降雨-径流条件下混合层深度模拟试验

混合层深度是非点源污染模型中一个重要参变量,在模拟土壤溶质随地表径流迁移流失过程中,它决定了参与径流迁移的土壤溶质的范围及其具体流失量,为现有模型参数校正提供一定的数据支持。通过设计3种水文条件即自由排水状态（-5?cm）、土壤水分饱和状态和土壤渗流状态（5?cm）,采用人工模拟3种降雨强度（3,6和9?cm/h）,及同时分别外加模拟相对于降雨量的0,2,4和10倍径流量,研究土壤溶质迁移到地表径流过程中混合层深度。试验结果表明混合层深度与降雨强度呈线性增加关系;自由排水条件下,与地表径流量呈复杂正比例增加关系;土壤饱和条件和土壤渗流条件下,混合层深度与地表径流量均呈线性增加关系。研究结果发现混合层深度的实质是一个多向、复杂的动态溶质迁移变化量。     

不同栽培方式对马铃薯田间土壤温湿度及产量的影响

为了研究地膜覆盖和绿肥对提高我国西南高寒山区春播马铃薯田间耕层土壤温度和水分的影响,通过2009－2010年设置地膜覆盖和绿肥的不同处理,研究其对马铃薯田间土壤耕层温度、水分及产量的影响。结果表明：与传统栽培方式相比,播种后至封行前,地膜覆盖且施绿肥栽培方式和地膜覆盖栽培方式耕层土壤（0～20?cm）日平均温度提高3.6℃和2.9℃。地膜覆盖且施绿肥栽培方式、施绿肥栽培方式和地膜覆盖栽培方式田间土壤（0～21?cm）平均含水率提高了12.93%、6.3%和10.88%;封行后,地膜覆盖且施绿肥栽培方式和地膜覆盖栽培方式田间土壤平均含水率低6.35%和6.4%。地膜覆盖且施绿肥栽培方式和施绿肥栽培方式马铃薯的块茎产量增加25.6%和2.3%。因此,地膜覆盖且施绿肥栽培方式能显著地提高苗期耕层土壤温度、含水率和马铃薯的块茎产量。     

上层土壤厚度对模拟指流水分运动的影响

“上细下粗”的层状土壤中有可能产生指流,在有指流产生条件下,上层土壤的厚度是影响指流发展特征的主要因素之一。该试验通过在下层砂中模拟指流来研究上层土壤厚度对层状土壤中水分运动的影响。结果表明：指流域内的湿润锋到达一定深度的时间随着上层土壤厚度的增大而增加;稳定入渗率随着上层土壤厚度的增大而减小;并得出稳渗率和上层土的厚度呈线性关系;分别用经验函数模型和连续函数模型来模拟层状结构土壤水分的入渗,发现2种模型有各自的优缺点：经验函数模型虽然计算得到的整体误差较小,但在理论上不能很好的解释层状土壤水分入渗过程;连续函数模型相比较经验函数模型的缺点在试验初期误差较大,但该模型属于连续函数模型,符合实际的层状水分入渗过程。     

不同灌水下复合肥对冬小麦产量及农田净生态系统生产力的影响

合理灌溉和施用肥料是实现冬小麦节水增产增效的关键,该研究旨在为复合肥的大面积应用提供科学依据。2009～2010年,通过田间试验设置不同灌水与施肥水平,研究了不同灌水和施用量复合肥对冬小麦产量及农田净生态系统生产力（NEP）的影响。结果表明：各灌水施肥处理中,拔节期灌水60 mm、复合肥施肥水平1?350 kg/hm2时,冬小麦产量最大,为8?894.11?kg/hm2。在考虑施肥经济效益的前提下,不灌水、灌1水、灌2水下经济最佳施肥量分别为656、920.13与872.38 kg/hm2。常规施肥处理农田CO2排放量小于各复合肥处理;在冬小麦农田土壤呼吸作用强烈的拔节及灌浆期,拔节期灌水均能显著提高农田土壤CO2排放通量。考虑农田固碳,每公顷土地施复合肥1?800 kg处理最佳。     

