Effect of iron-quercetin complex on reduction of nitrite in in vitro and in vivo systems

This study investigated whether reducing agents such as quercetin and iron(II) facilitate formation of nitric oxide (NO) gas from orally ingested nitrite in an vivo study. When 3 mg/kg Na (15)NO2 was orally administered to rats with or without iron(II) or quercetin, Hb (15)NO, which is indicative of systemic (15)NO, was detected in the blood, with the maximum blood concentration of Hb (15)NO at 15 min after nitrite or nitrite plus quercetin treatment, whereas after administration of nitrite plus iron(II) or nitrite plus iron(II) and quercetin, the time was shortened to 10 min. Interestingly, iron(II), quercetin, or iron(II) plus quercetin did not affect the total amount of Hb (15)NO generated from orally administered Na (15)NO2. However, the systemic nitrite concentration was significantly decreased in the presence of iron(II) or iron(II) plus quercetin. These results may indicate that iron(II) is critical to the generation of NO gas from nitrite, whereas quercetin contributed little under the in vivo experimental conditions.     

Role of polyphenols in copper complexation in red wines.

Four monovarietal red wines, Tinta Roriz, Tinta Barroca, Touriga Nacional, and Touriga Francesa, were studied for their complexometric properties toward copper. For the purpose, ion selective electrode potentiometric titrations were carried out, and the data were treated by two methods suitable for heterogeneous ligands: the Scatchard plot, which provided the complexation capacity (CC(total) = maximum number of moles of sites per liter), and the differential equilibrium function (DEF), which provided the conditional stability constants of the sites effectively involved in the metal complexation (K(DEF)) at a given titration point. The different wines displayed similar properties: CC(total) ranged from 4.5x10(-3) (Tinta Barroca) to 4.9x10(-3) M (Touriga Francesa), and log K(DEF) values were between 4.2 and 6.5. The range of log(|Cu|(bound)/CC(total)) = log theta embraced in the titration was between -0.2 and -1.9. With regard to the natural levels of copper, from 4.4x10(-7) (Tinta Roriz) to 1.3x10(-6) M (Touriga Nacional), and ligands (CC(total)) in the wines, it can be expected that copper will be strongly complexed in the studied wines (log K(DEF) > 6). Studies carried out, in parallel, for solutions of isolated seed tannins and skin polyphenols (mainly anthocyans) showed that their contribution to the CC(total) of the wines was <40% for tannins and <2% for skin polyphenols. However, skin polyphenols were shown to be much stronger copper ligands (log K(DEF) = 6.7, log theta = -1.5) than tannins (log K(DEF) = 4.5, log theta = -1.5).     

Stability of plant sterols in ingredients used in functional foods

The content of plant sterol (PS) and their oxidation products (POPs) in eight ingredients used to enrich functional foods was studied. A gas chromatographic (GC) technique with mass-spectrometric detection was used for identification, while GC with a flame ionization detector (GC-FID) was used for quantification. β-Sitosterol was the most abundant phytosterol, and the main POPs found were derived from this compound (7α/β-hydroxysitosterol, 7-ketositosterol, and sitostanetriol). The total amount of POPs found in the ingredients ranged from 29.03 to 110.02 μg/100 g PS. The β-sitosterol oxidation rates ranged from 10 to 50 μg β-sitosterol oxides/100 g of β-sitosterol. In view of this low rate of oxidation in the ingredients tested, it can be concluded that the PS remain stable in these ingredients. Significant correlations (p < 0.01) were found between total oxysitosterols versus β-sitosterol contents (R(2) = 86.5%) and between total POPs and total PS (R(2) = 81.6%).     

