田林老山中山杉木人工林生产力及营养元素循环的研究

广西田林县老山林场中山区气候冷凉潮湿,土壤肥力较高,能满足杉木速生要求。17年生杉木人工林乔木层的生物量达138.46t/ha,平均净生产量为8.15t/ha·a,与杉木中心产区相当。乔木层对N,P,K,Ca,Mg5种营养元素的吸收量为224.04kg/ha·a,其中42.3％存留在林木层,42.5％通过凋落物,15.2％通过降雨淋洗归还土壤。通过凋落物归还是N,P,Ca,Mg归还的主要途径,K的归还主要通过降雨淋洗;K,Ca,Mg的循环系数较大,分别达到0.58,0.68和0.60;N,P相对较小,分别为0.48和0.33。林木正处于生长旺盛阶段,杉木对5种营养元素的吸收量、存留量和归还量以及循环系数都有较高水平,生物量积累也较大。     

In situ net N transformations in pine,fir, and oak stands of different ages on acid sandy soil, 3 years after liming

Summary The effect of liming on in-situ N transformations was studied in two stands of different ages of each of Scots pine (Pinus sylvestris L.), Douglas fir [Pseudotsuga menziesii (Mirb.) Franco], and common oak (Quercus robur L.). The stands were located on acid sandy soils in an area with high atmospheric N input. The organic matter of the upper 10-cm layer of the soil, including the forest floor, had a relatively high N content (C: N ratio <25) in all stands. Using a sequential core technique, N transformations were measured in both control plots and plots that had been limed 3 years previously with 3 t ha^-1 of dolomitic lime. Limed plots had a higher net NO _inf3 ^sup- production and a higher potential for NO _inf3 ^sup- leaching than the controls in all stands except that of the younger oak. Net N mineralization did not differ significantly between limed and control plots in oak stands and younger coniferous stands but was significantly lower in the limed plots of the older coniferous stands. It is concluded that long-term measurements of net N mineralization in limed forest soils are needed to evaluate the effect of liming with respect to the risk of groundwater pollution.     

The effect of precipitation and application rate on dicyandiamide persistence and efficiency in two Irish grassland soils

The nitrification inhibitor dicyandiamide (DCD) has had variable success in reducing nitrate () leaching and nitrous oxide (N₂O) emissions from soils receiving nitrogen (N) fertilizers. Factors such as soil type, temperature and moisture have been linked to the variable efficacy of DCD. As DCD is water soluble, it can be leached from the rooting zone where it is intended to inhibit nitrification. Intact soil columns (15 cm diameter by 35 cm long) were taken from luvic gleysol and haplic cambisol grassland sites and placed in growth chambers. DCD was applied at 15 or 30 kg DCD/ha, with high or low precipitation. Leaching of DCD, mineral N and the residual soil DCD concentrations were determined over 8 weeks high precipitation increased DCD in leachate and decreased recovery in soil. A soil × DCD rate interaction was detected for the DCD unaccounted (proxy for degraded DCD). In the cambisol, degradation of DCD was high (circa 81%) and unaffected by DCD rate. In contrast, DCD degradation in the gleysol was lower and differentially affected by rate, 67 and 46% for the 15 and 30 kg/ha treatments, respectively. Variation in DCD degradation rates between soils may be related to differences in organic matter content and associated microbiological activity. Variable degradation rates of DCD in soil, unrelated to temperature or moisture, may contribute to changing DCD efficacy. Soil properties should be considered when tailoring DCD strategies for improving nitrogen use efficiency and crop yields, through the reduction of reactive nitrogen loss.     

不同施氮量对夏玉米产量、氮肥利用率及氮平衡的影响

通过田间小区试验研究了不同施氮量对夏玉米产量、氮肥利用率、硝酸盐淋溶及氮平衡的影响。结果表明,施氮对夏玉米子粒有显著的增产作用,但随施氮量的增加产量变化不大。氮肥利用率在9.2%~22.6%之间,随施氮量的增加而降低。施氮可明显提高0~160 cm剖面土壤NO3--N含量,而且随深度的增加NO3--N含量呈降低趋势,累积峰主要在20~60 cm之间。玉米收获后,随着施氮量的增加氮素的损失量增加,各施氮处理的硝态氮残留量在121~221 kg/hm2之间,以N250处理的残留量最高,残留率近65%。     

The effect of situational variability in climate and soil, choice of animal type and N fertilisation level on nitrogen leaching from pastoral farming systems around Lake Taupo, New Zealand

Agricultural systems with grazing animals are increasingly under scrutiny for their contribution to quality degradation of waterways and water bodies. Soil type, climate, animal type and nitrogen (N) fertilisation are contributors to the variation in N that is leached through the soil profile into ground and surface water. It is difficult to explore the effect of these factors using experimentation only and modelling is proposed as an alternative. An agro-ecosystem model, EcoMod, was used to quantify the pastoral ecosystem responses to situational variability in climate and soil, choice of animal type and N fertilisation level within the Lake Taupo region of New Zealand. Factorial combinations of soil type (Oruanui and Waipahihi), climate (low, moderate and high rainfall), animal type (sheep, beef and dairy) and N fertilisation level (0 or 60 kg N/ha/yr) were simulated. High rainfall climates also had colder temperatures, grew less pasture and carried fewer animals overall which lead to less dung and urinary N returned. Therefore, even though a higher proportion of N returned ultimately leached at the higher rainfall sites, the total N leached did not differ greatly between sites. Weather variation between years had a marked influence on N leaching within a site, due to the timing and magnitude of rainfall events. In this region, for these two highly permeable soil types, N applied as fertiliser had a high propensity to leach, either after being taken up by plants, grazed and returned to the soil as dung and urine, or due to direct flow through the soil profile. Soil type had a considerable effect on N leaching risk, the timing of N leaching and mean pasture production. Nitrogen leaching was greatest from beef cattle, followed by dairy and sheep with the level of leaching related to urine deposition patterns for each animal type and due to the amount of N returned to the soil as excreta. Simulation results indicate that sheep farming systems with limited fertiliser N inputs will reduce N leaching from farms in the Lake Taupo catchment.     

