Steve R. Temple

Crop-yield and economic comparisons of organic, low-input, and conventional farming systems in California's Sacramento Valley

We compared the crop yields and economic performance of organic, low- input, and conventional farming systems over an eight-year period based on research from the Sustainable Agriculture Farming Systems (SAFS) Project in Californias Sacra- mento Valley. The SAFS Project consisted offour farming-system treatments that differed in material input use and crop rotation sequence. The treatments included four-year rotations under conventional (conv-4), low-input, and organic management, and a con- ventionally-managed, two-year rotation (conv-2). The four-year rotations included pro- cessing tomato, safflower, corn, and bean and a winter grain and/or legume double- cropped with bean. The conv-2 treatment was a tomato and wheat rotation. In the low- input and organic systems, inorganic fertilizer and synthetic pesticide inputs were reduced or eliminated largely through crop rotation, legume cover crops, composted manure applications, and mechanical cultivation. All crops, except safflower, demonstrated significant yield differences across farming systems in at least some years of the experiment. Yields of tomato and corn, the most nitrogen (N)-demanding crops in the rotations, responded most years to the farming- system years treatments, while bean and the winter grain/legume displayed treatment differences less often and instead tended to vary more with yearly growing conditions. Nitrogen availability and/or weed competition appeared to account for lower crop yields in the organic and low-input systems in some years. The economics of all farming systems depended mainly on the costs and profits associated with tomato production. The most profitable system was the conv-2 system due to the greater frequency of tomato in that system. Among the four-year rotations, the organic system was the most profitable. However, this systems dependence on price premiums leads to some concern over its long-term economic viability. Among the low-input cropping systems, corn demonstrated clear agronomic and economic advantages over conventional production methods. Based upon these findings, we suggest that future research on organic and low-input farming systems focus on developing cost-effective fertility and weed management options based upon improved understanding of N dynamics and weed ecology.

Changes of Tomato Yield and Fruit Elemental Composition in Conventional, Low Input, and Organic Systems

ABSTRACT The Sustainable Agriculture Farming System (SAFS) Project was begun in 1988 to compare conventional 4-year and 2-year rotations receiving synthetic fertilizers and pesticides to low input and organic farming systems. In 1998 and 1999, we evaluated the influence of 10 years of organic, low input, and conventional management practices on soil chemical properties, processing tomato yields, and fruit mineral composition. The organic system had highest soil total C, N, soluble P, exchangeable Ca, and K levels as a result of 10 years of manure application and cover crop use. In both years, fruit yields were similar in the three farming systems. Organic fruits contained highest amounts of P, and Ca. Conventionally-grown tomatoes were richer in N, and Na, while the low input system had an intermediate values for N, P, and Na, and the lowest Ca concentration of the three systems.

Stem and Crown Rot of Chickpea in California Caused by Sclerotinia trifoliorum

The identities of Sclerotinia isolates obtained from chickpea plants showing stem and crown rot were determined using morphological characteristics, variations in group I introns, and internal transcribed spacer (ITS) sequences. Isolates could be separated into two groups based on growth rates at 22°C, fast growing (about 40 mm per day) versus slow growing (about 20 mm per day). All fast-growing isolates induced stronger color change of a pH-indicating medium than did slow-growing isolates at 22°C. The slow-growing isolates contained at least one group I intron in the nuclear small subunit rDNA, whereas all fast-growing isolates lacked group I introns in the same DNA region. ITS sequences of the slow-growing isolates were identical to sequences of Sclerotinia trifoliorum. Those of the fast-growing isolates were identical to sequences of S. sclerotiorum. Finally, the slow-growing isolates showed ascospore dimorphism, a definitive character of S. trifoliorum, whereas the fast-growing isolates showed no ascospore dimorphism. Isolates of both species were pathogenic on chickpea and caused symptoms similar to those observed in the field. This study not only associated the differences between S. sclerotiorum and S. trifoliorum in growth rates, group I introns, ITS sequences, and ascospore morphology, but also represented the first report that S. trifoliorum causes stem and crown rot of chickpea in North America.

Detection and Differentiation of Phaeoisariopsis griseola Isolates with the Polymerase Chain Reaction and Group-Specific Primers

Specific detection of the two major groups of Phaeoisariopsis griseola(Andean and Mesoamerican) from infected common bean (Phaseolus vulgaris) leaves was achieved by amplification of different-sized DNA fragments with polymerase chain reaction (PCR) using group-specific primer pairs. These primer pairs were designed based on DNA sequences of cloned random amplified polymorphic DNA (RAPD) fragments. Using this method, P. griseola isolates from diverse geographical regions (five countries) were differentiated into the two previously established groups. Various sources of fungal tissue and DNA extraction methods were tested in order to develop a rapid PCR-based method to detect and differentiate P. griseola isolates. A simple and rapid sonication method was developed that allowed for PCR detection of P. griseola from mycelia or synnemata and conidia collected from angular leaf spot lesions on bean leaves.

Sclerotinia Stem Rot of Garbanzos

Author(s): Frate, Carol A; Mueller, Shannon C; Temple, Steve R; Davis, R Michael | Abstract: Sclerotinia rot (white mold) is a fungal disease of garbanzos and other crops in California. While much remains unknown about Sclerotinia rot, this publication will help you identify it and manage its severity and spread.

Ascochyta Blight of Garbanzos

Author(s): Frate, Carol A; Mueller, Shannon C; Temple, Steve R | Abstract: Ascochyta blight is a major disease of garbanzos in California. Learn how to control of the disease after harvest in infected fields and prevent its spread into new areas.