Importance of information on tillage practices in the modelling of environmental processes and in the use of environmental indicators

Tillage has been and will always be integral to crop production. Tillage can result in the degradation of soil, water, and air quality. Of all farm management practices, tillage may have the greatest impact on the environment. A wide variety of tillage equipment, practices and systems are available to farmers, providing opportunities to enhance environmental performance. These opportunities have made tillage a popular focus of environmental policies and programs such as environmental indicators for agriculture. This paper provides a very brief examination of the role of tillage in crop production, its effect on biophysical processes and, therefore, its impact on the environment. Models of biophysical processes are briefly examined to demonstrate the importance of tillage relative to other farm management practices and to demonstrate the detail of tillage data that these models can demand. The focus of this paper is an examination of the use of information on tillage in Canada's agri-environmental indicators initiative, National Agri-environmental Health Analysis and Reporting Program (NAHARP). Information on tillage is required for several of the indicators in NAHARP. The type of data used, its source, and its quality are discussed. Recommendations regarding the collection of tillage data and use of tillage information are presented.     

Sampling and Mapping a Soil Erosion Cover Factor by Integrating Stratification,Model Updating and Cokriging with Images

Cost-efficient sample designs for collection of ground data and accurate mapping of variables are required to monitor natural resources and environmental and ecological systems. In this study, a sample design and mapping method was developed by integrating stratification, model updating, and cokriging with Landsat Thematic Mapper (TM) imagery. This method is based on the spatial autocorrelation of variables and the spatial cross-correlation among them. It can lead to sample designs with variable grid spacing, where sampling distances between plots vary depending on spatial variability of the variables from location to location. This has potential cost-efficiencies in terms of sample design and mapping. This method is also applicable for mapping in the case in which no ground data can be collected in some parts of a study area because of the high cost. The method was validated in a case study in which a ground and vegetation cover factor was sampled and mapped for monitoring soil erosion. The results showed that when the sample obtained with three strata using the developed method was used for sampling and mapping the cover factor, the sampling cost was greatly decreased, although the error of the map was slightly increased compared to that without stratification; that is, the sample cost-efficiency quantified by the product of cost and error was greatly increased. The increase of cost-efficiency was more obvious when the cover factor values of the plots within the no-significant-change stratum were updated by a model developed using the previous observations instead of remeasuring them in the field.     

高能重离子辐照下国产RPV钢A508-3的硬化行为

目的 研究在563 K的温度条件下,高能重离子辐照导致国产RPV钢A508-3的硬化行为。方法 使用回旋加速器提供的352.8 MeV Fe²¹⁺对A508-3钢试样进行辐照,使其依次达到0.15、0.30、1.50 dpa的损伤水平。借助辐照终端的梯度减能装置,在样品表面至25 μm的深度范围内产生一个准均匀分布的原子离位损伤坪区,并使用纳米压痕仪和维氏显微硬度计测量了试样的硬度。结果 考虑到压痕尺寸效应的影响,采用Nix-Gao模型对硬度数据进行拟合,由于高能Fe离子产生了较厚的损伤区,辐照试样中的软基效应明显减弱。辐照后的试样出现明显的硬化现象,且随着辐照剂量的增大,硬化增量有饱和趋势。通过辐照前和辐照至0.15 dpa试样的微硬度数据,得出其与纳米硬度之间的线性关系(Hv0=0.85 H0)。结论 借助A508-3辐照前后的硬度数据,计算发现试样的屈服强度增量与辐照剂量之间存在一种幂函数关系,这为A508-3钢中子-离子辐照硬化的映射关系研究提供了基础数据。     

中国主粮作物生物炭产量效应的Meta分析

为定量评估生物炭对主粮作物产量的影响,收集了公开发表的116篇相关文献,共866对数据,采用Meta分析法定量分析了生物炭对我国主粮作物产量的影响及其影响因子,同时构建结构方程模型(SEM)进一步解释了因子间的交互关系.结果表明,与不施用生物炭相比,生物炭施用后可改善主粮田土壤理化性质,提高主粮作物产量,平均增产率为8.77%.其中,当生物炭pH为7～8时,平均增产率最大,可达26.49%;其C/N<60时,平均增产率为13.73%,显著高于C/N≥60的平均增产率.将生物炭施入酸性或中性土壤中,更能发挥其增产效应.当施炭量为10～20 t·hm^-2时,小麦和玉米的平均增产率最大;施炭量为15～25 t·hm^-2时,水稻平均增产率最大.但是,不同施炭水平的水稻增产率相近,可考虑损失部分产量,适当减施以兼顾经济效益.此外,生物炭增产效应会随施用年限增加而不断减弱,一般3 a后增产不显著.SEM表明生物炭施用量不仅直接影响主粮作物产量,还通过改善土壤肥力间接影响主粮作物产量,而生物炭C/N和pH仅通过改善土壤肥力影响主粮作物产量.因此,今后...     

