Environment, production practices, and genetic differences are known to influence the number of days between developmental stages of soybeans [Glycine max (L.) Merr.], but the yield response to differences in days between various stages is poorly understood. Twice weekly observations were made on 10 central Iowa replicated field trials over a 3‐year period to determine the date that each plot reached several specific stages of plant development. These dates and final seed yields were utilized to investigate whether number of days between specific stages of development were associated with final seed yield. All sites were mapped as Webster silt loams (a member of the fine‐loamy, mixed noncalcareous, mesic family of typic haplaquolls). Variations among the 119 cultivars represented in the study accounted for more of the differences in days between developmental stages than did sites or years. There was no association between seed yield and number of days between any two vegetative stages of development. The length of the seed development period [days from stage R4 (pods 2 cm long at top four nodes) to R7 (pods yellowing)] was more highly correlated with seed yield than was the length of any other developmental period. Plots which initiated flowering later and matured later tended to be the highest yielding plots. Longer periods of pod development [days from stage R2 (flowers at top node) to R4] tended to be associated with lower yields. The three locations which also included fertility variables showed that differences in the P and K fertility levels utilized did not influence the number of days between any two developmental stages. These findings provide breeders with another potential selection criterion and production researchers with a better understanding of how environmental and production practice differences influence soybean yields.

Research was conducted in North Carolina at two locations from 1997 through 2000 to determine net returns of 10 cropping systems during a 4‐yr cropping cycle that included peanut (Arachis hypogaea L.), cotton (Gossypium hirsutum L.), soybean [Glycine max (L.) Merr.], and corn (Zea mays L.). Cylindrocladium black rot [caused by Cylindrocladium parasiticum] (CBR) increased when soybean was included in the rotation sequence or when peanut was grown continuously. The CBR‐resistant cultivar NC 12C increased yield compared with the susceptible cultivar NC 7 when this disease was present. Cotton was a better rotation crop than corn at one of two locations with respect to peanut yield and gross economic value in the final year of the study. Net returns were substantially lower when peanut was marketed for export in the current federal program rather than at the quota price. However, the profitability ranking among cropping systems changed little regardless of marketing system. Crop yield and net return were influenced by crop selection, weather conditions, and commodity prices during the 4 yr.

Target spot of soybean (Glycine max (L.) Merr.) caused by Corynespora cassiicola (Berk. & Curt.), although found in most soybean-growing countries, is considered to be a disease of limited importance (1) and has never been reported to cause soybean yield loss in the southeastern United States (2,3). Soybean plants submitted to the North Carolina Plant Disease and Insect Clinic (NCPDIC) in August 2004 from Beaufort, Robeson, Wilson, and Johnston counties, NC had symptoms consistent with target spot. Symptoms consisted of roughly circular, necrotic leaf lesions from minute to 11 mm in diameter, though typically approximately 4 to 5 mm in diameter, and with a yellow margin. Large lesions occasionally exhibited a zonate pattern often associated with this disease. Microscopic examination of the lesions revealed the presence of spores (conidia) typical of C. cassiicola (1). Conidia were mostly three to five septate with a central hilum at the base and ranged in size from 7 to 22 wide × 39 to 520 μm long. Three commercial soybean fields near Blackville, SC (Barnwell County) were severely affected by this disease and it caused premature defoliation. Nineteen of twenty-seven maturity group VII and VIII genotypes in the 2004 Clemson University soybean variety trial near Blackville, SC had visible symptoms of target spot. Heavy rainfall associated with hurricanes during September 2004 probably enhanced the incidence of this disease, and yield suppression due to target spot was estimated at 20 to 40% in some fields. In 2005, 20 of 161 soybean samples submitted to the NCPDIC or collected in surveys from 16 counties were positive for target spot on the basis of microscopic examination. Target spot also was diagnosed in six counties (Baldwin, DeKalb, Elmore, Fayette, Macon, and Pickens) in Alabama and in four additional counties (Bamberg, Hampton, Orange-burg, and Calhoun) in South Carolina in 2005. Records from the NCPDIC indicate that target spot had not been diagnosed on soybean in North Carolina since 1981. The large increase in incidence of target spot in the southeast may be related to changes in weather patterns, changes in pathogen virulence, and/or the introduction of more susceptible host genotypes. References: (1) J. B. Sinclair. Target spot. Page 27 in: Compendium of Soybean Diseases. G. L. Hartman et al. eds. The American Phytopathological Society, St. Paul, MN, 1999. (2) J. A. Wrather et al. Plant Dis. 79:1076. 1995. (3) J. A. Wrather et al. On-line publication. doi:10.1094/PHP-2003-0325-01-RV. Plant Health Progress, 2003.

Because metabolic processes in plants are dependent on water‐soluble carbohydrates (WSC), information concerning the effects of different factors on the WSC contents of plants should be useful in the development of improved practices. Soybean [Glycine max (L.) Merrill] plant samples from field fertility experiments on Webster soil (Typic Haplaquoll) were collected and analyzed during two growing seasons to study the effect of different variables on WSC contents of different plant parts at various stages of plant development. WSC in dried plant samples were extracted with hot water and determined using a phenolsulfuric acid colorimetric method with glucose as a standard. The WSC content of leaves and petioles increased between 0900 and 1300 hours daily. WSC contents generally were higher in 1971 than in 1972. Differences in WSC among cultivars and fertility levels were relatively small. Percentages of WSC in leaves increased throughout the growing season, but in stems and petioles increased only until seed development became rapid. WSC contents of stems, petioles, and pods decreased as the seeds developed. This decrease may indicate that soluble CHO (metabolically active carbohydrate) becomes a limiting factor for seed production during the seed‐filling period.

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