 and 0.55, and for mineralizable N 0.46 and 0.21, respectively. No significant correlations were found for total soil C or N. For crop parameters, only weed pressure (r 2 of 0.55 and 0.44) and straw biomass (0.30 and 0.34) yielded significant correlations. The correlation with weed pressure was an indirect effect due to better competition by weeds compared to rice under low soil fertility levels. For most parameters, standard errors of prediction were lower than reported in the literature. This indicates that the small range of variability within a field might be the limiting factor in predicting these parameters. It also illustrates the limited use of correlation coefficients in PLSr model validations. We concluded that NIR spectrometry shows promise for SSM, although its predictive power for parameters may vary from site to site. Moreover, predictive models remain unique for specific agroecosystems, and therefore have to be calibrated for every area. The fast and accurate predictions for Ca and Mg concentrations in the soil could be especially important in diagnosing and combating grass tetany, which strongly depends upon Ca and Mg concentrations in the soil.

Cross-resistance to bispyribac-sodium and bensulfuron-methyl in Echinochloa phyllopogon and Cyperus difformis

Water-seeded and continuously flooded rice in California is mostly grown as a continuous crop and weeds are the most serious rice production problem. Echinochloa phyllopogon (Stapf) Koss and Cyperus difformis L. are adapted to this aquatic system and compete with rice, causing heavy economic losses. Flooding cannot fully suppress these weeds. Heavy reliance on few available herbicides resulted in the evolution of herbicide resistance in populations of both weeds in California rice fields. Resistance to bensulfuron-methyl (ALS inhibitor) is widespread among C. difformis populations. E. phyllopogon has evolved resistance to several herbicides, including bispyribac-sodium (ALS inhibitor), which has not yet been commercially used. A resistant (R) E. phyllopogon was also much more tolerant to bensulfuron-methyl than a susceptible (S) biotype. Understanding the patterns and mechanisms of cross-resistance in key weeds of rice to bensulfuron-methyl and bispyribac-sodium is relevant for the successful deployment of this new herbicide and for the management of herbicide resistance in California rice. Whole-plant bioassays were conducted to compare responses between E. phyllopogon and C. difformis to bispyribac-sodium and bensulfuron-methyl and to detect the involvement of cyt P-450 monooxygenases in E. phyllopogon resistance to bensulfuron-methyl using the cyt P-450 inhibitors piperonyl butoxide and malathion (previous studies had already shown cyt P-450-mediated resistance to bispyribac-sodium). ALS activity was assayed on leaf extracts from young R and S plants of both species for a range of bispyribac-sodium and bensulfuron-methyl concentrations. The dose–response studies confirmed cross-resistance in R E. phyllopogon ; minimum and maximum ratios (R/S) of the GR 50 values of resistant to susceptible plants were 9 and >25.5 for bispyribac-sodium and bensulfuron-methyl, respectively. cyt P-450 contributed to bensulfuron-methyl resistance in R E. phyllopogon. C. difformis was also cross-resistant (R/S ratios: >10 for bispyribac-sodium and >26 for bensulfuron-methyl). ALS assays demonstrated that, unlike R E. phyllopogon, cross-resistance in R C. difformis was due to reduced ALS sensitivity. C. difformis ALS was more sensitive to bispyribac-sodium ( I 50=138.87 nM) than to bensulfuron-methyl ( I 50=6724.56 nM) . Also, ALS inhibition in R and S E. phyllopogon was higher with bispyribac-sodium. Thus, binding differences between both herbicides at the target site are suggested. This study reveals that cross-resistance between bensulfuron-methyl and bispyribac-sodium in both weeds involves degradation enhancement through monooxygenases and target-site alteration.

Occurrence, Distribution, Epidemiology, Cultivar Reaction, and Management of Rice Blast Disease in California.

Rice blast, caused by Pyricularia grisea, was first found in California in 1996. Disease surveys have shown the blast disease is spreading at a moderate rate in California rice fields. Although no effective major resistance genes are known to occur in widely grown commercial California cultivars, there appear to be differences among the cultivars with respect to field susceptibility to the pathogen. P. grisea was recovered from rice crop residue and commercial seedlots which are suggested as possible sources of initial P. grisea inoculum in California rice fields. Examination of weather data indicates that environmental conditions in California rice-producing areas are permissive for rice blast but generally not optimal for epidemic development. Spore trapping determined that the majority of P. grisea conidia are generally not released until approximately 6:00 A.M. and would not have sufficient time for infection before leaf wetness periods end. Azoxystrobin showed positive results with respect to reduction of neck blast incidence and yield increases in small-plot and large-scale fungicide trials.

Soil Sampling Techniques for Determining the Effect of Cultural Practices on Rhizoctonia oryzae-sativae Inoculum in Rice Field Soils.

