Critical loads mapping in Poland: Lessons learned

Since 1990 the Institute for Ecology of Industrial Areas, acting as National Focal Center, is actively involved in an international research programme aimed at the calculation and mapping of critical loads of acidifying compounds. Following the methodological guidelines elaborated under the leadership of UN/ECE Task Force on Mapping and Coordination Center for Effects, national maps of critical loads and their exceedances for acidity, sulphur and nitrogen have been produced. These maps have already been utilized in derivation of European maps of critical loads of acidity and sulphur submitted to the UN/ECE LRTAP Convention as scientific input to the negotiations on the Second Sulphur Protocol. The lessons learned from the critical loads mapping exercise can be summarized as follow:

石灰性紫色土渍水氧化还原状况的研究

本文通过模拟培育试验，研究了石灰性紫色土渍水状态下氧化还特征。结果表明，石灰性紫色土与普通紫色土，不饱和紫色土相比，不易向强还原状况发育，这些其富含碳酸钙和低量的活性铁有关；不同种类有机物料对其还原程度的影响是不同的；表征土壤氧化还原过程的强度因素Ｅｈ和数量因素还原性物质含理有很好的相关性，并与水稻的生长状况相一致，当土壤Ｅｈ小于－１００ｍＶ，还原物总量大于３．６３ｃｍｏｌ＾（＋）／ｋｇ时，土壤极     

Deforestation, tillage and cropping systems effects on seepage and runoff water quality from a Nigerian Alfisol

Conversion of tropical forest ecosystems to agricultural land use can have drastic impact on quality of natural waters as related to temporal changes in the sediment load and concentrations of dissolved nutrients. Long-term experiments were conducted in two phases to assess seepage and runoff water quality changes from an Alfisol owing to changes in land use in a sub-humid region of southwestern Nigeria. Phase I, from 1978 to 1981, studied the impact of deforestation and tillage methods, and Phase II, from 1982 to 1987, evaluated the impact of cropping systems and soil restorative practices. The six treatments evaluated in Phase I, involving combination of deforestation and tillage methods, were: (1) manual clearing (MC) with no-till (NT); (2) MC with plow-till (PT), which involved plowing to about 20 cm depth followed by harrowing; (3) shear blade (SB) clearing with NT; (4) treepusher-rootrake (TP) clearing with NT; (5) TP clearing with PT; (6) traditional farming (TF) involving slash-and-burn agriculture without use of fertilizer and amendments. The TF treatment was discontinued during Phase II. Therefore, the five treatments evaluated in Phase II were: (1) alley cropping with Leucaena leucocephala (Lam.) De Wit planted on the contour at 4 m interval; (2) restorative fallowing with mucuna (Mucuna utilis Lam.) on severely degraded soil; (3) mucuna fallowing on moderately degraded watersheds; (4) ley farming, involving establishment of pastures and grazing, on severely degraded watersheds; (5) ley farming on moderately degraded watersheds. Pastures included a mixture of Guinea grass (Panicum maximum Jacq.) and centro (Centrosema pubescens Benth). All treatments were imposed on watersheds of 2–4 ha each, and were replicated twice. Each watershed was equipped with a rate measuring H-Flume, a water stage recorder, a runoff sampler and a storage tank. In addition, a single lysimeter was installed in each treatment to monitor crop water use and nutrient transport in seepage water.Sediment concentration in water runoff was measured for both phases whereas nutrient concentrations in runoff and seepage waters were measured in Phase II only. Land clearing and tillage methods affected sediment concentration in runoff water. Mean sediment concentration during the first season after deforestation was 5.5 gl⁻¹ for MC and 9.7 gl⁻¹ for TP. Within the NT system, mean sediment concentration was 4.0 gl⁻¹ for MC, 3.9 gl⁻¹ for SB, and 8.0 gl⁻¹ for TP. Sediment concentration was also low for NT compared with PT, 5.3 gl⁻¹ vs. 9.1 gl⁻¹. Alley cropping decreased sediment concentration under maize (Zea mays L.) from 2.5 gl⁻¹ to 0.44 gl⁻¹. Mean sediment concentration was 4.3 gl⁻¹ under maize and 0.2 gl⁻¹ under cowpea (Vigna unguiculata L. Walp) with alley cropping, compared with 1.4 gl⁻¹ under maize and 0.04 gl⁻¹ under cowpea grown after pastures. There were seasonal and cropping system effects on sediment concentration. Both alley cropping and mucuna cover decreased sediment concentration. Nutrient concentration in runoff was influenced by cropping systems treatments, and was higher without than with alley cropping. Although the total runoff was less, nutrient concentration was greater in water runoff from pastures and mucuna fallow than from maize. The maximum nutrient concentrations were much higher in seepage water than in surface runoff. Manual clearing, no-till, alley cropping and use of cover crops decreased transport of sediments and dissolved elements in surface runoff and seepage water.     

