模拟强降雨条件下硝态氮在土壤剖面的累积及淋溶研究

[目的]为了探讨硝态氮在土壤中累积和淋溶水平。[方法]采用野外冬小麦田间试验,选定不同降雨强度和施肥水平,分析土壤不同深度水分含量和硝态氮含量。[结果]降雨强度和土壤施肥水平是有效影响土壤氮素在土壤中运移和淋溶的重要因素,表现在:土壤降雨强度越大,施肥水平越高,会造成土壤中主要氮素类型硝态氮明显的流失。此外,土壤质地类型也是造成土壤氮素流失的重要因素,表现为土壤质地砂性越强,其淋溶效果越明显。[结论]土壤施肥水平和降雨强度是影响土壤氮素流失的重要因素。     

模拟雨水连续淋洗下土壤化学性状动态变化特征的研究

本文从研究正常降雨对土壤性状的影响出发,进行了模拟雨水对酸性紫色土和石灰性紫色土的连续淋洗试验。试验结果表明在模拟雨水连续淋洗150天的过程中,土壤中钙、镁、钾、钠等盐基离子几乎都显示出一定程度的净淋溶特征,土壤中各盐基离子的动力学变化特征几乎都与抛物线扩散方程吻合。淋洗结束后土壤酸度未发生显著变化,但两种土壤CEC值均有所降低。     

Conservation tillage and macropore factors that affect water movement and the fate of chemicals

A thorough understanding of how conservation tillage influences water quality is predicated on knowledge of how tillage affects water movement. This paper summarizes the effects of conservation tillage on water movement and quality mainly based on long-term experiments on Luvisols at the North Appalachian Experimental Watershed near Coshocton, OH, USA. Conservation tillage can have a much larger effect on how water moves through the soil than it does on the total amount percolating to groundwater. Soil macroporosity and the proportion of rainfall moving through preferential flow paths often increase with the adoption of conservation tillage and can contribute to a reduction in surface runoff. In some medium- and fine-textured soils most of the water that moves to the subsoil during the growing season (May–October) is probably transmitted by macropores. If a heavy, intense storm occurs shortly after surface application of an agricultural chemical to soils with well-developed macroporosity, the water transmitted to the subsoil by the macropores may contain significant amounts of applied chemical, up to a few per cent, regardless of the affinity of the chemical for the soil. This amount can be reduced by an order of magnitude or more with the passage of time or if light rainstorms precede the first major leaching event. Because of movement into the soil matrix and sorption, solutes normally strongly adsorbed by the soil should only be subject to leaching in macropores in the first few storms after application. Even under extreme conditions, it is unlikely that the amount of additional adsorbed solute transported to groundwater will exceed a few per cent of the application when conservation tillage is used instead of conventional tillage. In the case of non-adsorbed solutes, such as nitrate, movement into the soil matrix will not preclude further leaching. Therefore, when recharge occurs during the dormant season thorough flushing of the soil, whether macropores are present or not, can move the remaining solutes to groundwater. Thus, the net effect of tillage treatment on leaching of non-adsorbed solutes should be minimal.     

Impact of sod-cutting and choppering on nutrient budgets of dry heathlands

Heathlands are endangered by both atmospheric nutrient deposition and natural succession. High-intensity management measures are considered necessary, as low-intensity measures (e.g. mowing, prescribed burning) are not able to compensate for atmospheric nutrient loads. Choppering (i.e. the near-complete removal of the O-layer) has several advantages over sod-cutting, including less waste material, faster vegetation recovery and lower costs. This raises the question addressed in this study as to the extent to which choppering and sod-cutting affect nutrient budgets in dry heathlands.We compared the quantities of N, Ca, K, Mg, and P removed by choppering and sod-cutting in the Lueneburg Heath (NW Germany). Nutrient balances were calculated by analysing atmospheric inputs, elevated leaching rates following management, and output due to the removal of above-ground biomass and humus horizons.Nutrient loss was particularly high after removal of O- and A-horizons. In contrast, increased leaching after management was of minor importance for nutrient budgets. Although considerably more nutrients were removed by sod-cutting than by choppering (e.g. N: 1712/1008 kg ha⁻¹), nutrient output by choppering was still sufficient to compensate for 60.7 years of net N-input. Choppering was able to remove more N per volume unit than sod-cutting due to higher N-contents in the organic layer than in the A-horizon. For this reason, choppering is more economical than sod-cutting and, thus, should be considered the preferable method at sites not dominated by Molinia caerulea. A combination of high-intensity measures with prescribed burning would appear to be suitable as this would ensure more selective removal of N.     

