G. A. Porter

Petiole nitrate content of Maine-grown Russet Burbank and Shepody potatoes in response to varying nitrogen rate

Russet Burbank and Shepody potatoes were grown with at-planting nitrogen fertilizer rates varying from 0 to 270 kg ha−1 following small grains and red clover. Petiole samples were collected from the 4th and 5th leaflets at four to six dates each during the 1986 to 1989 growing seasons. The samples were dried and analyzed for NO3−N content. Petiole NO3−N levels were strongly related to nitrogen rate regardless of cultivar, growing season, and cropping system. Differences among treatments and NO3−N content varied substantially as the growing season progressed with petiole NO3−N levels declining rapidly in underfertilized plots as the plants aged. Petiole NO3−N levels were higher at midseason following red clover than following small grains. Sampling 50 to 60 days after planting (DAP) is most appropriate as a tool for scheduling supplemental nitrogen applications. At 50 DAP, critical petiole NO3−N levels were 1.6 and 1.7% for Russet Burbank and Shepody, respectively. Petiole NO3−N levels above 2.2% at 50 DAP resulted in lower yields of Russet Burbank than when petiole NO3−N levels were in the 1.6 to 2.2% range. Petiole NO3−N testing should be particularly useful as a diagnostic tool in management strategies which make maximum use of previous crop residues, organic amendments, and soil reserves as nitrogen sources.

Comparison of alternative pest and soil management strategies for Maine potato production systems

Potato acreage and total production in Maine have declined steadily since the 1960s. In 1991, a University of Maine research team established a large-scale, long-term, comparative study of three factors that form the foundation of productive potato cropping systems: soil management, pest management, and variety choice. This study, the Potato Ecosystem Project, included 96 main plots (5.8 ha total) and near-by “component studies.” The project contrasted amended vs. unamended soil management strategies; conventional vs. reduced-input vs. bio-intensive pest management strategies; and disease and stress susceptible vs. tolerant potato varieties. Given recent concerns over resistance to pesticides and increasing costs of agricultural chemical inputs, the reduced-input and bio-intensive pest management systems provided encouraging results. Weed growth was similar in the conventional and reduced-input systems. Colorado potato beetle thresholds were exceeded less often and their densities were lower in the bio-intensive system than in the reduced-input and conventional systems. Lady beetles, which are major aphid predators, were more abundant in the bio-intensive pest management system compared with the reduced-input and conventional systems in 5 of the 6 years. Tuber yield and quality were maintained at a high level in the reduced-input system, although difficulties with plant disease, nutrient and weed management contributed to significantly lower yields in the bio-intensive pest management system. Economic analysis indicated that from 1993 to 1996, the reduced-input system had a greater return over variable cost (avg.

Response of Russet Burbank and Shepody potatoes to nitrogen fertilizer in two cropping systems

973 ha -1 ) than the conventional (avg.

Potato nutrient management in sustainable cropping systems

890ha -1 ) and bio-intensive pest management systems (avg.

Effects of moldboard plowing, chisel plowing and rotation crops on the Rhizoctonia disease of white potato

578ha -1 ). The amended soil management system achieved rapid improvements in soil quality: soil organic matter, water stable aggregates, potassium, and soluble inorganic phosphorus contents increased while requirements for synthetic fertilizers were reduced. These improvements in soil quality enhanced late-season crop vigor, canopy duration and tuber quality, and increased yields by 13% and 30% over the unamended system in 1994 and 1995, respectively, but not in 1996. Improved crop vigor in the amended soil management system also benefited weed control efforts by encouraging a more weed-suppressive potato crop. In the biointensive pest management system, in which weeds were controlled mechanically, the amended soil management system had less weed biomass than the unamended soil management system in 1994 and 1995. Conversely, the amended soil management system consistently increased flea beetle populations and, in one of two years, the incidence of Rhizoctonia. The choice of potato variety also affected pest dynamics. Total aphid density (all aphid species considered together) and almost all disease ratings were higher on ‘Superior’ than ‘Atlantic’ potato.

