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PubMed2001

Application technique and irrigation method affect imidacloprid control of silverleaf whiteflies (Homoptera: Aleyrodidae) on poinsettias.

Subirrigation systems are increasingly used to water and fertilize greenhouse crops. They also appear to be well suited for the application of systemic pesticides. We conducted two studies to look at interactive effects ofimidacloprid application technique and irrigation method on plant uptake of imidacloprid and whitefly control. Drench applications of imidacloprid resulted in much higher concentrations in the leaves than applications to the bottom of pots after 14 d. However, imidacloprid efficacy in subirrigated plants was better if the imidacloprid was applied to the bottom of the pot than when an equal amount was applied as a drench. In drip-irrigated plants, imidacloprid efficacy was greater after a drench than after an application to the bottom of the pots. A second study showed that drench applications to drip-irrigated plants result in high imidacloprid concentrations in the bottom of the canopy, whereas bottom applications to subirrigated plants result in a more even distribution of imidacloprid throughout the plant. Surprisingly, the high leaf imidacloprid concentrations in the bottom layer of drip-irrigated plants did not result in improved whitefly control. Imidacloprid efficacy was better in subirrigated, bottom-treated plants than in drip-irrigated, drenched plants. Overall, results from these studies indicate that imidacloprid is very effective when applied to the bottom of subirrigated pots.

Agriculture↗

PubMedDate not supplied

Regulation of nitrous oxide emissions from soils irrigated with dairy farm effluent.

Animal slurries and effluents are commonly applied to soil as a source of organic N fertilizer. By increasing inorganic N, applying animal effluents may also increase soil nitrous oxide (N2O) emissions. Our objectives were to (i) determine if dairy farm effluent (DFE) irrigation increased short-term N2O emissions from a surface-drained peat soil and a freely drained mineral soil and (ii) see if this increase could be attributed to increased N availability, increased soil water content, or a combination of both factors. We measured short-term N2O emissions following DFE irrigation in spring and autumn, using closed chambers. Nitrous oxide emissions from DFE-irrigated soils (50 kg N ha(-1), 20-mm hydraulic loading) were compared with soils receiving inorganic nitrogen and water (50 kg N ha(-1), 20 mm), inorganic N only (50 kg N ha(-1)), water only (20 mm), and no treatment. Nitrous oxide emissions increased immediately following DFE irrigation to both soils, and were generally greater than emissions following the application of inorganic fertilizer with water. Increased N20 emissions following DFE irrigation coincided with increased soil water contents and mineral N and CO2 emissions. We suggest that DFE application increased N2O emissions more than inorganic N fertilizer by enhancing denitrification either by increasing C availability and/ or decreasing soil aeration following increased respiration. These findings suggest that the proportion of N applied to the soil and emitted as N2O may at times be greater for organic N fertilizers than inorganic N fertilizers, particularly if the organic N fertilizer contains sufficient available C to enhance denitrification.

Agriculture↗

PubMedDate not supplied

Impact of preferential flow at varying irrigation rates by quantifying mass fluxes.

Solute concentration and soluble dye studies inferring that preferential flow accelerates field-scale contaminant transport are common but flux measurements quantifying its impact are essentially nonexistent. A tile-drain facility was used to determine the influence of matrix and preferential flow processes on the flux of mobile tracers subjected to different irrigation regimes (4.4 and 0.89 mm h(-1)) in a silt loam soil. After tile outflow reached steady state either bromide (Br; 280 kg ha(-1)) or pentafluorobenzoic acid (PFBA; 121 kg ha(-1)) was applied through the irrigation system inside a shed (3.5 x 24 m). Bromide fluxes were monitored at an irrigation rate of 4.4 mm h(-1) while PFBA fluxes were monitored at an irrigation rate of 0.89 mm h(-1). At 4.4 mm h(-1) nearly one-third of the surface-applied Br was recovered in the tile line after only 124 mm of irrigation and was poorly fit by the one-dimensional convective-dispersive equation (CDE). On the other hand, the one-dimensional CDE fit the main PFBA breakthrough pattern almost perfectly, suggesting the PFBA transport was dominated by matrix flow. Furthermore, after 225 mm of water had been applied, less than 2% of the applied PFBA had been leached through the soil compared with more than 59% of the applied Br. This study demonstrates that the methodology of applying a narrow strip of chemical to a tile drain facility is appropriate for quantifying chemical fluxes at the small-field scale and also suggests that there may be a critical input flux whereby preferential flow is initiated.

Agriculture↗

PubMed2006

Leaching of N-nitrosodimethylamine (NDMA) in turfgrass soils during wastewater irrigation.