水浸提银杏黄酮苷工艺的多元回归分析

用SPSS 10 .0 7统计软件包对水浸提银杏黄酮苷的工艺参数进行了多元回归统计分析 ,并根据回归拟合的多项式数学模型 ,讨论了水浸提法的较佳工艺条件。     

绿黄隆在土壤中的迁移特性

应用土壤薄层层析（ＴＬＣ）法测定了１４Ｃ－绿黄隆在１０种土壤中的移动率，其Ｒｆ值为０．６５～１．０，表明绿黄隆在供试土壤中分别属可移动性和极易移动性。用大面积土柱淋溶法测得３种土壤柱在模拟降雨下的淋溶动态及其参数，经计算，在黄潮土、黄棕壤和红壤中，使１４Ｃ－绿黄隆垂直移动透过１０ｃｍ土层所需连续降水量分别为７５，８０和９４ｍｍ。绿黄隆在土壤中的迁移性与土壤ＰＨ值密切相关，随ｐＨ值增高其移动性和淋溶性增大。绿黄隆随水迁移性较强，它有可能对农业生态环境产生不良影响。     

木材液相乙酰化及抗收缩效果的研究

本文研究了三种木材液相乙酰化的影响因素以及乙酰化木材的抗收缩效果。用乙酸酐作为乙酰剂和以二甲苯作为溶剂,处理材的增重与反应温度和时间存在着线性关系。反应的最佳温度为120℃,时间为7～11h,乙酸酐和二甲苯的容量比为1:1。乙酰化显著地提高了木材的尺寸稳定性。抗收缩率与处理材的增重成正比。当处理材的增重大于15％时可取得满意的抗收缩效果,抗收缩率达到60％以上。乙酰化木材经过了三次干燥—浸水循环试验,其结果表明乙酰化所取得的抗收缩效果有很强的抗流失性。本研究证实:乙酰化是提高木材尺寸稳定性的有效措施,对提高材质有重要意义。     

A flexible approach to managing variability in grain yield and nitrate leaching at within-field to farm scales

We up-scaled the APSIM simulation model of crop growth, water and nitrogen dynamics to interpret and respond to spatial and temporal variations in soil, season and crop performance and improve yield and decrease nitrate leaching. Grain yields, drainage below the maximum root depth and nitrate leaching are strongly governed by interaction of plant available soil water storage capacity (PAWC), seasonal rainfall and nitrogen supply in the water-limited Mediterranean-type environment of Western Australia (WA). APSIM simulates the interaction of these key system parameters and the robustness of its simulations has been rigorously tested with the results of several field experiments covering a range of soil types and seasonal conditions in WA. We used yield maps, soil and weather data for farms at two locations in WA to determine spatial and temporal patterns of grain yield, drainage below the maximum root depth and nitrate leaching under a range of weather, soil and nitrogen management scenarios. On one farm, we up-scaled APSIM simulations across the whole farm using local weather and fertiliser use data and the average PAWC values of soil type polygons. On a 70 ha field on another farm, we used a linear regression of apparent soil electrical conductivity (EC_a) measured by EM38 against PAWC to transform an EC_a map of the field into a high resolution (5 m grid) PAWC map. We then used regressions of simulated yields, drainage below the maximum root depth and nitrate leaching on PAWC to upscale the APSIM simulations for a range of weather and fertiliser management scenarios. This continuous mapping approach overcame the weakness of the soil polygons approach, which assumed uniformity in soil properties and processes within soil type polygons. It identified areas at greatest financial and environmental risks across the field, which required focused management and simulated their response to management interventions. Splitting nitrogen applications increased simulated wheat yields at all sites across the field and decreased nitrate leaching particularly where the water storage capacity of the soil was small. Low water storage capacity resulted in both low wheat yields and large leaching loss. Another management option to decrease leaching may be to grow perennial vegetation that uses more water and loses less by drainage.Paper from the 5th European Conference on Precision Agriculture (5ECPA), Uppsala, Sweden, 2005     

尿素在砖红壤中的淋失特征——Ⅰ．NH^＋4-N的淋失

通过室内大型模拟土柱研究不同尿素施甩量与砖红壤中NH4-N的淋失关系。结果表明：各施肥处理渗漏液中20cm处NH^ 4-N的最高浓度值与施肥量大小成正相关，60cm和120cm处渗漏液中NH^ 4-N浓度值与施肥量关系不大，但120cm处渗漏液中NH ^4-N浓度仍超过水体富营养化标准0．2mg／L。在砖红壤中，尿素以NH^ 4-N形态大量淋失的可能性不大。