Charlotte V. Eberlein

Computer control system for spatially varied water and chemical application studies with continuous-move irrigation systems

A microcomputer driven open-loop digital control system for implementing spatially variable water and chemical application from center pivot and linear-move irrigation systems is described. The control system is comprised of readily available commercial components and provides an effective means of implementing variable rate water and chemical application in crop production studies for evaluating potential benefits. The control system was implemented on a three-span 100 m linear-move irrigation system and on a 39-ha commercial center pivot irrigation system. Water and chemical application were monitored to document control system performance. The results show that spatially varied water and chemical application was achieved with the same accuracy as that of conventional uniform application. This paper provides details on the control system hardware and software and documents field performance.

Broadleaf weed control and potato crop safety with postemergence rimsulfuron, metribuzin, and adjuvant combinations

The effects of postemergence rimsulfuron, metribuzin, and adjuvant combinations on potato crop safety and weed control were evaluated in field studies conducted at the University of Idaho Aberdeen Research and Extension Center in 1999 and 2000. Rimsulfuron at 26 g ai/ha plus metribuzin at 0, 140, or 280 g ai/ha was combined with nonionic surfactant (NIS), crop oil concentrate (COC), or methylated seed oil (MSO) in a 3 by 3 factorial with two controls. Under cool, cloudy conditions in 1999, initial ‘Russet Burbank’ potato injury was greater when metribuzin was included in the tank mixture than when rimsulfuron was applied alone, regardless of adjuvant. Under warmer conditions in 2000, however, adding MSO or COC to the tank mixture caused more injury than adding NIS. Rimsulfuron did not provide acceptable season-long common lambsquarters control in 1999 (76%) or in 2000 (88%), regardless of adjuvant. Rimsulfuron combined with metribuzin at 140 or 280 g/ha provided ≥95% common lambsquarters control both years, regardless of adjuvant. Among adjuvants, using MSO (1999 and 2000) or COC (2000) in the spray mixture improved common lambsquarters control compared with using NIS. Tuber yield and quality were not reduced as a result of metribuzin rate or adjuvant treatments either year compared with the weed-free control. Nomenclature: Metribuzin; rimsulfuron; common lambsquarters, Chenopodium album L. #3 CHEAL; potato, Solanum tuberosum L. ‘Russet Burbank’. Additional index words: Crop oil concentrate, crop safety, herbicide injury, methylated seed oil, nonionic surfactant. Abbreviations: ALS, acetolactate synthase; COC, crop oil concentrate; MSO, methylated seed oil; NIS, nonionic surfactant; PNW, Pacific Northwest; POST, postemergence; PRE, preemergence; WAT, weeks after treatment.

Susceptibility of five nightshade (Solanum) species tophytophthora infestans

The susceptibility of leaves and berries of five night-shade species to infection by the potato late blight pathogenPhytophthora infestans was tested. American black nightshade (Solanum americanum) and eastern black nightshade (Solanum ptycanthum) were resistant to infection. However, two accessions (entire-edged and dentate-edged leaf) of hairy nightshade (Solanum sarrachoides), cutleaf nightshade (Solanum triflorum), and bitter or climbing nightshade (Solanum dulcamara) were susceptible. Survival of the pathogen in susceptible species was tested under different environmental conditions. The pathogen survived for at least 2 wk in both hairy nightshade accessions when plant material was kept in soil at a temperature of 20 C. However,P. infestans survived 48 h at −15 C only in the entire-leaf hairy nightshade accession. In the laboratory, oospores of the pathogen were formed in inoculated plants of the two hairy nightshade accessions, cutleaf nightshade, and ‘Russet Burbank’ potato, but not in American black nightshade, bitter nightshade, or eastern black nightshade.ResumenSe probó la susceptibilidad a la infección del patógeno del tizón tardíoPhytophthora infestans en hojas y bayas de cinco especies de dulcamara (hierba mora). Fueron resistentes a la infección la dulcamara negra americana (Solanum americanum) y la dulcamara negra del este (Solanum ptycanthum). Sin embargo, dos accesiones (de hoja lisa y hoja dentada) de la dulcamara pilosa (Solanum sarrachoides), dulcamara de hoja partida (Solanum triflorum) y dulcamara amarga o trepadora (Solanum dulcamara) fueron susceptibles. La supervivencia del patógeno en las especies susceptibles se probó bajo diferentes condiciones de medio ambiente. El patógeno sobrevivió por lo menos por dos semanas en ambas accesiones pilosas cuando la planta se mantuvo en el suelo a una temperatura de 20 C. Sin embargo,P. infestans sobrevivió 48 horas a −15 C solamente en la accesión de dulcamara de hoja pilosa entera. En el laboratorio, las oosporas del patógeno se formaron en las plantas inoculadas de dos accesiones pilosas, dulcamara de hoja partida y la variedad Russet Burbank pero no en la dulcamara negra americana, la dulcamara amarga o en la dulcamara negra del este.

