John Luna

Multi-function agricultural biodiversity: pest management and other benefits

Abstract This paper reviews two aspects of agricultural biodiversity. 1. The ways in which agricultural biodiversity may be increased to favour pest management are examined. At the simplest level, the structure within a monoculture may be altered by changing management practices to benefit natural enemies. At the other extreme, annual and perennial non-crop vegetation may be integrated with cropping, and biodiversity increased at the landscape level. 2. The existence of a hierarchy for the types of benefits of increased biodiversity is discussed. Vegetational diversity can lead to suppression of pests via ‘top-down’ enhancement of natural enemy populations and by resource concentration and other ‘bottom-up’ effects acting directly on pests. Whilst such low-input pest management mechanisms are attractive in their own right, other (non-pest management related) benefits may simultaneously apply. These range from short-term benefits in crop yield or quality, longer term benefits for sustainability of the farming system and, ultimately, broad societal benefits including aesthetics, recreation and the conservation of flora and fauna. Examples are given of such multi-function agricultural biodiversity. Diese Arbeit betrachtet zwei Aspekte landwirtschaftlicher Biodiversitat. 1. Die Moglichkeiten, landwirtschaftliche Biodiversitat zur Unterstutzung eines Schadlingsmanagements zu erhohen, werden untersucht. Im einfachsten Fall kann die Struktur innerhalb einer Monokultur durch veranderte Managementpraktiken geandert werden, so dass naturliche Gegenspieler davon profitieren. Im anderen Extrem konnen einjahrige und mehrjahrige Nichtnutzpflanzen in die Kultur integriert werden und die Biodiversitat steigt auf Landschaftsebene an. 2. Das Vorhandensein einer Hierarchie der verschiedenen Typen von Vorteilen einer erhohten Biodiversitat wird diskutiert. Pflanzliche Diversitat kann durch top-down Forderung von Populationen naturlicher Gegenspieler, durch Ressourcenkonzentration und durch andere bottom-up Effekte, die direkt auf Schadlinge einwirken, zu einer Unterdruckung von Schadlingen fuhren. Wahrend solche low-input Mechanismen des Schadlingsmanagements durch sich selbst attraktiv sind, ergeben sich gleichzeitig auch andere Vorteile, die nicht mit dem Schadlingsmanagement zusammenhangen. Diese reichen von kurzfristigen Vorteilen bei Ertrag oder Qualitat der Nutzpflanzen uber mittelfristige Vorteile bei der Nachhaltigkeit des Bewirtschaftungssystems bis hin zu breiten, gesellschaftlichen Vorteilen, welche asthetische Aspekte, Erholung und Schutz von Flora und Fauna einbeziehen. Beispiele fur solche multifunktionelle landwirtschaftliche Biodiversitat werden vorgestellt.

Conservation tillage for organic agriculture: Evolution toward hybrid systems in the western USA

Organic farming has been historically dependent on conventional tillage operations to convert perennial pasture leys to annual crop rotations, incorporate crop residues, compost and cover crops, as well as to mechanically kill existing vegetation. Conventional tillage, however, has long been known to lead to soil degradation and erosion. A recently developed no-till organic production system that uses a roller–crimper technology to mechanically kill cover crops was evaluated in two states in the western United States. In Washington, pumpkins (Cucurbita spp.) grown in a no-till roller–crimper (NT-RC) system produced yields 80% of conventional tillage, but with fewer weeds. However, in California on-farm research trials in organic cotton (Gossypium barbadense L.), tomato (Lycopersicon esculentum Mill.), eggplant (Solanum melongena L.) and cowpea (Vigna unguiculata (L.) Walp.), the no-till system produced virtual crop failure, or yields less than 20% of the standard production method. The major problems associated with rolled cover crops in California included reduced crop seedling emergence, planter impediment with excessive residue, lack of moisture and delay in transplanting of vegetable crops due to continued growth of cover crops, in-season crop competition from cover crop regrowth and impracticability of using cultivators. Further, excessive dry residue during summer in California can present the risk of fire. In both California and Oregon, considerable success has been demonstrated with zone tillage (strip tillage) in conventionally produced field and vegetable crops. In a replicated Oregon trial, the organic strip tillage treatment produced 85% of the broccoli (Brassica oleracea L.) yield compared to a conventional tillage treatment. Our studies suggest that the zone tillage concept may offer opportunities to overcome many of the agronomic challenges facing no-till.

Weed Ecology and Nonchemical Management under Strip-Tillage: Implications for Northern U.S. Vegetable Cropping Systems