N-nitrosodimethylamine (NDMA) is a carcinogenic by-product of chlorination that is frequently found in municipal wastewater effluent. NDMA is miscible in water and negligibly adsorbed to soil, and therefore may pose a threat to ground water when treated wastewater is used for landscape irrigation. A field study was performed in the summer months under arid Southern California weather conditions to evaluate the leaching potential of NDMA in turfgrass soils during wastewater irrigation. Wastewater was used to irrigate multiple turfgrass plots at 110 to 160% evapotranspiration rate for about 4 mo, and leachate was continuously collected and analyzed for NDMA. The treated wastewater contained relatively high levels of NDMA (114-1820 ng L(-1); mean 930 ng L(-1)). NDMA was detected infrequently in the leachate regardless of the soil type or irrigation schedule. At a method detection limit of 2 ng L(-1), NDMA was only detected in 9 out of 400 leachate samples and when it was detected, the NDMA concentration was less than 5 ng L(-1). NDMA was relatively persistent in the turfgrass soils during laboratory incubation, indicating that mechanisms other than biotransformation, likely volatilization and/or plant uptake, contributed to the rapid dissipation. Under conditions typical of turfgrass irrigation with wastewater effluent it is unlikely that NDMA will contaminate ground water.

Biodegradation, Environmental↗

PubMed2006

Influence of irrigation methods and an adjuvant on the persistence of carbaryl on pakchoi.

Influence of irrigation methods and use of an adjuvant on the persistence of the carbaryl (1-naphthyl N-methylcarbamate) on pakchoi [Brassica rapa L. subsp. chinensis (Rupr.) Olsson] was studied using a commercial enzyme linked immunosorbent assay kit. After applying carbaryl at a.i. 10.6 g L(-1) with or without an adjuvant (Latron B-1956) to leaves, plants were provided water daily by either overhead or basal application. Pesticide residue on leaf tissues was examined immediately after pesticide application and on 2, 4, 6, and 8 d after pesticide application. Use of the adjuvant did not affect the initial deposit of the pesticide, however pesticide persistence was improved with the adjuvant regardless of irrigation. Overhead irrigation contributed to rapid loss of the pesticide by washing carbaryl from the leaf surface. The longest half-life of carbaryl (6.5 d) was detected on plants receiving basal irrigation plus the adjuvant while the shortest half-life (2 d) was observed when plants were treated with overhead irrigation and no adjuvant.

Biodegradation, Environmental↗

PubMed1993

Jongkees' formula re-evaluated: order effects in the response to alternate binaural bithermal caloric stimulation using closed-loop irrigation.

Normal limits for the response to caloric irrigation typically are specified as percentage of reduced vestibular response (RVR) and directional preponderance (DP). These measures are calculated using Jongkees' formula without regard to which ear is stimulated first. To assess the influence of the order in which the caloric stimuli are delivered we reviewed the responses to closed loop caloric irrigation of two groups of normal subjects and a group of unselected patients. Results indicated a consistent declining trend in response from the first caloric administration to the last administration in all groups and subgroups except in male patients over 60 years of age. Consequently, a significant bias in RVR was observed. Specifically, with the order of irrigation left cold, right cold, left warm, right warm, the mean percentage RVR for both the patients and control subjects was about a 5% right RVR. The bias resulted in right-sided unilateral hypofunction being diagnosed 2.4 times more often than left-sided hypofunction in patients aged 16-59. Our results differ from the previous literature that describes the effect of order on the response to caloric irrigation; this discrepancy may be related to our use of a closed-loop system for caloric irrigation. We conclude that vestibular laboratories should account for the effect of order in their patients' responses to caloric stimulation. We offer suggestions on how Jongkees' formula can be corrected for the effect of order.

Adolescent↗

PubMed1991

Anopheline ecology and malaria infection during the irrigation development of an area of the Mahaweli Project, Sri Lanka.

A study on adult anopheline ecology and malaria vector incrimination was carried out from 1986 to 1989 during irrigation development in an area of the Mahaweli Project in eastern Sri Lanka. Eleven potential vector species were collected resting indoors or by using human or bovid bait, and from light trap catches. Overall, Anopheles vagus (Donitz), An. annularis (van der Wulp), and An. subpictus (Grassi) were the most prevalent, and An. culicifacies (Giles) and An. barbirostris (van der Wulp) were the least prevalent species. The abundance of An. aconitus (Donitz), An. jamesii (Theobald), An. pallidus (Theobald), and An. subpictus increased after irrigation development, while An. annularis, An. barbirostris, An. culicifacies and An. varuna (Iyengar) decreased. Populations of An. nigerrimus (Giles), An. tessellatus (Theobald), and An. vagus did not change substantially. Seven species were infected with malaria parasites, as determined by enzyme-linked immunosorbent assays (ELISA) done on mosquito head-thorax triturates. The main species involved were An. annularis, at peak abundance during the 1986-1987 period of development leading to the onset of irrigation, and An. subpictus, during times of seasonal abundance in the post-irrigation period of 1988 to 1989. Although occurring at low abundance, An. culicifacies was involved in malaria transmission irregularly throughout the study period. While there was strong ELISA-based evidence implicating An. subpictus as a major post-irrigation vector, confirmation of its vector status must await dissection and ELISA-based evidence of P. vivax and P. falciparum sporozoite infection rates in salivary glands.