Effects of pest and soil management systems on potato diseases

Russet Burbank and Shepody potatoes were grown with at-planting N fertilizer rates ranging from 0 to 270 kg ha−1 during 1986 through 1989. Experiments were conducted each year following small grains and red clover. Total yields and tuber size were strongly increased by N on most sites where potatoes followed small grains. Specific gravities declined with increasing N rate. Total yields of Russet Burbank and Shepody were optimized at an average of 196 and 211 kg ha−1 of N, respectively, following small grains.The effect of N fertilizer on yields was much less dramatic following red clover. Total yields averaged 88% of maximum with only 45 kg ha−1 of N applied, compared to 77% of maximum for this N rate following small grains. Total yields for the two varieties were optimized at 126 and 136 kg ha−1, respectively. U.S. #1 yields were generally not increased at N rates above 45 to 90 kg ha−1 following red clover and tuber size was not increased at rates above 90 to 135 kg ha−1. Based on these studies, the N fertilizer credit for red clover grown prior to potatoes can be up to 75 kg ha−1. Maintenance of tuber quality necessitates conservative use of N fertilizer when potatoes are grown following legumes. The highest N rates tested suppressed total yields of Russet Burbank, a late-season, indeterminate variety, by approximately 9% averaged over cropping systems.CompendioPapas Russet Burbank y Shepody fueron cultivadas bajo dosis de fertilizante nitrogenado que variaban de 0 a 270 kg ha−1, a continuacion del cultivo de paqueños granos y trebol rojo. Durante las temporadas de cultivo 1986 a 1989 se tomaron muestras de peciolos del 4to. y 5to. folíolo en 4 a 6 fechas para cada una. Se secaron y analizaron las muestras para determinar su contenido en NO3−N. Los niveles de NO3−N en los peciolos estuvieron estrechamente relacionados a las dosis de nitrógeno independientemente del cultivar, temporada y sistema de cultivo. Las diferencias entre tratamientos y el contenido de NO3−N variaron sustancialmente conforme avanzaba la temporada de cultivo, con niveles de NO3−N en los peciolos declinando rápidamente en las parcelas no fertilizadas conforme las plantas envejecían.Los niveles de NO3−N en los peciolos fueron más altos a media temporada a continuatión de trebol rojo que a continuación de los pequeños granos.Lo más apropiado es tomar las muestras a los 50 a 60 días después de la siembra (DDS) como un medio para programar la aplicación de nitrógeno suplementario. A los 50 DDS los niveles críticos de NNO3−N en los peciolos fueron 1,6 y 1,7% para Russet Burbank y Shepody, respectivamente. Los niveles de NO3−N en los peciolos, por encima de 2,2%, a los 50 DDS, correspondieron a rendimientos más bajos de Russet Burbank en comparación con los rendimientos obtenidos cuando los niveles de NO3−N en los peciolos fueron de 1,6 a 2,2%. El muestreo de NO3−N en los peciolos podría ser particularmente util como diagnóstico en las estrategias de manejo que hacen uso máximo de residuos de cultivos anteriores, enmiendas orgánicas y reservas del suelo, como fuentes de nitrógeno.

ASCORBIC ACID AND GLYCOALKALOID CONTENT OF ATLANTIC AND SUPERIOR POTATO TUBERS AS AFFECTED BY SUPPLEMENTAL IRRIGATION AND SOIL AMENDMENTS

