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or inject acid (e.g., sulfuric acid) into the irrigation water (chemigation). However, surface application of S o is ineffective in dry environments and difficult to do in fields mulched with geotextile fabric (“weed mat”), while acid chemigation is

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Salem, OR (lat. 45°00′N, long. 122°56′W). Plants were spaced 3 ft apart within the row, 10 ft between rows and were drip irrigated with a perennial grass planted between the rows. An existing microsprinkler system, used by the grower for chemigation and

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Abstract

Oxadiazon was applied conventionally as a granular and compared to the emulsifiable concentrate injected into sprinkler irrigation system (chemigation) at 60- day intervals on 20 species of container-grown ornamentals. In general, phytotoxicity increased proportional to the number of applications and was most prevalent during cold weather. Moderate to severe phytotoxicity at 2 × and 4 × rates was observed on aucuba (Aucuba japonica Thunb.), azalea [Rhododendron (AZ) ‘Formosa’ and R. (AZ) ‘Fashionaire’], liriope [Liriope muscari (Decne) L. H. Bailey], pampas grass [Cortaderia selloana (Schult. & Schult. f.) Asch. & Graebn.], Japanese black pine (Pinus thunbergiana Franco), and red tip photinia (Photinia ‘Fraseri’ Dress). Increased injury was observed on aucuba, Japanese black pine, and azalea when oxadiazon was applied via chemigation. On the other species, the degree of phytotoxicity was proportional to the rate applied. Both monocots showed moderate (18%) to severe (45%) injury. The only cultivar with significant growth reductions after 8 months was the ‘Formosa’ azalea when chemigated. The only species with reduced marketability due to the herbicide was liriope. After the second application, the weight and number of weeds decreased proportional to the herbicide rate or number of applications. Chemical name used: 3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2(3H)-one (oxadiazon).

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The injection of chemicals into irrigation systems is discussed in terms of injection systems, concentration injections, bulk injections, quantity of chemicals to be injected, injection system calibration, and injection periods. Sufficient clean-water flush time should be scheduled to purge irrigation lines of injected chemicals unless it is desired to leave that particular chemical in the irrigation system for maintenance purposes. Chemical injection rates vary with desired chemical concentration in the irrigation water, concentration of the stock solution, volume of chemical to be injected, and duration of each injection. All injection systems should be calibrated and maintained in proper working order. This information is presented to assist irrigation system designers and operators with chemigation system design, scheduling, and management.

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Abstract

Six cultivars of broccoli [Brassica oleracea L. (Italica Group)] were grown from transplants in Spring and Fall 1984 at Bixby, Okla. The objectives were to evaluate yield losses due to wirestem (caused by Rhizoctonia solani Kuhn) and/or wind injury, cultivar differences in susceptibility, and fungicide effectiveness. Fungicide treatments included an untreated control and application of iprodione at 1.14 kg·ha−1 as either a drench with the starter fertilizer solution or through sprinkler irrigation (chemigation). Iprodione seemed useful for control of R. solani, although the proportion of injured plants infected by R. solani was significantly reduced only in the fall. However, the fungicide treatments did not increase marketable yields significantly over the control. No significant differences in susceptibility to R. solani were shown among the cultivars. Most injured plants not infected by R. solani apparently sustained wind damage. ‘Excalibur’ was especially susceptible to wind-induced stem breakage. Chemical names used: 3-(3,5-dichlorophenyl)-N-(l-methylethyl)-2,4-dioxo-l-imidazolidinecarboxamide (iprodione).

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An evaluation of the effect of bed width (24, 28, 32, and 36 inches) on the control of a mixed population of nutsedge [yellow nutsedge (Cyperus esculentus) and purple nutsedge (C. rotundus)] was conducted with an emulsifiable concentrate formulation of a 1,3-dichloropropene (1,3-D) and chloropicrin (CP) mixture (1,3-DCP) for application through drip irrigation systems. Beds were mulched with either 1.4-mil-thick virtually impermeable film (VIF) or 0.75-mil-thick high-density polyethylene (HDPE) and 1,3-DCP was applied at 35 gal/acre by surface chemigation or via subsurface chemigation 6 inches deep within the bed. HDPE was more permeable to gaseous 1,3-D than VIF so that 1 day after treatment (DAT), 1,3-D gas concentration at the bed centers under VIF was significantly higher than under HDPE. Dissipation of 1,3-D gas with HDPE occurred within 7 DAT, but dissipation with VIF took ∼10 days. In bed centers, 1,3-D concentrations 1 DAT were in the range of 2.3 to 2.9 mg·L–1 whereas in bed shoulders concentrations ranged from 0.1 to 0.55 mg·L–1. In 2002 and 2003, 1,3-D concentration in shoulders of narrower beds was significantly higher than in the wider beds, but dissipated more rapidly than in wider beds. Lower initial 1,3-D concentrations were observed with HDPE film in shoulders than with VIF and the rate of dissipation was lower with VIF. At 14 DAT, nutsedge plants were densely distributed along bed shoulders (19 to 27 plants/m2) with little or no emergence in the centers of beds (fewer than 5 plants/m2), but with no response to bed width. Nutsedge density increased with time, but the nature of the increase differed with bed width. The most effective nutsedge suppression was achieved with 36-inch beds, which had densities of 11–13 plants/m2 on bed centers and 53 plants/m2 on bed shoulders by 90 DAT. Nutsedge suppression was initially more effective with VIF than with HDPE film, so that no nutsedge emerged in the centers of beds mulched with VIF compared with 2–7 plants/ m2 with HDPE by 14 DAT. On bed shoulders there were 2–7 plants/m2 with VIF and 32–57 plants/m2 with HDPE. Increase in nutsedge density with time was greater with VIF so that by 90 DAT nutsedge densities on bed centers and shoulders were greater than with HDPE in 2002 and the same as with HDPE in 2003. Subsurface chemigation did not consistently improve suppression of nutsedge when compared with surface chemigation. Concentrations of 1,3-D in bed shoulders irrespective of bed width were nonlethal. Initial superior nutsedge suppression with VIF did not persist. Nutsedge control in a sandy soil with 1,3-DCP chemigation is unsatisfactory with one drip-tape per bed.