黄土高原藓类生物结皮对表层土壤水分运动参数的影响

生物结皮普遍存在于干旱和半干旱地区土壤表层,对土壤水分有重要影响。为了进一步探究生物结皮对表层土壤水力学特性和水分运动过程的影响,该研究以黄土高原风沙土和黄绵土上发育的藓结皮为研究对象,通过野外采样与室内试验相结合,测定了藓结皮覆盖土壤和无结皮土壤的Boltzmann变换参数、土壤水分扩散率、入渗过程、比水容量和非饱和导水率,对比分析了有无藓结皮覆盖对表层土壤水分运动参数的影响。结果表明:藓结皮覆盖抑制了表层土壤水分的扩散,藓结皮覆盖土壤的Boltzmann变换参数和水分扩散率分别比无结皮土壤降低7.9%～27.3%和99.2%～99.6%;藓结皮覆盖后表层土壤渗透性显著降低,其水分入渗参数(初始入渗率、稳定入渗率、平均入渗率、累积入渗量)和非饱和导水率分别降低了17.1%～55.4%和84.8%～92.3%;藓结皮显著提升了表层土壤的持水和供水能力,藓结皮层的水分常数(田间持水量、萎蔫系数、重力水含量、有效水含量和易利用水含量)比无结皮土壤高40.9%～1 233.3%,土壤水吸力在100k Pa时的比水容量比无结皮土壤高7.4%～1 540.5%;相比黄绵土,藓结皮覆盖对风沙土的渗透性影响较小,而对土壤持水和供水性的影响较大。综上,黄土高原藓结皮覆盖降低了土壤渗透性,同时显著提高了表层土壤的水分有效性,这可能导致土壤表层在雨后截留较多水分,进而使土壤水分分布趋于浅层化,并改变该地区的土壤水分有效性和植物水分利用策略。     

连年秸秆覆盖对玉米产量及土壤微生物残体碳积累的影响

为明确连年秸秆覆盖对玉米产量及土壤微生物残体碳的影响,从而揭示秸秆覆盖条件下土壤有机碳积累的微生物学机制,该研究基于田间8 a长期定位小区试验,比较了不覆盖秸秆(CK)和覆盖秸秆(SM)两处理中玉米产量,同时利用一阶动力学模型对土壤(0～10 cm和10～20 cm)中有机碳、微生物残体碳及两者比例的年际变化进行了拟合。结果表明:1)秸秆覆盖在前5 a内没有显著提高玉米产量,第6年开始产量显著增加;在前2～3 a没有显著提高土壤有机碳和微生物残体碳含量;2)利用一阶动力学模型参数得到,SM处理显著提高了表层土壤有机碳、微生物残体碳以及两者比例的最大值,较CK处理分别高12%、39%、6%;3)SM处理显著延长了表层土壤有机碳、微生物残体碳以及两者比例达到最大值的时间,较CK处理分别多13、12和2.5 a,然而SM处理并没有显著影响下层土壤有机碳、微生物残体碳及两者比例的变化。因此,秸秆覆盖能够通过显著提高表层微生物残体碳及其对土壤有机碳的贡献,进而有利于对整个耕层土壤有机碳的固持。     

水耕年限对黄棕壤发育的水稻土的表面化学性质的影响

利用采自江苏省农业科学院果园的旱地黄棕壤(对照)和由黄棕壤发育水耕20年和60年的水稻土,研究了土壤黏粒和粉粒的矿物组成,胶体和土体的化学性质随水耕年限的变化.粉粒的X-射线衍射图谱表明,3种供试土壤发育母质相似,胶体的矿物组成随水耕年限的变化不大.动电电位和表面负电荷的测定结果也表明,胶体表面化学性质未发生明显变化.随水耕年限增加,土壤黏粒含量降低,导致土体性质发生明显变化,土壤CEC和结构电荷量随水耕年限增加显著减少.     

