Sulfate and Calcium Movement in an Allophanic Soil—The Relevance of Ion‐Pair Adsorption in the Soil–Plant System

Cooperative adsorption involving anions and cations, termed ion‐pair adsorption (IPA), is reported to increase the retention of some ions in certain soils. Sulfate and calcium can exhibit such interaction, and this affects their movement through the soil. Ion‐pair adsorption is shown here in miscible displacement experiments with a variable‐charge soil. The relevance of IPA under more realistic conditions is further investigated in a pot experiment. Rapeseed (Brassica napus) was grown at two different irrigation regimes and with two sulfur fertilizer sources. Calcium sulfate (CaSO₄·2H₂O) was used to induce IPA in contrast to potassium sulfate (K₂SO₄). The results suggest that IPA reduces sulfate and calcium leaching only in the short term. Continued irrigation dissipates the differences between the two fertilizer sources. Final soil ion concentrations and the plant uptake could not be related to IPA, evidencing the short‐term relevance of IPA. The influence of IPA on the bioavailability of calcium and sulfate to plants still demands further study.     

稀土壳聚糖螯合盐对水产颗粒饲料性能的影响

研究了在饲料中添加稀土壳聚糖螯合盐（ＲＥＣＣ）对水产颗粒饲料性能的影响。根据鲫（Ｃａｒａｓｓｉｕｓａｕｒａｔｕｓ）鱼苗的营养需求配制４种类型的ＲＥＣＣ试验日粮，即１号饲料（０．００％）、２号饲料（０．０８％）、３号饲料（０．１６％）和４号饲料（０２４％）。测定４种饲料的粉化率和溶失率。结果显示，添加稀土壳聚糖螯合盐后可以降低饲料的 粉化率，饲料中添加０．１６％的稀土壳聚糖螯合盐效果尤其明显（Ｐ＜０．０１）；在饲料中添加ＲＥＣＣ可以显著降低饲料的溶失率（Ｐ＜０．０５），并可以提高和改善水产颗粒饲料的性能。     

Effects of grazing strategy on limiting nitrate leaching in grazed grass‐clover pastures on coarse sandy soil

Urinations of ruminants on grazed pastures increase the risk of nitrate leaching. The study investigated the effect of reducing the length of the grazing season on nitrate leaching from a coarse sandy, irrigated soil during 2006–2007 and 2007–2008. In both years, precipitation was above the long‐term mean. The experiment was initiated in a 4‐yr‐old grass‐clover sward in south Denmark. Three treatments were as follows grazing only (G), spring cut followed by grazing (CG) and both spring and autumn cuts with summer grazing (CGC). Nitrate leaching was calculated by extracting water isolates from 80 cm depth using ceramic suction cups. Because of considerable variation in measured nitrate concentrations, the 32 installed suction cups per treatment were insufficient to reveal differences between treatments. However, weighted nitrate leaching estimations for G, CG and CGC showed estimated mean nitrate N concentrations of 23, 19 and 13 mg/L for an estimated proportion area occupied by urine patches of 0.33, 0.26 and 0.16, respectively. Thus, N concentrations in G and CG exceeded the EU limit of 11.3 mg N/L. Under the prevailing conditions, the time of urination did not appear important. The estimated background leaching calculated from suction cups presumably not situated under urine patches resulted in mean nitrate N concentrations of 2.6 mg/L.     

Nitrate leaching losses under Miscanthus grass planted on a silty clay loam soil

Abstract. Nitrate leaching under newly planted Miscanthus grass was measured for three years. The crop received either no fertilizer-N or an annual spring application of 60 kg or 120 kg N ha^-1. During three winters soil water was collected from porous cup probes installed 90 cm deep. Nitrate leaching was calculated from the mean drain flow recorded in two drain gauges multiplied by the mean nitrate-N concentration in the soil water solutions collected. In the first year soil water nitrate concentrations were high on all treatments and N losses were 154, 187 and 228 kg ha^-1 respectively on the unfertilized treatment and those that received 60 or 120 kg N ha^-1. Leaching losses in the second and third years were, in turn, 8, 24 and 87 kg ha^-1 and 3, 11 and 30 kg ha^-1 for the unfertilized treatment and for the 60 and 120 kg N ha^-1 treatments respectively. Leaching losses were closer to those recorded under extensively managed grassland than arable land. The large losses in the first year were probably due to the previous agricultural management at the site and excessive inputs of N on the fertilized plots. In the second and third year, lower drainage volumes may also have influenced losses. The results show that Miscanthus , once established, can lead to low levels of nitrate leaching and improved groundwater quality compared with growing arable crops.     