Methods were evaluated to quantify sclerotia in rice fields affected with aggregate sheath spot disease. Recovered sclerotia were compared with disease ratings at harvest for paddies subjected to various postharvest cultural straw management practices. Sclerotial inoculum level was not always correlated with subsequent disease incidence in rice aggregate sheath spot disease, suggesting alternative sources of inoculum and other factors influencing disease development. Straw management practices affected the inoculum load of Rhizoctonia oryzae-sativae, as determined by methods recovering sclerotia from California rice field soil samples. Traditional wet sieving of soil samples was improved using a potassium carbonate solution to float heavier sclerotia that normally remained in the sediment. The relationship of inoculum in the soil from seedbeds and the incidence of resulting disease measured just before harvest was investigated over 3 years at three sites. A linear dose-response was found at only one site where the number of floating sclerotia was more strongly correlated with disease incidence than total number of sclerotia (floating plus nonfloating sclerotia). Floating sclerotia were more easily counted using a water floatation extraction (WFE) than were total sclerotia by using a potassium carbonate floatation extraction (PCFE) or a combination of the two assays (WFE + PCFE), and the WFE more accurately predicted disease incidence than did either PCFE or WFE + PCFE. All assays detected significant differences between inoculum levels as influenced by various straw residue management practices, with removal of straw residue significantly reducing number of soil-borne sclerotia.

Abiotic processes influencing fipronil and desthiofipronil dissipation in California, USA, rice fields

AbstractFipronil insecticide dissipated in California rice fields, producing half‐lives of 10.5 to 125h in water and 44.5 to 533 h in soil, depending on the formulation applied and the resulting differences in water solubility. The major degradation products were desthiofipronil in water and fipronil‐sulfide in soil, while the sulfone and amide were less abundant. Fipronil was photolyzed rapidly to desthiofipronil in deionized water in the laboratory (t½ = 7.97–9.42 h) and even faster in the presence of H2O2 (t½ = 0.874–4.51 h). Fipronil was also hydrolyzed to amide in base (t½ = 542 h at pH 9) and volatilized slowly from water (H = 6.60 × 10−6 m3·atm/mol) properties not explaining its rapid field water dissipation. Desthiofipronil was more stable than fipronil to direct photolysis (t½ = 120–149 h), was indirectly photolyzed in the presence of H2O2 (t½ = 0.853–3.76 h), and was nonvolatile from water. The desthiofipronil observed in field water was formed photochemically from fipronil, accumulated due to slower photolysis and lack of volatility from water, but eventually dissipated.

Shading and the growth and photosynthetic responses of Ammannia coccinnea

The effects of shade on the growth and CO2 exchange rate (CER) of Ammannia coccinnea Wild., a noxious weed in water‐seeded rice, were determined under glasshouse conditions. Shade substantially reduced A. coccinnea growth when imposed early and maintained throughout the growing season. However, plants transferred from full light to 18% or 50% sunlight 30 or 45 days after seeding had only slightly less dry weight than unshaded plants. Constant shade reduced growth severely (94%). In contrast, plants that were shaded for 45 days and then placed in full light largely recovered from the effects of shading by final harvest. The ability of A. coccinnea to reduce the effects of shade appears related to increased partitioning to leaves, increased specific leaf area and decreased dark respiration rates. The ability of the weed to recover from shade appears related to its ability to greatly increase CER in new leaves in response to increased light. Plasticity in A. coccinnea morphology and physiology appears to explain its persistence in California rice fields and suggests that management strategies that rely on shade alone may not improve control of this weed.

Abiotic processes influencing fipronil and desthiofipronil dissipation in California, USA, rice fields.

Fipronil insecticide dissipated in California rice fields, producing half-lives of 10.5 to 125 h in water and 44.5 to 533 h in soil, depending on the formulation applied and the resulting differences in water solubility. The major degradation products were desthiofipronil in water and fipronil-sulfide in soil, while the sulfone and amide were less abundant. Fipronil was photolyzed rapidly to desthiofipronil in deionized water in the laboratory (t1/2 = 7.97-9.42 h) and even faster in the presence of H2O2 (t1/2 = 0.874-4.51 h). Fipronil was also hydrolyzed to amide in base (t1/2 = 542 h at pH 9) and volatilized slowly from water (H = 6.60 x 10(-6) m3.atm/mol), properties not explaining its rapid field water dissipation. Desthiofipronil was more stable than fipronil to direct photolysis (t1/2 = 120-149 h), was indirectly photolyzed in the presence of H2O2 (t1/2 = 0.853-3.76 h), and was nonvolatile from water. The desthiofipronil observed in field water was formed photochemically from fipronil, accumulated due to slower photolysis and lack of volatility from water, but eventually dissipated.

Emissions of methyl halides and methane from rice paddies.

