农户种植耕地的来源与差异研究--以云南省525户农户为例

基于云南省525户农户的随机问卷调查结果,研究农户种植耕地的来源与差异。结果显示,农户种植耕地绝大部分来源于自家承包地,而只有少部分来源于转入;农户之间的耕地流转活动仍处于较低水平,农户家庭种植面积相对偏小且较为细碎化,应采取措施来促使农户转入耕地。     

水稻花粉扩散源强估算方法研究

[目的]验证二维通量积分法估算水稻花粉源强的可行性。[方法]利用2008年南京开花期稻田水稻花粉扩散的源强试验资料,分析花粉在稻田上方的分布规律和影响因素,并利用二维通量积分法计算源强大小。[结果]水稻花粉在源内的分布规律不受品种、田块面积的影响,花粉数量在下风方向逐步累积,随离中心距离的分布呈现倒“S”型规律,水稻冠层上方花粉浓度随高度增加而递减,影响冠层上方花粉分布的主要因素是稻田上方的风向、风速和开花量。两优培九花粉扩散源强为开花期花粉总量的1．8％,符合实际情况。[结论]二维通量积分法是估算水稻花粉扩散源强简单而有效的方法。     

Evaluation of Agricultural Nonpoint Source (AGNPS) model for small watersheds in Korea applying irregular cell delineation

The Agricultural Nonpoint Source (AGNPS) model was tested in two small agricultural watersheds in Korea. The model was calibrated for 412.5 ha located in the Balhan watershed. The rainfall amount distinguishing between antecedent moisture conditions (AMC) I and II was changed to calibrate the runoff volume. A validation was performed for 274.1 ha located in the Banwol watershed, with similar land use and soil characteristics as the 412.5 ha in the Balhan watershed. The input data were extracted from multiple GIS layers using the Geographic Resources Analysis Support System (GRASS)-AGNPS interface. The AGNPS model was modified to treat the undisturbed forest areas as irregular cells instead of the uniform cell division currently used by AGNPS. Simulated results from the irregular cell-based scheme (ICS) and the uniform grid scheme (UGS) of ANGPS were compared with the observed data. The ICS increased runoff volume and decreased peak flow rate and sediment yields from the watershed compared to the UGS. The ICS significantly reduced the number of cells in a watershed and provided better agreement for surface runoff and peak flow rate compared to the UGS.     

南京沿江典型蔬菜生产系统土壤重金属异常的源解析

以南京沿江典型蔬菜生产系统为研究对象,通过测定并分析表层土壤、剖面土壤、肥料及大气降尘中重金属含量,揭示了土壤重金属异常的空间变异特征以及土壤重金属的来源。结果表明,(1)研究区表层土壤镉(Cd)、砷(As)、汞(Hg)、铅(Pb)、铜(Cu)、锌(Zn)和铬(Cr)平均含量均高于南京市土壤背景值,部分样点土壤Cd含量超过了国家土壤环境质量标准的二级标准,在土壤中呈现较高的累积;(2)除Cr以外,其他表层土壤重金属均呈现东南偏高西北偏低的空间分布特征,与土壤有机质的空间分布规律一致;(3)土壤重金属累积和分布状况与研究区的地形、周边工农业布局以及风向有关;(4)除土壤重金属累积的自然背景原因以外,农业施肥和大气沉降对土壤重金属的累积具有非常重要的贡献。     

基于APCS-MLR模型和地统计学相结合的矿区农田土壤砷源解析

为了研究矿区周边农田土壤As等重金属的污染特征和来源情况,在云南会泽铅锌矿区采集了42个农田土壤样品,测定了9种元素含量,利用绝对主成分得分–多元线性回归(APCS-MLR)受体模型定量解析了土壤中As的来源和贡献率,并结合地统计学方法揭示了As的不同来源及其贡献的空间分布状况.结果表明:①研究区土壤As的平均含量为7...     

三江源区不同退化程度高寒草甸表土层的土壤水分变化特征

土壤水分是影响青藏高原高寒草甸生态过程和生态承载能力关键因素之一,掌握其变化特征对于高寒地区生态保护和修复具有重要意义.基于HOBO土壤温湿度仪器监测数据,分析2019年8月至2020年8月三江源区不同退化程度(未退化(ND)、轻中度退化(LMD),重度退化(HD))下高寒草甸表土层土壤3个层级L1(0-5 cm)、L...     