Nutritional properties of starch in buckwheat products: studies in vitro and in vivo

The nutritional characteristics of buckwheat starch were studied to identify the possibility for reduced postmeal metabolic responses to various buckwheat products. The in vitro rate of starch hydrolysis and resistant starch (RS) formation in boiled buckwheat groats and in a series of breads, baked with 30-70% of buckwheat flour (BWF) or groats (BWG), respectively, were evaluated in vitro. In parallel, postprandial glucose and insulin responses and also the satiety score to BWG and wheat bread with 50% BWG as compared with the reference white wheat bread (WWB) were studied in healthy humans. The highest concentration of RS was found in boiled BWG (6% total starch basis). The RS level in bread products based on different proportions of BWF or BWG (30-70%) varied from 0.9 to 4.4%. The rate of in vitro amylolysis was significantly lower (P < 0.05) in all buckwheat products in comparison with the reference WWB. The calculated hydrolysis indices (HI) were lowest in boiled BWG (HI = 50) and in bread with 70% BWG (HI = 54). Consumption of boiled BWG or bread based on wheat flour and 50% BWG induced significantly lower postprandial blood glucose and insulin responses compared with the WWB. The calculated glycemic and insulinemic indices (GI and II) for boiled BWG were 61 and 53 and for the buckwheat bread, 66 and 74, respectively. The highest satiety score was found with boiled BWG. It is concluded that buckwheat has potential use in the design of foods with lower GI properties.     

Inactive corrinoid-compound significantly decreases in Spirulina platensis grown in a cobalt-deficient medium.

Spirulina platensis NIES-39 was grown under open culture system in the presence or absence of CoSO(4) (12 microg/L) and/or vitamin B(12) (10 microg/L) to confirm whether CoSO(4) and/or vitamin B(12) stimulate or are essential for growth of the algal cells and for accumulation of vitamin B(12). The addition of CoSO(4) and/or vitamin B(12) could not affect both cell growth and cell yield of the alga. The amount of corrinoid-compound was increased significantly by the addition of CoSO(4) but not by vitamin B(12). A C18 reversed-phase HPLC pattern of the Spirulina corrinoid-compound increased by the addition of CoSO(4) was identical to that of authentic pseudovitamin B(12), which is inactive for human. These results indicate that the algal cells grown in the absence of CoSO(4) are suitable for use of human health foods because the inactive corrinoid-compound can be reduced significantly.     

Comparative study on pressure and temperature stability of 5-methyltetrahydrofolic acid in model systems and in food products

A comparative study on the pressure and temperature stability of 5-methyltetrahydrofolic acid (5-CH(3)-H(4)folate) was performed in model/buffer systems and food products (i.e., orange juice, kiwi puree, carrot juice, and asparagus). Effects of pH and ascorbic acid (0.5 mg/g) on 5-CH(3)-H(4)folate stability in buffer systems were studied on a kinetic basis at different temperatures (from 65 to 160 degrees C) and different pressure/temperature combinations (from 100 to 700 MPa/from 20 to 65 degrees C). These studies showed that (i) the degradation of 5-CH(3)-H(4)folate in all model systems could be described by first-order reaction kinetics, (ii) the thermostability of 5-CH(3)-H(4)folate was enhanced by increasing pH up to 7, (iii) 5-CH(3)-H(4)folate was relatively pressure stable at temperatures lower than 40 degrees C, and (iv) ascorbic acid enhanced both the thermo- and barostabilities of 5-CH(3)-H(4)folate. In food products, temperature and pressure stabilities of 5-CH(3)-H(4)folate were studied at different temperatures (70-120 degrees C) and different pressure/temperature combinations (from 50 to 200 MPa/25 degrees C and 500 MPa/60 degrees C). 5-CH(3)-H(4)folate in orange juice and kiwi puree was relatively temperature (up to 120 degrees C) and pressure (up to 500 MPa/60 degrees C) stable in contrast to carrot juice and asparagus. Addition of ascorbic acid (0.5 mg/g) in carrot juice resulted in a remarkable protective effect on pressure (500 MPa/60 degrees C/40 min) and temperature degradation (120 degrees C/40 min) of 5-CH(3)-H(4)folate.     