Animals↗

PubMed2003

Persistence of Escherichia coli O157:H7 on lettuce plants following spray irrigation with contaminated water.

Irrigation water collected at farms growing crops for human consumption was artificially contaminated with E. coli O157:H7 and used to irrigate lettuce plants. Plants in a growth chamber were spray irrigated either once or intermittently with water contaminated with 10(2) or 10(4) CFU of E. coli O157:H7 per ml and were then sampled over a 30-day period. Only plants exposed to 10(2) CFU/ml on day 1 did not harbor the pathogen at the end of the sampling period. All other treatments resulted in contaminated plants at harvest. Plants irrigated with 10(4) CFU/ml contained high levels (up to 5 log CFU/g) of the pathogen at harvest. The results obtained in this study underscore the assertion that spray irrigation (the application of water directly to plant leaves) is linked to the contamination of crops and suggest that repeated exposure increases the E. coli O157:H7 level on the plant.

Aerosols↗

PubMed2004

Persistence of enterohemorrhagic Escherichia coli O157:H7 in soil and on leaf lettuce and parsley grown in fields treated with contaminated manure composts or irrigation water.

Outbreaks of enterohemorrhagic Escherichia coli O157:H7 infections associated with lettuce and other leaf crops have occurred with increasing frequency in recent years. Contaminated manure and polluted irrigation water are probable vehicles for the pathogen in many outbreaks. In this study, the occurrence and persistence of E. coli O157:H7 in soil fertilized with contaminated poultry or bovine manure composts or treated with contaminated irrigation water and on lettuce and parsley grown on these soils under natural environmental conditions was determined. Twenty-five plots, each 1.8 by 4.6 m, were used for each crop, with five treatments (one without compost, three with each of the three composts, and one without compost but treated with contaminated water) and five replication plots for each treatment. Three different types of compost, PM-5 (poultry manure compost), 338 (dairy manure compost), and NVIRO-4 (alkaline-stabilized dairy manure compost), and irrigation water were inoculated with an avirulent strain of E. coli O157:H7. Pathogen concentrations were 10(7) CFU/g of compost and 10(5) CFU/ml of water. Contaminated compost was applied to soil in the field as a strip at 4.5 metric tons per hectare on the day before lettuce and parsley seedlings were transplanted in late October 2002. Contaminated irrigation water was applied only once on the plants as a treatment in five plots for each crop at the rate of 2 liters per plot 3 weeks after the seedlings were transplanted. E. coli O157:H7 persisted for 154 to 217 days in soils amended with contaminated composts and was detected on lettuce and parsley for up to 77 and 177 days, respectively, after seedlings were planted. Very little difference was observed in E. coli O157:H7 persistence based on compost type alone. E. coli O157:H7 persisted longer (by > 60 days) in soil covered with parsley plants than in soil from lettuce plots, which were bare after lettuce was harvested. In all cases, E. coli O157:H7 in soil, regardless of source or crop type, persisted for > 5 months after application of contaminated compost or irrigation water.

Disease Outbreaks↗

PubMed2005

A simple method for the direct detection of Salmonella and Escherichia coli O157:H7 from raw alfalfa sprouts and spent irrigation water using PCR.