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Abstract

Pesticides were applied to ‘Rio Grande’ peach [Prunus persica (L.) Batsch] trees at recommended rates from bloom to harvest using three sprinkler configurations on a center pivot and an air-blast sprayer. Fruit scab infection rates with a patented sprinkler configuration (Piggy-back) that has spray nozzles mounted on a lower truss rod of the center pivot were equivalent on 12 and 23 June 1987 to those with the air-blast sprayer. Scab infection rates for standard impact-nozzles and for a deflector nozzle configuration were equivalent to each other, and tended to be lower than the infection rate for the unsprayed fruit, but higher than the rate for the air-blast sprayer or piggy-back configuration. Brown rot, bacterial spot, and insect catfacing (the other fruit defects observed at harvest) were independent of the method of pesticide application. It may be feasible to chemigate peach orchards with center-pivot irrigation systems.

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Field studies were conducted in 1987 and 1988 to determine the effect of various sprinkler-applied N-K fertigation treatments and 196N-280K (kg·ha-1) dry-blend application on pumpkin (Cucurbita moschata Poir.) flower development, fruit set, vine growth, and marketable yield response in a Plainfield sand. The number of male and female flowers that reached anthesis by 72 days after seeding (DAS) was highest with either 112N-112K or 112N-224K fertigation. Fertigation using either 56N-112K or 168N-224K delayed the start of flowering and reduced the total number of male and female flowers produced by 72 DAS. Fruit set decreased at the low N-K fertigation rate (56N-112K), but otherwise was unaffected by N-K fertility regime. Vine dry weight and stem elongation increased as the N fertigation rate increased, with relatively little effect from fertigated K. There was no field indication of excessive vegetative growth in any of the fertigation treatments. Highest yields of early set marketable fruit (pumpkins that set before 65 DAS), and total marketable yields were obtained with fertigation of 112N, in combination with either 112 or 224 kg·ha-1 fertigated K. Usable green and cull fruit production increased with increasing N-K fertigation rate. Dry-blend application of 196N-280K decreased early and total yields significantly. The results showed that sprinkler-applied 112N-112K split into five fertigations during the growing season (supplemented with a preplant dry-blend application of 28N-56K) produced high yields without compromising early fruit maturity.

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Halosulfuron is an alternative to methyl bromide for managing nutsedges (Cyperus spp.) in several vegetable crops. Field studies were conducted to evaluate eggplant growth and yield when halosulfuron was applied through drip-irrigation before transplant at four rates (0, 26, 39, or 52 g·ha–1 a.i.) or following transplant (26 g·ha–1 applied 1, 2, or 3 weeks after transplant) in spring and fall crops in 2002 and 2003. Inverse linear relationships were observed between rate of halosulfuron and eggplant growth and rate of halosulfuron and eggplant yield. Halosulfuron at 52 g·ha–1 reduced eggplant growth (crop height and canopy width) 19% to 22%. Eggplant fruit biomass at the first harvest was reduced 37% to 63% by halosulfuron applied before transplant. Eggplant was capable of recovering from the initial injury and there was no effect of halosulfuron rate on fruit biomass at the final harvest. Total season fruit biomass was reduced ≤4% from halosulfuron at 39 g·ha–1, while halosulfuron at 52 g·ha–1 reduced fruit biomass 33%. Delay in application of halosulfuron to 3 weeks after transplant (WAT) resulted in ≤7% reduction in fruit biomass and number for the entire season. When halosulfuron was applied 1 WAT, fruit biomass at the first two harvests was reduced >33%, however total season harvest from this treatment was >99% of the yield from the nontreated control. This preliminary study indicates that halosulfuron injected through drip tape may have the potential to assist in the replacement of methyl bromide for nutsedge management in eggplant. However, there are many issues that must be addressed and studied before adopting this practice in eggplant.

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Plasticulture, simply defined, is a system of growing crops wherein a significant benefit is derived from using products derived from plastic polymers. The discovery and development of the polythylene polymer in the late 1930s, and its subsequent introduction in the early 1950s in the form of plastic films, mulches, and drip-irrigation tubing and tape, revolutionized the commercial production of selected vegetable crops and gave rise to plasticulture. The later discovery of other polymers, such as polyvinyl chloride, polyproplene, and polyesters, and their use in pipes, fertigation equipment, filters, fittings and connectors, and row covers further extended the use of plastic components in this production system. The plasticulture system consists of plastic and nonplastic components: plastic mulches, drip irrigation, fertigation/chemigation, fumigation and solarization, windbreaks, stand establishment technology, season-extending technology, pest management, cropping strategies, and marketing.

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