Arbuscular mycorrhizae in a long-term field trial comparing low-input (organic, biological) and high-input (conventional) farming systems in a crop rotation

 Arbuscular mycorrhizal (AM) root colonization was studied in a long-term field trial in which four farming systems currently in use in Switzerland were continuously applied to a randomized set of plots at a single field site from 1978 till 1993. There were two low-input farming systems (organic and bio-dynamic) and two high-input (conventional) farming systems (according to Swiss guidelines of integrated plant production with and without farmyard manure). The systems had an identical 7-year crop rotation and tillage scheme and differed essentially only in the amount and type of fertilizer supplied and in plant protection management. The percentage of root colonization by AM fungi was determined in field samples 2–3 times over the growing season in crops in the rotation, namely in winter wheat (Triticum aestivum L. cv. Sardona), vetch-rye and grass-clover. We found the percentage of root length colonized by AM fungi to be 30–60% higher (P≤0.05) in the plants grown in soils from the low-input farming systems than in those grown in conventionally farmed soils. Approximately 50% of the variation of AM root colonization was explained by chemical properties of the soils (pH, soluble P and K, exchangeable Mg), the effect of soluble soil P being most pronounced. The potential of the field soils from the differently managed plots to cause symbiosis with AM fungi was tested in a glasshouse experiment, using wheat as a host plant. Soils from the low-input farming systems had a greatly enhanced capacity to initiate AM symbiosis. The relative differences in this capacity remained similar when propagules of the AM fungus Glomus mosseae were experimentally added to the soils, although overall root colonization by AM fungi was 2.8 times higher. Received: 27 August 1999     

Meeting the UK's climate change commitments: options for carbon mitigation on agricultural land

Abstract. Under the Kyoto Protocol, the European Union is committed to an 8% reduction in CO₂ emissions, compared to baseline (1990) levels, during the first commitment period (2008–2012). However, within the overall EU agreement, the UK is committed to a 12.5% reduction. In this paper, we estimate the carbon mitigation potential of various agricultural land-management strategies (Kyoto Article 3.4) and examine the consequences of UK and European policy options on the potential for carbon mitigation.
We show that integrated agricultural land management strategies have considerable potential for carbon mitigation. Our figures suggest the following potentials (Tg yr⁻¹) for each scenario: animal manure, 3.7; sewage sludge, 0.3; cereal straw incorporation, 1.9; no-till farming, 3.5; agricultural extensification, 3.3; natural woodland regeneration, 3.2 and bioenergy crop production, 4.1. A realistic land-use scenario combining a number of these individual management options has a mitigation potential of 10.4 Tg C yr⁻¹ (equivalent to about 6.6% of 1990 UK CO₂-carbon emissions). An important resource for carbon mitigation in agriculture is the surplus arable land, but in order to fully exploit it, policies governing the use of surplus arable land would need to be changed. Of all options examined, bioenergy crops show the greatest potential. Bioenergy crop production also shows an indefinite mitigation potential compared to other options where the potential is infinite.
The UK will not attempt to meet its climate change commitments solely through changes in agricultural land-use, but since all sources of carbon mitigation will be important in meeting these commitments, agricultural options should be taken very seriously.     

Analysis of soil-vegetation systems' sensitivity to changes of climate-dependent carbon turnover parameters

 The nonlinear model of the carbon cycle in soils (NAMSOM) was used to analyze the sensitivity of soil organic matter levels to variations in carbon turnover parameters. We were able to predict the sensitivity of soil organic matter levels to variations of climate-dependent carbon turnover parameters, which allowed us to compare the sensitivity of soil organic matter levels to net primary productivity of plant communities and plant debris decomposition rate constants across the range of soils in the European part of Russia. The results indicate that meadow steppes show the lowest sensitivity to variations of these parameters. In passing from meadow steppes to the northern taiga and to semideserts, the sensitivity increases. In general, soil organic matter levels of boreal forest ecosystems are about 2–3 times more sensitive to input and decomposition of plant debris than to decomposition of humus. In subboreal grassland ecosystems the sensitivity to humus decomposition increases and becomes closer to the degree of sensitivity shown by soil organic matter levels to variations of productivity and decomposition of plant debris. The proposed method may be useful for predicting the response of ecosystems to climatic change. Received: 1 December 1997     