Release Rates of Ammonium‐Nitrogen,Nitrate‐Nitrogen,Phosphorus, Potassium,Magnesium, Iron,and Manganese from Seven Controlled‐Release Fertilizers

Abstract

Samples of seven controlled‐release fertilizers, Nutricote Total 13–13–13, Nutricote Total 18–6–8, Osmocote Plus 15–9–12, Osmocote 13–13–13, Polyon 18–6–12, Polyon 14–14–14, and Plantacote 14–8–15, were placed in leaching columns containing acid‐washed sand. Samples of all leachates were analyzed weekly to determine release rates of ammonium‐nitrogen (N), nitrate‐N, phosphorus (P), potassium (K), magnesium (Mg), manganese (Mn), and iron (Fe). Release rates for P from all products were slower than those for NH₄‐N, NO₃‐N, and K. Release of Mg, Mn, and Fe was very poor, with less than 50% of the total amount of each of these elements ever being released from the prills for some products. Nutricote products released Fe and Mn more effectively than did Osmocote or Plantacote.     

五味子果汁饮料的研制

[目的]研制具有五味子特色口味的果汁饮料。[方法]以五味子浆果果汁为原料,应用常温浸提法、絮凝澄清技术和超高压技术制备五味子果汁饮料。[结果]确定了五味子果汁的澄清条件：絮凝剂为壳聚糖,添加量为0.05 g/L,处理时间为4.0 h。在该条件下,五味子果汁的透光率达99.99%,pH为2.82,总酚含量为0.232 mg/ml。储存试验证明,五味子果汁饮料经澄清处理,饮料的稳定性优于原始饮料。[结论]应用常温浸提技术、絮凝澄清技术和超高压技术可以生产出具有五味子特色的果汁饮料。     

Soil salinity in Aceh after the December 2004 Indian Ocean tsunami

The 2004 Indian Ocean tsunami inundated about 37,500 ha of coastal farmland in Aceh, and crops planted after the tsunami were severely affected by soil salinity. This paper describes the changes of soil salinity over time on tsunami affected farms and the implications for resuming crop production after natural disasters.Soil salinity and salt leaching processes were assessed across the tsunami affected region by measuring soil apparent electrical conductivity (ECa) using an electromagnetic induction soil conductivity instrument (EM38) combined with limited soil analysis. The ECa was measured 5 times between August 2005 and December 2007 in both the vertical (EMv) and horizontal (EMh) dipole orientations at 23 sites across Aceh. The level of salinity and direction of salt movement were assessed by comparing changes in mean profile ECa and relative changes in EMv and EMh.Eight months after the tsunami the average soil salinity in the 0-1.2 m soil depth varied from ECe 22.6 to 1.6 dS m⁻¹ across sites in the affected region and three years after the tsunami it varied from 13.0 to 1.4 dS m⁻¹. Soil salinity tended to be higher in rice paddy areas that trapped saline tsunami sediments and held seawater for longer periods. Leaching of salts occurred slowly by both vertical displacement and horizontal movement in surface waters. Hence, soil salinity persisted at a level which could reduce crop production for several years after the 2004 tsunami. High soil salinity persisted three years after the tsunami even though there had been more than 3000-7000 mm of accumulated rainfall to leach salts. The slow leaching is likely to have been due to the loss of functional drainage systems and general low relief of the affected areas.Monitoring of soil salinity with EM38 assisted local agricultural extension agencies to identify sites that were too saline for crops and determine when they were suitable for cropping again. The methodology used in this study could be used after similar disasters where coastal agriculture areas become inundated by seawater from storm surges or future tsunamis.     

Phosphorus balance and risk assessment in the rice–canola cropping system under different drainage strategies

