Basic Soil Productivity of Spring Maize in Black Soil Under Long-Term Fertilization Based on DSSAT Model

Increasing basic farmland soil productivity has significance in reducing fertilizer application and maintaining high yield of crops. In this study, we defined that the basic soil productivity （BSP） is the production capacity of a farmland soil with its own physical and chemical properties for a specific crop season under local environment and field management. Based on 22-yr （1990-2011） long-term experimental data on black soil （Typic hapludoll） in Gongzhuling, Jilin Province, Northeast China, the decision support system for an agro-technology transfer （DSSAT）-CERES-Maize model was applied to simulate the yield by BSP of spring maize （Zea mays L.） to examine the effects of long-term fertilization on changes of BSP and explore the mechanisms of BSP increasing. Five treatments were examined： （1） no-fertilization control （control）; （2） chemical nitrogen, phosphorus, and potassium （NPK）; （3） NPK plus farmyard manure （NPKM）; （4） 1.5 time of NPKM （1.5NPKM） and （5） NPK plus straw （NPKS）. Results showed that after 22-yr fertilization, the yield by BSP of spring maize significantly increased 78.0, 101.2, and 69.4% under the NPKM, 1.5NPKM and NPKS, respectively, compared to the initial value （in 1992）, but not significant under NPK （26.9% increase） and the control （8.9% decrease）. The contribution percentage of BSP showed a significant rising trend （P〈0.05） under 1.5NPKM. The average contribution percentage of BSP among fertilizations ranged from 74.4 to 84.7%, and ranked as 1.5NPKM〉NPKM〉NPK〉NPKS, indicating that organic manure combined with chemical fertilizers （I.5NPKM and NPKM） could more effectively increase BSP compared with the inorganic fertilizer application alone （NPK） in the black soil. This study showed that soil organic matter （SOM） was the key factor among various fertility factors that could affect BSP in the black soil, and total N, total P and/or available P also played important role in BSP increasing. Compared with the chemical fertilization, a balanced chemical plus manure or straw fertilization （NPKM or NPKS） not only increased the concentrations of soil nutrient, but also improved the soil physical properties, and structure and diversity of soil microbial population, resulting in an iincrease of BSP. We recommend that a balanced chemical plus manure or straw fertilization （NPKM or NPKS） should be the fertilization practices to enhance spring maize yield and improve BSP in the black soil of Northeast China.

Cropping frequency and N fertilizer effects on soil water distribution from spring to fall in the semiarid Canadian prairies

In the semiarid Canadian prairies, water is the most limiting and nitrogen (N) the second most limiting factor influencing spring wheat (Triticum aestivum L.) production. The efficiency of water-and nitrogen use needs to be assessed in order to maintain this production system. The effects of cropping frequency and N fertilization on trends in soil water distribution and water use were quantified for an 18-yr (1967-1984) field experiment conducted on a medium textured Orthic Brown Chernozem (Aridic Haploboroll) in southwestern Saskatchewan, Canada. Soil water contents were measured eight times each year and plant samples were taken at five phenological growth stages. The treatments studied were continuous wheat (Cont W), summer fallow - wheat, F-(W) and summer fallow - wheat - wheat, F-W-(W) each receiving recommended rates of N and phosphorus (P) fertilizer, and (F)-W-W and (Cont W) each receiving only P fertilizer, with the examined rotation phase shown in parentheses. Soil water conserved under fallow during the summer months averaged 25 mm in the root zone, and was related to the initial water content of the soil, the amount of precipitation received, its distribution over time, and potential evapotranspiration. Under a wheat crop grown on fallow, soil water contents between spring and the five-leaf stage remained relatively constant at about 250 mm, but those under a stubble crop, with 40 mm lower spring soil water reserves, increased slightly until about the three-leaf stage. During the period of expansive crop growth (from the five-leaf to the soft dough stage) soil water was rapidly lost from all cropped phases at rates of 1.87 mm.day–1 for F-(W) (N+P), 1.23 mm.day–1 for Cont W (N+P) and 1.17 mm.day–1 for Cont W (+P). The initial loss was from the 0 - 0.3 m depth, but during the latter half of the growing season from deeper depths, although rarely from the 0.9 - 1.2 m depth. In very dry years (e.g., 1973, with 87 mm precipitation between spring and fall) summer fallow treatments lost water. In wet years with poor precipitation distribution (e.g., 1970, with 287 mm precipitation between spring and fall but 142 mm of this in one week between the three- and five-leaf stage) even cropped treatments showed evidence of leaching. The above-ground biomass water use efficiency for Cont W was 19.2 and 16.7 kg.ha–1.mm–1, respectively, for crops receiving (N+P) and P fertilizer only. Grain yield water use efficiency (8.91 kg.ha–1.mm–1) was not significantly influenced by cropping frequency nor N fertilizer. The 18 years of detailed measurements of plant and soil parameters under various crop management systems provide an invaluable source of information for developing and testing simulation models.