Methyl halide gases are important sources of atmospheric inorganic halogen compounds, which in turn are central reactants in many stratospheric and tropospheric chemical processes. By observing emissions of methyl chloride, methyl bromide, and methyl iodide from flooded California rice fields, we estimate the impact of rice agriculture on the atmospheric budgets of these gases. Factors influencing methyl halide emissions are stage of rice growth, soil organic content, halide concentrations, and field-water management. Extrapolating our data implies that about 1 percent of atmospheric methyl bromide and 5 percent of methyl iodide arise from rice fields worldwide. Unplanted flooded fields emit as much methyl chloride as planted, flooded rice fields.

Mechanisms of Resistance to Bispyribac-Sodium in an Echinochloa phyllopogon Accession

Abstract Weeds are a major problem for rice production in California, and late watergrass (Echinochloa phyllopogon (Stapf) Koss) is one of the most serious weeds in water-seeded rice. Severe infestations can reduce yields by more than 50%. Flooding only partially controls this weed; thus, farmers rely heavily on herbicides. Resistance to several herbicides, including bispyribac-sodium, an acetolactate synthase (ALS) inhibitor not yet commercially used, has developed in late watergrass populations of California rice. Knowing the mechanisms of bispyribac resistance is relevant to designing herbicide management strategies for delaying resistance development to enhance the successful introduction of this new herbicide. We examined whether an insensitive ALS and cyt P-450-dependent detoxification were possible resistance mechanisms in a bispyribac-sodium-resistant (R) late watergrass population collected in California rice fields, which was previously determined to be resistant to molinate, thiobencarb, and fenoxaprop-ethyl. ALS activity was assayed on leaf extracts from young R and susceptible (S) plants for a range of bispyribac-sodium concentrations, and cross-resistance to another ALS inhibitor, bensulfuron-methyl, was evaluated using whole-plant bioassays. Resistance was not due to reduced ALS sensitivity to bispyribac-sodium in R plants, although the R accession was highly cross-resistant to bensulfuron-methyl. Although S and R plants had similar ALS activity (mg acetoin mg protein−1) without herbicide, more (P

Methane pool and flux dynamics in a rice field following straw incorporation

Concerns for air quality have led to legislation restricting rice straw burning in some parts of the world. Consequently, growers must dispose of large amounts of residual rice straw by incorporation into the soil, which may have large effects on CH 4 emissions from those fields. Our objective was to characterize how this recent change in management has affected overall CH 4 emissions in a California rice field and establish relationships between organic matter availability, CH 4 pool sizes and CH 4 fluxes. Closed chamber measurements were used to monitor diurnal and post drain fluxes, to describe the seasonal pattern of CH 4 emissions and estimate total CH 4 fluxes on a large on-farm field trial during the 1997 growing season. Soil redox, temperature and plant growth and yield were also monitored. To establish relationships between CH 4 pool sizes and fluxes, soil interstitial CH 4 concentrations were monitored in the field and available organic matter in the spring was estimated with a laboratory incubation. Redox values in the soil were found to be 50 mV lower in plots in which straw had been incorporated (−275 mV) than those in which it had been burned (−225 mV). No significant treatment differences were seen in total soil organic matter contents in the spring. However, available organic matter was 1.5 times higher in straw incorporated than straw burned plots. Methane emissions peaked between 22.00 and 23.00 h on two different diurnal sampling dates. Methane emission after draining was about 10% of the flooded period total. A 5-fold increase in total CH 4 emissions over the rice growing season was observed in plots in which rice straw had been incorporated each fall for 4 yr. Total cumulative CH 4 flux, 1 May–1 October 1997, was 8.87 g C m −2 in incorporated, winter flooded plots; 9.52 g C m −2 in incorporated, non-winter flooded plots; 1.63 g C m −2 in burned, winter flooded plots; and 2.25 g C m −2 in burned, non-winter flooded plots. Soil CH 4 concentrations at 10–15 cm depth was strongly associated with emissions to the atmosphere ( r=0.89). A model developed by Nouchi et al. (1994) [Nouchi, I., Hosono, T., Aodi, K., Minami, K., 1994. Seasonal variation in methane flux from rice paddies associated with methane concentration in soil water, rice biomass and temperature and it's modeling. Plant and Soil 161, 195-208.] which could predict the CH 4 flux based on soil CH 4 concentrations and temperature was fit to our data. The model was very successful at predicting flux rates and cumulative fluxes because conductance (CH 4 flux divided by CH 4 concentration in soil water) was highly correlated with soil temperature ( r=0.88) throughout the period of high CH 4 emissions. Organic matter availability and CH 4 pool and flux dynamics were altered by straw incorporation practices as evidenced by increased conductance at the same interstitial CH 4 concentration and increased emissions per unit available organic matter in rice straw incorporated plots.