Changes in Soil Properties and Vegetable Growth in Preparation for Organic Farming in Hawaii

Changes in soil properties and vegetable growth were quantified on a low-fertility tropical soil. Four treatments (two composts, urea, and control) were applied to an Oxisol (Rhodic Haplustox, Wahiawa series) in a field on Oahu, Hawaii. Chinese cabbage (Brassica rapa, Chinensis group) and eggplant (Solanum melongena) were grown sequentially as test crops. Soil quality as measured by hot-water-soluble carbon, dehydrogenase activity, and cation exchange capacity (CEC) increased by compost amendments. Total organic carbon or carbon dioxide (CO₂) respiration rate did not correlate with the soil amendments. Nitrogen (N) nutrition was the main factor that improved growth and carotenoid content in cabbage. The urea treatment promoted better growth in cabbage, whereas good-quality compost, made of grass clippings/tree trimmings, lime, and rock phosphate yielded better growth in eggplant, suggesting organic N requires time to mineralize and to be available to crops.     

辽宁设施栽培土壤盐分累积变化规律研究

对辽宁省主要设施栽培地区土壤盐分累积变化规律的凋查研究结果表明：（1）设施栽培土壤盐分含量和电导率较露地土壤有明显增加，且变化幅度较大，是露地的2.0～6.0倍。沈阳、北宁两地设施土壤的盐分含量分别为1347.48mg／kg（CV=59.3％），1274.25mg／kg（CV＝40.5％）。（2）设施土壤连续种植到4年左右为盐分累积的高峰期，此时土壤的平均含盐量为1861.28mg／kg，EC值为0.53mS／cm，已超过所种作物的生育障碍临界点（EC〉0.5mS／cm）。此后，盐分含量因设施使用率的降低及采取的相关措施而有一定程度的降低。（3）设施土壤各盐分离子的含量均较露地土壤大大增加，盐分的累积以NO3^-、SO4^2-和Ca^2＋的相对富集为主要特征。（4）盐分在设施土壤中的运移同时存在着向下迁移和向表层聚集两种方式，且以表聚为主。各盐分离子的含量随土层深度的增加而降低，NO3^-、CI^-、Ca^2＋、Na^＋的累积迁移量较大，在0～100cm各土层内的含量都高于对应露地层次，其中，硝酸盐的大量累积和向下迁移势必对环境造成不利影响。     

Chemical changes induced by methyl jasmonate in oilseed rape grown in the laboratory and in the field

The effect of methyl jasmonate (MJ) spraying on the chemistry of Brassica plants was investigated. Glucosinolates (GLS) in the leaves, stems, and roots of laboratory-grown oilseed rape (Brassica rapa subsp. oleifera cv. Tuli and Valo) 3 and 7 days after MJ treatment were analyzed. Volatile organic compounds (VOCs) from whole oilseed rape plants were collected 3 days after MJ treatment. GLS were also analyzed from field-grown oilseed rape (cv. Valo) treated with MJ. The production of indolyl GLS in laboratory-grown oilseed rape, especially the concentration of 4-hydroxy-3-indolylmethyl (4-OH-glucobrassicin) in leaves, stems, and roots, 3-indolylmethyl (glucobrassicin) in stems, and 4-methoxy-3-indolylmethyl (4-methoxyglucobrassicin) in roots, was induced after MJ treatment. The VOC emission profile changed after MJ treatment, and homoterpene (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) was detected only in MJ-treated plants. The GLS concentration in the field-grown plants was significantly higher in MJ-treated plants than in control plants. These results suggest that spraying with MJ induces the production of secondary compounds, that is, GLS and VOCs, in Brassica plants. The induction of VOC emissions in oilseed rape is comparable to that caused by insect feeding damage. Thus, MJ-treated crop plants may become less palatable to insect herbivores and more attractive to natural enemies of herbivores.     