Particle Size Characteristics of Soil in Karst Area with Different Land Use Pattern—A Case Study of Shuifang Spring,Jinfo Mt.,Chongqing

This paper tried to analyze the particle size characteristics of the soil samples in Shuifang Spring catchment area,Jinfo Mt.,Chongqing with different land use patterns that are horse race grassland, rhododendron bush,bamboos,and the grassland near the Shuifang spring.The different land usepattern in karst area is of great affection to the particle size characteristics of soil.The median diameter of the karst surface layer soil becomes gradually smaller and smaller in following sequence:horse race grassland,grassland near the Shuifang Spring,

Application of Mulching Materials of Rainfall Harvesting System for Improving Soil Water and Corn Growth in Northwest of China

The ridge and furrow rainfall harvesting（RFRH） system is used for dryland crop production in northwest of China.To determine the effects of RFRH using different mulching materials on corn growth and water use efficiency（WUE）,a field experiment was conducted during 2008-2010 at the Heyang Dryland Experimental Station,China.Four treatments were used in the study.Furrows received uncovered mulching in all RFRH treatments whereas ridges were mulched with plastic film（PF）,biodegradable film（BF） or liquid film（LF）.A conventional flat field without mulching was used as the control（CK）.The results indicated that the average soil water storage at depths of 0-200 cm were 8.2 and 7.3%,respectively higher with PF and BF than with CK.However,LF improved soil water storage during the early growth stage of the crop.Compared with CK,the corn yields with PF and BF were increased by 20.4 and 19.4%,respectively,and WUE with each treatment increased by 23.3 and 21.7%,respectively.There were no significant differences in corn yield or WUE with the PF and BF treatments.The net income was the highest with PF,followed by BF,and the 3-yr average net incomes with these treatments were increased by 2 559 and 2 430 CNY ha-1,respectively,compared with CK.BF and PF had similar effects in enhancing the soil water content,crop yield and net income.Therefore,it can be concluded that biodegradable film may be a sustainable ecological alternative to plastic film for use in the RFRH system in northwest of China.

Non-limit passive soil pressure on rigid retaining walls

This paper aims to reveal the depth distribution law of non-limit passive soil pressure on rigid retaining wall that rotates about the top of the wall(rotation around the top(RT) model). Based on Coulomb theory, the disturbance degree theory, as well as the spring-element model, by setting the rotation angle of the wall as the disturbance parameter, we establish both a depth distribution function for sand and a nonlinear depth distribution calculation method for the non-limit passive soil pressure on a rigid retaining wall under the RT model, which is then compared with experiment. The results suggest that under the RT model: the non-limit soil pressure has a nonlinear distribution; the backfill disturbance degree and the lateral soil pressure increase with an increase in the wall rotation angle; and, the points where the resultant lateral soil pressure acts on the retaining wall are less than 2/3 of the height of the wall. The soil pressure predicted by the theoretical calculation put forward in this paper are quite similar to those obtained by the model experiment, which verifies the theoretical value, and the engineering guidance provided by the calculations are of significance.