喀斯特地区泡核桃林土壤酶、微生物量及无机氮的动态研究

【目的】泡核桃林的土壤质地是决定核桃产量的重要因素。开展喀斯特地区泡核桃林土壤肥力状况及微生物群体功能年际变化的研究，不仅有助于指导泡核桃科学高效地生产，而且能为该地区的石漠化治理、土地修复实践提供理论基础。【方法】对喀斯特地区不同种植年限（4、5、6、7 年）泡核桃林土壤酶活性、微生物生物量（碳、氮）及无机氮（硝态氮、铵态氮）的变化及其相关性进行测定和分析。【结果】（1）泡核桃种植 5、6 年后，土壤酶活性普遍高于种植 4、7 年。（2）随着种植年限的增加，微生物量碳呈先增后降的趋势，而微生物量氮逐渐增加，且种植 5、6、7 年后差异不显著；泡核桃种植 4 年后的微生物量碳氮含量均极显著低于其他年限。（3）随着种植年限的增加，铵态氮含量呈波动式变化，硝态氮先增后减，且种植 6 年后的硝态氮含量极显著高于其他年限处理。（4）酶活性、微生物量和无机氮含量均随着土层深度（0~10、10~20、20~30 cm）的增加而降低，显示出明显的“表聚现象”。（5）酶活性、微生物量和无机氮含量三者之间具有不同程度的相关性。【结论】总体来看，泡核桃林的建立有利于喀斯特地区的土壤发育。在泡核桃种植 7 年后，应注重水肥管理以提升泡核桃果实的质量，同时为该区的生态恢复提供基础条件。     

Nitrate leaching in a silage maize field under different irrigation and nitrogen fertilizer rates

Quantification of the interactive effects of nitrogen (N) and water on nitrate (NO₃) loss provides an important insight for more effective N and water management. The goal of this study was to evaluate the effect of different irrigation and nitrogen fertilizer levels on nitrate-nitrogen (NO₃-N) leaching in a silage maize field. The experiment included four irrigation levels (0.7, 0.85, 1.0, and 1.13 of soil moisture depletion, SMD) and three N fertilization levels (0, 142, and 189 kg N ha⁻¹), with three replications. Ceramic suction cups were used to extract soil solution at 30 and 60 cm soil depths for all 36 experimental plots. Soil NO₃-N content of 0-30 and 30-60-cm layers were evaluated at planting and harvest maturity. Total N uptake (NU) by the crop was also determined. Maximum NO₃-N leaching out of the 60-cm soil layer was 8.43 kg N ha⁻¹, for the 142 kg N ha⁻¹ and over irrigation (1.13 SMD) treatment. The minimum and maximum seasonal average NO₃ concentration at the 60 cm depth was 46 and 138 mg l⁻¹, respectively. Based on our findings, it is possible to control NO₃ leaching out of the root zone during the growing season with a proper combination of irrigation and fertilizer management.     

Bracken effects on inorganic nitrogen leaching from an upland podzol

Leaching of inorganic N species to stream waters from upland areas of the UK is increasing, reflecting the increases in atmospheric deposition of nitrogen species due to increased levels of vehicular emissions. Bracken cover in UK uplands is also increasing overall ( Taylor, 1986 ), and the architectural nature of bracken has been shown to both increase deposition of atmospheric constituents to soils and change their chemical and physical nature. We have tested the nutrient status of upland podzols from the Lake District, Cumbria, UK, from under both moorland grass and bracken. The results show reduced levels of base cations and nitrate throughout the profile and decreases in the organic matter content of surface horizons as a consequence of bracken encroachment. We also report increased ammonium concentrations in lower soil horizons under bracken, possibly leading to increased leaching to stream waters. These results suggest either increased leaching of soil nutrients due to bracken encroachment or increased storage of nutrients within the bracken rhizome system. Results also suggest changes in either microbial activity or the microbial community of podzols, possibly due to the allelopathic nature of bracken. This may have caused changes in the soil nutrient dynamics, possibly accounting for some of the changes seen. We hypothesize that increased bracken cover within the British uplands has the potential to increase leaching of inorganic nitrogen to upland streams.     

榨菜生长过程中硝酸盐分布规律初研

按照榨菜的正常播种时间和生长季节,连续3 a对榨菜移栽苗、返青苗、榨菜茎膨大初期、膨大期、成熟期及雨水节后期按GB/T 15401-94方法进行了硝酸盐含量的测定,从900多个检测数据中发现了硝酸盐蓄积量从移栽到成熟过程中的分布规律.     

水载型木材防腐剂有效成分的加速固着方法

以铬化砷酸铜(CCA)为代表的水载型防腐剂,逐渐被其他主要有效成分为铜的水载型防腐剂取代,这类防腐剂中的.针对水载型防腐剂抗流失性差的缺点,介绍4种用于加速防腐剂中有效成分在木材中固着的方法,分析了这些方法对水载型防腐剂中有效成分的固着效果,并就如何加速ACQ中有效成分的固着研究进行了分析和展望.