Potential phosphorus and sediment loads from sources within a dairy farmed catchment

Phosphorus (P) losses from intensively farmed dairy pastures can impair surface water quality. One of the first steps in mitigating this loss is to determine where in a field the potential for P loss is greatest. This study compared P export in overland flow from grazed pasture with areas that receive elevated P inputs and stock traffic (e.g. gateway, water trough, stream crossing and cattle lane). Intact soil blocks were removed, simulated rainfall applied and overland flow analysed for P fractions and suspended sediment (SS). Soil bulk density, hydraulic conductivity, porosity, Olsen P and water soluble P were also measured. P loss from the sites was in the order: trough > crossing > gateway > pasture. Total P losses from the trough averaged 4.20 mg P/m² while the pasture exported 0.78 mg P/m². In addition, runoff from lane soil was measured with total P averaging 5.98 mg P/m², however the method used was different from the other soils. Using stepwise linear regression, Olsen P or H₂O-P, % bare ground and % saturation were the most commonly occurring variables to predict P loss among the sites. This suggests that locating and minimizing the size of these areas in fields has the potential to significantly decrease P loss to surface waters.     

Oxygen exchange between nitrogen oxides and H2O can occur during nitrifier pathways

Interpretation of the oxygen isotopic signature of soil-derived N₂O may be flawed when it is based on reaction stoichiometry and fractionation alone. In fact, oxygen (O) exchange between H₂O and intermediates of N₂O production pathways may largely determine this O isotopic signature. Although in our previous work we conclusively proved the occurrence of O exchange during N₂O production by denitrification of NO₃⁻, its occurrence in N₂O production pathways by nitrifiers remains unclear. The aim of this study was to examine the likeliness of O exchange during various stages of N₂O production in soil via nitrification, nitrifier denitrification and denitrification. We evaluated a set of scenarios on the presence of such exchange using data from a series of ¹⁸O and ¹⁵N tracing experiments. The measured actual O incorporation from H₂O into N₂O (AOI) was compared with the theoretical maximum O incorporation (MOI) from various scenarios that differed in their assumptions on the presence of O exchange. We found that scenarios where O exchange was assumed to occur exclusively during denitrification could not explain the observed AOI, as it exceeded the MOI for 9 out of 10 soils. This demonstrates that additional O exchange must have occurred in N₂O production through nitrifier pathways. It remains to be determined in which steps of these pathways O exchange can take place. We conclude that O exchange is likely to be mediated by ammonia oxidizers during NO₂⁻ reduction (nitrifier denitrification), and that it could possibly occur during NO₂⁻ oxidation to NO₃⁻ by nitrite oxidizers as well.     

三江源兴海地区西北针茅产量影响因子的主成分分析

利用主成分分析法和多元逐步回归法分析影响三江源兴海地区西北针茅（Stipa sareptana Beckervat．krylovii）牧草产量的因子。结果表明,影响西北针茅牧草产量的主成分因子以水分因子为主,温度和光照因子其次;以各因子为自变量,西北针茅牧草产量为因变量,进行多元逐步回归分析,建立产量回归方程,方程的相关系数达0．9873,各因子影响牧草产量的大小为4月降水量＞4～8月降水量＞7月降水量＞8月日照时数＞6月日照时数。     

春小麦群体库的形成及其特性分析

以春小麦两个品种内麦19和永良4为试材，在不同密度、施肥量处理下对春小麦群体库均形成与特性以及在产量形成中的作用进行了系统研究。结果表明，春小麦籽粒体积(库容量)随生育进程呈单峰曲线变化，籽粒干物重的增长(库的充实)随生育进程呈S型曲线变化；每穗结实粒数(库)与开花期群体干物质源的供应呈显著正相关。籽粒体积与灌浆速率及粒重呈极显著正相关，由此说明扩大库容(籽粒体积)，可以促进源的生产、运转与积累，提高籽粒重量。