Influence of high-fluorine environmental background on crops and human health in hot spring-type fluorosis-diseased areas

Drinking water-type fluorosis is the most harmful endemic disease in China with the largest number of sufferers. Although the implementation of the policy to alter water sources to lower fluoride level has effectively controlled the spread of this kind of endemic disease,its prevalence could not thoroughly be stopped because the high-fluoride environmental background in these endemically diseased areas could still do harm to human health through food chain. Therefore,it is necessary to conduct a more deep-going study on the drinking water-type fluoro-sis. To investigate the effect of high fluorine environmental background on crops and human health in the hot spring-type fluorosis-diseased areas,local water,paddy soil,rice,whole vegetables and soils around their roots were sampled for analysis. The results were compared with those of the control groups in fluorosis-free areas which are similar to the fluorosis-diseased areas both in natural background and in social background. It is indicated that rice and vegetables can accumulate water-soluble fluorine either in soils or in irrigating water,and different crops have different abilities of fixing fluorine. The contents of fluorine in different parts of vegetables in the fluorosis-diseased and fluorosis-free areas were statistically categorized. The results showed that the fluorine contents of roots,tubers,leaves and flowers of vegetables in the fluorosis-diseased areas are 3.56,1.17,3.07 and 3.23 mg/kg,respectively. However,comparisons showed that in the fluorosis-free areas,the fluorine contents are 2.17,0.70,1.91 and 2.52 mg/kg,respectively. Moreover,different parts of a crop also show significantly different fluorine fixation abilities. It is demonstrated that the fluorine contents of the strongly metabolic parts are relatively high. For example,the fluo-rine contents of roots,leaves and flowers of vegetables are much higher than those of stems. The fluorine fixation ability of seeds is very weak. In order to reduce the risk of human body’s exposure to fluoride,the impact of hot spring water on the capability of crops to fix fluorine should be reduced as much as possible. It is of great importance to prevent crops from being irrigated with hot spring water and it is advisable to grow crops with relatively low ca-pabilities to enrich fluorine,such as those with seeds or tubers as the main edible parts in the areas which are se-verely affected by hot spring water.

荸荠收获机弹簧辊式泥果分离装置研制

针对荸荠收获泥果分离难、果实损伤率高的问题,根据旱地环境下荸荠采收作业需求,该研究提出一种由正反旋弹簧并排布置的荸荠收获机弹簧辊式泥果分离装置。通过对荸荠与弹簧辊的相对运动过程动力学分析,确定了影响荸荠收获泥果分离的关键因素为弹簧外径、螺距、相邻弹簧间距、高度差及弹簧转速、线径、作业速度。利用EDEM软件建立泥果混合物离散元模型,对弹簧辊结构参数与工作参数进行单因素试验,分析各因素对泥果分离效果的影响。以荸荠筛分率和土壤筛分率为指标进行二次回归正交试验,得到弹簧辊最佳参数组合为外径100 mm、螺距30 mm、间距9 mm、转速420 r/min,该参数组合下荸荠筛分率为80.00%,土壤筛分率为80.69%。进行仿真验证试验,对比试验结果与模型预测值,荸荠筛分率平均相对误差为2.09%,土壤筛分率平均相对误差为2.42%。以明果率、伤果率、破皮率、挖净率为指标开展模拟采挖试验,分析不同线径弹簧辊的泥果分离能力,确定12 mm线径弹簧兼具较好的振动筛分性能和较低的损伤率。通过实际收获试验测得作业速度0.21 m/s,作业效率0.19 m^(2)/s,碎土率75.61%,明果率82.42%,伤果率14.73%,破皮率7.01%。研究结果可为荸荠收获机研制和优化改进提供参考。

New artificial boundary condition for saturated soil foundations

Anew artificial boundary model based on multi-directional transmitting and viscous-spring artificial boundary theories is proposed to absorb stress waves in a saturated soil foundation in dynamic analysis. Since shear waves （S-waves） are the same in a saturated soil foundation and a single-phase medium foundation, a tangential visco-elastic boundary condition for a single-phase medium foundation can also be used for saturated soil foundations. Thus, the purpose of the artificial boundary proposed in this paper is primarily to absorb two types of P-waves in a saturated soil foundation. The main idea is that the stress of the P-waves in the saturated soil foundation is decomposed into two types. The first type of stress, δra＇ is absorbed by the first artificial boundary. The second type of stress, δrb, is balanced by the stress generated by the second artificial boundary. Ultimately, both types of P-waves （fast-P-waves and slow-P-waves） are absorbed by the artificial boundary model proposed in this paper. In particular, note that the fast-P-waves and slow-P-waves are absorbed at the position of the first boundary. Thus, the artificial boundary model proposed herein can simultaneously absorb P-fast waves, P-slow waves and shear waves. Finally, a numerical example is given to examine the proposed artificial boundary model, and the results show that it is very accurate.