Changes in Mercury Deposition in a Mining and Smelting Region as Recorded in Tree Rings

The adsorption of lead onto date palm fibers (palm fibers) and leaf base of palm (petiole) has been examined in aqueous solution by considering the influence of various parameters such as contact time, solution pH, adsorbent dosage, particle sizes, ionic strength, and temperature. The adsorption of Pb(II) increased with an increase of contact time. The optimal range of pH for Pb(II) adsorption is 3.0?C4.5. The linear Langmuir and Freundlich models were applied to describe the equilibrium isotherms, and both models fitted well. The monolayer adsorption capacity of Pb(II) on palm fibers and petiole was found as 18.622 and 20.040 mg/g, respectively, at pH 4.5 and 25°C. Dubinin-Radushkevich (D-R) isotherm model was also applied to equilibrium data. The mean free energy of adsorption (2.397 and 4.082 kJ/mol) onto palm fibers and petiole, respectively, may be carried out via physisorption mechanism. Pseudo-first-order rate equation and pseudo-second-order rate equation were applied to study the adsorption kinetics. In comparison to first-order kinetic model, pseudo-second-order model described well the adsorption kinetics of Pb(II) onto palm fibers and petiole from aqueous solution. From the results of the thermodynamic analysis, Gibbs free energy ??G, enthalpy change ??H, and entropy ??S were determined. The positive value of ??H suggests that interaction of Pb(II) adsorbed by palm fibers is endothermic. In contrast, the negative value of ??H indicates that interaction of Pb(II) ions by petiole is exothermic. The negative value of ??G indicates that the adsorption of Pb(II) ions on both palm fibers and petiole is a spontaneous process.     

Antimony Accumulation in Wheat Seedlings Grown in Soil and Water

The purposes of the research were (1) to estimate the ability of wheat Triticum aestivum L. to uptake antimony (Sb) from contaminated soil and water, (2) to study effects of Sb bioaccumulation on the plant development and distribution of macro- and trace elements in the plants, and (3) to compare uptake of Sb and some other elements by wheat seedlings grown in solid (soil) and liquid (water) media. Both soil-grown and water-grown plants were capable of accumulating large amounts of Sb. In roots, concentration of Sb was always greater than in leaves, suggesting that roots can prevent transfer of the trace element to upper plant parts. Uptake of Sb by the plants grown in water was significantly greater compared to Sb uptake by the plants grown in soil. Antimony bioaccumulation resulted in variations in concentrations of some nutrients in different plant parts and decrease of the seedling biomass.     

Antioxidant vitamins in barley green biomass

Two malting hulled varieties (Sebastian, Malz) and one nonmalting hull-less variety (AF Lucius) were used to assess vitamins C and E in the green biomass of young plants of spring barley ( Hordeum vulgare L.) in three stages of growth and development (BBCH 29, 31, 32-33). The samples from sampling I (BBCH 29) had statistically significantly higher vitamin C content and vitamin E activity compared to sampling I (BBCH 31). The highest average vitamin content was determined in the malting variety Sebastian (vitamin C, 520 mg 100 g(-1) DM; vitamin E, 73.06 mg kg(-1) DM) compared to the varieties Malz (501 mg 100 g(-1) DM; 61.84 mg kg(-1) DM) and AF Lucius (508 mg 100 g(-1) DM; 67.81 mg 100 g(-1) DM). The locality Krome?r?i?z? (Czech Republic, CR), with vitamin C and E contents of 524 mg 100 g(-1) DM and 68.74 mg kg(-1) DM, respectively, proved to be more suitable for growing green biomass compared to the locality Z?abc?ice (CR) (content of vitamins C and E, 477 mg 100 g(-1) DM and 66.39 mg kg(-1) DM, respectively). During the research period (2005-2007), it was determined that the green mass of young plants of spring barley was a significant source of vitamins C and E in the growth stage BBCH 29; in later samplings (BBCH 32-33) the vitamin levels dropped (by as much as 48%). These vitamins are important antioxidants for human health. Therefore, "green barley" can be recommended for the preparation of natural dietary supplements and is preferred to synthetic vitamin preparations.     

