Oxidation and fate of chromium in soils

Abstract

The ammonia electrode method was used to characterize soil organic nitrogen. Amide-N, α-amino-N and hexosamine-N were estimated by measuring the ammonium-N derived from each organic-N with an ammonia electrode after hydrolysis of standard compounds followed by certain treatments. Each organic-N was recovered quantitatively from each standard compound in the presence and absence of soil. Twenty soil samples were analyzed for the above forms of organic nitrogen by both the distillation and electrode methods. The results obtained by the ammonia electrode method for each form of organic nitrogen agreed closely with those obtained by the distillation method. The electrode method was preferred for subsequent soil studies since it is simple and sensitive.     

Amendment of drilling fluid-affected soils with calcium salts

Land disposal of waste drilling fluid is an environmental concern because of the high salt content and the presence of potential toxic elements. A water-based drilling fluid was tested in a laboratory column study to determine the feasibility of leaching excessive salt without mobilizing chromium (Cr). The drilling fluid-affected two Alfisols with similar mineralogy, acidity, and texture were treated with gypsum (CaSO₄ · 2H₂O), calcium carbonate (CaCO₃), or calcium phosphate (CaHPO₄) (0 to 2% of weight). The electrical conductivity (EC) increased and the sodium adsorption ratio (SAR) decreased with increasing Ca-salt concentration. The pH did not vary significantly with the changes in the concentrations of gypsum and calcium phosphate. The pH of the mixtures increased in proportion to the concentration of added calcium carbonate. The hydraulic conductivity increased and the mobility of the soil particles decreased with increasing Ca-salt concentration. The Cr mobility decreased by gypsum and CaCO₃ treatments but it increased by calcium phosphate treatment. The soil with a higher content of organic matter and cation exchange capacity (CEC) showed a higher hydraulic conductivity and lower Cr mobility than the other soils at the same levels of the treatment. The results of this study suggest that the amendment of drilling fluid-affected soils with CaCO₃ and gypsum can enhance the leaching of excessive salt and reduce the Cr mobility. Among loamy soil, those with a higher CEC and organic matter content are more suitable for land disposal of drilling fluid.     

Nutrient Allocation of ‘TifEagle’ Bermudagrass as Influenced by Trinexapac-Ethyl

ABSTRACT

Inhibiting shoot growth of dwarf bermudagrass [Cynodon dactylon(L.) Pers. × C. transvaalensis Burtt-Davey] with a plant-growth retardant, trinexapac-ethyl (TE), may redirect nutrients and photosynthate away from leaf tissue to promote root growth and improve nutrient-use efficiency. Two greenhouse experiments evaluated three rates of TE, 0.025, 0.05, and 0.075 kg a.i. ha^?1, applied every three weeks on ‘TifEagle’ bermudagrass for 12 weeks. Lysimeters constructed to United State Golf Association specifications were arranged in a randomized complete block design with four replications. Increased TE rates quadratically reduced clipping yield 38%–75%, improved turf quality 6%–13%, and enhanced chlorophyll concentrations 30%–70% over the untreated grass. Dry-root mass increased with TE rate 11%–37% after 12 weeks. Total clipping nutrients recovered from five sampling dates were reduced by approximately 50%, 85%, and 90% for turf receiving TE at 0.025, 0.05, and 0.075 kg ha^?1 3 wk^?1, respectively. Thatch (stolons and rhizomes) and roots had higher nitrogen (N) concentration and retention with increased TE rate, suggesting inhibited leaf growth increased N storage in belowground plant tissue. Overall, TE may effectively enhance turf quality, root growth, and nutrient-use efficiency of dwarf-type bermudagrasses. Chemical name used: trinexapac-ethyl, [4-(cyclopropyl-[α]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethylester].     

含可溶物玉米酒糟添加于肉牛犊日粮的试验研究

1引言玉米酒糟副产品已越来越常见,这也促使畜牧生产商不断的投诸于这种饲料。依阿华肉牛研究中心发现：在依阿华州,较饲育场其它生产商相比,牛犊饲养人员较少的利用这一饲料资源。而由Leopold可持续农业发展中心基金赞助的一项维期三年的试验项目正是旨在研究评价不同的饲喂生产雌性肉牛牛犊的方案。（注：此报告为第一年的研究结果。）