日喀则市农业生态足迹研究

采用水资源足迹和化石能源供给地概念,对日喀则市2005年农业活动的生态足迹进行实证分析.结果表明:日喀则市农业综合足迹为334 153.27 hm2,占日喀则市总足迹的77.6%,其中,化石能源地足迹仅占农业综合足迹的13.3%,表明农业现代化程度不高.对农业综合足迹贡献最大的是耕地和牧草地,二者合占65.6%,主要原因是大量使用农用化学品和牧草地严重超载;生产足迹占农业综合足迹的82.8%,说明农村占用的大部分资源主要用来进行资源再生产.对日喀则市农业综合足迹的实证研究表明,资源产量法可以有效减小土地面积法引起的生态赤字扩大化现象,将肉、蛋、奶产品作为次级产品更能反映牧草地利用现状.      

Reduced ozone by air filtration consistently improved grain yield in wheat

This study considered effects of reduced [O₃] on wheat yield. Open-top chamber charcoal filtered air treatments were compared with non-filtered treatments for field-grown wheat. 30 experiments meeting requirements were found, representing nine countries in North America, Europe and Asia. 26 experiments reported improved yield and 4 experiments reduced yield by filtration, a significant positive effect. Average yield improvement was 9%. Average daytime [O₃] was reduced by filtration from 35 to 13 nmol mol⁻¹. Filtration efficiency was 63% for O₃ and 56% for SO₂. For NO_x it was observed that NO₂ was reduced and NO increased by filtration. Thus, filters convert NO₂ to NO. Most experiments reported low or very low [SO₂] and [NO_x]. Thus, O₃ can be concluded to be the main phytotoxic component in the experiments. Elevated [NO₂] was observed in one experiment. The conclusion is that current [O₃] over large parts of the world adversely affect wheat yield.     

Evaluation of physiological, growth and yield responses of a tropical oil crop (Brassica campestris L. var. Kranti) under ambient ozone pollution at varying NPK levels

A field study was conducted to evaluate the impact of ambient ozone on mustard (Brassica campestris L. var. Kranti) plants grown under recommended and 1.5 times recommended NPK doses at a rural site of India using filtered (FCs) and non-filtered open top chambers (NFCs). Ambient mean O₃ concentration varied from 41.65 to 54.2 ppb during the experiment. Plants growing in FCs showed higher photosynthetic rate at both NPK levels, but higher stomatal conductance only at recommended NPK. There were improvements in growth parameters and biomass of plants in FCs as compared to NFCs at both NPK levels with higher increments at 1.5 times recommended. Seed yield and harvest index decreased significantly only at recommended NPK in NFCs. Seed quality in terms of nutrients, protein and oil contents reduced in NFCs at recommended NPK. The application of 1.5 times recommended NPK provided protection against yield loss due to ambient O₃.     

Fungicidal Impact on Chickpea–Mesorhizobium Symbiosis

Abstract

The effects of carbendazim, captan, thiram, and mancozeb, on plant vitality, chlorophyll content, N uptake, protein content, nodulation, and seed yield in chickpea (Cicer arietinum) were assessed in a controlled environment. Seeds treated with fungicides at 1 and 1.5 g. a.i./kg seed had no significant adverse effect on plant vigor, seed yield, and N and protein contents. In contrast, fungicides applied at 2 g. a.i./kg of captan, thiram and mancozeb, significantly reduced the measured parameters. In general, the toxicity of fungicides in terms of seed yield increased in the following order: Control = carbendazim > thiram > captan > mancozeb. Total chlorophyll content in foliage declined consistently with fungicides dose rates and application days. Seeds treated with lower rates of fungicides significantly increased nodulation (nodule number per plant and its dry mass) and were compatible with chickpea inoculum used in this study. Although carbendazim at 2 g a.i./kg seed had no phytotoxic effect assessed under greenhouse conditions, it significantly reduced the chlorophyll content, nodulation (60 d) and N content in shoots.     