Abstract In northern U.S. vegetable cropping systems, attempts at no-till (NT) production have generally failed because of poor crop establishment and delayed crop maturity. Strip tillage (ST) minimizes these problems by targeting tillage to the zone where crops are planted while maintaining untilled zones between crop rows, which foster improvements in soil quality. ST has been shown to maintain crop yields while reducing energy use and protecting soils in vegetable crops, including sweet corn, winter squash, snap bean, carrot, and cole crops. Despite potential benefits of ST, weed management remains an important obstacle to widespread adoption. Increased adoption of ST in cropping systems for which effective, low-cost herbicides are either limited (e.g., most vegetable crops) or prohibited (e.g., organic systems) will require integration of multiple cultural, biological, and mechanical approaches targeting weak points in weed life cycles. Weed population dynamics under ST are more complex than under either full-width, conventional tillage (CT) or NT because weed propagules—as well as factors influencing them—can move readily between zones. For example, the untilled zone in ST may provide a refuge for seed predators or a source of slowly mineralized nitrogen, which affects weed seed mortality and germination in the tilled zone. Greater understanding of such interzonal interactions may suggest manipulations to selectively suppress weeds while promoting crop growth in ST systems. Previous studies and recent experiences in ST vegetable cropping systems suggest a need to develop weed management strategies that target distinct zones while balancing crop and soil management tradeoffs. For example, in untilled zones, optimal management may consist of weed-suppressive cover crop mulching, combined with nitrogen exclusion and high-residue cultivation as needed. In contrast, weed management in the tilled zone may benefit from innovations in precision cultivation and flame-weeding technologies. These short-term strategies will benefit from longer-term approaches, including tillage-rotation, crop rotation, and cover cropping strategies, aimed at preventing seed production, promoting seed predation and decay, and preventing buildup of problematic perennial weeds. However, a concerted research effort focused on understanding weed populations as well as testing and refining integrated weed management strategies will be necessary before ST is likely to be widely adopted in vegetable cropping systems without increased reliance on herbicides. Nomenclature: Carrot, Daucus carota L.; cole crops, Brassica spp.; snap bean, Phaseolus vulgaris L.; sweet corn, Zea mays L.; winter squash, Cucurbita moschata Duchesne ex Poir. Resumen En los sistemas de cultivos de vegetales del norte de Estados Unidos, los intentos de producción con cero labranza (NT) generalmente han fallado debido a un establecimiento pobre y madurez tardía del cultivo. El cultivo en bandas (ST) minimiza estos problemas al enfocar la labranza en la zona donde los cultivos son plantados mientras que mantiene zonas sin labrar entre las líneas del cultivo, lo cual mejora la calidad del suelo. ST ha mostrado la capacidad de mantener el rendimiento del cultivo al tiempo que reduce el uso de energía y protege el suelo en cultivos de vegetales, incluyendo maíz dulce, calabacín de invierno, frijol común, zanahoria y coles. A pesar de los beneficios potenciales de ST, el manejo de malezas continúa siendo un obstáculo importante para su mayor adopción. El incremento en la adopción de ST en sistemas de cultivos para los cuales herbicidas efectivos y de bajo costo son, ya sea, limitados (e.g., mayoría de cultivos de vegetales) o prohibidos (e.g., sistemas orgánicos), requerirá la integración de múltiples estrategias culturales, biológicas, y mecánicas dirigidas a los puntos débiles en los ciclos de vida de las malezas. Las dinámicas de poblaciones de las malezas en ST son más complejas que en labranza de cobertura total, labranza convencional (CT) o NT, porque los propágulos de las malezas, además de los factores que los influencian, pueden moverse ampliamente entre zonas. Por ejemplo, la zona no labrada en ST podría proveer refugio para depredadores de semillas o podría ser una fuente de nitrógeno de lenta mineralización, los cuales afectan la mortalidad y la germinación de las semillas de las malezas en la zona labrada. Un mayor entendimiento de tales interacciones entre zonas podría sugerir manipulaciones para suprimir las malezas selectivamente mientras se promueve el crecimiento del cultivo en sistemas ST. Estudios previos y experiencias recientes en sistemas de cultivos de vegetales en ST indican la necesidad de desarrollar estrategias de manejo de malezas que apuntan a zonas específicas mientras balancean los conflictos entre el manejo del cultivo y del suelo. Por ejemplo, en zonas sin labrar, el manejo óptimo podría consistir en usar cultivos de cobertura para la supresión de malezas, en combinación con la exclusión de nitrógeno y el uso del cultivo con altos residuos cuando sea necesario. En contraste, el manejo de malezas en la zona labrada podría beneficiarse de innovaciones en tecnología de cultivadores de precisión y de quemadores de llama. Estas estrategias de corto plazo se beneficiarán de estrategias de largo plazo orientadas a prevenir la producción de semillas, promover la depredación y degradación de semillas, y a prevenir el incremento de malezas perennes problemáticas. Sin embargo, un esfuerzo concertado de investigación enfocado no solo en entender las poblaciones de malezas, sino que en evaluar y refinar las estrategias integradas de malezas, será necesario antes de que ST sea ampliamente adoptada en sistemas de cultivos de vegetales sin una dependencia mayor en herbicidas.

Energy and economic savings from the use of legume cover crops in Virginia corn production

Energy analysis provides a measure of the effectiveness of sustainable agricultural systems in reducing inputs purchased from off-farm sources. This study compares the total (direct plus indirect) energy costs of growing corn for silage using manufactured N fertilizer or N-fixing legume cover crops. The cover crop either was killed with herbicide in a no-till system or disked in the spring. Economically competitive alternative crop production practices are identified. In both the no-till and the disked versions, cover-cropped treatments used about half as much energy per hectare as the corresponding winter fallow N-fertilizer treatments. Using vetch to provide N significantly lowered energy use per unit of crop output compared with the N-fertilized treatments. For the treatments that used hairy vetch, either alone or in combination with big/lower vetch, net revenue was statistically equivalent to that of standard-practice treatments in each year of the study.

Diurnal Abundance and Spatial Distribution of Armyworm, (Lepidoptera: Noctuidae) in No-till Corn

Armyworm, Pseudaletia unipuncta (Haworth), spatial and diurnal abundance in no-till corn was sampled at six-h intervals (at 0200,0800, 1400, and 2000) during three 24 h periods. During the early gr...