Study on micro-water-collecting technique in dryland field of spring maize

This paper analyses the effect of water storage and soil moisture conservation by means of micro water collecting technique in the dryland field of spring maize. The results indicate that the rainfall infiltration depth is deeper by means of micro water collecting treatment than that of the control. In micro water collecting treatment, the amount of soil water storage within 0～200 cm of soil layers increases by 50.5 mm, 13.5～58.6 mm, and 24.5 mm respectively during seedling stage, the critical stage of water requirement and the ripening and harvesting stage compared with the control. The micro water collecting technique not only has the function of regulating and adjusting the amount and distribution of field evapotranspiration, but also can raise the water use efficiency, which results in an obvious effect of increasing crop yield, especially in the dry years.

土壤水分对不同抗旱性春小麦品种叶片保护性酶活性及产量的影响

【目的】研究土壤水分对不同抗旱性春小麦品种叶片保护性酶活性及产量的影响,为选育春小麦抗旱品种及制定节水高产措施提供理论依据。【方法】在大田条件下,以抗旱性较强的品种新春46号、抗旱性中等的品种新春37号、抗旱性较弱的品种新春26号为材料,设置3种水分处理,研究土壤水分对不同抗旱性春小麦品种旗叶超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性、丙二醛(MDA)含量及产量的影响。【结果】随着水分亏缺程度的加剧,春小麦旗叶SOD、CAT活性在扬花期呈升高的趋势,而在灌浆期则呈先升高后降低的趋势;POD活性在扬花期呈先升高后降低的趋势,灌浆期则呈升高的趋势;MDA含量呈升高的趋势;SOD、POD活性表现为抗旱性较强的品种新春46号>抗旱性中等的品种新春37号>抗旱性较弱的品种新春26号,MDA活性在春小麦品种间则呈相反的趋势。收获穗数、穗粒数和产量均随着水分亏缺程度的加剧而降低,抗旱性较强的品种新春46号在有限灌溉和亏缺灌溉处理下,其收获穗数和穗粒数降低幅度小于新春37号和新春26号,且产量高于新春37号和新春26号。【结论】抗旱性较强的品种新春46号在有限灌溉和亏缺灌溉条件下,旗叶SOD、POD酶活性较高,MDA含量较低,活性氧清除能力较强,有效延缓了小麦植株的衰老,收获穗数和穗粒数较抗旱性中等的新春37号和抗旱性较弱的新春26号下降幅度低,在水分亏缺条件下有利于获得较高的产量。

西北旱塬免耕的产量效应受降水特征和施肥显著影响

【目的】在冬小麦-夏春玉米轮作体系,研究不同降水年型条件下西北雨养农业区耕作与施肥对作物产量的影响,为西北旱塬作物高产稳产提供理论依据。【方法】基于2005年甘肃陇东旱塬设置的土壤耕作与培肥长期定位试验(3年冬小麦—1年春玉米),主处理为传统耕作和免耕,副处理为不施肥(CK)、单施氮肥(N)、单施磷肥(P)、单施农家肥(M)、氮磷配施(NP)和氮磷配施农家肥(NPM)。结合对冬小麦和玉米产量的分析,探究不同耕作与施肥处理下作物产量在不同降水年型的差异机制。【结果】降水年型、耕作和施肥方式显著影响冬小麦和玉米产量。无论何种降水年型或耕作方式,配施有机肥的NPM处理作物产量(冬小麦3441 kg/hm^(2),春玉米8991 kg/hm^(2))均显著高于其他施肥处理,并且NPM处理对作物的增产效果在丰水年型更为明显。在丰水年型,相对于传统耕作,免耕处理的作物产量无明显差异,但在干旱及平水年型下,免耕冬小麦平均产量分别下降了15.6%和25.7%,玉米平均产量分别下降了17.9%和4.6%;与传统耕作相比,免耕处理下的冬小麦和玉米水分利用效率在干旱年型分别下降了6.7%和17.0%,冬小麦水分利用效率在平水年型下降了24.0%。免耕处理下土壤有机质、全氮、全钾、速效氮、速效磷和速效钾含量显著高于传统耕作。【结论】在西北半干旱雨养农业区,干旱及平水年型免耕虽然提高了土壤养分含量,但降低了作物水分利用效率,这是导致作物产量降低的主要原因。因此,需要根据降水情况选择耕作方式,提高西北黄土旱塬作物产量的稳定性。