Strategies for Management of Sicyos polyacanthus Cogn. (Cucurbitaceae) in Sugarcane Crops of Tucumán,Argentina

Abstract

Sicyos polyacanthus is one of the most important weed in sugarcane crops of Tucumán (Argentina). The objective of this work was to establish strategies that would decrease the weed incidence in the crop to a minimum level. The study was carried out during 1998–2003 at five localities of sugarcane production of Tucumán (Argentina). The plots were 20 m long (192 m²) with 6 furrows and each plot was replicated five times. Treatments were: (i) Mechanical–chemical cultivation without fire; (ii) Mechanical–chemical culltivation with fire; (iii) Mechanical cultivation with handle pulled and with fire; (iv) Mechanical cultivation with handle pulled without fire; (v) Mechanical and chemical variants with fertilization and without fertilization; (vi) Mechanical and chemical variants with watering and without watering; (vii) Fallow and rotation, at the sugarcane crop renovation; (viii) Mechanical and chemical variants for plant cane and ratoon cane; and (ix) Mulching of harvest rests. The results suggest that besides the use of preemergent herbicides, fire marks the entry point of control, influencing fluxes and seed viability. It appears that fallow, mulching, and rotation of crops is fundamental for eliminating seeds that live short time in the soil and increase the mortality rate of species.     

Comparison of a diurnal vs steady-state ozone exposure profile on growth and yield of oilseed rape (Brassica napus L.) in open-top chambers in the Yangtze Delta, China

Most available exposure-response relationships for assessing crop loss due to elevated ozone (O₃) have been established using data from chamber and open-top chamber experiments, using a simulated constant O₃ concentration exposure (square wave), which is not consistent with the diurnal variation of O₃ concentration that occurs in nature. We investigated the response of oilseed rape (Brassica napus L.) to O₃ as affected by two exposure regimes: one with a diurnal variation (CF100D) and another with a constant concentration (CF100). Although the two exposure regimes have the same mean O₃ concentration and accumulated O₃ concentration above 40 ppb (AOT40), our results show that O₃ at CF100D reduced biomass and number of pods/plant more than O₃ at CF100. Both O₃ exposures resulted in larger seed weights/100 pods compared to CF. Numbers of seeds/100 pods were reduced by CF100, while numbers of seeds/100 pods in the CF100D chambers were comparable to those in CF. Our results suggest that chamber experiments that use a constant O₃ exposure may underestimate O₃ effects on biomass and yields.     

Effects of ozone on growth, yield and leaf gas exchange rates of four Bangladeshi cultivars of rice (Oryza sativa L.)

To assess the effects of tropospheric O₃ on rice cultivated in Bangladesh, four Bangladeshi cultivars (BR11, BR14, BR28 and BR29) of rice (Oryza sativa L.) were exposed daily to charcoal-filtered air or O₃ at 60 and 100 nl l⁻¹ (10:00-17:00) from 1 July to 28 November 2008. The whole-plant dry mass and grain yield per plant of the four cultivars were significantly reduced by the exposure to O₃. The exposure to O₃ significantly reduced net photosynthetic rate of the 12th and flag leaves of the four cultivars. The sensitivity to O₃ of growth, yield and leaf gas exchange rates was not significantly different among the four cultivars. The present study suggests that the sensitivity to O₃ of yield of the four Bangladeshi rice cultivars is greater than that of American rice cultivars and is similar to that of Japanese rice cultivars and that O₃ may detrimentally affect rice production in Bangladesh.     

Application of a Random Forest algorithm to predict spatial distribution of the potential yield of Ruditapes philippinarum in the Venice lagoon, Italy

We present a modelling framework that combines machine learning techniques and Geographic Information Systems to support the management of an important aquaculture species, Manila clam (Ruditapes philippinarum). We use the Venice lagoon (Italy), the first site in Europe for the production of R. philippinarum, to illustrate the potential of this modelling approach. To investigate the relationship between the yield of R. philippinarum and a set of environmental factors, we used a Random Forest (RF) algorithm. The RF model was tuned with a large data set (n = 1698) and validated by an independent data set (n = 841). Overall, the model provided good predictions of site-specific yields and the analysis of marginal effect of predictors showed substantial agreement among the modelled responses and available ecological knowledge for R. philippinarum. The most influent environmental factors for yield estimation were percentage of sand in the sediment, salinity, and water depth. Our results agree with findings from other North Adriatic lagoons. The application of the fitted RF model to continuous maps of all the environmental variables allowed estimates of the potential yield for the whole basin. Such a spatial representation enabled site-specific estimates of yield in different farming areas within the lagoon. We present a possible management application of our model by estimating the potential yield under the current farming distribution and comparing it to a proposed re-organization of the farming areas. Our analysis suggests a reduction of total yield is likely to result from the proposed re-organization.     