三峡库区消落带湿地土壤有机碳及其组分特征

湿地生态系统土壤有机碳库的组分变化对于全球碳平衡起着极其重要的作用。本研究选取三峡库区消落带湿地3个海拔梯度的土壤,以从未淹没的样地作为对照,研究消落带湿地不同海拔梯度土壤有机碳组分的特征。结果表明:土壤有机碳、易氧化有机碳、水溶性碳水化合物有机碳和和微生物生物量碳均以消落带小于未淹没样地。在消落带,海拔最低、淹没持续时间较长且正处于水位波动期的样地土壤有机碳、易氧化碳和微生物生物量碳显著低于其他样地,而土壤矿化碳显著高于其他样地。相关性分析表明,土壤有机碳与微生物生物量碳(R~2=0.94)的正相关性显著高于与易氧化有机碳(R~2=0.88)、水溶性有机碳(R~2=0.73)及其水溶性碳水化合物(R~2=0.70)之间的正相关性,但是与矿化碳之间无显著的相关性。因此,土壤微生物生物量碳是消落带湿地土壤有机碳随不同海拔梯度变化的最敏感的组分。     

玉米茎秆汁液对土壤的减水减沙效益及其机理

为研究土壤改良剂玉米茎秆汁液对中国西部地区水土流失的影响和机理,该文通过室内土壤理化性质测定和人工模拟降雨试验,研究了地表施加玉米茎秆汁液对土壤团聚体的平均重量直径、土壤有机质质量分数和土壤减水减沙效益的影响。试验以未施加任何玉米茎秆汁液的黄土坡面为对照,设计单位面积玉米茎秆汁液施加量1 041.7 mL/m2,施加汁液体积分数25%和50%,降雨强度为50 mm/h,研究玉米茎秆汁液施加对土壤减水减沙的影响。结果表明,玉米茎秆汁液的施加可以增加土壤有机质的含量,提高土壤团聚体的平均重量直径,降低产流产沙速率。对照、体积分数25%和50%汁液施加下的土壤团聚体平均重量直径分别为0.18、0.46和0.51 mm,土壤有机质质量分数分别为5.70%、6.75%和7.17%。较对照,体积分数25%和50%汁液施加下,土壤的减水效益分别为45.81%和48.34%,减沙效益分别为65.00%和75.47%。玉米茎秆汁液的减水减沙效益随时间的推移而降低,月均减水、减沙效益降低量约为1.25%和1.41%,研究中施加体积分数25%和50%汁液的土壤减水减沙效益约可持续3和4.5 a。综上,玉米茎秆汁液作为土壤改良剂在施加量为1 041.7 mL/m2时,茎秆汁液与水的体积比为1:1时,效果较好。该研究可以为将玉米茎秆汁液作为土壤改良剂用于土壤侵蚀的防治提供施放参考。     

脲酶硝化双抑制剂缓释肥提高番茄产量及NPK养分吸收

为提高番茄肥料的利用效率,该文采用恒温培养和土培试验研究了自制番茄专用缓释肥（special slow-realease fertilizer for tomato,TSRF1和TSRF2）在酸、中、碱性土中的氮素释放特性以及对番茄产量、NPK养分吸收利用的影响。结果表明,在3种不同土壤中,氮素释放累积量均表现为普通复合肥（ordinary compound fertilizer,OCF）>商品缓释肥（commercial slow-release fertilizer,MSRF）>自制专用肥（special compound fertilizer for tomato,TCF）>自制专用缓释肥1（TSRF1）>自制专用缓释肥2（TSRF2）,且各施肥处理在3种不同土壤类型上的氮素累积释放量大小表现为碱性土>中性土>酸性土。在整个培养期,各施肥处理在3种不同土壤中氮素相对累积释放率大小总体表现为碱性土>中性土>酸性土,且土壤中不同形态氮素累积量均是铵态氮大于硝态氮。铵态氮、硝态氮的累积量大小也表现为碱性土>中性土>酸性土。不同形态氮在3种土壤中的累积释放量动态释放以一级动力学方程拟合最好（r=0.963～0.998）。采用一级动力学方程,不同形态氮素的最大释放量表现为总N>NH4+-N>NO3--N,这与土壤中各形态氮素养分的累积释放特性变化规律表现一致。在土培试验中,两种专用缓释肥（TSRF2和TSRF1）显著提高了番茄果实干物质量,较TCF、MSRF和OCF处理分别增加了18.18%、7.24%、31.40%和13.45%、2.96%、26.15%,且番茄产量在各处理之间的差异达到显著水平。各处理对氮素的积累量大小顺序为TSRF2>TSRF1>MSRF>TCF>OCF,对磷的吸收上表现为TSRF1>TSRF2>MSRF>TCF> OCF,钾素吸收积累量的趋势与氮素基本相同。与普通复合肥相比,两种专用缓释肥处理的N、P、K利用率分别增加了10.66%、20.53%和18.62%（TSRF1）,14.94%、18.48%和21.95%（TSRF2）。两种专用缓释肥（TSRF2和TSRF1）在抑制剂的作用下,能够延缓肥料中N素养分的释放,增加番茄植株对氮磷钾养分的吸收,从而提高了NPK养分利用率和番茄产量。     