室内模拟降雨条件下土壤水分入渗及再分布试验

降雨入渗对城市绿化、防洪排涝、农业生产等方面有着重要的意义。采用室内模拟降雨,使用时域反射仪采集相关数据,从土壤含水率变化特征和湿润锋运移特点等方面,研究了在垂向一维条件下不同雨强降雨对水分入渗的影响,探讨在降雨条件下土壤水分的再分布情况,从而确定试验所用砂壤土保水性最优土层范围。结果表明：降雨结束后,土壤水分的再分布主要受土水势控制,随着时间的延长,蒸发作用逐渐占据主导地位;试验所用砂壤土的最佳保水性土层深度为20～35 cm,可为植物的选栽提供参考。     

黄土塬区土壤水分分布特征及其对不同土地利用方式的响应

该文就陕西省长武黄土塬区主要土地利用方式下0～20 m土壤剖面水分分布特征及其与土壤质地的关系进行了调查与分析,以期服务于土地利用方式的优化配置及区域水文水资源研究。结果表明,黄土剖面古土壤层物理黏粒含量较黄土层高约2%～6%,质地较重;0～20 m剖面田间持水率和萎蔫湿度分别为(21.39±0.13)%和(8.06±0.45)%。黄土深层土壤水分分布特征与黄土-古土壤序列有关,一般情况下,一层黄土和一层古土壤构成一次湿度高低起伏,并有随深度增加湿度变大的趋势。荒草地、18年苹果园地、8年生及23年生苜蓿草地0～20 m土层平均湿度分别为18.89%、15.45%、14.77%和10.59%,连作高产小麦地0～13 m土层平均湿度为18.74%。高产麦田和荒草地3 m以下土层没有发生干燥化现象;18年苹果园地在10 m以上土层发生了中度和轻度为主的土壤干燥化现象;8年苜蓿草地在10 m以上土层发生了重度、中度和轻度的土壤干燥化现象,其中重度干燥化现象出现在4 m以上土层;而23年苜蓿在整个20 m土层都发生了重度和中度的土壤干燥化现象,其中重度干燥化现象出现在17 m以上土层。可以看出,高耗水型人工林草因水分负平衡所导致土壤干燥化,随年限增加渐进地向深层土层发展,这在苜蓿草地上表现的更为突出。     

Chemical fractionation of phosphorus in calcareous soils of Hamedan,western Iran under different land use

We investigated the effects of land uses on P distribution and availability in selected calcareous soils under different management practices. KCl‐P (labile P), NaOH‐P (Fe‐Al‐bound P), HCl‐P (Ca‐bound P), and residual P (Res‐P) fractions at 0–30 cm depth were determined for soils planted to garlic, orchard, pasture, potato, leafy vegetables, and wheat. Trends in P distribution between chemical fractions were similar between land uses. Ca‐bound P was the most abundant P fraction in the soils, constituting between 61% and 78% of the total P, whereas P associated with labile was less abundant (< 2%). Soils under leafy vegetables and wheat along with pasture presented the highest and lowest values in all fractions of P, respectively. Labile P generally was highest for leafy vegetables and potato. Labile P and Fe‐Al‐bound P comprised < 1.4% and 8% of total P, respectively. Residual P ranged from ≈ 14% (potato and garlic) to 31% (pasture). Long‐term fertilization increased P allocation to inorganic fractions, as Ca‐bound P contained 78% of total P for potato and garlic and 74% for leafy vegetables but 61% for pasture. A strong positive correlation between labile P and Fe‐Al‐bound P (r = 0.534, p < 0.01), labile P and Ca‐bound P (r = 0.574, p < 0.01), Ca‐bound P and Fe‐Al‐bound P (r = 0.504, p < 0.01), Olsen‐P and CaCl₂‐P (r = 0.821, p < 0.01) was found. Principal‐component analysis showed that the first four components accounted for most of the variation, 32.5%, 16.9%, 12.9%, and 7.9% of total variation, respectively.     