The U.S. Food and Drug Administration recognizes that raw seed sprouts are an important cause of foodborne disease and is now recommending that either spent irrigation water or final product be screened for Salmonella and Escherichia coli O157:H7 as a means of assuring the safety of product intended for consumption. In an effort to streamline such testing efforts, a simple method to preconcentrate pathogens from sprouts and spent irrigation water was investigated to facilitate the direct (without prior cultural enrichment) detection of pathogens using the PCR technique. Alfalfa sprouts and spent irrigation water were seeded with Salmonella enterica serovar Typhimurium and E. coli O157:H7 at 10(-1) to 106 CFU/g or CFU/ml, respectively. Samples were blended (sprouts only) and then centrifuged at high speed to sediment the total bacterial population. The precipitate was processed for DNA isolation, PCR amplification, and amplicon confirmation by Southern hybridization. Mean pathogen recoveries after centrifugation ranged from 96 to 99% for both pathogens in both matrices. Using primers targeting the invA gene for Salmonella Typhimurium and the stx genes of E. coli O157:H7, it was possible to detect both pathogens in alfalfa sprouts at seeding concentrations as low as 10 CFU/g. PCR detection limits for both pathogens from spent irrigation water were 10(-1) CFU/ml, the equivalent of 100 CFU/liter of water. Because spent irrigation water is constitutionally simple, it is particularly well suited for bacterial concentration by simple centrifugation steps. In this study, progress was made toward development of a rapid, inexpensive, and sensitive method for the detection of sprout-associated pathogens that is relevant to current industrial practices and needs.

Colony Count, Microbial↗

PubMed2000

Anopheline ecology and malaria transmission at a new irrigation project area (Bargi Dam) in Jabalpur (Central India).

Anopheline ecology and malaria transmission were studied in a newly irrigated area of the Bargi Project, District Jabalpur, Madhya Pradesh, Central India. Observations were made for 2 years (1993-95) in 10 villages along the Bargi irrigation canal, which are situated between 44 km (head end of canal) and 78 km (tail end of canal) from the dam site. Anopheles annularis was the predominant species in the head-end villages and its abundance was directly related to the opening of the canal, whereas Anopheles culicifacies was the most abundant species in tail-end villages, where irrigation is limited. Anopheles culicifacies showed 2 typical peaks not related to canal irrigation. Site-related differences in species prevalence were significant in both immatures and adults. Malaria infection was due to Plasmodium vivax and Plasmodium falciparum. The annual parasite incidence in children and adults was significantly higher in head-end villages (>4-fold) as compared to that in tail-end villages. However, seasonal trends in the prevalence of P. falciparum and P. vivax were the same in each group, with some fluctuations. In this study, preliminary results of the investigation are presented, demonstrating the trends in anopheline ecology and parasite prevalence in relation to the dynamics of irrigation development.

Adolescent↗

PubMed2002

Effects on crops of irrigation with treated municipal wastewaters.

The fertilizing potential of treated municipal wastewater (oxidation ditch) and crop sanitary acceptability for direct human consumption were evaluated in Mendoza, Argentina. Two experiments were performed on a pilot plot planted with garlic (1998) and onions (1999) using furrow irrigation with three types of water in 10 random blocks: treated effluent (2.5 x 10(3) MPN Escherichia coli/100 ml, 3 helminth eggs/l, and Salmonella (positive); and well water (free of microorganisms), with and without fertilizer. Two responses were evaluated: (1) crop yield, and (2) crop microbiological quality for human consumption at different times after harvest. Crop yields were compared using Variance analysis. Crops' sanitary acceptability was assessed using a two-class sampling program for Salmonella (n=10; c=0), and a three-class program for E. coli (n=5, c=2, M=10(3) and m=10 MPN/g) as proposed by the International Commission on Microbiological Specifications for Foods (ICMSF) for fresh vegetables. Wastewater irrigation acted as well water with fertilizer, increasing garlic and onion yields by 10% and 15%, respectively, compared to irrigation with well water with no fertilizer. Wastewater-irrigated garlic reached sanitary acceptability 90 days after harvest, once attached roots and soil were removed. Onions, which were cleaned immediately after harvest, met this qualification earlier than garlic (55 days). Neither the wastewater-irrigated crops nor the control crops were microbiologically acceptable for consumption raw at harvest.

Conservation of Natural Resources↗

PubMed2002

[Influence of saltwater irrigation on the yield and quality of Cynodon dactylon under desert conditions].

Responses of six varieties (Suwannee, Coast cross, Tifton44, Tifton68, Tifton78 and Tifton85) of Cynodon dactylon to irrigation-water salinity were investigated in field by means of a double line source experimental design. The digestibility of the grass by goat was analyzed using the rumen gastric justice digestion method. The results showed that the six varieties grew well, and had a high yield of fresh grass when eletro-conductivity (Eci) < 10 ds.m-1. Particularly when Eci = 4.4 ds.m-1, the fresh grass yield of Coast cross, Suwannee, Tifton44, Tifton68, Tifton78 and Tifton85 was respectively increased by 142.1%, 61.1%, 136%, 121.1%, 202.3% and 109.7%, in comparison with fresh water (Eci = 1.2) irrigation. Dry matter yield was also elevated with the increasing salinity of irrigated water. There was no obvious effect of salinity on crude protein, fiber and ash contents in the six varieties. Goats were fond of eating the hay irrigated by saline water, perhaps because of its higher digestibility. At least, the yield and quality of Cynodon dactylon were not effected by saltwater irrigation.