Sustainable nutrient management involves a set of management practices designed to conserve soil resources, to maintain or enhance productivity, and to help reduce growers’ reliance on chemical fertilizers. Sustainable nutrient management systems will most certainly rely heavily on the use of legume rotation crops and/or organic soil amendments. To realize the full benefit to the crop ecosystem, sustainable nutrient management programs will also likely require longer crop rotations with less frequent potato production. There is considerable research evidence indicating that these systems can maintain or increase productivity while having positive impacts on nutrient supply, soil physical properties, and soil conservation. However, their successful adoption and continued use on a large scale will require resolution of uncertainties related to economic risk associated with inconsistent nutrient availability in alternative nutrient management systems, potential environmental risks associated with excessive P applications in animal manures, and the potential for increased potato pest incidence resulting from manure application.ResumenEl manejo sostenible de nutrientes incluye un conjunto de practicas diseñadas para conservar los recursos del suelo, mantener o intensificar la productividad y ayudar a los agricultores a reducir la dependencia que tienen en los fertilizantes químicos. Los sistemas de manejo sostenible de nutrientes confía mayormente en el uso de leguminosas como cultivos de rotación y/o enmiendas orgánicas del suelo. Para darse cuenta del beneficio del ecosistema del cultivo, el programa de manejo sostenible de nutrientes requerirá de períodos más largos de rotación y de cultivos de papa menos frecuentes. Existe una considerable evidencia de investigación que indica que estos sistemas pueden mantener o incrementar la productividad y al mismo tiempo tienen un impacto positivo sobre el suministro de nutrientes, propiedades físicas del suelo y su conservación. Sin embargo, su completa adopción y uso continuado en gran escala requerirá de resolver ciertas dudas relacionadas con el riesgo económico asociado a la disponibilidad irregular de nutrientes en los sistemas de manejo alternativo, riesgos potenciales del medio ambiente asociados con una excesiva aplicación de fósforo contenido en el estiércol y el potencial para implementar la incidencia de enfermedades como resultado de la aplicación de estiércol.

Evaluation of potato clones for resistance to stem canker and tuber black scurf in field studies following artificial inoculation with Rhizoctonia solani AG-3 in Maine∗

Two tillage practices, chisel plowing (30 cm) and deep moldboard plowing (22 cm), and five rotation crops (oats, lupine, buckwheat, broccoli and peas) were studied for their effects on the soil population ofRhizoctonia solani AG-3 and on Rhizoctonia disease on potato. All rotation crops were harvested except buckwheat, which was treated as a green manure crop. Chisel plowing significantly reduced (p = 0.05) the incidence and severity of stem lesions on potato caused byR. solani AG-3. In 1990, oats after moldboard plowing significantly increased disease when compared to other crops and broccoli after chisel plowing decreased disease severity. Soil populations ofR. solani AG-3 were significantly lower with chisel plowing. No interactions between tillage and rotation crops were observed.Rhizoctonia solani Kühn is a soil inhabiting plant pathogen found worldwide that affects many plant species including white potato (Solanum tuberosum L.).R. solani attacks potato at one or more stages in development resulting in distinct disease symptoms (25) often termed the Rhizoctonia disease complex of potato. In Maine, only strains AG-3 and AG-5 ofR. solani (4, 5) have been identified as attacking potato and causing four distinct types of symptoms: 1) black scurf (sclerotia) on tubers, 2) stem cankers, 3) aerial tubers and top rosetting, and 4) killing of sprouts.Crop rotation has been reported to reduce the incidence and severity ofR. solani on potato, but no single rotation method controls completely or to a high degree of reliability (11, 23, 24, 26). Deep moldboard plowing has been shown to reduce diseases caused byR. solani andSclerotium rolfsii Sacc. in crops other than potatoes (2, 7, 15, 19, 20). However, Gudmestadet al. (6) reported that deep moldboard plowing increased the severity ofR. solani on stems and stolons of potatoes.The reduction of diseases caused byR. solani andS. rolfsii by moldboard plowing is attributed to low inoculum densities in the upper soil layer by the burial of sclerotia to depths where germination and infection were prevented (14, 15, 19, 20). However, disking to a depth of 5–7 cm did not affect disease as the inoculum remained in the root zone (14, 15). Gurkin (7) states that the rationale for deep moldboard plowing is to promote decay of organic matter, remove organic matter from the infection court and to bury the sclerotia below the infection court. Cultural control techniques are largely preventive and are designed to reduce the quantity or the activity of inoculum by means of crop rotation, tillage practices, green manure crops, etc. (22).This study was conducted to determine individual effects and possible interactions of deep moldboard plowing versus chisel plowing in various rotation crops on the presence ofR. solani AG-3 in the soil and on the incidence of Rhizoctonia disease complex of potato.CompendioDos prácticas de labranza, aradura con arado de púas (30 cm) y aradura profunda con arado de vertedera (22 cm), y rotatión con cinco cultivos (avena, lupino, trigo sarraceno, brócoli, y arvejas) fueron estudiadas para determinar sus efectos en la población de Rhizoctmia solani AG-3 en el suelo y sobre la Rhizoctoniosis de la papa. Todos los cultivos en rotación fueron cosechados con exceptión del trigo sarraceno, que fue tratado como un cultivo de abono verde. La aradura con pũas redujo significativamente (p = 0.05) la incidencia y severidad de las lesiones en el tallo de la papa causadas por R. solani AG-3.En 1990, la enfermedad se incrementó significativamente cuando se produjo avena después de la aradura con arado de vertedera en comparación con los otros cultivos, y el brócoli después de una aradura con arado de púas disminuyó la intensidad de la enfermedad. Las poblaciones de R. solani AG-3 en el suelo fueron significativamente más bajas al usarse la aradura con púas. No se observaron interacciones entre la labranza y los cultivos en rotatión.

