土壤数值分类模型的建立及应用──RSCM的建立

本文以吉林省安县盐渍草甸草原区域土壤为例，以多种多元统计分析方法相结合作为骨架，在土体型函数表达式等一系列新概念的基础上，建立了区域土壤数值分类模型它有效地解决了土体构型的数值化，从而建立了任何部面相互比较的定量基础准。     

Activity and biomass of soil microorganisms at different depths

We measured microbial biomass C and soil organic C in soils from one grassland and two arable sites at depths of between 0 and 90 cm. The microbial biomass C content decreased from a maximum of 1147 (0–10 cm layer) to 24 g g^-1 soil (70–90 cm layer) at the grassland site, from 178 (acidic site) and 264 g g^-1 soil (neutral site) at 10–20 cm to values of between 13 and 12 g g^-1 soil (70–90 cm layer) at the two arable sites. No significant depth gradient was observed within the plough layer (0–30 cm depth) for biomass C and soil organic C contents. In general, the microbial biomass C to soil organic C ratio decreased with depth from a maximum of between 1.4 and 2.6% to a minimum of between 0.5 and 0.7% at 70–90 cm in the three soils. Over a 24-week incubation period at 25°C, we examined the survival of microbial biomass in our three soils at depths of between 0 and 90 cm without external substrate. At the end of the incubation experiment, the contents of microbial biomass C at 0–30 cm were significantly lower than the initial values. At depths of between 30 and 90 cm, the microbial biomass C content showed no significant decline in any of the four soils and remained constant up to the end of the experiment. On average, 5.8% of soil organic C was mineralized at 0–30 cm in the three soils and 4.8% at 30–90 cm. Generally, the metabolic quotient qCO₂ values increased with depth and were especially large at 70–90 cm in depth.     

小麦种质资源耐深播性评价体系研究

为建立准确、简单易行的种质资源耐深播评价体系,以15份耐深播能力存在不同程度差异的小麦种质为材料,在大田环境下,研究6个播种深度(5 cm、7 cm、9 cm、11 cm、13 cm、15 cm)下小麦出苗率、出苗时间、苗高、地中茎长、胚芽鞘长、胚芽鞘横截面积及初生根长的差异,筛选小麦耐深播评价的最佳播种深度及其密切相关性状指标,并采用加权耐深播系数法对15份小麦种质进行耐深播综合评价。结果表明,11 cm播种深度能够较好地区分不同小麦种质出苗率差异,可作为小麦种质耐深播评价的最佳深度。在11 cm播种深度下,15份小麦种质的出苗率与出苗时间、苗高、胚芽鞘长、地中茎长存在显著或极显著相关性,可作为小麦种质资源苗期耐深播性评价的主要评价指标;采用加权耐深播系数法将15份小麦种质划分为4个耐深播等级。研究结果将为小麦耐深播育种及机理研究提供重要的理论依据和种质材料。     

黄土区裸露坡地径流养分流失模型的建立与验证

在自然降雨条件下,黄土区坡耕地土壤表层中的养分会随地表径流流失,从而加剧了土壤质量和生产力的下降并造成严重的农业面源污染,使得准确预测黄土区养分随地表径流的流失过程尤为重要。现有的养分流失模型着重于估算长时段的养分流失总量,且未考虑开始产流前入渗水对交换层养分的稀释作用。根据不同降雨时段的养分迁移特性,将整个降雨过程划分为三个阶段:(1)从降雨开始(t_0)至交换层土壤完全饱和(t_(sa)),(2)从交换层土壤完全饱和(t_(sa))至开始产流(t_p),(3)从开始产流(t_p)至降雨结束。在运动波模型近似解析解的基础上建立了综合雨滴击溅、扩散和入渗作用的养分流失近似解析模型;并进行了降雨试验,以率定模型参数和验证模型的可靠性。结果表明:径流及养分的模拟值可与实测值精确匹配(R~2 0.8,纳什效率系数NSE 0.347)。养分流失模型中的雨滴诱导水分转移速率e_r取值在0.006～0.023 cm·min~(–1)之间,交换层深度d_e取值在0.68～1.32 cm之间;雨滴诱导水分转移速率e_r可显著影响硝态氮和铵态氮的峰值流失速率,e_r的增大使得养分流失过程中流失速率减小阶段的衰减速率更快;而交换层深度d_e可显著影响硝态氮和铵态氮损失率的总体变化范围,即随交换层深度的增大,养分的峰值流失速率和流失总量也随之增大。因此,应采取植被覆盖或深层施肥等措施,减弱雨滴动能、降低交换层养分含量以达到减少养分流失的目的。     

