种植密度对适宜机械化栽培高粱品种产量及生理特性的影响

以适宜机械化种植的高粱品种辽杂37和晋杂34为试验材料,分别对6个密度处理的产量、产量构成因素、叶面积指数、叶绿素含量、光合速率及群体透光率进行了测定与分析。结果表明：辽杂37和晋杂34均在密度为13.5万株/hm ²时产量最高,分别可达10 551.0和10 324.5kg/hm ²。其中辽杂37在12.0万~15.0万株/hm ²、晋杂34在12.0万~13.5万株/hm ²密度时穗数、穗粒数和穗粒重协调效果较好,可保持较高产量水平。当密度达到15.0万株/hm ²时,随着密度的继续增加将导致群体光合速率和透光率大幅度下降,影响干物质积累和产量形成。     

小麦生产概况及其发展

小麦是世界第一大口粮作物,是人类生活所依赖的重要食物来源,全球约35%~40%的人口以小麦为主要粮食。2016年世界小麦种植面积约22 010.76万hm ²,约占全球谷物种植面积的30.7%,远超过玉米、水稻、大豆,居世界谷物种植面积之首。本文论述了世界小麦生产概况,包括小麦的种类、分布及主要生产国的基本情况,重点论述了中国小麦的生产和发展情况。随着社会的发展和科学技术的进步,中国的小麦生产能力逐步发展,主要体现在3个方面：一是种植面积起伏变化大,二是单产稳步提升,三是总产持续增长。无论是冬小麦还是春小麦,高产高效栽培技术和优良品种对产量的提升都起到了重要作用,我国小麦生产水平有了很大提高。     

Relationships between soil macroaggregation and humic carbon in a sandy loam soil following conservation tillage

Purpose

Humic substances are recalcitrant and might act as persistent binding agents to form macroaggregates. The focus of this study is in investigating the contribution of humic carbon (HC) to soil aggregation in response to various tillage and residue managements.

Materials and methods

Arable soils following 8-year contrasting managements were collected to determine aggregate size distribution and stability and HC fractions including humic acid (HA) and fulvic acid (FA). The contribution of HC to aggregation was divided into three special effects including positive effect (PE), negative effect (NE), and combined effect (CE), and these effects were measured using aggregate fractionation techniques.

Results and discussion

As well as to promote structural stability, HC bounds predominantly with the silt + clay fraction and secondarily with microaggregates to form larger aggregates. The PE increased with increasing aggregate size, whereas the NE followed the opposite pattern. A positive CE was observed for large and small macroaggregates, whereas the CE for microaggregates and the silt + clay fraction was negative. Compared to continuous tillage, reduced- and no-tillage decreased the PE for large and small macroaggregates by 1.58–30.98% at the 0–20 cm depth, and straw returning also slightly decreased the corresponding PE relative to straw removing. By contrast, a significantly higher NE for small macroaggregates at the 0–10 cm depth while 6.33–81.11% decreases in CE for large and small macroaggregates at the 0–10 cm depth as well as for large macroaggregates at the 10–20 cm depth, were observed under reduced- and no-tillage. The extraction of HC significantly reduced the aggregate stability and reduced- and no-tillage effectively limited its decrease magnitude. Small macroaggregates and microaggregates made larger contributions to soil HC accumulation than did other fractions. An averagely increased contribution from large or small macroaggregates was observed under both reduced-/no-tillage and straw returning at the 0–20 cm depth. A significant and positive relationship was found between the mass proportion of macroaggregates and the HC accumulation in 0–20 cm soil. Large macroaggregates had significantly higher HA/FA ratios than small macroaggregates, and reduced- and no-tillage significantly increased these ratios both in large and in small macroaggregates. The CE for large or small macroaggregates was also significantly negatively correlated with their HA/FA ratios.

Conclusions

Overall, the HC accumulation in soil is likely to play a key role in macroaggregation, but conservation tillage might decrease the contribution magnitude of HC to large or small macroaggregation through increasing the corresponding HA/FA ratios.

     

Influence of organic and inorganic passivators on Cd and Pb stabilization and microbial biomass in a contaminated paddy soil

Purpose

Soil contamination with heavy metals, such as Cd and Pb, has caused severe health and environmental risks all over the world. Possible eco-friendly solutions for Cd and Pb immobilization were required to reduce its mobility through various cost-effective amendments.