Cultivar and seedpiece spacing effects on potato competitiveness with weeds

Field studies were conducted in 1991 and 1992 to evaluate the effects of cultivar, row spacing, and within-row spacing on potato yield and quality under weedy and weed-free conditions. Cultivars tested were Russet Burbank, an indeterminate, large-vined cultivar, and Frontier Russet, a determinate, small-vined cultivar. The two cultivars were grown under weedy and weedfree conditions with either 76 or 91 cm row spacings in factorial combination with either 15, 25, or 35 cm within-row spacings. The major competitive weeds were redroot pigweed, common lambsquarter and hairy nightshade. The weedy plots consistently produced less vine and tuber biomass and less total and U.S. No. 1 tuber yield than the weed-free plots. The time of weed emergence strongly affected potato competitiveness with weeds. In 1991, weeds emerged after potatoes, giving the crop some competitive advantage. In 1992, weeds emerged before the potatoes, resulting in heavy competition and large decreases in vine and tuber production for both cultivars. Reductions in U.S. No. 1 tuber yield were proportionally greater than the reductions in total yield. Weedy plots in 1991 and 1992 produced 25% and 68% less total yield and 43% and 92% less U.S. No. 1 yield, respectively, than weed-free plots. Russet Burbank was more competitive with weeds than Frontier Russet. Frontier Russet suffered substantial losses in productivity due to the presence of weeds, even under moderate weed pressure in 1991. Decreasing the row width from 91 to 76 cm did not provide a competitive advantage for potatoes as measured by vine or tuber biomass, or tuber yield. Decreasing within-row spacing under weedy conditions provided some competitive advantage and resulted in higher vine and tuber biomass and greater total tuber yield. The closer within-row spacing resulted in a substantial decrease in U.S. No. 1 yield with Russet Burbank but a slight increase with Frontier Russet. There were several significant interactions involving cultivar, weed level, and within-row spacing. These were due, in part, to each cultivar’s unique response to inter-and intraspecies competition. Cultivar had a greater influence on competitiveness than any plant spatial arrangement.CompendioEn 1991 y 1992, se condujeron estudios de campo para evaluar los efectos del cultivar, y del espaciamiento entre surcos y entre semillas sobre el rendimiento y la calidad de la papa en presencia y ausencia de malezas. Los cultivares probados fueron Russet Burbank, un cultivar indeterminado de gran follaje, y Frontier Russet, un cultivar determinado de pequeño follaje. Los dos cultivares fueron mantenidos en presencia y en ausencia de malezas, con 76 o 91 cm entre surcos, en una combinación factorial con 15, 25 o 35 cm entre semillas. Las principales malezas competidoras fueron el amaranto verde (Amaranthus retroflexus), el quenopodio común (Chenopodium album) y la hierba mora velluda (Solanum sp.). Las parcelas con malezas produjeron consistentemente un menor follaje y biomasa de tubérculos y un menor rendimiento total y de tubérculos U.S. No. 1 que las parcelas sin malezas. El momento de emergencia de las malezas afectó fuertemente la competencia de la papa con las mismas. En 1991, las malezas emergieron después de las papas, dando al cultivo cierta ventaja de competencia. En 1992, las malezas emergieron antes que las papas, dando lugar a una fuerte competencia y gran reducción en el follaje y en la producción de tubérculos de ambos cultivares. Las reducciones en los rendimientos de tubérculos U.S. No. 1 fueron proporcionalmente mayores que las reducciones en los rendimiento totales. En 1991 y 1992, las parcelas con malezas produjeron rendimientos totales 25% y 68% menores, y 43% y 92% menos en tubérculos U.S. No. 1 que las parcelas libres de malezas, respectivamente. Al competir con las malezas. Russet Burbank fue mejor que Frontier Burbank. Frontier Burbank sufrió pérdidas considerables en productividad debido a la presencia de las malezas, incluso bajo una presión moderada de éstas en 1991. Disminuyendo el ancho del surco de 91 a 76 cm no se logró para las papas ventaja alguna de competencia, usando como medida el desarrollo del follaje o la biomasa de tubérculos, o el rendimiento total. La disminución del espacio entre semillas dentro del surco, bajo la presencia de malezas, proveyó cierta ventaja de competencia dando por resultado un mayor follaje y una mayor biomasa de tubérculos, así como también un mayor rendimiento total. Cuanto menor fue el espacio entre semillas dentro del surco, sustancialmente menor fue el rendimiento de Russet Burbank en tubérculos U.S. No. 1, pero para Frontier Burbank hubo un pequeño incremento. Hubo varias interacciones significativas incluyendo al cultivar, nivel de malezas y espacio entre semillas dentro del surco. Estas se debieron, en parte, a la respuesta particular de cada cultivar a la competencia entre y dentro de las especies. El cultivar tuvo una mayor influencia sobre la competencia que cualquier arreglo de espacio de las plantas.