蜡样芽孢杆菌及其生物被膜对有机酸及乙醇的抗性比较

为比较蜡样芽孢杆菌及其生物被膜对环境压力的抗性,该文主要研究了4种有机酸（乙酸、柠檬酸、乳酸和苹果酸）和乙醇对蜡样芽孢杆菌及其生物被膜存活率的影响。结果表明：生物被膜态蜡样芽孢杆菌对乙酸的抗性高于浮游态菌。扫描电镜结果显示,经乙酸处理后,浮游态蜡样芽孢杆菌的细胞表面严重受损,而生物被膜态菌的表面形态未发生明显变化。在柠檬酸、乳酸、苹果酸和乙醇存在的条件下,生物被膜态蜡样芽孢杆菌比浮游态菌表现出更强的压力抗性,特别是在高浓度（有机酸16%～20%,乙醇50%～60%）的情况下,该现象尤为显著。因此,在食品工业中控制被膜态蜡样芽孢杆菌对预防和阻止食品腐败非常重要。该研究结果为实际生产中有效控制蜡样芽孢杆菌及其生物被膜的形成提供参考。     

氮肥对水稻不同生长期土壤不同深度氮素渗漏的影响

为了探明太湖地区氮肥施用对水稻不同生长期稻田土壤氮素渗漏的影响,利用渗漏管进行了原位监测。结果表明：①土壤各层(20 ~ 40、40 ~ 60、60 ~ 80和80 ~ 120 cm)渗漏液中铵态氮(NH4+-N)的平均浓度在水稻分蘖期较高,而硝态氮(-N)和全氮(TN-N)的平均浓度则在苗期相对较高。渗漏液中NH4+-N和TN-N浓度随土壤深度增加基本呈降低趋势。②以土壤80 ~ 120 cm深处渗漏量为进入地下水的氮素渗漏量,发现TN-N渗漏量占施肥量的比例为1.69% ~ 2.04%。分蘖期的NH4+-N渗漏量相对较多,而苗期-N和TN-N相对较多,总TN-N渗漏量中NH4+-N和-N基本无差异。③氮肥用量增加降了氮肥利用效率,加剧了土壤各层氮素渗漏风险。当施氮量由N 200增至270 kg/hm2时,氮肥表观利用率下降7.14%,下渗至地下水中的TN-N增加12.3%。     

不同施肥与生物质炭配施对水稻田面水氮磷流失及产量的影响

通过研究减氮施肥及施用生物质炭对田面水氮磷流失风险和水稻性状的影响,结果表明:不同施肥处理田面水总氮、溶解性氮、铵态氮浓度均在施肥后第2天达到最高,然后迅速下降,并于7d后趋于稳定,稳定后浓度分别是顶峰值的5.6％～16.3％,8.4％～23.7％和25.0％～46.1％;不同施肥处理田面水总磷浓度在施肥后第3天达到最高,而后迅速下降,一周后趋于稳定;可溶磷浓度在施肥后4～5 d内处于一个平稳的状态,而后平缓下降至施肥前水平.氮磷浓度在减氮(20％)施肥条件下与常规施肥相比均降低.减氮施肥对产量的影响不大,但减氮施肥结合生物质炭处理水稻产量与常规施肥相比提高了24.6％,达到7 391.5 kg/hm2;减氮施肥降低了氮素流失风险,但减氮施肥结合生物质炭处理则明显提高田面水中总磷的浓度,增加磷素流失的风险.在施肥后1周内是控制氮磷流失风险的最佳时期,此时若遇暴雨,将导致氮磷随径流大量流失.     

长期施用有机肥对草甸碱土碳库管理指数的影响

基于1995年在黑龙江省大庆市肇州县进行的长期定位试验,研究了长期施用有机肥对草甸碱土活性有机质和碳库管理指数的影响。采用3种浓度的KMnO₄(33,167,333mmol/L)氧化法测定了土壤高活性有机质、中活性有机质和活性有机质3部分含量。结果表明,长期施用有机肥能增加草甸碱土活性有机质各组分含量和碳库管理指数。活性有机质各组分含量和碳库管理指数在施用有机肥1~5a的处理间均呈上升的变化趋势,并与玉米产量趋势相一致,在施用有机肥第5a时,均达到最高值,施用有机肥5~16a的处理间,均呈现逐渐下降趋势,最终趋于稳定。中活性有机质和活性有机质与总有机质均达到极显著性正相关,而高活性有机质与总有机质无显著性相关,活性有机质各组分与碳库管理指数也均达到极显著性正相关。研究表明,总有机质不能很好地评价草甸碱土的土壤肥力,而中活性有机质、活性有机质和碳库管理指数能更为客观地反映草甸碱土的土壤肥力,可作为草甸碱土改良的良好评价指标。