Copper (II) complexation in northern California rice field waters: an investigation using differential pulse anodic and cathodic stripping voltammetry

Differential pulse anodic stripping voltammetry (DPASV) and competitive ligand equilibration-cathodic stripping voltammetry (CLE-CSV) demonstrated that≥99% of the dissolved copper in five rice field waters, one river water and a catchment basin water collected at sites in northern California is complexed by natural organic matter. Concentrations of natural copper complexing ligands (C L) ranged from 81 to 426 nM determined by CLE-CSV using the competitive ligand 8-hydroxyquinoline and from 156 to 1374 nM using DPASV. Experimental values for conditional stability constants (with respect to free Cu 2+) of natural copper–organic ligand complexes (log K′ CuL) fell in the range 10.2–11.2 using DPASV and 11.1–11.5 using CLE-CSV. DPASV analyses revealed evidence of organic matter adsorption to the electrode surface at low dissolved organic carbon (DOC) concentrations (i.e. 200 μg l −1 DOC for a 10-min deposition period), for some but not all water samples. Examination of lyophilized, filtered rice field water using scanning electron microscopy (SEM) and pyrolysis gas chromatography mass spectrometry (pyr-GC/MS) did not reveal differences that could be associated with surface active material. Uncomplexed copper accounts for only minor amounts of total copper in rice field waters and natural ligands are expected to influence its effectiveness as an agrochemical.

Phenotypic plasticity of Ammannia spp. in competition with rice

SummaryThe annual broadleaved weeds Ammannia auriculata Wild, and A. coccinea Rottb. are widespread and competitive in California rice (Oryza sativa L.) fields. We studied Ammannia spp. biology in a greenhouse pot experiment. Weeds were grown alone and in competition with rice (cv. M–202), and harvested six times over 122 days. Compared with growth alone, competition reduced Ammannia spp. total plant dry weight (DW), shoot DW and leaf area in all but the first harvest. However, weed height differed at only one harvest (85 days after planting). Ammannia spp. responded to competition with increased shoot:root DW ratios, increased stem:other shoot DW ratios, decreased stem diameters, fewer but elongated internodes and fewer branches. This suggests that light capture was more important than nutrient capture for maintaining Ammannia spp. growth. The weeds appear to lodge easily in rice fields because competitive growth responses make them top heavy and unstable. Weed seed DW declined by 97% in competition, which showed the importance of crop interference to Ammannia spp. control. Plasticity may help Ammannia spp. to escape common control practices (e.g. high crop plant densities or early herbicide application), and probably contributes to its widespread distribution. Thus, Ammannia spp. plasticity should be more fully considered when designing management strategies.

Remote sensing of foliar chemistry of inundated rice with imaging spectrometry

The applicability of imaging spectrometry to the measurement of foliar chemistry of herbaceous wetland vegetation was assessed for cultivated rice. Multiple samples were obtained from five California rice fields for analyses of nitrogen and lignin concentrations, and Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) images were obtained in August 1992. Multiple linear regression (MLR) was used to develop calibration equations for nitrogen and lignin based on AVIRIS reflectance (R) spectra transformed as the first difference of absorbance [log(1/R)]. Transformed AVIRIS absorbances were not as well correlated to lignin ( r su2 = 0.44) as to nitrogen ( r 2 = 0.74); the relative standard error of calibration (SEC) for nitrogen was 11%. To further test the predictive ability of this technique with respect to nitrogen concentration, four new calibration equations were derived based on each possible set of three fields. With each new subset of the data, MLR selected different wavelengths for the nitrogen calibration equation. Coefficients of multiple determination (r 2) ranged from 0.69 to 0.85, with relative standard SECs ranging from 8.4% to 11.4%. Each of these equations was then used to predict the nitrogen concentration of samples in the omitted field, resulting in relative standard errors of prediction (SEP) ranging up to 37%. Results from this study suggest that calibration equations derived from multiple linear regression of AVIRIS spectra can be used to predict the nitrogen concentration of rice in the field. It was not possible to derive a general equation for the detection of nitrogen concentration with AVIRIS because the calibration equations developed with MLR were based on a different set of wavelengths for each subset of the data.

Conjunctive use of farmland adds value: Winter flooding of ricelands provides waterfowl habitat

California rice fields are home to a rich diversity of plant and animal species, and are an integral component of the waterfowl habitat in the Pacific Flyway. Adoption of novel straw incorporation techniques that leave residual rice seed accessible to foraging wildlife coupled with winter flooding to create stable winter wetlands habitat should greatly improve bird health and subsequent fecundity in northern nesting grounds. From the agronomic standpoint, however, the efficacy of these incorporation techniques and their long-term impact on rice production remain to be demonstrated. Recognizing that future straw management options must meet both production agriculture and environmental stewardship objectives, the University of California has undertaken a 5-year, multidisciplinary research and demonstration program to address these issues.