重庆三峡库区耕地土壤重金属含量的空间变异性研究

对重庆三峡库区耕地土壤重金属含量的空间变异性研究结果表明,Hg和Cr服从对数正态分布,拟合得到Hg与Cr的半方差函数模型分别为幂函数和球状模型,且在一定范围内存在空间相关性;采用Kriging内插法对未测点重金属进行最优估计,所绘制的Kriging插值图反映了该区耕地土壤重金属Hg和Cr的空间变异特征。     

Nitrogen to sulphur ratio in rapeseed and in rapeseed protein and its use in diagnosing sulphur deficiency

This study investigated the variation of nitrogen to sulphur ratios in rapeseed (N/S)_t and in rapeseed protein (N/S). Under S‐sufficient conditions the (N/ S)_t ratios varied considerably between different varieties, with low glucosinolate varieties having higher ratios than high glucosinolate varieties. In contrast, (N/S)_p remained relatively constant at about 11.5 for all varieties tested, though significant effects of N and S nutrition on the (N/S) ratio were present. The ratio increased in the S‐deficient samples. Results of yield responses to S fertilizer and (N/S)₍from six field experiments were used to see if (N/S)_t could indicate the S status of the crop. Although yield losses due to S shortage tended to occur when (N/S)_t was greater than 10, the relationship was not sufficiently reliable for use in diagnosis.     

不同生态恢复措施下宁夏黄土丘陵典型草原土壤质量评价

为了研究生态恢复措施对草原土壤性状和土壤质量的影响,2016年在宁夏黄土高原丘陵区典型草原,以放牧草地(FM)为对照,研究了封育(FY)、水平沟(SP)和鱼鳞坑(YL)3种恢复措施对0～40 cm土壤理化性质和生物学特性的影响,评价了各措施下的土壤质量.结果表明:1)FM土壤容重最高,土壤黏粒含量、田间持水量和总孔隙度较低;FY、SP和YL措施间土壤物理性质差异不显著(P＞0.05).2)土壤有机质、全氮和速效氮以FY最高,SP和YL较低;全磷与速效钾含量以FM最高,SP最低.3)土壤蔗糖酶和脲酶活性呈FY＞SP＞YL＞FM;蛋白酶和磷酸酶呈FY草地最高,YL最低;细菌、放线菌和真菌在各处理间变化各异,微生物总量呈FY＞FM≈SP＞YL,但微生物生物量碳、氮呈FY＞YL≈SP＞FM(P＜0.05):土壤因子间存在一定的相关性.4)隶属函数结合因子分析法评价的土壤质量综合得分为FY＞SP＞FM＞YL.因此封育是最有利于研究区退化草地土壤质量恢复的措施,研究结果可以为宁夏典型草原生态建设提供理论基础.     

伊朗西部地区哈马丹市农业土壤钾地位的多元统计分析

Multivariate statistical technique was used to determine the potassium (K⁺) status and to assess soil fertility and K leaching potential in some calcareous soils. Water-soluble K⁺ (H₂O-K) and ammonium acetate-extractable K⁺ (NH₄OAc-K) ranged from 0.019 to 0.590 (mean value 0.095) and 0.390 to 3.320 (mean value 0.954) cmolc kg^-1, respectively. The nitric acid-extractable K⁺ (HNO₃-K) varied from 1.03 to 13.63 (mean value 5.37) cmol_c kg^-1. The proportion of H₂O-K ranged from 0.34% to 14.8% of HNO₃-K, and 2.2% to 53.2% of NH₄OAc-K. The proportion of NH₄OAc-K ranged from 5.8% to 80% of HNO₃-K (mean value 23% of HNO₃-K). The tendency of the soil to lose K⁺ by leaching was examined by determining K⁺-Ca²⁺ exchange isotherms. The soils mostly had moderate to high values of K⁺ sorption capacity, ranging from 10% to 58% (mean value 28%) of added K⁺. The Gapon coefficient varied widely from 1.1 to 12.0 (L mol^-1)^-1/2. Clay minerals were dominated by illite, smectites and vermiculite with small amounts of kaolinite. Principal component analysis (PCA) showed that the first four components accounted for 27.7%, 21.4%, 13.8%, and 8.9% of total variation, respectively. The non-hierarchical cluster analysis (k-means clustering) grouped 75 sampling sites into six clusters, based on the similarity of soil quality characteristics. The results suggested that such classes could form a basis for variable-rate application to maintain an adequate K⁺ status for crop production and to reduce potential K⁺ loss from soil by leaching.     