粤东凤凰山茶区土壤不同形态铅含量及其影响因素

通过对粤东凤凰山茶区12个大型茶园土壤和茶叶进行采样,采用连续提取法将茶园土壤Pb分为可交换态、碳酸盐结合态、铁锰氧化态、有机束缚态和残渣态,探讨茶园土壤Pb的5种化学形态分布与土壤理化性质、茶叶Pb含量的相关性关系。结果发现,土壤中Pb的5种化学形态分布的规律为残渣态〉铁锰氧化态〉交换态〉有机束缚态〉碳酸盐态。土壤有机质与可交换态Pb含量呈显著负相关,与碳酸盐结合态Pb呈极其显著负相关,而土壤pH值与土壤可交换态Pb呈显著负相关,与碳酸盐态Pb和有机束缚态Pb呈极其显著正相关。茶区12个茶园土壤样品的Pb生物有效性系数范围在0.029～0.113,平均值为0.061;Pb可迁移性系数范围在0.021～0.078,平均值为0.044。凤凰山茶叶Pb含量的范围在1.39～1.82 mg/kg之间,平均为1.56 mg/kg。茶叶中的Pb含量与土壤氧化物结合态Pb、有机束缚态Pb呈显著正相关,与土壤有机质呈极其显著正相关。     

Changes in water retention properties due to the application of sugar foam in red soils

This work describes the influence of the application of sugar foam (an organic residue from sugar beet industry) on water retention properties, over an extended period of time (>25 years), in two red soils in the La Mancha region of Spain. The properties of gravimetric moisture at field capacity, gravimetric moisture in the permanent wilting point and available water retention capacity both in the original soil - without the addition of sugar foam - and in the soil affected by the addition of sugar foam are compared. For this purpose, the profiles are characterised macro morphologically. Chemical, physical-chemical and mineralogical parameters are determined, in addition to determining the water retention curves of each soil with tensiometers and Richards pressure plates.The sugar foam applied to the soil altered its physical and chemical properties. An increase in contents of organic matter (3.5% versus 1.4%), calcium carbonate (40.8% versus 0%) and pH (8.2 versus 6.3) are observed in the superficial horizon of the studied soils, although there is no such significant increase in electrical conductivity (0.33 dS/m versus 0.25 dS/m). With regard to the physical properties, the depth of horizon A increases (32 cm versus 12 cm), the stoniness reduces (5% versus 25%), the structure is well developed, due to the texture becomes finer (silty versus sandy clay loam), and, finally, the bulk density reduces (0.79 g cm⁻³ versus 1.19 g cm⁻³).The gravimetric moisture at field capacity was 49% in the soil altered with sugar foam, versus 12% in the non-altered soil; the gravimetric moisture in the permanent wilting point was 14.5% versus 8% and the available water retention capacity was 34.5% and 4%, respectively. It can be concluded that the increase of calcium carbonate, organic matter and the reduction of bulk density are the most influential factors in this process. The scientific novelty of this work is that the hydro-behaviour of the soil due to the addition of sugar foam improves the characteristic values of moisture and, therefore, the agronomical qualities of the soil.     

Influence of water table level and soil properties on emissions of greenhouse gases from cultivated peat soil

A lysimeter method using undisturbed soil columns was used to investigate the effect of water table depth and soil properties on soil organic matter decomposition and greenhouse gas (GHG) emissions from cultivated peat soils. The study was carried out using cultivated organic soils from two locations in Sweden: Örke, a typical cultivated fen peat with low pH and high organic matter content and Majnegården, a more uncommon fen peat type with high pH and low organic matter content. Even though carbon and nitrogen contents differ greatly between the sites, carbon and nitrogen density are quite similar. A drilling method with minimal soil disturbance was used to collect 12 undisturbed soil monoliths (50 cm high, Ø29.5 cm) per site. They were sown with ryegrass (Lolium perenne) after the original vegetation was removed. The lysimeter design allowed the introduction of water at depth so as to maintain a constant water table at either 40 cm or 80 cm below the soil surface. CO₂, CH₄ and N₂O emissions from the lysimeters were measured weekly and complemented with incubation experiments with small undisturbed soil cores subjected to different tensions (5, 40, 80 and 600 cm water column). CO₂ emissions were greater from the treatment with the high water table level (40 cm) compared with the low level (80 cm). N₂O emissions peaked in springtime and CH₄ emissions were very low or negative. Estimated GHG emissions during one year were between 2.70 and 3.55 kg CO₂ equivalents m⁻². The results from the incubation experiment were in agreement with emissions results from the lysimeter experiments. We attribute the observed differences in GHG emissions between the soils to the contrasting dry matter liability and soil physical properties. The properties of the different soil layers will determine the effect of water table regulation. Lowering the water table without exposing new layers with easily decomposable material would have a limited effect on emission rates.