Materials and methods

A laboratory incubation study was conducted to assess the efficiency of biochar (BC), zeolite (ZE), and rock phosphate (RP) as passivators for the stabilization of Cd and Pb in paddy soil as well as soil microbial biomass. Various extraction techniques were carried out: a sequential extraction procedure, the European Community Bureau of Reference (BCR), toxicity characteristic leaching procedure (TCLP) test, and single extraction with CaCl₂. The impact of passivators on soil pH, dissolved organic carbon (DOC), and microbial biomass (carbon, nitrogen, and phosphorus) was examined in the metal contaminated soil.

Results and discussion

The results showed that the exchangeable portion of Cd in soil was significantly reduced by 34.8, 21.6, and 18.8% with ZE, RP, and BC at a 3% application rate, respectively. A similar tendency of reduction in Pb soluble portion was observed by ZE (9.6%), RP (20%), and BC (21.4%) at a 3% application rate. Moreover, the TCLP leachate of Cd and Pb was apparently reduced by 17 and 30.3% with BC at a 3% application dose, respectively, when compared to the control. Soil pH, nutrients, and microbial biomass C, N, and P were significantly increased with the addition of BC, RP, and ZE passivators.

Conclusions

The results showed that the incorporation of BC, ZE, and RP significantly reduced the Cd and Pb mobility in paddy soil as well as enhanced soil nutrients and microbial biomass. Overall, among all the amendments, rice straw derived-BC performed better for Cd and Pb immobilization in paddy soil.

     

Will spent mushroom substrate application affect the dissipation and plant uptake of phthalate esters?

Journal of Soils and Sediments - The objective of this study was to investigate whether spent mushroom substrate (SMS) amendment was an appropriate way to reduce di(2-ehylhexyl) phthalate (DEHP)...     

贵州省绥阳县麻黄洞土壤渗透水-洞穴水元素变化特征及气候响应

[目的]探究白云岩洞穴上覆土壤渗透水—洞穴水水化学元素变化特征及相互关系,揭示岩溶水Ca,Mg,Sr元素比值变化与洞外气候的响应关系。[方法]以贵州省绥阳县双河洞洞穴系统中的麻黄洞为研究对象,通过麻黄洞4个洞穴水点和上覆3个土壤点土壤渗透水的定期监测、采样和室内实验,并运用统计分析方法和元素比值法对各监测指标进行比较分析。[结果]①麻黄洞上覆土壤渗透水主要水化学指标表现为旱季雨季、洞穴水主要水化学指标表现为雨季旱季的季节性变化特征。②洞穴水EC,Ca~(2+),Mg~(2+),HCO~-_3,Sr~(2+)离子浓度约为土壤渗透水的2～6倍,表明表层岩溶带岩溶过程对洞穴水水化学元素具有重要影响。③土壤渗透水对地表降雨和温度变化具有积极响应,旱季滞留于土壤中的大量矿质元素是导致4月份土壤渗透水中Ca,Mg,Sr浓度出现高值的主要原因。④洞穴水Mg/Ca、Sr/Ca比值变化及其相关性,反映了洞穴水受到来源、水—岩相互作用、洞穴水脱气沉积和先期方解石沉淀过程(PCP)等机制影响的协同性及洞穴上覆主要岩溶过程差异,因此其比值变化能够间接表现洞外温度和降雨变化。[结论]土壤渗透水、洞穴水水化学元素具有明显的月间波动和季节性变化特征,且监测点间具有显著差异。两种类型水Ca,Mg,Sr比值变化及相关性对地表降雨和温度变化具有积极响应。     

植被恢复对黄土高原矿区重构土壤理化性质、酶活性以及真菌群落的影响

[目的]研究黄土高原矿区重构土壤植被恢复对土壤理化性质、酶活性以及真菌群落的影响,准确评价植被恢复对该地区的土壤生态恢复效果。[方法]在内蒙古自治区准格尔旗选择3种典型植被恢复类型(灌木、乔木、草地)和未复垦地采集0—20 cm土壤样品,采用扩增子测序技术分析了土壤真菌多样性和群落组成,同时结合土壤理化性质探讨了不同植被恢复类型影响真菌群落多样性的重要因素。[结果]①与未复垦地相比,3种典型植被恢复类型不仅对土壤理化性质和酶活性均有明显提升,还提高了土壤真菌可操作分类单元(OUTs)和多样性指数,且差异显著,以灌木的效果最好。②真菌主要菌门相对丰度在各样地变化趋势为子囊菌门(Ascomycota)担子菌门(Basidiomycota)球囊菌门(Glomeromycota),相对丰度之和已超过50%,土壤真菌群落结构在4个样地之间保持了一定的稳定性。③土壤含水量为影响真菌群落结构的最主要因素。[结论]植被恢复影响土壤理化性质、酶活性及真菌群落多样性,黄土高原矿区生态恢复是一个漫长的过程,在生态恢复过程中,宜种植灌木来改善重构土壤的生态环境。     

