Ferric iron transformation in soils with rotation of irrigated rice-upland crops and effect on soil tillage properties

We examined the relationship between the form of iron and the tillability (defined as the degree of ease of pulverizing a soil into small clods) of soils in upland fields that had been converted from paddy fields. The amount of iron (Fe.e) extractable with acetate buffer (pH 3.0) decreased from 0.959 g kg_-1 in a field that has been continuously used as a paddy field to 0.104 g kg-I in a field that had been converted into an upland field for a period of 5 y. There was no significant change in the free iron oxide content under upland conditions. These results indicate that ferric iron oxides are gradually crystallized to less reactive forms after the conversion of a paddy field into upland conditions. Both soil tillability (represented by the mean clod diameter after tillage) and the stability of the soil microstructure (represented by the sediment volume) also increased during the 3-y period after conversion and then remained constant for the last 2-y period of the study. On the basis of these results, two mechanisms for the improvement of soil tillability can be proposed as follows: crystallization of ferric iron oxides increased their resistance to microbiological reduction and due to this stabilization the iron oxides as a cementing reagent that contributed to the soil microstructure, which in turn affected the soil tillability. During the first year after drainage, however, there was no significant correlation between the soil tillability and amount of Fe_ac, presumably because the soil was not sufficiently dry in the first year after conversion, and the iron oxides did not affect appreciably the soil structure.     

EFFECT OF BIODEGRADABLE CHELATING LIGAND ON IRON BIOAVAILABILITY AND RADISH GROWTH

The effect of chelating ligands on iron (Fe) uptake and growth of radish (Raphanus sativus L.) was investigated. The ethylenediaminetetraacetic acid (EDTA) increased ⁵⁵Fe uptake in roots of radish though its subsequent translocation from roots to shoots and leaves did not increase. About 70%—80% of the total ⁵⁵Fe was distributed in the roots while about 5%—15% and 11%—17% were in shoots and leaves, respectively. The EDTA increased iron uptake into the roots of radish, but not in the above ground parts of the plant. The growth of radish (Raphanus sativus L.) decreased drastically in alkaline condition (pH > 9), even though the concentration of iron was sufficient in the growth medium. The growth of radish was enhanced successfully by the addition of hydroxyiminodisuccinic acid (HIDS) and EDTA. This might be because HIDS and EDTA solubilize iron from its precipitation with hydroxides at higher pH, and increase iron bioavailability. The influence of EDTA and HIDS on radish growth was comparable. Increase of radish growth by ethylenediaminedisuccinic acid (EDDS) and methylglicinediacetic acid (MGDA) was less than those by EDTA and HIDS. Considering the reproducibility of the radish growth (biomass production) at pH 10, HIDS is supposed to be more effective compared to EDTA.     

铸铁、铸钢激光表面改性材料及工艺研究

磨损、空蚀是农机具及泵装置使用中安全可靠性的主要问题。由于磨损、空蚀的侵蚀、剥蚀，不仅造成了农机具及水泵部件的破坏，还引起工作能力的恶化。该文在氧乙炔合金粉末喷焊研究的基础上，利用2 kW-CO₂连续横流激光器，采用Ni基合金粉末，在铸铁和铸钢部件上进行了激光表面改性试验研究。并采用磁致伸缩仪对试样的抗磨蚀能力进行了测试。试验结果证实，经过激光表面改性处理试样，不仅热变形极小而且抗磨损、空蚀能力大幅度提高。     

农用柴油机合金抗磨铸铁气缸套的研究

气缸套是发动机的重要摩擦副之一,它的抗磨性能直接影响着发动机的寿命。由于农用柴油机经常处于尘埃较多的场合工作,所以其磨损更快。该文旨在强化气缸套以延长其使用寿命。研究采用在铸铁中加入各种合金元素使其在较软基体上生成高硬度点。这是一种既可保证一定的储油能力减少磨损又因具有硬质点而提高抗磨能力的有效方法。以不同材料配方制造的气缸套进行了热机快磨试验,结果表明该气缸套具有优异的抗磨性能及储油能力,且成本增加不大,是较理想的更新换代产品。     

Short‐Term Effect of Lime,Phosphorus, and Iron Amendments on Water‐Extractable Lead and Arsenic in Orchard Soils

