赤红壤有效磷分级指标的研究

用盆栽试验方法得到玉米幼苗干物质相对积累量与赤红壤土壤有效磷含量的关系曲线可以用一元二次响应方程来拟合,土壤Olsen P含量的响应方程为:y=-0.4831x2+13.88x+2.664,决定系数为0.9555**;土壤Mehlich 3 P含量的响应方程为:y=-0.2621x2+9.4821x+18.891,决定系数为0.9400**。赤红壤区的土壤有效磷分级指标为:Olsen P,小于4.0 mg kg-1为"极低",4.0~6.8 mg kg-1为"低",6.8~10.5 mg kg-1为"中",大于10.5 mg kg-1为"高";Mehlich 3 P,小于3.6mg kg-1为"极低",3.6~7.5 mg kg-1为"低",7.5~12.0 mg kg-1为"中",大于12.0 mg kg-1为"高"。     

控释肥残膜对小麦各生育期土壤微生物和酶活性的影响

为了探明控释肥树脂残膜对土壤环境可能造成的影响,采用小麦池栽试验研究了控释肥树脂残膜对土壤有关微生物数量和酶活性的影响。结果表明,控释肥树脂残膜使土壤细菌和放线菌数量分别相对增加了19.01%～62.87%和17.03%～132.39%,土壤脲酶、转化酶、中性磷酸酶活性分别提高了17.39%～85.71%、31.77%～158.40%、35.14%～189.47%,但对过氧化氢酶活性无明显影响。施肥处理（施肥不施残膜和施肥施残膜处理）显著增加了土壤转化酶和中性磷酸酶活性;但对土壤细菌和放线菌数量、过氧化氢酶和脲酶活性没有显著影响。控释肥树脂残膜施用量在90～360g/m2 范围内,对土壤细菌和放线菌数量以及有关土壤酶活性没有产生不良影响。     

小麦–玉米轮作体系长期施肥对塿土微生物量碳、氮及酶活性的影响

以20年塿土小麦玉米轮作体系长期肥料定位试验为平台,探讨不同施肥模式下土壤化学肥力要素、微生物量碳氮及酶活性的响应。试验包括不施肥（CK）、单施氮肥（N）、氮磷（NP）、磷钾（PK）、氮磷钾（NPK）、NPK+秸秆（SNPK）以及不同量有机肥+NPK（M1NPK、M2NPK）等8种施肥模式。结果表明,与CK相比,长期施用NP提高土壤有机碳含量达34.0%、全氮34.0%、全磷58.5%、速效磷608.9%、微生物量碳23.3%、微生物量氮54.0%、蔗糖酶53.9%、脲酶132.6%、碱性磷酸酶29.9%以及脱氢酶40.9%。长期施用NPK与NP效果相似,钾素效果甚微。作物秸秆还田配合氮磷钾化肥与氮磷钾相比没有明显影响土壤有机碳、氮和磷水平,但是显著提高微生物量碳的含量（29.5%）、碱性磷酸酶（23.0%）和脱氢酶（26.9%）的活性。有机肥配合氮磷钾与其它施肥处理相比,显著提升土壤化学肥力要素、微生物量碳氮和酶活性,特别是引起了磷素的大量富集（速效磷含量大于150 mg/kg）。因此,塿土不施有机物情况下,氮磷配合可以提高土壤化学和生物肥力,作物秸秆还田配合氮磷钾化肥的培肥效果优于氮磷钾化肥配合,而合理的有机无机肥配合是塿土提升化学肥力和保证生物健康的最佳施肥模式。     

不同磷效率油菜根际土壤磷活化机理研究

筛选和培育耐低磷植物是缓解磷矿资源缺乏和提高磷肥利用效率的有效途径之一。本研究在前期材料筛选的基础上,通过根箱试验研究不同磷效率油菜根际土壤磷活化机理,其结果如下:在施磷和不施磷处理条件下,磷高效油菜品种B56（HG）的吸磷量和生物量均高于磷低效品种B10（LG）;两油菜品种根际土壤中的NaHCO3-Pi, NaHCO3-Po和 NaOH-Pi,NaOH-Po四种磷素形态均有显著的亏缺现象;磷高效品种（HG）根际土壤上述四种磷素形态亏缺程度大于磷低效品种（LG）,但Resin-P则出现富集,并且HG的富集程度大于LG,这可能与HG具有较高吸磷能力有关。两油菜品种根际土壤HCl-Pi 和 残渣态磷（Residual-P）没有发生明显的亏缺现象。相比较而言,HG能分泌更多的酸性磷酸酶,该酶活性与NaHCO3-Po含量呈显著的负相关,说明酸性磷酸酶对有机磷矿化起着非常重要的作用。     

Considering sink strength to model crop production under elevated atmospheric CO2

Climatic changes and elevated atmospheric CO₂ concentrations will affect crop growth and production in the near future. Rising CO₂ concentration is a novel environmental aspect that should be considered when projections for future agricultural productivity are made. In addition to a reducing effect on stomatal conductance and crop transpiration, elevated CO₂ concentration can stimulate crop production. The magnitude of this stimulatory effect (‘CO₂ fertilization’) is subject of discussion. In this study, different calculation procedures of the generic crop model AquaCrop based on a foregoing theoretical framework and a meta-analysis of field responses, respectively, were evaluated against experimental data of free air CO₂ enrichment (FACE) environments. A flexible response of the water productivity parameter of the model to CO₂ concentration was introduced as the best option to consider crop sink strength and responsiveness to CO₂. By varying the response factor, differences in crop sink capacity and trends in breeding and management, which alter crop responsiveness, can be addressed. Projections of maize (Zea mays L.) and potato (Solanum tuberosum L.) production reflecting the differences in responsiveness were simulated for future time horizons when elevated CO₂ concentrations and climatic changes are expected. Variation in future yield potential associated with sink strength could be as high as 27% of the total production. Thus, taking into account crop sink strength and variation in responsiveness is equally relevant to considering climatic changes and elevated CO₂ concentration when assessing future crop production. Indicative values representing the crop responsiveness to elevated CO₂ concentration were proposed for all crops currently available in the database of AquaCrop as a first step in reducing part of the uncertainty involved in modeling future agricultural production.     