基于无人机遥感影像的覆膜农田面积及分布提取方法

针对基于无人机遥感的覆膜农田识别研究甚少的现状,该文以云南省昭通市鲁甸县为研究区,获取了研究区中地表类型复杂程度不同的2幅航空影像(复杂区影像和简单区影像)作为试验数据,利用灰度共生矩阵对原始航片影像进行纹理特征提取并选择纹理特征最佳提取参数;然后基于随机森林算法进行纹理特征重要性评价,优选纹理特征,结合原始数据进行最大似然初步分类;运用众数分析进行分类后处理;最后结合图像形态学算法与面积阈值分割法提取出了最终的覆膜农田面积及分布。通过试验结果发现,依据该文提出的方法,复杂区和简单区覆膜农田识别的总体精度、Kappa系数、产品精度、用户精度和面积误差分别达到了94.84%、0.89、92.48%、93.39%、0.38%和96.74%、0.93、97.39%、94.63%、1.95%。该文提出的融合监督分类和图像形态学算法的覆膜农田提取方法可以简单、快速的将地膜连成块,形成覆膜农田对象,进而通过面积阈值分割法获取高精度的覆膜农田分布信息。该方法可以为精准覆膜农田识别算法的发展提供参考。     

岩溶山区磷石膏堆场重金属迁移对耕地质量的影响及污染风险管控

[目的]探讨磷石膏堆场周边耕地土壤重金属含量的变化、成因及污染风险,为磷化工产业可持续发展及水土环境重金属污染的治理提供科学依据。[方法]通过对贵州省中部磷石膏堆场进行实地调查与采样开展分析和研究。[结果]磷石膏堆场排水、侵蚀冲沟水及洼地积水中Cd,Hg,As的含量都超过农田灌溉水质一类标准(水作)水质限值,特别是Cd。在磷石膏堆场周边50～300 m范围内,玉米地、蔬菜地、水稻土中Cd的含量分别超过农用地土壤污染风险筛选值的4.87～9.43倍、8.83～19.13倍和3.83～13.42倍,堆场周边旱作土主要是Cd,As,Zn的污染风险,而水稻土则主要是Cd,As,Hg,Zn的污染风险;大部分蔬菜地土壤和水稻土中Cd的含量超过农用地土壤污染风险管控值。[结论]天然降雨对露天磷石膏堆场产生的侵蚀及淋溶作用是重金属迁移的主要原因,在地表水流方向上耕地重金属污染风险随着堆场距离的增加而逐步减小。兴修排灌设施及调整种植结构是减少磷石膏堆场周边耕地重金属污染的有效途径。     

湘西重点生态功能区贫困县扶贫绩效评价

[目的]探讨湖南省湘西土家族苗族自治州在扶贫开发过程中能否协调生态保护、生产发展和生活改善三者关系,以期实现扶贫资源的集中整合,寻求重点生态功能区贫困县扶贫开发的适宜模式。[方法]基于精准扶贫战略,结合三生共赢理论构建扶贫绩效评价指标体系,采用主客观赋权法确定指标权重,进而计算2010—2016年研究区生产、生活、生态指数及扶贫综合成效指数。[结果](1)湘西州各县扶贫绩效不断提高,6a间扶贫成效综合指数增长2～4倍,尤其是在精准扶贫战略实行后,扶贫成效显著;(2)贫困区生产指数平均增长5.8倍,提高最快,但研究区不能偏重生产发展而忽略生活、生态方面的改善;(3)重点生态功能区贫困县的扶贫开发需要考虑区域特色,协调好生产、生活、生态三者关系,以此实现可持续发展。[结论]湘西重点生态功能区贫困县的首要任务是摆脱贫困,但在发展经济的同时,保护生态环境与改善生活条件同等重要。