This research was conducted to quantify total phosphorus (TP) losses in poorly drained-consolidated paddy fields equipped with different surface and shallow subsurface drainage systems including drain depth of 0.9 m and drain spacing of 30 m (D_0.9L₃₀), drain depth of 0.65 m and drain spacing of 30 m (D_0.65L₃₀), drain depth of 0.65 m and drain spacing of 15 m (D_0.65L₁₅), drain spacing of 15 m and drain depths of 0.65 and 0.9 m as alternate depths (Bilevel). Typical surface drainage system of consolidated paddy fields was also considered as conventional practice of the study area (control). The subsurface drained fields were under year-round crop production of rice-canola, while the surface drained fields experienced only rice cropping once a year. During three rice-canola-rice growing seasons, TP losses through drainage and leaching in the D_0.9L₃₀, Bilevel, D_0.65L₃₀, D_0.65L₁₅ and control treatments were respectively, 1.12, 0.98, 1.44, 1.53 and 24.48 kg ha^?1, equivalent to about 3.9%, 3.4%, 5.1%, 5.3% and 85.7% of applied triple superphosphate fertilizer. In the rice growing seasons, TP losses through surface runoff were higher than those through subsurface drainage effluents. Shallow subsurface drainage systems were promising for the study area compared surface drainage as phosphorus risks were reduced by 79%, 77%, 64% and 57% through D_0.9L₃₀, Bilevel, D_0.65L₃₀ and D_0.65L₁₅, respectively. These results demonstrated that, by providing suitable condition for winter cropping, subsurface drainage systems can diminish concerns related to phosphorus losses from poorly drained paddy fields in the north of Iran.     

Comparisons of terrestrial and aquatic bioassays for oil-contaminated soil toxicity

Background  Petroleum products are widely used in various sections of industry and they are one of the most abundant sources of environmental contamination. These products are classified by their physico-chemical properties such as boiling point, density and viscosity. Oil contamination in the environment is primarily evaluated by measuring the chemical concentrations of petroleum products in the solid or water phase. The results of chemical analyses do not correspond directly with the harmful environmental effects of petroleum products on the soil flora and fauna, because the interactions between oil compounds and the production of their methabolites in soil are not measured in chemical assessments. These kinds of effects of complex chemical mixtures in soil can be estimated by bioassays. Therefore, ecotoxicological tests are important for estimating soil quality in the risk assessment of oil-contaminated soil sites. Objectives  The objective of this study was to examine the oil-contaminated soil site of a closed petrol station with both chemical and ecotoxicological methods. The goals of this study were to compare the sensitivity of the terrestrial and aquatic bioassays and to compare the toxicity responses of aquatic bioassays determined from three different extraction procedures. In addition, our aim was to characterise a cost-effective battery of bioassays that could be applied to a comparison of oil-contaminated soils. It was in our interest to investigate oil-contaminated soil with oil concentrations of 2500–12000 mg/kg and to find out the possible differences between terrestrial and aquatic toxicity tests. Methods  Six soil samples from a closed petrol station were examined for toxicity with terrestrial and aquatic tests. Terrestrial tests includedEnchytraeus albidus survival and reproduction assays and seed germination assays using wheat, cress, lettuce, and red clover seeds and growth inhibition assays of onions. The toxicities of the water-extractable fractions of the soil samples obtained from three different extractions were tested with aquatic bioassays based on plants (onion and duckweed growth inhibition tests), microbes (luminescent bacteria test), and enzyme inhibition (reverse electron transport test, RET). Chemical analyses of the solid samples were carried out simultaneously. Results. Oil concentrations ranged from 2500 to 12000 mg/kg, BTEX varied from 300 to 2800 mg/kg, and fuel additives: MTBE and TAME from 0.0 1 to 260 mg/kg. Only the sample contain-ing 12000 mg/kg oil had a significant toxic impact on all test organisms. Soil samples with oil concentrations 2500–6200 mg/ kg had no or only slight adverse effects on the test organisms with one exception, theE. albidus reproduction test. TheE. albidus survival and reproduction tests were the most sensitive bioassays of the terrestrial tests, and the luminescent bacteria test of the aquatic tests.     

Adaptive optimization of crop production and nitrogen leaching abatement under yield uncertainty

The study develops a bio-economic crop management model that internalizes the environmental cost of nitrate pollution, accounts for stochastic weather, and includes an option for split fertilization. The integrated model is designed to indicate whether a producer can benefit from applying fertilizer several times during the growing season, in response to crop needs, rather than a single time, at sowing. The model is parameterized for the cultivation of spring malting barley (Hordeum vulgare L.) in Southern Finland. The costs of negative externalities from nitrogen leaching are internalized in the landowner’s decision problem through a pollution tax. The results indicate that without a pollution tax a single application of fertilizer gauged to meet the needs of the entire season is optimal. With a tax, the benefits of split application - applying varying amounts of fertilizer at selected stages of the growing season - increase significantly. In comparison to a single application of fertilizer at sowing, split fertilization improves yields, increases the total amount of fertilizer used, and reduces nitrogen leaching.