痕量灌溉管不同埋深对番茄生长、产量和水分利用效率的影响

为了探索日光温室番茄栽培时痕量灌溉管适宜埋深,以番茄仙客1号为试材,研究了春季日光温室栽培条件下,痕量灌溉管不同埋深对灌溉量、产量和品质的影响。试验结果表明,灌溉管埋深20cm和30cm处理与表面覆土相比,分别增产6.1%和15.2%,同时品质有所改善。灌溉管埋深10cm、20cm和30cm与表面覆土相比,耗水量分别降低15.7%、10.6%和5.7%,水分利用效率分别提高13.5%、19.6%和24.0%。灌溉管埋深30cm处理产量和水分利用效率最高。因此,灌溉管埋深30cm是本试验条件下日光温室春茬番茄较适宜的灌溉管埋设深度。     

稻秆还田深度对盆栽冬小麦结构和生理特性的影响

为了明确稻秆还田深度影响小麦生长发育的生理机制,采用盆栽试验研究了不同稻秆还田深度对小麦出苗、根系发育、根系结构、旗叶光合特性、旗叶SOD和CAT活性及胚乳细胞中淀粉体的影响。结果表明,(1)稻秆还田深度对小麦出苗率没有显著影响,但影响出苗整齐度;(2)15cm的稻秆还田深度能显著促进小麦根系生长,增加次生根数目,提高根冠比、根系总吸收面积、活性吸收面积及根系TTC还原强度;(3)不同稻秆还田深度对拔节期小麦次生根皮层结构影响不大,但对导管结构影响较大,还田深度越深,导管发育越慢;(4)15cm的稻秆还田深度能显著提高小麦旗叶叶绿素含量和光合速率,在生育后期能延缓旗叶叶绿素的降解速度,增加小麦产量;(5)15cm的稻秆还田深度能提高小麦生育后期旗叶中SOD和CAT的活性,延缓叶片的衰老;(6)15cm的稻秆还田深度能延缓小麦胚乳细胞中淀粉体发育时间。     

Dynamics and modeling of soil water under subsurface drip irrigated onion

Subsurface drip irrigation provides water to the plants around the root zone while maintaining a dry soil surface. A problem associated with the subsurface drip irrigation is the formation of cavity at the soil surface above the water emission points. This can be resolved through matching dripper flow rates to the soil hydraulic properties. Such a matching can be obtained either by the field experiments supplemented by modeling. Simulation model (Hydrus-2D) was used and tested in onion crop (Allium cepa L.) irrigated through subsurface drip system during 2002-2003, 2003-2004 and 2004-2005. Onion was transplanted at a plant to plant and row to row spacing of 10 cm × 15 cm with 3 irrigation levels and 6 depths of placement of drip lateral. The specific objective of this study was to assess the effect of depth of placement of drip laterals on crop yield and application of Hydrus-2D model for the simulation of soil water. In sandy loam soils, it was observed that operating pressures of up to 1.0 kg cm⁻² did not lead to the formation of cavity above the subsurface dripper having drippers of 2.0 l h⁻¹ discharge at depths up to 30 cm. Wetted soil area of 60 cm wide and up to a depth of 30 cm had more than 18% soil water content, which was conducive for good growth of crop resulting in higher onion yields when drip laterals were placed either on soil surface or placed up to depths of 15 cm. In deeper placement of drip lateral (20 and 30 cm below surface), adequate soil water was found at 30, 45 and 60 cm soil depth. Maximum drainage occurred when drip lateral was placed at 30 cm depth. Maximum onion yield was recorded at 10 cm depth of drip lateral (25.7 t ha⁻¹). The application of Hydrus-2D confirmed the movement of soil water at 20 and 30 cm depth of placement of drip laterals. The model performance in simulating soil water was evaluated by comparing the measured and predicted values using three parameters namely, AE, RMSE and model efficiency. Distribution of soil water under field experiment and by model simulation at different growth stages agreed closely and the differences were statistically insignificant. The use of Hydrus-2D enabled corroborating the conclusions derived from the field experimentation made on soil water distribution at different depths of placement of drip laterals. This model helped in designing the subsurface drip system for efficient use of water with minimum drainage.     

