A field study was conducted over 2 yr to compare efficacy and economics of glyphosate-resistant, sulfonylurea-tolerant, and conventional soybean (Glycine max) weed control programs. Herbicide programs in the three soybean systems provided at least 90% control of browntop millet (Brachiaria ramosa), prickly sida (Sida spinosa), yellow nutsedge (Cyperus esculentus), pitted morningglory (Ipomoea lacunosa), and hemp sesbania (Sesbania exaltata) in most cases and postemergence (POST)-only programs were as effective as preemergence (PRE) followed by POST programs. Control of hyssop spurge (Euphorbia hyssopifolia) ranged from 93 to 100% in glyphosate-resistant soybean and from 88 to 100% in conventional soybean, but control was 60 to 100% in sulfonylurea-tolerant soybean. Sicklepod (Senna obtusifolia) control was at least 91% in glyphosate-resistant and sulfonylurea-tolerant soybean but was 81% for the standard SAN 582 plus imazaquin PRE and acifluorfen plus bentazon early POST treatment in conventional soybean. In glyphosate-resistant soybean, glyphosate applied sequentially resulted in an average yield of 3,020 kg/ha with a net return of $407/ha. In sulfonylurea-tolerant soybean, chlorimuron applied sequentially yielded 2,500 kg/ha with a net return of $271/ha. Conventional soybean yield with the standard herbicide program was 2,770 kg/ha with a net return of $317/ha. Yields for the cultivars were equivalent when the same standard herbicide program was used. When weed control is satisfactory and herbicide costs relatively comparable, yield potential of the cultivar and seed cost, including any technology fee, would be key factors in selecting a weed management system.

We used a retrospective approach to identify hydrologic metrics with the greatest potential for ecological relevance for use as resource management tools (i.e., hydrologic indicators) in rapidly urbanizing basins of the Puget Lowland. We proposed four criteria for identifying useful hydrologic indicators: (1) sensitive to urbanization consistent with expected hydrologic response, (2) demonstrate statistically significant trends in urbanizing basins (and not in undeveloped basins), (3) be correlated with measures of biological response to urbanization, and (4) be relatively insensitive to potentially confounding variables like basin area. Data utilized in the analysis included gauged flow and benthic macroinvertebrate data collected at 16 locations in 11 King County stream basins. Fifteen hydrologic metrics were calculated from daily average flow data and the Pacific Northwest Benthic Index of Biological Integrity (B-IBI) was used to represent the gradient of response of stream macroinvertebrates to urbanization. Urbanization was represented by percent Total Impervious Area (%TIA) and percent urban land cover (%Urban). We found eight hydrologic metrics that were significantly correlated with B-IBI scores (Low Pulse Count and Duration; High Pulse Count, Duration, and Range; Flow Reversals, TQmean, and R-B Index). Although there appeared to be a great deal of redundancy among these metrics with respect to their response to urbanization, only two of the metrics tested – High Pulse Count and High Pulse Range – best met all four criteria we established for selecting hydrologic indicators. The increase in these high pulse metrics with respect to urbanization is the result of an increase in winter high pulses and the occurrence of high pulse events during summer (increasing the frequency and range of high pulses), when practically none would have occurred prior to development. We performed an initial evaluation of the usefulness of our hydrologic indicators by calculating and comparing hydrologic metrics derived from continuous hydrologic simulations of selected basin management alternatives for Miller Creek, one of the most highly urbanized basins used in our study. We found that the preferred basin management alternative appeared to be effective in restoring some flow metrics close to simulated fully forested conditions (e.g., TQmean), but less effective in restoring other metrics such as High Pulse Count and Range. If future research continues to support our hypothesis that the flow regime, particularly High Pulse Count and Range, is an important control of biotic integrity in Puget Lowland streams, it would have significant implications for stormwater management.

Recently, halosulfuron injury in soybean through off-target movement of halosulfuron when applied to rice fields has been reported. Sulfonylurea-tolerant (ST) soybean varieties have enhanced tolerance for sulfonylurea herbicides and might provide an option for mitigating injury to soybean from halosulfuron drift. Experiments were conducted to evaluate the effect of halosulfuron on growth and yield of selected soybean varieties with ST trait alone and stacked with glyphosate resistance trait. Soybean plants were treated with halosulfuron at 0, 0.0043, 0.0087, 0.017, 0.034, and 0.069 kg ai/ha rate at the V3 growth stage in the greenhouse and at 0.034 kg/ha rate (labeled use rate in rice) in the field studies. All soybean varieties containing the ST trait exhibited some halosulfuron injury, but survived the halosulfuron application in the greenhouse. In field studies, a single POST application of halosulfuron at 0.034 kg/ha to soybean at three-trifoliolate leaf stage or at full bloom stage resulted in halosulfuron injury to a certain extent regardless of ST trait. Halosulfuron did not have a significant effect on yield of ST varieties compared to their respective nontreated controls. Severe halosulfuron injury in two non-ST varieties resulted in yield loss.

Soybean [Glycine max (L.) Merr.] generally yields more when rotated with another crop rather than grown continuously. The specific reasons for this yield response are unknown. The objective of this study was to investigate the extent to which a soybean‐corn (Zea mays L.) rotation limited the buildup of host‐specific pathogens of soybean, and to evaluate whether plant diseases were involved in the rotation effect. Incidence and severity of seven diseases and seed yield were recorded at two locations in the field in 1987 and 1988 for soybean maintained in four cropping sequences ranging from annual alternation with corn to 1,2, or 5 yr of continuous cropping. Brown stem rot (BSR) caused by the fungus Phialophora gregata (Allington & D.W. Chamberlain) W. Gains was found to be the most prevalent disease during both years and at both locations. Rhizoctonia root rot (Rhizoctonia solani Kühn) and stem canker (Diaporthe phaseolorum Cooke. & Ellis Sacc. var. Cavlivora Athow & Caldwell) were noted in 1987 at both locations among <5% of all plants monitored. The BSR‐prevalence ratings were relatively high (mean 60%) for Hodgson 78, a susceptible cultivar, and relatively low (mean 22%) for BSR101, a resistant cultivar. Seed yield data from the various cropping sequences for the two cultivars indicated no clear relationship between BSR severity and seed yield. In 1987, rotation with corn resulted in a yield benefit to both cultivars. In 1988, both yield and development of BSR were adversely affected by drought. A comparison of the seed yield of severely infected and uninfected plants within cropping sequence indicated that BSR had a minimal effect on soybean yield in 1988. Therefore, within the conditions of this study, the yield benefit to soybean from rotation with corn did not appear to be due to the reduced incidence of plant diseases.

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