牡蛎壳粉和石灰改良酸性水稻土对磷有效性、形态和酶活性的影响

我国南方粮食主产区土壤酸化治理是提升耕地地力促进粮食增产的重要内容,目的是探究酸化土壤改良剂牡蛎壳粉和石灰对水稻土酸度、磷有效性和形态以及酶活性和相关功能基因的影响.盆栽试验设计2种改良剂的3个施用量（0.05%、0.10%和0.15%）,以水稻为试验作物.结果表明：①牡蛎壳粉和石灰均显著提高土壤pH,降低土壤交换性酸,且改良效果随着改良剂用量增加而提高,相同用量下石灰对土壤酸性的改良效果高于牡蛎壳粉;② 4种有效磷提取剂提取的土壤有效磷测定结果表明,牡蛎壳粉和石灰显著提高H₂SO₄-P、Bray-1 P和Olsen-P含量,其中Olsen-P含量随改良剂用量的增加而提高.③土壤中不同形态无机磷含量表现为：Fe-P>Al-P>Ca-P,石灰和牡蛎壳粉显著提高Al-P和Fe-P含量,分别提高26.3%~37.4%和7.9%~23.7%;0.15%改良剂显著增加Ca-P含量;④石灰和牡蛎壳粉对土壤DHA、ALP、IPP活性和phoD基因拷贝数具有提高作用,而对土壤ACP活性、phoC和pqqC拷贝数表现为降低;⑤改良剂（0.10%和0.15%）显著提高水稻产量,0.15%用量的石灰和牡蛎壳粉分别提高水稻产量34.2%和46.8%,但对秸秆生物量无显著影响.相关分析表明,土壤无机磷和有效磷含量与pH和ALP活性呈显著正相关,改良剂通过消除土壤酸化和提高土壤磷酸酶活性来改善土壤磷营养状况,这对促进作物产量具有积极作用.     

节水灌溉和控释肥施用耦合措施对单季稻田CH4和N2O排放的影响

以我国华东地区典型单季稻水稻田(江苏宜兴)的原柱状土为研究对象,通过两年土柱观测试验,研究不同灌溉管理模式(长期淹水CF、间隙灌溉Ⅱ、控制灌溉CI)和氮肥施用(不施氮CK、尿素Urea和控释肥CRF)耦合措施对水稻生长期内CH4和N2O排放和产量的影响,以期优选典型单季稻田减排增效的水肥管理模式.结果表明,两种节水灌溉方式(CI和Ⅱ)均显著影响稻田土壤CH4和N2O排放量及二者的综合温室效应(GWP)和排放强度(GHGI),与CF相比,Ⅱ和CI均显著提高了 N2O排放量(P＜0.05),降低了 CH4排放量(P＜0.05),进而二者的GWP和GHGI分别显著降低28.9％～71.4％和14.3％～70.4％(P＜0.05);两种节水灌溉模式相比,CI较Ⅱ模式呈现较好的CH4减排优势,排放总量降低了 57.7％～91.8％,而二者的N2O排放量无显著性差异(P＞0.05),最终CI对GWP和GHGI的减排效应略优于Ⅱ模式2.0％～56.2％.施用氮肥(Urea和CRF)均显著促进N2O排放18.4％～2547.8％(P＜0.05),其中CRF处理N2O排放量均略高于Urea处理32.7％～78.6％,但无显著性差异(P＞0.05);CH4排放总量对施氮处理的响应随水分管理模式的不同而不同,总体而言,施用CRF较Urea对稻田土壤GWP和GHGI均无显著影响(P＞0.05).相关分析表明,2018年CF模式的Urea处理和Ⅱ模式的Urea、CRF处理中N2O排放通量与田面水NH4+-N浓度分别呈现显著(P＜0.05)和极显著的正相关关系(P＜0.01),而二者在2019年CI模式的CK和CRF处理中呈现相反规律;2018年CI模式下CK、CRF处理的N2O排放通量与田面水NO3--N浓度呈极显著的正相关关系(P＜0.01).节水灌溉和氮肥施用对水稻产量均呈显著影响(P＜0.05),与CF相比,两种节水灌溉模式(Ⅱ、CI)水稻产量均下降了 14.7％～37.7％;CRF处理较Urea处理略提高水稻产量2.5％～7.4％(P＜0.05).综合考虑稻田土壤GWP、GHGI和水稻产量,节水模式与控释肥施用对稻田土壤减排增产的耦合效应仍有待进一步研究.     