花生与绿肥轮作对土壤含水量和土壤肥力的影响

探讨在冬春裸地上种植绿肥对后茬作物春花生养分含量、土壤含水量和土壤肥力的影响,为山东地区春花生等冬闲田建立一种合理的轮作方式提供理论依据。在田间试验条件下,设置了春花生—冬闲田、夏花生—冬小麦、春花生—二月兰和春花生—毛叶苕子4种轮作处理。结果表明:种植二月兰和毛叶苕子绿肥作物,可促进后茬作物花生氮磷钾养分增加,二月兰增加程度高于毛叶苕子。种植二月兰和毛叶苕子绿肥作物,可提高后茬作物花生土壤含水量和土壤肥力,在0~20 cm土层中,2021年,与春花生—冬闲田相比,春花生—二月兰、春花生—毛叶苕子土壤相对含水量分别升高了4.70%、6.14%,在20~40、40~60 cm土层中也表现出相似趋势,2022年与2021年相比,表现出相似规律;与春花生—冬闲田相比,春花生—二月兰处理有机质、碱解氮、有效磷和速效钾含量平均增加了5.71%、8.98%、7.22%和7.72%,春花生—毛叶苕子处理有机质、碱解氮含量平均增加了4.54%、14.91%。可以利用春花生种植期间的冬春裸地种植一季冬绿肥,促进后茬作物养分积累量增加,改善土壤肥力。

民勤县石羊河湿地公园春季土壤动物群落特征

2023年3-5月,对甘肃民勤石羊河公园4个功能区5个植被型组7个不同植物群系的土壤动物群落特征进行了调查。结果表明:共收集到土壤动物46个类群1488头,隶属于3门5纲13目25科。中小型土壤动物和大型土壤动物分别占97.38%和2.62%,线虫在群落结构中占绝对优势。中小型土壤动物中的优势类群为头叶属、真头叶属、臭蚁属;占总捕获量的48.58%;常见类群为丽突属、拟丽突属、短体属、鞘属、半懒甲螨属等16个类群,占总捕获量的47.13%;稀有类群有椎实螺属、耳萝卜螺属、两坑螺属、虹蛹螺属、逍遥蛛属等14个类群,占总捕获量的4.29%。大型土壤动物主要为拟步甲科和叩甲科,其中优势类群为琵琶甲属、蒙小鳖甲和尖尾东鳌甲,均为荒漠草原沙地种类。沙枣群系和油蒿群系土壤动物的个体数、类群数、丰富度指数和Shannon-Wiener多样性指数均高于其他植物群系,优势度指数则较低。7个植物群系的土壤动物群落结构的相似性为中等不相似和极不相似。沙枣群系、白刺群系、多枝柽柳群系的土壤动物具有明显的表聚性,而油蒿群系、芨芨草群系和芦苇群系中的土壤动物垂直分布具有异质性。

长期施用有机肥对半干旱区春小麦产量及其水分利用效率和土壤有机碳的影响

以国家土壤质量安定观测试验站黄绵土区的农田长期定位试验为研究对象,研究长期施用有机肥对半干旱区春小麦产量及其水分利用效率和有机碳的影响。结果表明,连续种植7年春小麦,施肥显著影响小麦产量及其水分利用效率,以化肥与有机肥配施(NPKM)处理效果最好,较单施化肥(NPK)、单施有机肥(OM)处理春小麦产量和水分利用效率分别增加了7.18%和7.82%、5.91%和3.83%;在定位施肥初期(前3年),NPKM和NPK处理的效果优于OM,在第4年三者无差异,而第5年及之后,NPKM和OM处理的效果明显好于NPK处理。长期NPKM和OM处理较NPK处理0~20 cm土层土壤有机碳含量分别显著增加了36.88%和31.98%,有机碳储量分别显著增加了31.17%~41.94%和27.80%~35.81%,表层0~10 cm的增加效果显著好于10~20 cm土层。不同施肥处理对0~20 cm土层土壤微生物生物量碳(MBC)的影响表现为NPKM>OM>NPK>CK,且差异显著,长期NPKM和OM处理较NPK处理土壤MBC分别显著增加了46.4%和28.7%,长期单施NPK处理可显著增加土壤MBC含量,但对有机碳影响不明显。综上所述,长期NPKM或OM处理可显著增加黄绵土小麦地土壤有机碳和MBC含量,增加有机碳储量,有利于农田土壤固碳增汇,提高小麦产量及其水分利用效率。

