Search Results
Ten crops were evaluated for potential use as field bioassay species for cinmethylin and chlorimuron application rates in two soil types. Cinmethylin injured sweet corn (Zea mays L.) and grain sorghum [Sorghum bicolor (L.) Moench] at concentrations as low as 0.28 kg·ha-1 on either soil type, while broadleaf crops were tolerant. Chlorimuron injured sweet corn, grain sorghum, radish (Raphanus sativus L.), cucumber (Cucumis sativus L.), and watermelon [Citrullis lanatus (Thunb.) Mansf.] at rates ≥ 2.5 g·ha-1, and squash (Cucurbita pepo L.) at rates ≥ 5.0 g·ha-1 on a Dothan sand. In a Congaree silt loam, chlorimuron injured cucumber at rates ≥ 5.0 g·ha-1, sweet corn, watermelon, and squash at rates ≥ 10 g·ha-1, and grain sorghum, radish, and cotton (Gossypium hirsutum L.) at rates ≥ 20 g·ha-1. Soybean and snapbean (Phaseolus vulgaris L.) were tolerant to chlorimuron in both soil types. Cinmethylin activity was not altered by soil type, but with chlorimuron greater crop injury was observed in the Dothan sand than in the Congaree silt loam. Sweet corn and grain sorghum were the most sensitive indicator species to cinmethylin and cucumber was the most sensitive to chlorimuron in both soils. Plant emergence and population alone are not valid indicators for crop tolerance to herbicides. Quantitative measurements such as shoot dry weight were more indicative of crop susceptibility to chlorimuron than plant populations. Chemical names used: exo -1-methyl-4-(1-methylethyl)-2 -[(2-methylphenyl) methoxy]-7-oxabicyclo[2.2.1]heptane (cinmethylin); 2-[[[[(4-chloro-6-methoxy-2-pyrimidinyl)amino] carbonyl]amino] sulfonyl]benzoic acid (chlorimuron).
New Mexico-mined raw leonardite was characterized by comparing it with the International Humic Substances Society's Standard Leonardite. In the first experiment, adding as little as 1/64 leonardite (v/v) to a sand medium increased tomato [Lycopersicon esculentum (L.) Mill. `Mountain Pride'] root and shoot growth compared with plants produced with fertilizer alone. Growth increased linearly with increasing leonardite levels, from 0% to 25%; however, 50% leonardite inhibited growth. In a second experiment, leonardite alone had no effect on plant height, shoot or root fresh and dry weight, or total leaf area, but stimulated growth when combined with a complete fertilizer. Adding 1/3 leonardite (v/v) (the highest level) and a complete fertilizer increased plant height 40%, total leaf area 160%, shoot fresh weight 134%, root fresh weight 82%, shoot dry weight 133%, and root dry weight 400%.
The addition of leonardite may increase, or at least maintain, production quality of ornamental plants and permit reductions in fertilizer inputs. The objective of this study was to determine the effects of a Utah-mined leonardite on early stages of zinnia (Zinnia elegans Jacq. `Small World Pink') and marigold (Tagetes patula L. `Janie Yellow') growth. The Utah leonardite was characterized by comparing it to the International Humic Substances Society's leonardite standard. Zinnia and marigold seedlings and transplants were grown in sand and 1 sand: 1 peat media (by volume) with leonardite additions of 0%, 3.125%, 6.25%, and 12.5%. Both species showed positive growth responses to 3.125% leonardite in each medium compared to fertilizer alone. Plant responses to increased leonardite additions were generally quadratic, and optimal leonardite levels were estimated. For growing zinnias, optimal conditions were determined to be 7.5% leonardite in a sand medium for seedlings and 8% in a sand-peat mixture for transplants. A sand-peat medium containing 7% leonardite was determined to be optimal for growing marigold seedlings and transplants. Addition of leonardite to growing medium offers promise for reducing fertilizer use during production of some ornamental plants.
A 2-year greenhouse study was conducted at Clemson University, Clemson, S.C., in 2003 and 2004 to determine drought responses of six bermudagrass (Cynodon spp.) cultivars at four irrigation intervals. Cultivars selected from the 2002 National Turfgrass Evaluation Program Bermudagrass Trial were `SWI-1012', `Arizona Common', `Tift No.3', `Tifsport', `Aussie Green', and `Celebration'. Treatments included 5-, 10-, and 15-day irrigation intervals plus a control (irrigated daily). Volumetric soil water content (VSWC) and evapotranspiration (ET) rates were recorded every 3 days. Turfgrass quality (TQ) was observed weekly and root weight was measured at the end of a 6-week study. `Aussie Green' and `Celebration' produced the highest TQ rating (>7) at week 4 when watered daily. After 4 weeks of the 5-day irrigation interval, all cultivars showed unacceptable quality ratings (<7). However, `Aussie Green' and `Celebration' were able to maintain an acceptable TQ rating (7), compared to `Arizona Common' (5.1) and `Tift No.3' (5.8) at week 2 (5-day treatment). `Celebration' produced 114% and 97% greater root weight than `Tifsport' and `Aussie Green', respectively, when pooled across all irrigation treatments. At the 15-day irrigation interval treatment, six bermudagrass cultivars pooled together produced 78%, 22%, and 11% greater root weight vs. control, 5-day, and 10-day treatments, respectively. When pooled for all treatments, `Aussie Green' and `Celebration' VSWC was 5% and 7% lower than `Tift No.3', and ET rates were 26% and 30% greater than `Arizona Common'. Based on these results, irrigating bermudagrass in 5-day intervals should be carefully monitored.