浒苔生物炭与木醋液复配改良碱化土壤效果及提高油葵产量

为探究浒苔生物炭与木醋液复配改良碱化土壤效果及提高作物产量,以龟裂碱土为例,通过田间试验研究不同生物炭施加量(0、1％、2％和4％)与不同木醋液稀释倍数(0、2％)复配对土壤pH、碱化度、全盐、容重、速效磷、有机质、盐分离子、油葵生长和产量的影响,不施加生物炭和木醋液视为对照(CK).结果表明,2％浒苔生物炭+2％木醋液(V2BC2)改良龟裂碱土的综合效果最佳;在最佳处理条件下:①浒苔生物炭与木醋液复配能改善土壤理化性质,具体表现为作物生长期内土壤平均pH、碱化度和全盐含量显著降低,较CK分别降低12.14％、40.63％和42.75％,土壤容重显著减小,较CK减小20.78％;②浒苔生物炭与木醋液复配能显著降低土壤Na+、Cl-和SO42-含量,较CK分别降低47.17％、45.32％和33.33％,提高土壤K+和Ca2+含量,其他离子含量的差异不显著;③浒苔生物炭与木醋液复配显著提高土壤养分含量及有效性,增强土壤酶活性,与CK相比,速效磷提高2.88倍,有机质提高58.76％,土壤脲酶、碱性磷酸酶和蔗糖酶活性分别提高0.92、1.02和2.29倍;④油葵产量在V2BC2处理时最高,为3 546.7 kg-hm-2,较CK增产2 325.3 kg-hm-2.因此,浒苔生物炭与木醋液复配能进一步提高盐碱土改良效果及作物产量.     

控释尿素不同施用条件下冬小麦产量和氮素利用效应

采用田间试验方法研究了控释尿素不同施用条件对冬小麦产量、氮素利用和经济效益的影响。试验共设7个处理,即CK （空白处理,不施氮肥）、100%PU10/0（普通尿素全量基施,N 240 kg＆#183;hm-2）、100%PU6/4（60%的普通尿素基施、40%的普通尿素于拔节期追施,N 240 kg＆#183;hm-2）、80%PU6/4（60%的普通尿素基施、40%的普通尿素于拔节期追施,N 192 kg＆#183;hm-2）、100%CRU（全量树脂包膜控释尿素基施,N 240 kg＆#183;hm-2）、80%CRU（80%树脂包膜控释尿素基施,N 192 kg＆#183;hm-2）和40%CRU＋40%PU（40%树脂包膜控释尿素＋40%的普通尿素基施,N 192 kg＆#183;hm-2）。结果表明,无论是产量效应还是氮素利用效应,树脂包膜控释尿素（CRU）处理总体优于普通尿素（PU）处理,尤其树脂包膜控释尿素和普通尿素配施（40%CRU＋40%PU）效果最佳,以7709 kg＆#183;hm-2的产量、36.44%的氮肥吸收利用率、15946元＆#183;hm-2的相对净收入达到处理间最高水平。该处理在减少氮素投入量的情况下,不仅促进了冬小麦增产,而且显著提高了肥料的利用率,拥有较高的产投比。因此,树脂包膜控释尿素和普通尿素的配施处理（40%CRU＋40%PU）是本试验条件下最优的氮肥处理。     

Daily Bank Erosion Rates in the Lower Yellow River Before and After Dam Construction

During the period of water impoundment and sediment detention of the Sanmenxia Reservoir, riverbank erosion processes played a key role in the channel evolution of the Lower Yellow River (LYR). However, research into bank erosion rates of the LYR has been neglected due to the lack of direct field monitoring. In this study, an indirect method is proposed to determine bank erosion rates at daily time scales by outlining a detailed calculation procedure using measured hydrological data. A total of 810 data points of daily bank erosion rates before and after the construction of Sanmenxia Dam was calculated at seven hydrometric sections along the LYR, with the corresponding values of the bank stability coefficient and the width‐to‐depth ratio also being calculated. Empirical relations were then developed to estimate the daily bank erosion rates, using these parameters at the sections. Temporal and spatial variability in daily bank erosion rates in the LYR before and after dam construction were also investigated, revealing that: (1) the bank erosion rates had a mean value of 16.7‐29.1 m/day in the braided reach, with a maximum value of 290.0 m/day, while they were relatively low in the meandering reach, with a mean value of 2.5 m/day; (2) the erosion rates before dam construction were slightly greater than those after dam construction, with the difference reaching 5‐10 m/day in the braided reach, decreasing in the transitional reach gradually, and being slight in the meandering reach.