Postemergence Weed Control with Rimsulfuron and Various Adjuvants in Potato (Solanum tuberosum)1

Field studies assessed weed control and potato injury with rimsulfuron applied postemergence at various rates in combination with various adjuvants. Weed control was influenced by choice of adjuvant and rimsulfuron rate. Rimsulfuron at 0, 9, 18, 26, and 35 g ai/ha was applied with nonionic surfactant (NIS), crop oil concentrate (COC), methylated seed oil (MSO), or silicone-polyether copolymer (SIL). Potato injury was less than 5% for all rimsulfuron rates and adjuvant combinations. Redroot pigweed was controlled greater than or equal to 93% by all treatments except rimsulfuron at 9 g/ha + SIL. Except for redroot pigweed, rimsulfuron treatments with SIL controlled kochia, hairy nightshade, common lambsquarters, and volunteer oats less than with other adjuvants. At lower rimsulfuron rates, weed control with rimsulfuron + MSO tended to be greater than with rimsulfuron + NIS or rimsulfuron + COC. Common lambsquarters control was 75% or less regardless of rimsulfuron rate or adjuvant. Tuber yield generally increased with increasing rimsulfuron rates. Depending on rimsulfuron rate, tuber yield was 10 to 15% lower with rimsulfuron + NIS or rimsulfuron + COC compared to rimsulfuron + MSO, while tuber yield was 18 to 37% lower with rimsulfuron + SIL compared to rimsulfuron + NIS, rimsulfuron + COC, or rimsulfuron + MSO. Nomenclature: Rimsulfuron; common lambsquarters, Chenopodium album L. #3 CHEAL; hairy nightshade, Solanum sarrachoides # SOLSA; kochia, Kochia scoparia L. Shrad. # KCHSC; potato, Solanum tuberosum L. ‘Russet Burbank’; redroot pigweed, Amaranthus retroflexus L. # AMARE; volunteer oat, Avena sativa L. # AVESA. Additional index words: Crop oil concentrate, methylated seed oil, nonionic surfactant, organosilicone. Abbreviations: COC, crop oil concentrate; MSO, methylated seed oil; NIS, nonionic surfactant; PNW, Pacific Northwest; POST, postemergence; PRE, preemergence; SIL, silicone-polyether copolymer; WAT, weeks after treatment.