Relative abundance and activity of melanized hyphae in different soil ecosystems

Here we report on the frequency of melanized fungal hyphae in 323 soils, covering different land use types. The proportion of total hyphae that was melanized averaged 61%. Arable fields with loamy sand, heathlands and city parks on sandy soils had the highest percentage of melanized hyphae. In addition to the frequency determinations, a microcosm study was performed on the role of melanized hyphae in two different ecosystems: an ex-arable field and a forest. Melanized hyphae appeared to be part of the active hyphae in the forest soil but not in the ex-arable soil. In conclusion, our results indicate that (1) melanized hyphae represent a large proportion of the total fungal biomass in soils and that (2) their function might differ between ecosystems.     

蚯蚓（Eiseniafetida）细胞色素P450及抗氧化酶系对环境浓度苯并（a）芘的响应

以赤子爱胜蚓（Eiseniafetida）为供试生物,草甸棕壤为供试土壤,以蚯蚓微粒体细胞色素P450含量、抗氧化酶系以及谷胱甘肽转移酶活性为指标,进行了土壤中苯并（a）芘[B（a）P]暴露与酶活性的量-效关系研究。结果表明,在接近沈抚灌区实地污染状况B（a）P（0．1～2．0mg·kg-1）暴露下,第1、3、7以及第14d取样时,P450和SOD有较好的响应：SOD在第1、3d显著升高,而在第7、14d时降低;P450总体表现为低浓度B（a）P诱导下降低,高浓度下升高的趋势。CAT、POD以及GST的敏感性相对较差。比照其他4个指标,蚯蚓P450的敏感性更为优异,具有较好的应用前景。指标敏感性总体表现为：P450〉SOD〉CAT／POD〉GST。     

不同处理方式对奶牛粪细菌群落多样性及群落结构的影响

以腐熟牛粪、新鲜牛粪以及蚯蚓粪为材料,提取其微生物总DNA,利用细菌16SrDNAV3区扩增及变性梯度凝胶电泳（PCR-DGGE）法,分析了3种材料中细菌的多样性以及细菌群落结构的相似性。结果表明,蚯蚓粪的细菌多样性最丰富,腐熟牛粪次之,新鲜牛粪的细菌多样性最小。蚯蚓粪和腐熟牛粪的细菌群落结构有40%的相似性;蚯蚓粪和新鲜牛粪的细菌群落结构的相似性为25%;新鲜牛粪和腐熟牛粪的细菌群落结构的相似性则为35%。     

不同浓度硫酸盐对水稻土中异化铁还原过程的影响

研究不同电子受体之间的竞争关系对揭示厌氧水稻土中微生物作用导致的氧化还原过程变化机理具有重要的理论意义。本研究采用土壤泥浆厌氧培养、人工合成氧化铁体系接种土壤浸提液厌氧培养及接种铁还原菌纯培养等试验方法,通过向培养体系中添加SO24-,探讨了硫酸盐作为竞争电子受体对不同铁还原体系中Fe（Ⅲ）还原的影响。结果表明,在2种水稻土的泥浆培养过程中,Fe（Ⅲ）还原速率均随着SO24-浓度增加而降低,但Fe（Ⅱ）的最终累积量却较对照处理有明显的增加。添加硫酸盐对Fe（Ⅲ）还原速率（k）的影响表现为：石灰性水稻土〉酸性水稻土;而最终Fe（Ⅱ）累积增加率则为：酸性水稻土〉石灰性水稻土。由接种不同水稻土浸提液的培养试验看出,添加SO24-后Fe（Ⅲ）还原受到显著的抑制,但随着培养时间延长Fe（Ⅲ）还原反应依然可以进行,并且Fe（Ⅱ）累积量最终达到与CK相同的水平。在接种铁还原菌的纯培养试验中,添加SO24-对供试的4株铁还原菌的Fe（Ⅲ）还原过程并未产生抑制效应,表明铁还原菌本身并不受硫酸盐的影响。     

土壤电动修复中电极切换对土壤微生物群落的影响

通过细菌计数和Biolog方法,研究了在3.0V·cm^-1的电压梯度下,不同电场切换周期（24h、5h、10min和1min）对土壤微生物群落的影响。结果表明,电压梯度为3.0V·cm^-1的电场作用能够促进土壤微生物的活性,但会轻微地降低土壤微生物功能多样性,电场切换不能改变这种电场对微生物群落的影响;长时间的电场处理下,电极反应对微生物数量和功能多样性损害严重,切换电场电极能有效消除电极效应,电场电极切换周期≤5h时,可保护电极附近土壤微生物多样性,当切换周期≤10min时,不仅可保护土壤微生物多样性,而且可以保护微生物数量。研究结果说明了电场电极切换能有效降低电极反应对微生物群落的影响,揭示了电场电极切换对土壤微生物群落影响的规律,为电场电极切换方法在污染土壤电动强化生物修复技术中的深化和应用提供理论依据。