不同灌水处理对春玉米土壤水分、耗水特征及产量的影响

【目的】探究不同灌水定额对春玉米全生育期耗水特征及产量的影响,优化克拉玛依地区春玉米节水灌溉制度,以提高当地水分利用效率。【方法】于2021年5—9月在克拉玛依农业综合开发区开展春玉米田间试验,设置6个灌水处理W1(225 m^(3)/hm^(2))、W2(300 m^(3)/hm^(2))、W3(375 m^(3)/hm^(2))、W4(450 m^(3)/hm^(2))、W5(525 m^(3)/hm^(2))、W6(600 m^(3)/hm^(2)),探究不同灌水定额对春玉米耗水特征及产量的影响。【结果】①各生育期不同灌水处理0~100 cm土层土壤含水率随土层深度增加呈“增-减-增”的变化趋势。W5处理在喇叭口期、抽雄散粉期、乳熟期、完熟期较W1、W2、W3、W4、W6处理0~100 cm土层土壤贮水量平均增加了2.35%~9.11%、0.21%~4.37%、0.39%~1.79%、0.60%~4.48%。②完熟期W5处理百粒质量显著高于W1处理和W2处理,但与W3、W4、W6处理无显著性差异。W5处理穗粒数较其他处理显著提高10.49%~36.01%,穗长较其他处理显著提高8.31%~27.12%。③综合评判模型计算得出W5处理(525 m3/hm^(2))综合评价指数最高。【结论】因此,全生育期灌水10次,灌水定额为525 m3/hm^(2)是克拉玛依地区最优灌水处理。

基于被动区土弹簧刚度降低过程的基坑围护结构计算增量法及软化p-y曲线

基坑围护结构的计算常采用基于杆系有限元的增量法,被动区土弹簧刚度在基坑开挖作用下发生动态降低导致土抗力软化,目前缺少在非线性地基模型基础上对该问题的研究。通过引入两个刚度变化系数来综合量化被动区土弹簧参数随基坑开挖的动态变化过程,建立了基于该过程的基坑围护结构计算增量法。针对非线性地基模型,提出了细化增量法进行数值计算。采用线弹性、理想弹塑性以及双曲线3种基本土弹簧模型计算得到被动区软化p-y曲线,对比显示,基于双曲线基本模型得到的等效水平抗力系数变化曲线更符合实际规律。工程实例计算显示,基于基本土弹簧为双曲线的计算结果与不同开挖阶段墙的位移监测数据对应更好。参数分析显示,与被动区土体极限抗力pu相关的刚度变化系数对计算结果影响较大,采用此方法应着重关注被动区pu的计算方法及开挖卸荷对pu的影响。

基于MODIS的普洱市春旱时空演变分析

受季风气候的影响,21世纪以来普洱市春季干旱频发,为了探究春季农业干旱的周期性,论文以普洱市为研究区,利用MODIS增强型植被指数EVI和合成的地表温度LST数据计算温度植被干旱指数TVDI模型,对2001—2022年1—4月普洱市春旱进行时空演变分析。结果表明:时间上,2001—2022年TVDI总均值为0.59,近22年的TVDI呈下降趋势,其干旱类型以中旱为主,年内3月、4月是全市最严重时期,2月次之,1月最弱;空间上,2001—2022年1—4月普洱市春旱南北部旱情呈增强趋势,东西部呈减轻趋势,除小部分地区(景东中部及东部、镇沅东部、景谷东部)旱情不稳定外,整体上旱情较为稳定,其干旱重心转移幅度较小,主要分布在景谷与思茅区,整体往南西方向偏移。

