基于室内高光谱数据的多种类型土壤有机质估算模型比较

基于高光谱数据的土壤有机质反演是土壤遥感及精准农业的重要研究内容,然而不同的光谱处理及建模方法使得模型的估算能力及精度差异明显,限制了模型之间的通用性。为了构建陕西省土壤有机质含量估算的最优模型,以陕西省9种主要土壤类型的216个土样的光谱反射曲线和土壤有机质含量为数据基础,将光谱反射曲线进行一阶微分d(R)、倒数对数log(1/R)、倒数对数一阶微分d[log(1/R)]和包络线去除N(R)4种变换,结合一元线性回归(SLR)、偏最小二乘回归(PLSR)和支持向量机回归(SVR)3种建模方法构建了不同的土壤有机质含量估算模型。结果显示:不同类型土壤的反射光谱曲线总体态势基本一致,吸收特征位置基本相同,且土壤有机质含量与光谱反射率呈负相关态势;基于d [log(1/R)]光谱变换构建的SVR估算模型精度最高,建模集和验证集的判断系数(R~2)分别为0.9210、0.8874,验证均方根误差(RMSE)为2.18,相对分析误差(RPD)达到2.8751,是估算陕西省土壤有机质含量的最优模型,PLSR次之,SLR最差。     

Seasonal influence of climate manipulation on microbial community structure and function in mountain soils

Microbial communities drive soil organic matter (SOM) decomposition through the production of a variety of extracellular enzymes. Climate change impact on soil microbial communities and soil enzymatic activities can therefore strongly affect SOM turnover, and thereby determine the fate of ecosystems and their role as carbon sinks or sources.To simulate projected impacts of climate change on Swiss Jura subalpine grassland soils, an altitudinal soil transplantation experiment was set up in October 2009. On the fourth year of this experiment, we measured microbial biomass (MB), microbial community structure (MCS), and soil extracellular enzymatic activities (EEA) of nine hydrolytic and oxidative extracellular enzymes in the transplanted soils on a seasonal basis.We found a strong sampling date effect and a smaller but significant effect of the climate manipulation (soil transplantation) on EEA. Overall EEA was higher in winter and spring but enzymes linked to N and P cycles showed higher potential activities in autumn, suggesting that other factors than soil microclimate controlled their pool size, such as substrate availability. The climate warming manipulation decreased EEA in most cases, with oxidative enzymes more concerned than hydrolytic enzymes. In contrast to EEA, soil MB was more affected by the climate manipulation than by the seasons. Transplanting soils to lower altitudes caused a significant decrease in soil MB, but did not affect soil MCS. Conversely, a clear shift in soil MCS was observed between winter and summer. Mass-specific soil EEA (EEA normalized by MB) showed a systematic seasonal trend, with a higher ratio in winter than in summer, suggesting that the seasonal shift in MCS is accompanied by a change in their activities. Surprisingly, we observed a significant decrease in soil organic carbon (SOC) concentration after four years of soil transplantation, as compared to the control site, which could not be linked to any microbial data.We conclude that medium term (four years) warming and decreased precipitation strongly affected MB and EEA but not MCS in subalpine grassland soils, and that those shifts cannot be readily linked to the dynamics of soil carbon concentration under climate change.     

运用直线加平台法确定黑土区玉米氮磷施肥量

施肥量的确定一直是玉米高产栽培研究的主要课题之一。分别运用肥料效应函数法和直线加平台法,对按照直线加平台法设计的在黑土上春玉米的田间试验结果进行了统计分析,发现利用直线加平台法设计的田间试验结果也可以用来建立肥料效应函数,并根据肥料效应函数求得相应的施肥量。利用肥料效应函数得到的最高产量推荐施氮量和最大利润推荐施氮量分别为107.4 kg hm-2和103.2 kg hm-2,而最高产量推荐施磷量和最大利润推荐施磷量分别45.5 kg hm-2和41.3 kg hm-2。利用直线加平台法得到氮、磷的推荐施肥量分别为73.9和38.0 kg hm-2,明显低于用肥料效应函数法求得的推荐施肥量。对于肥料效应函数无法处理的试验数据,利用直线加平台法仍然可以对实验数据进行处理并得出实验结果,后者是肥料效应函数法的补充。     