Allegany: a late season golden nematode resistant variety.

Long-term cropping systems research is important in order to reduce production costs, to control crop pests, and to optimize the sustainability of agro-ecosystems. Soil amendment use, improved disease management practices, and careful cultivar choice are some of the potential components for improving potato production systems. This research was conducted in long-term cropping systems plots in order to evaluate the impact of soil amendments, pest management practices, and cultivar on foliar and soil-borne potato diseases and to assess the relationships of soil and pest management practices to disease levels and soil microbial activity. Fungicide applications for management of foliar diseases varied between the pest management systems (e.g., biological, reduced input, and conventional). Incidence of potato foliar diseases was quantified five times during the cropping season. The impact of soil amendment and pest management practices on soil microbial activity and tuber-borne diseases was also investigated. Low incidences of foliar and selected soil-borne diseases were recorded. Disease levels varied between years, cultivars, pest management, and soil amendments. Significant differences between cultivars were detected for early blight, white mold, and black dot. The cultivar Superior had higher incidence of white mold and black dot, while cv Atlantic had higher early blight incidence. Pest management system significantly affected foliar early blight incidence in 1998, but not in 1997. Pest management system did not affect late blight, white mold, or black dot incidence, or tuber disease incidence in either year. The addition of soil amendments significantly impacted tuber black dot incidences. Microbial activity responded to increasing temperature as the season progressed and was significantly enhanced by the addition of manure and compost soil amendments; however, lower disease incidence was not associated with increased microbial activity. While pest management practices were not major determinants of disease levels in these experiments, the results show that soil amendments can increase incidence of selected tuber diseases and microbial activity in soils.ResumenLa investigación sobre sistemas de cultivo a largo plazo es importante para reducir costos de producción, controlar enfermedades y optimizar la sostenibilidad de los sistemas agro ecológicos. Las enmiendas de suelo, prácticas mejoradas de manejo de enfermedades y cuidadosa elección del cultivar, son algunos de los componentes potenciales para mejorar los sistemas de producción de papa. Esta investigación fue realizada en parcelas de cultivo a largo plazo, con el objeto de evaluar el impacto de enmiendas de suelo, manejo de enfermedades y cultivar empleado, sobre las enfermedades foliares y las transmitidas por el suelo y de evaluar las relaciones del suelo y prácticas de manejo de plagas con los niveles de enfermedad y actividad microbiana del suelo. Las aplicaciones de funguicidas para el control de enfermedades foliares, varió con los sistemas de manejo sanitario (biológico, gasto reducido y convencional). La incidencia de enfermedades foliares se evaluó cinco veces durante el desarrollo del cultivo. También se investigó el efecto de enmiendas, prácticas de control sobre la actividad microbiana del suelo y las enfermedades transmitidas por tubérculos. Se registró baja incidencia de enfermedades foliares y transmitidas por el suelo. Los niveles de enfermedad variaron entre años, cultivares, manejo sanitario y enmiendas de suelo. Se detectaron diferencias significativas entre cultivares para tizón temprano, moho blanco y mancha negra. La variedad Superior tuvo la más alta incidencia de moho blanco y mancha negra, mientras que el cultivar Atlantic tuvo mayor incidencia de tizón temprano. El sistema de manejo sanitario afectó significativamente la incidencia de tizón temprano, moho blanco o mancha negra en 1998, pero no en 1997. El sistema de manejo sanitario no afectó la incidencia de tizón tardío, moho blanco, mancha negra o enfermedades al tubérculo en ambos años. La aplicación de enmiendas al suelo influenció significativamente la incidencia de mancha negra en el tubérculo. La actividad microbiana respondió al aumento de temperatura a medida del avance de la estación y fue significativamente incrementada cuando se agregó al suelo enmiendas de estiércol y compost; sin embargo, la baja incidencia de enfermedad no estuvo asociada con el incremento de la actividad microbiana. Aunque las prácticas de manejo sanitario no fueron un determinante del nivel de enfermedades en estos experimentos, los resultados demuestran que las enmiendas pueden incrementar la incidencia de determinadas enfermedades al tubérculo y la actividad microbiana del suelo.