Response of winter wheat yield and soil microbial biomass to fertilization with ridge mulching-furrow planting in the dry highlands of the Loess Plateau北大核心CSCD

As the typical planting pattern of winter wheat in the dry highlands of the Loess Plateau, ridge mulching-furrow planting (RMFP) has played an important role in fertilizer efficiency of different fertilizers, and the differences in fertilizer efficiency further influence the diversity of the structure of soil microbial communities. The effects of different fertilization practices on winter wheat yield formation, soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), and soil microbial biomass phosphorus (SMBP) were investigated by field experiments during 2014-2016 in the winter wheat growing region of the dry highlands in southern Shanxi. The treatments included four groups, farmer fertilization (FF), monitoring fertilization (MF), monitoring fertilization combined application of manure (MFM), and monitoring fertilization combined application of bio-organic fertilizer (MFB). Results showed a significant increase in winter wheat yield by optimized and balanced fertilization, and the grain yield of MFB was highest among all treatments, with a value of 4 107-5 400 kg/hm2, which was 14.5%-23.2% (P < 0.05) higher than that of FF. The effects of different fertilization treatments on the winter wheat yield formulation mainly depended on spike number; however, no effect was found on kernel number per spike and 1 000-grain weight. Soil microbial biomass was affected by both growth period and fertilization patterns, i.e., the content of SMBC from jointing to flowering stage was highest during the winter wheat growth period, whereas the maximum values of SMBN and SMCP were found during the jointing stage. Changes in the rates of SMBC, SMBN, and SMBP during the entire growth period were less than 50%; however, the average contribution rate of optimized fertilization on SMBC, SMBN, and SMBP reached 90%. Compared to single chemical fertilizer applications, the combined application chemical fertilizer and manure or bio-organic fertilizer significantly improved the contents of SMBC, SMBN, and SMBP; however, the contents of SMBC and SMBN between MFM and MFB had no significant difference, whereas the SMBP of MFB was 19.8%-47.1% (P < 0.05) higher than that of MFM owing to the effect of mixed phosphorus bacteria. The soil microbial biomass C/N and C/P of the different treatments were 6.9-9.8 and 14.4-41.0, respectively, and maximum values occurred during the flowering stage. Given the above, the combined application of reasonable chemical fertilizer and bio-organic fertilizer can effectively improve the winter wheat yield and soil microbial biomass under RMFP cultivation in the dry highlands of the Loess Plateau. © 2018 Science Press. All rights reserved.     

Effects of planting density on the microclimate of rice population with different panicle-types and its yield components北大核心CSCD

Split-plot field experiments, with variety as the main plot, were designed to analyze the microclimate and character of R498 (curved panicle) and R499 (erect panicle) varieties of rice during the full heading day and on the 20th day after full heading. The planting densities assigned to the subplots were 0.23 m (line spacing) × 0.12 m (hole spacing), 0.27 m × 0.14 m, 0.33 m × 0.17 m, 0.38 m × 0.20 m, and 0.40 m × 0.21 m. The results showed that for all the planting densities, the maximum temperature of R499 increased by 1.52 ℃ on an average during the full heading stage, but decreased by 0.66 ℃ on the 20th day after full heading, in comparison to those of R498. The mean daily light intensities of R498 and R499 in sparse planting (0.38 m × 0.20 m, 0.40 m × 0.21 m) were higher than those of other planting density treatments during the full heading stage, being 43.56% and 16.22% higher, respectively, than that of the lowest daily light intensity. The daily light intensity of R498 was hindered by close planting (0.23 m × 0.12 m, 0.27 m × 0.14 m) while that of R499 was inhibited by sparse planting on the 20th day after the full heading stage. The rates of decrease of vertical light intensity of R498 and R499 in sparse planting were the highest among all the planting density treatments, their rates of decrease being 97.96% and 92.56%, respectively, during the full heading stage, and 94.81% and 91.10%, respectively, on the 20th day after the full heading stage. When the planting density was decreased, the variability of plant height, tiller number, and panicle curvature were greater for R499 than those of R498. The rates of incidence of sheath blight for R498 and R499 in the planting specification of 0.38 m × 0.20 m were 66.67% and 68.89%, respectively, which was the most serious among all the planting density treatments. On increasing the effective spike number and panicle weight, both R498 and R499 produced the highest yields with the planting specification of 0.27 m × 0.14 m, among all the planting density treatments. Even when the density was excessively reduced, the value of yield components did not increase any further. Thus, it is better to plant rice with curved panicles (R498) in a reasonable planting density (neither too close nor too sparse), and to plant rice with erect panicles in a reasonably close planting density. © 2018 Science Press. All rights reserved.