Potential carbon stock in Japanese forest soils – simulated impact of forest management and climate change using the CENTURY model

Forest management and climate change may have a substantial impact on future soil organic carbon (SOC) stocks at the country scale. Potential SOC in Japanese forest soils was regionally estimated under nine forest managements and a climate change scenario using the CENTURY ecosystem model. Three rotations (30, 50, 100 yr) and three thinning regimes were tested: no‐thinning; 30% of the trees cut in the middle of the rotation (e.g. 15 year in a 30‐yr rotation) and thinned trees all left as litter or slash (ThinLef) and the trees from thinning removed from the forest (ThinRem). A climate change scenario was tested (ca. 3 °C increase in air temperature and 9% increase in precipitation). The model was run at 1 km resolution using climate, vegetation and soil databases. The estimated SOC stock ranged from 1600 to 1830 TgC (from 6800 to 7800 gC/m²), and the SOC stock was largest with the longest rotation and was largest under ThinLef with all three rotations. Despite an increase in net primary production, the SOC stock decreased by 5% under the climate change scenario.     

农田土壤氮素径流损失的影响因素及其防治措施研究

根据当前国内外在农田土壤氮素运移转化机理方面已取得的研究成果,简要回顾了农田土壤氮素损失产生的环境污染危害,分析了影响土壤氮素径流损失的主要因素。在此基础上,提出了优化水肥管理、合理施用氮肥、发展生态农业、调整种植结构、推广缓控释肥料等防治举措。     

Drought and salinity: A comparison of their effects on mineral nutrition of plants

The increasing frequency of dry periods in many regions of the world and the problems associated with salinity in irrigated areas frequently result in the consecutive occurrence of drought and salinity on cultivated land. Currently, 50% of all irrigation schemes are affected by salinity. Nutrient disturbances under both drought and salinity reduce plant growth by affecting the availability, transport, and partitioning of nutrients. However, drought and salinity can differentially affect the mineral nutrition of plants. Salinity may cause nutrient deficiencies or imbalances, due to the competition of Na⁺ and Cl^– with nutrients such as K⁺, Ca²⁺, and NO . Drought, on the other hand, can affect nutrient uptake and impair acropetal translocation of some nutrients. Despite contradictory reports on the effects of nutrient supply on plant growth under saline or drought conditions, it is generally accepted that an increased nutrient supply will not improve plant growth when the nutrient is already present in sufficient amounts in the soil and when the drought or salt stress is severe. A better understanding of the role of mineral nutrients in plant resistance to drought and salinity will contribute to an improved fertilizer management in arid and semi‐arid areas and in regions suffering from temporary drought. This paper reviews the current state of knowledge on plant nutrition under drought and salinity conditions. Specific topics include: (1) the effects of drought and salt stress on nutrient availability, uptake, transport, and accumulation in plants, (2) the interactions between nutrient supply and drought‐ or salt‐stress response, and (3) means to increase nutrient availability under drought and salinity by breeding and molecular approaches.     

华北地区夏玉米生产中磷素利用特征研究

为评估当前中国华北地区夏玉米生产中的磷素利用效率和影响因素,促进磷肥资源高效利用和降低损失和污染,本研究通过收集1980年以来公开发表的夏玉米田间试验的文献,对华北地区夏玉米磷肥试验数据进行收集、整理和分析,获得了夏玉米的籽粒与秸秆产量及其比例,以及施磷量与籽粒和秸秆磷含量的关系模型。研究发现,随着施磷量的增加,土壤-夏玉米作物系统的磷素表观盈亏量呈线性增加,在施磷达到75 kg/hm2时,磷素表观盈亏量为0。华北地区的夏玉米磷肥平均利用效率约为15%;增加氮肥施用量以及与磷合理配施有利于提高磷肥利用效率。整体上,夏玉米对磷酸二铵的利用效率高于过磷酸钙;有机肥和化肥配施可以有效提高磷肥利用效率。夏玉米‘天泰60’品种的磷肥利用效率最高。在华北地区夏玉米生产中,选用磷酸二铵以及适合的氮肥水平、有机肥与化肥配施,可以提高磷肥利用效率,降低磷肥损失和环境污染风险。     

中量元素肥对玉米生理指标和产量性状的影响

以丹玉39和沈玉17为供试品种,通过田间试验,研究了S肥和Mg肥不同的施用量对玉米生理指标和产量性状的影响,初步探讨合适的硫肥和镁肥施用量.结果表明,合理的施用S肥和Mg肥对玉米杂交种的叶面积指数、叶绿素含量等生理指标及穗长、穗粒数等产量性状的影响较大,一般以每公顷30 kg左右S肥、115 kg左右Mg肥比较合适,对玉米杂交种的增产会有显着的促进作用.     