Abstract

Lead arsenate was extensively used to control insects in apple and plum orchards in the 1900s. Continuous use of lead arsenate resulted in elevated soil levels of lead (Pb) and arsenic (As). There are concerns that As and Pb will become solubilized upon a change in land use. In situ chemical stabilization practices, such as the use of phosphate‐phosphorus (P), have been investigated as a possible method for reducing the solubility, mobility, and potential toxicity of Pb and As in these soils. The objective of this study was to determine the effectiveness of calcium carbonate (lime), P, and iron (Fe) amendments in reducing the solubility of As and Pb in lead‐arsenate‐treated soils over time. Under controlled conditions, two orchard soils, Thurmont loam (Hapludults) and Burch loam (Haploxerolls), were amended with reagent‐grade calcium carbonate (CaCO₃), iron hydroxide [Fe(OH)₃], and potassium phosphate (KH₂PO₄) and incubated for 16 weeks at 26°C. The experimental results suggested that the inorganic P increased competitive sorption between H₂PO₄ ^? and dihydrogen arsenate (H₂AsO₄ ^?), resulting in greater desorption of As in both Thurmont and Burch soils. Therefore, addition of lime, potassium phosphate, and Fe to lead‐arsenate‐contaminated soils could increase the risk of loss of soluble As and Pb from surface soil and potentially increase these metal species in runoff and movement to groundwater.     

Evaluation of Toxicity Level of Nickel on Growth,Photosynthetic Efficiency,Antioxidative Enzyme,and Its Accumulation in Cauliflower

A study was conducted to determine the toxicity level of nickel using cauliflower (Brassica oleracea L. var. botrytis) cv. Snowball grown in refined sand with complete nutrient solution for 79 days. At day 80, plants were separated into three lots. One lot was treated as the control (0.0001 mM Ni) while other two lots were supplied with excess nickel (Ni) at 0.1 and 0.5 mM. The toxicity symptoms of Ni appeared as chlorosis of young leaves. No curd was formed at 0.5 mM Ni supply. Excess Ni decreased biomass, chlorophyll, Hill reaction activity, and carbohydrate fraction, and enzyme activities of catalase, peroxidase, and acid phosphatase in leaves. Excess Ni increased concentration of starch, phenol, and nonprotein nitrogen and decreased protein nitrogen in leaves. Increase in Ni supply increased Ni concentration in all parts of cauliflower, whereas the concentration of phosphorus, sulfur, iron, and manganese decreased significantly.     

Application of micronutrients alone or with macronutrient fertilizers

Abstract

Micronutrients are applied alone to soils or with macronutrient fertilizers. Foliar application of Fe and other micronutrients is also practiced, and Mo is usually applied as a seed treatment. Since the soil application rates of B, Cu, Mn, and Zn are low, they are usually applied with macronutrient fertilizers by incorporation during the manufacturing process, bulk blending with or coating onto granular fertilizers, or with fluid fertilizers.

Chemical reactions between the micronutrient source and the macronutrient fertilizer may occur in the manufacturing process, in storage, or after soil application. These reaction products may vary widely, so care must be taken in selecting and processing micronutrient sources and macronutrient carriers so the resulting products will be available to plants. In general, plant availability of B sources is not affected during reaction. Care must be taken to apply boronated fertilizers uniformly and to avoid excessive rates, because the range between B deficiency and toxicity is very narrow. Crop response to Cu, Mn, and Zn varies with the micronutrient rate and source, macronutrient carrier, and method of application.     

白口铸铁机械性能研究及在农机制造中的应用(Ⅱ)

研究了变质处理和热处理两种方法对低铬白口铸铁的组织及机械性能的综合影响.结果表明,经变质处理的低铬白口铸铁,在铸态下冲击韧性最高可达6.9J/cm2;经950℃×8h退火后,硬度最低为HRC20.2;经920℃×4h水淬,150℃×30min回火后,冲击韧性最高为10.1J/cm2,具有在农机领域广泛应用的前景.     

高强度灰铸铁在薄壁缸体上的应用

采用扫描电镜、200h台架试验和1000h耐久试验等方法对高强度灰铸铁在薄壁缸体上的应用进行了试验研究。试验结果表明：碳当量控制在3.8%－4.1%（与菲亚特缸体的碳当量大体相当），采用低合金化及复合孕育剂，可稳定获得抗拉强度大于250MPa的高强度灰铸铁，其铸件硬度大于HB210，白口倾向小，硬度差仅为HB15－HB33，均达到菲亚特缸体的性能要求，对无缸套缸体的缸壁表面进行激光处理，比传统缸套的耐磨性提高一倍以上。