Preemergence Weed Control in Potato (Solanum tuberosum) with Ethalfluralin1

Abstract: Field studies were conducted to assess weed control and potato (Solanum tuberosum) tolerance to ethalfluralin. Ethalfluralin applied preemergence (PRE) alone at 1.05 kg ai/ha generally did not control weeds adequately. However, ethalfluralin at 1.05 kg/ha combined with either metribuzin at 0.28 kg ai/ha or rimsulfuron at 0.018 kg ai/ha controlled common lambsquarters (Chenopodium album), redroot pigweed (Amaranthus retroflexus), and green foxtail (Setaria viridis) ≥ 98%, which was similar to control observed with several currently registered herbicide mixtures. Volunteer oat (Avena sativa) control with either ethalfluralin at 1.05 kg/ha plus EPTC at 3.4 kg ai/ha or ethalfluralin plus metribuzin was equal to registered two-way mixtures. Ethalfluralin plus metribuzin did not adequately control hairy nightshade (Solanum sarrachoides), but ethalfluralin mixtures with either rimsulfuron or EPTC controlled hairy nightshade equal to or better than the registered two-way mixtures evaluated. A sequential application of ethalfluralin PRE followed by rimsulfuron or rimsulfuron plus metribuzin postemergence (POST) did not improve hairy nightshade control compared to ethalfluralin plus rimsulfuron applied PRE. Potato tolerance to herbicide treatments applied PRE or POST to potato was evaluated in weed-free studies. Ethalfluralin alone or with metribuzin was compared to mixtures of metribuzin with either pendimethalin or EPTC. Initial visual injury with ethalfluralin PRE was ≤ 4% both years. In 1996, initial injury with ethalfluralin POST was ≤ 4% and U.S. No. 1 and total tuber yields were not affected by herbicide treatment or application timing. However in 1997, initial injury from POST ethalfluralin at 1.05 or 2.1 kg/ha was 2 or 8% and increased to 9 or 17%, respectively, at potato row closure. Averaged over all herbicide treatments, POST applications reduced U.S. No. 1 and total tuber yield 7% relative to PRE applications in 1997. Nomenclature: EPTC, S-ethyl dipropyl carbamothioate; ethalfluralin, N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl)benzenamine; metribuzin, 4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one; pendimethalin, N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine; rimsulfuron, N-[[(4,6-dimethoxy-2-pyrimidinyl)amino] carbonyl]-3-(ethylsulfonyl)-2-pyridinesulfonamide; common lambsquarters, Chenopodium album L. #3 CHEAL; green foxtail, Setaria viridis (L.) Beauv. # SETVI; hairy nightshade, Solanum sarrachoides Sendter # SOLSA; redroot pigweed, Amaranthus retroflexus L. # AMARE; volunteer oat, Avena sativa L. # AVESA; potato, Solanum tuberosum L. ‘Russet Burbank.’ Additional index words: Injury, tolerance, AMARE, AVESA, CHEAL, SETVI, SOLSA. Abbreviations: PNW, Pacific Northwest; POST, postemergence; PRE, preemergence; WAT, weeks after treatment.

Evaluating an Automated Irrigation Control System for Site-Specific Herbigation1

Abstract: Site-specific herbigation using a linear-move irrigation system equipped with an automated irrigation control system was evaluated in a series of field trials conducted at the University of Idaho Aberdeen Research and Extension Center near Aberdeen, ID. In the first study, the experimental area was divided into site-specific management zones that were randomly assigned herbigation treatments of metolachlor at 0, 1.8, 2.7, or 3.6 kg ai/ha. In a second study, site-specific herbigation treatments of metribuzin at 0, 0.28, 0.42, or 0.56 kg ai/ha were applied. The tests covered a range in system flow rate from 29 to 90% of maximum design flow. Average metolachlor rates applied were within 1, 2, and 4% of the target 1.8, 2.7, and 3.6 kg/ha rates, respectively, and average metribuzin rates were on target at the 0.28 kg/ha rate and within 5 and 2% of the 0.42 and 0.56 kg/ha target rates, respectively. In a third study, potato (Solanum tuberosum) fields were divided into management zones, and low, medium, or high populations of Indian mustard (Brassica juncea) and foxtail millet (Setaria italica) were seeded in each zone. Different rates of a metolachlor plus metribuzin mixture were herbigated in each zone—higher rates in zones with high populations and lower rates in zones with low populations. Weed control was excellent in all zones. Results suggest good potential for site-specific herbigation when linear-move or center-pivot irrigation systems are equipped with the automated irrigation control system. Nomenclature: Metolachlor, 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide; metribuzin, 4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5-(4H)-one; Indian mustard, Brassica juncea (L.) Czern. et Coss. #3 BRSJU ‘Common Brown’; foxtail millet, Setaria italica (L.) Beauv. # SETIT; potato, Solanum tuberosum L. ‘Russet Burbank’ # SOLTU. Additional index words: Chemigation, herbicide application, precision agriculture, variable-rate application technology, Chenopodium album, Amaranthus retroflexus, AMARE, CHEAL. Abbreviations: CV, coefficient of variation; DF, dry flowable; EC, emulsifiable concentrate.