Zinc transformations in neutral soil and zinc efficiency in maize fertilization

The effect of six Zn sources (Zn-phenolate, Zn-EDDHA, Zn-EDTA, Zn-lignosulfonate, Zn-polyflavonoid, and Zn-glucoheptonate) was studied by applying different Zn levels to a representative Calcic Haploxeralf neutral soil (the predominant clay is montmorillonite) in incubation and greenhouse experiments. Zinc soil behavior was evaluated by sequential DTPA and Mehlich-3 extraction procedures. In the incubation experiment, the highest percentage recovery values of Zn applied to soil occurred in the water-soluble plus exchangeable fraction (29%) in fertilization with 20 mg of Zn kg(-1) of Zn-EDTA fertilizer. In the greenhouse experiment with maize (Zea mays L.), a comparison of different Zn carriers showed that the application of six fertilizers did not significantly increase the plant dry matter yield among fertilizer treatments. The highest yield occurred when 20 mg of Zn kg(-1) was applied as Zn-EDDHA fertilizer (79.4 g per pot). The relative effectiveness of the Zn sources in increasing Zn concentration in plants was in the following order: Zn-EDTA (20 mg kg(-1)) > Zn-EDDHA (20 mg kg(-1)) approximately Zn-EDTA (10 mg kg(-1)) > Zn-EDDHA (10 mg kg(-1)) approximately Zn-phenolate (both rates) approximately Zn-polyflavonoid (both rates) approximately Zn-lignosulfonate (both rates) approximately Zn-glucoheptonate (both rates) > untreated Zn. The highest amounts of Zn taken up by the plants occurred when Zn was applied as Zn-EDTA fertilizer (20 mg kg(-1), 7.44 mg of Zn per pot; 10 mg kg(-1) Zn rate, 3.93 mg of Zn per pot) and when Zn was applied as Zn-EDDHA fertilizer (20 mg kg(-1) Zn rate, 4.66 mg Zn per pot). After the maize crop was harvested, sufficient quantities of available Zn remained in the soil (DTPA- or Mehlich-3-extractable Zn) for another harvest.     

影响土壤中铬, 锰的氧化还原反应的环境因素

Disposal of chromium(Cr) hexavalent form,Cr(VI),in soils as additions in organic fertilizers,liming materials or plant nutrient sources can be dangerous since Cr(VI) can be highly toxic to plants,animals,and humans.In order to explore soil conditions that lead to Cr(VI) generation,this study were performed using a Paleudult(Dystic Nitosol) from a region that has a high concentration of tannery operations in the Rio Grande do Sul State,southern Brazil.Three laboratory incubation experiments were carried out to examine the influences of soil moisture content and concentration of cobalt and organic matter additions on soil Cr(VI) formation and release and manganese(Mn) oxide reduction with a salt of chromium chloride(CrCl 3) and tannery sludge as inorganic and organic sources of Cr(III),respectively.The amount of Cr(III) oxidation depended on the concentration of easily reducible Mn oxides and the oxidation was more intense at the soil water contents in which Mn(III/IV) oxides were more stable.Soluble organic compounds in soil decreased Cr(VI) formation due to Cr(III) complexation.This mechanism also resulted in the decrease in the oxidation of Cr(III) due to the tannery sludge additions.Chromium(III) oxidation to Cr(VI) at the solid/solution interface involved the following mechanisms:the formation of a precursor complex on manganese(Mn) oxide surfaces,followed by electron transfer from Cr(III) to Mn(III or IV),the formation of a successor complex with Mn(II) and Cr(VI),and the breakdown of the successor complex and release of Mn(II) and Cr(VI) into the soil solution.     