Subsoil retention of organic and inorganic nitrogen in a Brazilian savanna Oxisol

Abstract. Nitrogen (N) loss by leaching poses great challenges for N availability to crops as well as nitrate pollution of groundwater. Few studies address this issue with respect to the role of the subsoil in the deep and highly weathered savanna soils of the tropics, which exhibit different adsorption and drainage patterns to soils in temperate environments. In an Anionic Acrustox of the Brazilian savanna, the Cerrado, dynamics and budgets of applied N were studied in organic and inorganic soil pools of two maize (Zea mays L.) – soybean (Glycine max (L.) Merr.) rotations using ¹⁵N tracing. Labelled ammonium sulphate was applied at 10 kg N ha^?1 (with 10 atom%¹⁵N excess) to both maize and soybean at the beginning of the cropping season. Amounts and isotopic composition of N were determined in above‐ground biomass, soil, adsorbed mineral N, and in soil solution at 0.15, 0.3, 0.8, 1.2 and 2 m depths using suction lysimeters throughout one cropping season. The applied ammonium was rapidly nitrified or immobilized in soil organic matter, and recovery of applied ammonium in soil 2 weeks after application was negligible. Large amounts of nitrate were adsorbed in the subsoil (150–300 kg NO₃^?‐N ha^?1 per 2 m) matching total N uptake by the crops (130–400 kg N ha^?1). Throughout one cropping season, more applied N (49–77%; determined by ¹⁵N tracers) was immobilized in soil organic matter than was present as adsorbed nitrate (2–3%). Most of the applied N (71–96% of ¹⁵N recovery) was found in the subsoil at 0.15–2 m depth. This coincided with an increase with depth of dissolved organic N as a proportion of total dissolved N (39–63%). Hydrophilic organic N was the dominant fraction of dissolved organic N and was, together with nitrate, the most important carrier for applied N. Most of this N (>80%) was leached from the topsoil (0–0.15 m) during the first 30 days after application. Subsoil N retention as both adsorbed inorganic N, and especially soil organic N, was found to be of great importance in determining N losses, soil N depletion and the potential of nitrate contamination of groundwater.     

Some characteristics of organic soils irrigated with municipal wastewater

Soil irrigation with wastewater (WW) gives the opportunity to solve the problems of its disposal, final purification or reuse. Many studies have examined mineral soils upon continued WW application. The aim of this paper was to examine the properties of organic soils 3 years after WW application was discontinued. Peat‐muck soil planted with Populus spp. or Salix spp., and mineral‐muck soil under grasses were irrigated for 4 years with municipal WW at a low (comparable with intensive NPK fertilization) and high WW rate (600 and 1200 mm yearly, respectively). Soils were analysed for organic matter (OM), pH, bulk density (BD), water holding capacity (WHC), P₂O₅, Fe₂O₃, Al₂O₃, MnO, Zn, Pb, Cu, Cr, magnetic susceptibility (MS) and dehydrogenase and catalase activities. The results were compared with control soils which have never received WW. The study showed that only P₂O₅, MnO and catalase activity (CA) were significantly affected by former WW application. On average, P₂O₅ increased by 30 per cent, whereas MnO decreased by 35 per cent with no differences between the two WW rates. CA decreased by 18 per cent at the high WW rate. Most of tested characteristics were determined by soil type. The peat‐muck soil showed higher OM, WHC, P₂O₅, MnO, Pb and CA than mineral‐muck soil and lower BD, MS, Fe₂O₃, Al₂O₃ and Cr. Soil depth influenced Fe₂O₃, MnO, Zn, MS and enzyme activities, while basic soil properties (OM, pH, BD, WHC and P₂O₅) were not changed by soil depth. Heavy metals (Zn, Cr, Cu and Pb) were below upper permissible limits. Copyright © 2010 John Wiley & Sons, Ltd.