Crops, Agricultural↗

PubMed2002

[Extraction of organochlorine pesticides using ASE from wastewater irrigated agricultural soil].

The extraction efficiency of accelerated solvent extraction (ASE) was studied for organochlorine pesticide residuals in soil and compared with that of Soxhlet. The results showed that the efficiency of ASE was generally better than Soxhlet when used for DDT measurement, and equivalent to Soxhlet for BHCs. With ASE, organochlorine pesticide residues were detected in wastewater irrigated and non-wastewater irrigated soils from Tianjin. alpha-BHC, beta-BHC, delta-BHC, gamma-BHC, p,p'-DDE, p,p'-DDD, p,p'-DDT, o,p'-DDT ranged from 7.5 to 71.1 ng/g in wastewater irrigated vegetable and maize field and from 3.0 to 16.5 ng/g in wastewater irrigated paddy field. The eight pesticide residues from non-wastewater irrigated vegetable and maize field was in a range of 3.1-17.6 ng/g.

Agriculture↗

PubMed2002

The potential of intermittent irrigation for increasing rice yields, lowering water consumption, reducing methane emissions, and controlling malaria in African rice fields.

Rice production in sub-Saharan Africa has more than doubled in the last 3 decades and the potential to further develop rice-harvested areas is considerable. Several studies have demonstrated that the transformation of arable land into rice irrigation might create suitable habitats for large populations of disease vectors. Prominent among those are anopheline mosquitoes responsible for transmission of malaria. The method of irrigation on an intermittent basis during the rice-cropping calendar has gained renewed interest as a potentially effective malaria control strategy since the early 1980s. We review the experiences of the past 80 years with intermittent irrigation in the cultivation of rice. This method has been shown to reduce significantly the density of malaria vectors by curtailing their larval development. Furthermore, reduced methane emissions and water savings with at least equal yields were achieved in intermittently irrigated rice fields. We explore and discuss under what conditions intermittent irrigation might be beneficial in new rice-growing areas and identify steps that have to be taken to expand such programs in the future.

Africa South of the Sahara↗

PubMed1992

[Farm irrigation index for culturing Panax ginseng C.A. Meyer].

The growth and yield of annual and perennial Panax ginseng were observed by applying methods of mini-irrigation and irrigation under different negative pressures of soil humidometer. After four experiments optimum values of negative pressure were found to assist timely irrigation, thus providing scientific criteria of rational irrigation and automated mini-irrigation for culturing Panax ginseng.

Humidity↗

PubMed2004

Effect of irrigation water quality on organic matter, Cd and Cu mobility in soils of Central Mexico.

Untreated wastewater has been used for irrigation since 1912 at the Irrigation District 03, Central Mexico. Accumulated heavy metals are dominantly bound to the organic soil fraction. In a field study we evaluated the effect of wastewater irrigation on the quality of soil organic matter and the amount of water extractable Cu and Cd. In a column experiment we tested if water treatment affects the leaching of both metals and dissolved organic carbon (DOC) out of soils that have been irrigated for more than 90 years with untreated wastewater. The field study shows that long term irrigation increases the mineralizable carbon fraction and the DOC concentrations. The water extractable Cu and Cd concentrations also increase and correlate with DOC. In the column leachates the Cu concentrations also correlate with DOC, the Cd concentrations correlate with the sum of cations, chloride and DOC concentrations. Water treatment reduced Cd leaching, but it did have no substantial effect on Cu leaching.

Agriculture↗

PubMed2004

[Influence of water deficit and supplemental irrigation on nitrogen uptake by winter wheat and nitrogen residual in soil].

Pot experiment in greenhouse showed that water deficit at all growth stages and supplemental irrigation at tillering stage significantly decreased the nitrogen uptake by winter wheat and increased the mineral N residual (79.8-113.7 mg x kg(-1)) in soil. Supplemental irrigation at over-wintering, jointing or filling stage significantly increased the nitrogen uptake by plant and decreased the nitrogen residual (47.2-60.3 mg x kg(-1)) in soil. But, the increase of nitrogen uptake caused by supplemental irrigation did not always mean a high magnitude of efficient use of nitrogen by plants. Supplemental irrigation at over-wintering stage didn't induce any significant change in nitrogen content of grain, irrigation at filling stage increased the nitrogen content by 20.9%, and doing this at jointing stage decreased the nitrogen content by 19.6%, as compared to the control.

Absorption↗