模拟酸雨对红壤稀土元素释放的影响研究

模拟酸雨作用下红壤中稀土元素的释放水平大小依次为Pr＞Ce＞Nd＞Tb＞Sm＞La＞Er＞Ho＞Gd＞Dy＞Eu＞Y＞Lu≈Yb,轻稀土元素的释放水平要高于重稀土元素.酸雨对稀土元素的释放有明显的促进作用,且不同元素的CAR1/CCK、CR2/CCK比较接近(CAR1、CAR2和CCK分别表示pH4.5的酸雨、pH3.5的酸雨和对照3种情况下淋出液中稀土元素的含量).CAR1/CCK介于1.43～1.93之间,平均为1.61;CAR2/CCK介于1.76～2.27之间,平均为2.06,经过9 150～10 650 mm的模拟酸雨淋溶以后,pH4.5的酸雨使稀土总累积释放量平均提高37.61%,pH3.5的酸雨使稀土总累积释放量平均提高78.05%.稀土总释放量与Fe、Mn的释放量相关分析表明:多数红壤稀土总释放量与Fe、Mn的释放量呈显著或极显著性相关.初步推断红壤中的稀土释放可能是由于吸附载体Fe-Mn氧化物因H 的输入而解离所致.     

Landscape-scale soil quality change under different farming systems of a tropical farm in Hainan, China

Abstract. The impact of different tropical farming systems on soil quality was examined using a systematic sampling strategy. Total organic C, pH, extractable P, exchangeable K, bulk density, water stable aggregates, microbial biomass C, cation exchange capacity, soil depth, and clay content were determined. An assessment framework, including a minimum data set, linear scoring functions and weighted additive indices, was used to evaluate the soil quality of a tropical farm growing various crops in Hainan, China. Soil quality was evaluated according to four functions: water availability, nutrient availability, rooting suitability, and erosion resistance. Our results showed that soils were intrinsically lacking in nutrients and vulnerable to degradation, and that these problems were exacerbated by inappropriate management. There was strong evidence that long-term rubber farming caused soil acidification, soil compaction, and depletion of organic matter and nutrients. By contrast, conservation practices in coffee plantations protected or improved organic matter concentration and soil structure, resulting in higher soil quality indices.     

PH对红壤微生物生物量碳和生物量磷的影响

The impact of pH changes on microbial biomass carbon (Cmic) and microbial biomass phosphorus (Pmic) were examined for 3 red soils under citrus production with different lengths of cultivation. Soil pH significantly affected Cmic and Pmic. The Cmie and Pmic changes, as a function of soil pH, appeared to follow a normal distribution with the original soil pH value at the apex and as pH increased or decreased compared to the original soil pH, Cmic and Pmic declined. Moreover, there were critical pH values at both extremes (3.0 on the acidic side and 8.0 to 8.5 on the alkaline side), beyond which most of microorganisms could never survive. The effect of pH on Cmic and Pmic was also related to the original soil pH. The higher the original soil pH was, the less Cmic or Pmic were affected by pH change. It is suggested that soil microorganisms that grow in a soil environment with a more neutral soil pH range (i.e. pH 5.5-7.5) may have a greater tolerance to pH changes than those growing in more acidic or more alkaline soil pH conditions.     

树脂包膜尿素在稻田中的释放特征及与积温的关系

为了缓解农村劳动力短缺和适应农业机械化耕作的需要,水稻一次性施肥技术显得十分重要。该文采用埋袋法研究了一种用于一次性基施的树脂包膜尿素在水稻生长期内的释放规律,并对其释放与温度关系建立了数学模型。结果表明该树脂包膜尿素在稻田中释放80%的养分所需时间比标注的长。在水稻整个生育期内,其累计释放率可达到69%~83%。该树脂包膜尿素在田间的释放过程不存在明显的迟滞期,可分为快速释放阶段和缓慢释放阶段,且日均释放率为0.5%。其累计释放率与水稻移栽天数可用二次项方程描述。尽管试验地土壤相对含水率存在差异(60%~100%),但养分的累计释放率与气温积温和15 cm深处土壤积温显著相关(R~2=0.964和0.983)。这可为在不同气候条件下确定控释肥的施用量并掌握其释放情况提供一定的参考。