春季土壤温度在中国东北盛夏降水年际分量预测中的关键作用

全球变暖背景下,中国东北夏季洪涝干旱灾害发生频繁,对人类和自然系统造成严重影响。但是,目前东北夏季降水预测水平较低,远不能满足防灾、减灾的需求。中国东北汛期降水主要集中在盛夏(7~8月),其年际变率与年代际变率相当。本文聚焦在分析春季土壤温度在中国东北盛夏降水年际分量预测中的作用。研究发现中国东北盛夏降水年际分量与欧洲中东部春季土壤温度年际分量存在显著负相关关系、与青藏高原东部和西亚东北部春季土壤温度年际分量存在显著正相关关系。春季关键区土壤温度异常对应下游地区盛夏土壤温度异常,从而引起东亚盛夏大气环流异常,高空西风急流偏强偏北、西太平洋副热带高压偏强偏北,进而造成中国东北水汽辐合与上升增强,引起中国东北盛夏降水增强。进一步采用欧洲中东部、青藏高原东部和西亚东北部春季土壤温度年际分量建立了中国东北盛夏降水年际分量的季节预测模型,1979~2021年留一法交叉检验时间相关系数在GLDAS-Noah、ERA5和CRA/Land三套数据中最高可达0.64,2012~2021年的后报试验时间相关系数在三套数据中最高可达0.78,表明春季土壤温度在中国东北盛夏降水年际分量预测中起到关键作用。研究成果能够为提高中国东北夏季降水预测提供科学基础,并易于应用到实际预测。

冀西北旱作春玉米秸秆还田模式对土壤团聚体稳定性的影响

[目的]研究冀西北旱作区春玉米秸秆还田对土壤团聚体稳定性的影响,优化适宜旱作区春玉米秸秆还田模式。[方法]采用连续3年田间定位试验,设计秸秆还田翻耕(JF)、秸秆还田旋耕(JX)、秸秆还田大垄轮播(JL)3种还田模式,分析土壤不同粒径团聚体质量比、平均重量直径(MWD)和几何平均直径(GMD)。[结果]冀西北旱作区春玉米农田土壤以0.25~0.50 mm团聚体占比最高,在26.28%~31.84%,其次为>1.00~2.00 mm团聚体,<0.25 mm团聚体占比最低。秸秆还田能显著提高>1.00 mm团聚体比例(P<0.05),增幅顺序为JX>JL>JF,JF、JL、JX处理比CK土壤MWD分别提高了10.59%、12.94%、17.06%,土壤GMD分别提高了15.31%、16.33%、18.37%。秸秆还田后春季土壤团聚体大颗粒占比下降,微颗粒占比升高,稳定性下降。秸秆还田显著提高0~20 cm土层>1.00~2.00 mm团聚体占比,增加土壤团聚体稳定性,提高>20~40 cm土层0.25~0.50 mm和<0.25 mm团聚体占比,降低土壤团聚体稳定性。[结论]秸秆还田模式通过对秸秆的破碎程度、有机碳输入、影响微生物酶活性调节土壤团聚体结构及稳定性,冀西北旱作区春玉米秸秆还田旋耕对土壤团聚体稳定性提高最显著。

垂直弹射系统中缓冲及反后坐效应的建模方法

针对垂直弹射过程中,由缓冲以及弹射后坐引发的对发射性能与阵地产生的负面影响问题,从缓冲吸能角度,提出按缓冲器的塑性应变能-压缩量关系曲线拟合并求导解算缓冲力-压缩量关系模型的方法,有效规避了缓冲力波动所造成的拟合漂移问题,并据此构造了模拟缓冲器的线弹性-塑性弹簧模型;依据弹射试验数据,反演了反后坐效应的动态数据,据此构造了模拟反后坐效应的非线性粘弹性-塑性弹簧模型;通过力元、状态变量及牛顿迭代法的有机结合,在动力学模型中实现了上述二模型的高效解算。仿真结果表明:两模型计算稳定高效且缓冲特性与有限元仿真结果高度吻合、反后坐效应和试验数据符合良好,这验证了数据处理方法的有效性和建模方法的可信性,为后续含缓冲和反后坐效应的弹射动力学仿真提供了一种稳定而又可信的建模思路。