生态文明视角下四川省资源环境压力的时空变化特征

基于足迹家族原理,构建了由生态压力、温室气体(GHGs)排放、水资源压力构成的资源环境压力评价指标体系,并应用于四川省的资源环境压力评价。结果表明,1990—2013年四川省人均生态足迹增加109.57%,生物承载力变化不大,生态压力由中下(Ⅱ_a)升至很高(Ⅲ_b)等级;林业碳汇提高32.01%,GHGs排放虽保持较低(Ⅰ_b)等级,但其排放指数增高了234.97%;水足迹增速很小,水资源压力很低(Ⅰ_a);全省资源环境压力由很低(Ⅰ_a)升为中下(Ⅱ_a)。空间上,生态压力很低(Ⅰ_a)的是甘孜和阿坝,广元为中上(Ⅱ_b),成都、自贡和攀枝花等其余19市(州)很高(Ⅲ_b);GHGs排放状况,攀枝花很高(Ⅲ_b),内江较高(Ⅲ_a),乐山中上(Ⅱ_b),眉山中下(Ⅱ_a),甘孜、雅安和阿坝为碳汇(Ⅰ_a),成都、自贡和泸州等其余14市(州)均属较低(Ⅰ_b)等级;水资源压力方面,自贡、遂宁、眉山、内江和资阳很高(Ⅲ_b),成都较高(Ⅲ_a),泸州和达州为中上(Ⅱ_b),德阳为中下(Ⅱ_a),宜宾和攀枝花较低(Ⅰ_b),甘孜、阿坝和广安等其余10州(市)很低(Ⅰ_a);资源环境压力状况,阿坝、甘孜、雅安和广元很低(Ⅰ_a),凉山和绵阳较低(Ⅰ_b),广安、巴中和南充为中下(Ⅱ_a),宜宾、德阳、乐山和达州为中上(Ⅱ_b),泸州、资阳和成都较高(Ⅲ_a),遂宁、攀枝花、眉山、自贡和内江很高(Ⅲ_b)。研究表明,四川省的资源环境压力主要归因于较高的生态压力。今后的生态文明建设中,除了严守耕地生态红线以确保耕地生产力外,还要通过大力发展水电以优化能源消费结构,以及加强森林保育以提高碳汇潜力。     

Mechanized relay-cropping in an irrigated red-brown earth in south-eastern Australia

Abstract. Machinery was designed specifically for relay-cropping on permanent raised beds (150 mm high and 1.5 m wide) in northern Victoria. This machinery enabled maize ( Zea mays ) to be successfully sown at 2, 4 and 5 weeks before harvest, and 1 day after harvest (Control), of wheat ( Triticum aestivum ). The sowing equipment consisted of a four-row cultivator, behind which were four precision seeders. The wheels (250 mm in diameter) were spaced at 1.5 m to track along the base of the furrows. In one pass on each bed, the sowing equipment tilled two strips (each 50 mm wide, 30 mm deep and 50 mm from the outer row of wheat) and sowed maize, with little damage to the wheat crop. We extended the axle of the trailed harvester so that the wheels (250 mm in diameter) were 3 m apart, and moved the drawbar 300 mm to one side so that all wheels ran along the base of the furrows. There were no significant differences between treatments in yield (mean 2.9 t ha^-1) of dryland wheat, in final emergence percentage (mean 89%) or in early growth of irrigated maize. The maize yielded significantly less grain in the treatment sown at 5 weeks (9.6 t ha^-1), but not 2 or 4 weeks (mean 10.6 t ha^-1) before the wheat was harvested, than in the Control (10.8 t ha^-1). The wheat and maize yielded more grain than those grown traditionally as sole crops in northern Victoria.