黑土不同耕层厚度对玉米根系形态空间分布及其产量的影响

在重建不同厚度黑土层的定位模拟试验区开展免耕玉米大豆轮作试验,设3个黑土耕层厚度(10、20和30 cm),探究不同耕层厚度对玉米生育期间的根系形态及其产量影响。研究表明,玉米产量对不同耕层厚度反应敏感,30 cm耕层厚度处理玉米产量最高,比20 cm和10 cm耕层厚度显著高12.5%和24.1%,且玉米根系分布对耕层厚度响应差异明显。30 cm耕层厚度显著影响玉米0～10 cm土层根重密度,对10～30 cm土层根重密度及不同土层根长密度和比根长影响不明显。     

不同灌水定额条件下土壤含水率变化研究(英文)

[目的]研究不同灌水定额条件下土壤含水率变化。[方法]在4个田间试验小区布设间距为2m的3个点,使用人工手钻,钻成深度200cm、孔径44.3mm的探管孔。1试验小区不灌水,2试验小区灌水量为0.02999m3/m2,3试验小区灌水量为0.08996m3/m2,4试验小区灌水量为0.05997m3/m2,灌水方法采取畦灌。利用时域反射仪,对不同灌水定额入渗的土壤含水率进行测定。时间上,探测土壤含水率时间为灌水后4、20、28和44h;深度上,探测深度间距分别设为180、160、140、120、100、90、80、70、60、50、40、30、20、10cm。结合土壤质地特性,分析不同灌水定额下的土壤含水率随深度变化的曲线特征。[结果]不同土层深度土壤水分变化因灌溉水量不同而不同。①不灌水时,0～70cm土层土壤含水率为9.88%;70～100cm土层土壤含水率逐渐增大,达17.00%;100～120cm土层含水率达25.00%;120～180cm土层土壤含水率为24.45%。②灌水量为0.02999m3/m2时,0～30cm土层土壤含水率逐渐增大,达30.00%;30～60cm土层土壤含水率逐渐下降,降至25.00%;60～180cm土层土壤含水率为25.00%。该灌水定额适合农田灌溉节约用水。③灌水量为0.05997m3/m2时,0～30cm土层土壤含水率逐渐增大,达26.00%;30～100cm土层土壤含水率为32.50%,120～180cm土层土壤含水率恢复到未灌溉前状态。该灌水定额对农田节水和保墒具有重要意义。④灌水量为0.08996m3/m2时,0～180cm土层土壤含水率为25.86%。该灌水定额不利于农田灌溉节约用水。[结论]该研究结果对经济合理地利用水资源具有重要意义。     

Caesium-137 fallout depth distribution in different soil profiles and significance for estimating soil erosion rate

Caesium-137 (¹³⁷Cs) has been widely used for the determination of soil erosion and sediment transport rate. However, depth distribution patterns of ¹³⁷Cs in the soil profile have not been considered. As a result, the erosion rates may be over-estimated or underestimated. This paper presents the depth distribution of ¹³⁷Cs fallout in different soil profiles using published data. Three types of depth distribution functions of ¹³⁷Cs are given by using statistical regression methods, the exponential type, the peak type and the decreasing type (including uniform distribution). Relationships between ¹³⁷Cs loss and soil erosion rate are given by introducing the regression functions. The influence of depth distribution of ¹³⁷Cs on the estimation of the soil erosion rate was simulated. Simulation results showed that very different soil erosion rates could be deduced for different depth distributions when ¹³⁷Cs loss is the same, which indicates that the depth distribution pattern should be considered when soil erosion is estimated by using ¹³⁷Cs. Simulation results also suggested that it is most important to determine the depth distribution of ¹³⁷Cs near the soil surface and the annual relative loss of ¹³⁷Cs by using the depth distribution of ¹³⁷Cs as a criterion to estimate the soil erosion rate.