Use of foliar symptoms and plant height to predict yield loss in potatoes due to metribuzin injury

A model to predict yield loss due to metribuzin injury was developed using data from four experiments involving postemergence applications of metribuzin to numerous cultivars and breeding selections. Two explanatory variables, plant height proportion (PHR), defined as injured/uninjured, and percent foliar injury (FI), were used to predict yield loss. Three multiple regression models, including linear, quadratic, and a linear-log were considered and evaluated. Acceptance of the best model was based on comparison of fit as indicated by Residual Mean Squares, Adjusted R2, and Predicted Sums of Squares. The best fit was for a linear-log model utilizing percent foliar injury and a natural log transformation of the plant height proportion (injured/uninjured). The predictive model was statistically validated by utilizing residual analysis on an independent data set. The model can be used to simply and quickly predict yield losses due to metribuzin injuryCompendioSe desarrolló un modelo, para pronosticar la pérdida en rendimiento debida al dafio por metribuzin, utilizando la information de cuatro experimentos comprendiendo aplicaciones de posemergencia de metribuzin a numerosos cultivares y selecciones de mejoramiento. Para pronosticar la pérdida en rendimiento se utilizaron dos variables teóricas, la proportión de altura de planta (PHR), definida como dañada/no dañada, y el por ciento foliar de daño (FI). Se consideraron y evaluaron tres modelos de regresión múltiple, incluyendo la lineal, la cuadrática y una lineal-logaritmica. La aceptación del mejor modelo se basó en la comparación de su utilidad, de acuerdo a lo indicado por los Cuadrados Medios Residuales, la R2 Calculada y la Suma de Cuadrados Pronosticada. La mayor utilidad se obtuvo con un modelo lineal-logaritmico utilizando el por ciento de dafio foliar y una transformation de un logaritmo natural de la proportión de altura de planta (dañada/no dañada). El modelo de pronóstico fue comprobado estadísticamente utilizando un análisis residual en un grupo de datos independientes. El modelo puede ser utilizado para simplificar y pronosticar rápidamente las pérdidas en rendimiento de la papa debidas al daño por metribuzin.

‘Russet Burbank’ Potato Tolerance to Dimethenamid-p1

‘Russet Burbank’ potato tolerance to dimethenamid-p applied preemergence at 0.7, 1.4, or 2.9 kg ai/ha was assessed in field studies conducted at Aberdeen, ID and Ontario, OR. Although crop injury was evident approximately 2 wk after treatment, most injury had diminished by row closure 2- to 3-wk later. Initial injury did not translate to yield loss and U.S. No. 1 and total tuber yields in dimethenamid-p–treated plots were similar to yields in the untreated, weed-free control. Nomenclature: Dimethenamid-p; potato, Solanum tuberosum L. ‘Russet Burbank’. Additional index words: Crop safety, crop tolerance, herbicide injury. Abbreviations: EPTC, S-ethyl dipropyl carbamothioate; PNW, Pacific Northwest; WAT, weeks after treatment.

Imazamethabenz Persistence in a Wheat (Triticum aestivum)–Potato (Solanum tuberosum) Rotation1

Abstract: Potato crops often are grown in rotation with cereal crops such as wheat and barley. Imazamethabenz is a postemergence herbicide that selectively controls wild oat and certain other weeds in wheat and barley. Experiments were conducted at the University of Idaho Research and Extension Center, Aberdeen, ID, over a 3-yr period to evaluate the effect of irrigation management in an imazamethabenz-treated wheat crop on imazamethabenz persistence and injury in a subsequent potato crop. The experimental design was a split plot arrangement of a randomized complete block; main plots were seasonal irrigation amounts in wheat (20, 30, 40, or 50 cm), and subplots were imazamethabenz rates applied to the wheat crop (0, 0.26, 0.52, or 1.05 kg/ha). Soil analyses for imazamethabenz residues showed that herbicide degradation during the wheat growing season (i.e., 0 to 128 d after treatment [DAT]) followed first-order kinetics at all irrigation levels. Herbicide degradation rate increased with irrigation rate. Soil samples taken 338 or 351 DAT showed no detectable imazamethabenz residues (<10 ng/g) in most plots. However, some foliar injury to potato grown the year following imazamethabenz treatment was noted (<10% average injury), suggesting that potato is sensitive to imazamethabenz or imazamethabenz acid residues below the analytical detection limit. U.S. No. 1 and total potato tuber yield were not reduced by any treatment compared to the nontreated control. Therefore, under good growing conditions, potato can recover from mild imazamethabenz carryover injury without effects on tuber yield or quality. Nomenclature: Imazamethabenz-methyl; wild oat, Avena fatua L.; barley, Hordeum vulgare L.; potato, Solanum tuberosum L.; wheat, Triticum aestivum L. Additional index words: Irrigation management, carryover. Abbreviations: DAT, days after imazamethabenz treatment; OC, organic carbon; OM, organic matter; POST, postemergence; PRE, preemergence.