Mainechip: A new chipping potato variety for cool storage processing

Atlantic and Superior potato (Solanum tuberosum L.) tubers were collected at harvest from two field experiments in Maine during 1993 and 1994. Tubers were analyzed for ascorbic acid (ASC) and total glycoalkaloid (TGA) concentration within one month of harvest and after 4 to 5 months of storage at 10 C. ASC concentration was significantly higher in Superior than Atlantic at harvest and after storage. TGA concentration was consistently higher in Atlantic than Superior. Irrigation tended to slightly reduce ASC and increase α-solanine concentrations when applied too late in the season for yield benefits. Storage decreased tuber ASC content, but no specific pattern was observed for TGA changes. Soil amendment programs using compost and manure (22 Mg ha−1 potato compost + 45 Mg ha−1 manure) did not dramatically affect tuber ASC or TGA concentrations. ASC content of the tubers declined dramatically in storage, but no consistent pattern was found for tuber TGA changes. We conclude that genotype, growing environment, and storage time play much stronger roles in determining tuber ASC and TGA levels than do irrigation and soil management programs. We observed a negative relationship between the average tuber size of the assayed samples and ASC concentration in fall samplings; however, this relationship was not observed from storage. Average tuber size and TGA content generally displayed a negative relationship.CompendioSe recolectaron en Maine tubérculos de las variedades Atlantic y Superior (Solanum tuberosum L.) a la cosecha en dos experimentes de campo durante 1993 y 1994. Los tubérculos fueron analizados para determinar la concentración de ácido ascórbico (CAA) y el total de glicoalcaloides (TGA) a un mes de la cosecha y después de 4 a 5 meses de almacenamiento a 10 C. La CAA fue significativamente mayor en la variedad Superior que en Atlantic tanto a la cosecha como después del almacenamiento. La concentración de TGA fue consistentemente mayor en Atlantic que en Superior. La irrigación tendió a reducir ligeramente la CAA y a aumentar las concentración de solanina cuando fue aplicada demasiado tarde en la temporada para beneficiar el rendimiento. El almacenamiento disminuyó el contenido de ácido ascórbico de los tubérculos; sin embargo, no se observó ningún patron específico para los cambios de TGA. Los programas de enmiendas de suelo empleando abono y estiércol (22 t ha−1 de abono de papa + 45 t ha−1 de estiércol) no afectaron en forma dramática las concentraciones de AA o TGA; sin embargo, no se encontró ningún patrón consistente para los cambios de TGA en los tubérculos. Concluímos que el genotipo, el ambiente de crecimiento y el tiempo de almacenamiento cumplen papeles más decisivos en la determinación de la CAA y TGA de los tubérculos que los programas de irrigación y manejo de suelos. Observamos una relación negativa entre el promedio del tamano del tubérculo de las muestras analizadas y la concentración de AA en las muestras de otoño; sin embargo, no se observó esta relación en el almacenamiento. El promedio del tamaño del tubérculo y el contenido de TGA mostraron por lo general una relación negativa.