氮肥与密度互作对单粒精播花生根系形态、植株性状及产量的影响

为明确花生单粒精播适宜的氮肥水平和种植密度,本研究于2018年和2019年以‘花育22’为供试花生品种,设置3个氮肥水平(0 kg hm~(–2), N0; 60 kg hm~(–2), N1; 120 kg hm~(–2), N2), 3个种植密度(7.93万株hm~(–2), D1; 15.86万株hm~(–2),D2; 23.79万株hm~(–2), D3),采用二因素裂区试验设计,研究氮肥、密度及其互作对单粒精播花生根系形态、植株性状及产量的影响。氮肥对花生根长、根表面积、根体积、根干重的影响不显著,而密度的影响显著。单株根长、根表面积、根体积及根系干重随密度的增加而降低, D1显著高于D2和D3, D2、D3处理间差异不显著;单位面积根长、根表面积、根体积及根系干重随密度的增加而增加, D1显著低于D2和D3, D2、D3处理间差异不显著。氮肥和密度互作对2019年收获期单位面积根长、根表面积的影响显著,与D1相比, N1处理下D3的增幅显著高于N0和N2处理。氮肥及氮肥与密度互作对植株性状的影响存在年度和时期间的差异,主茎叶片数、侧枝数和主茎第一节间粗随密度增加有降低趋势。氮肥对荚果产量的影响不显著,荚果产量随密度的增加呈增加的趋势。产量与根体积、根干重、主茎叶片数、主茎高及侧枝长呈显著正相关。综上所述,在本试验条件下,花生单粒精播适宜的氮肥(N)水平为60 kg hm~(-2),种植密度为18.8万株hm~(-2)。     

草地土壤分离能力季节变化特征及其影响因素

土壤分离能力是土壤侵蚀机理模型的重要参数.受土壤性质、植被根系等因素影响,土壤分离能力呈现显著的季节变化.为研究草地土壤分离能力季节变化特征及其影响机制,以建植一年的柳枝稷、无芒雀麦草地及对照裸地为研究对象,以20 d为周期,测定土壤密度、黏结力和根系密度,并采集原状土样进行水槽实验(τ=6.5-23.4Pa),测量土壤分离能力,并运用相关分析、回归分析等方法,研究土壤性质及植被根系对土壤分离能力季节变化的影响.结果显示:柳枝稷和无芒雀麦草地具有类似的季节变化特征,而裸地与二者差异明显.4月中旬至6月下旬,草地土壤分离能力较大,此后土壤分离能力迅速下降;7月中旬直至10月上旬,草地土壤分离能力较低;10月下旬,土壤分离能力小幅回升;裸地土壤分离能力7、8月份较低,其余时间较高.裸地土壤分离能力试验期均值为柳枝稷草地的10.6倍,无芒雀麦草地的23.7倍.草地土壤分离能力的季节变化受根系密度和土壤黏结力的影响,随着根系密度与土壤黏结力增大,土壤分离能力呈指数形式降低,而土壤密度对土壤分离能力季节变化的影响并不显著.试验区内草地土壤分离能力可用水流剪切力、根系密度、根径和土壤黏结力等参数进行模拟(R2=0.636).研究结果可为土壤侵蚀机理模型的推广应用,以及小流域水土保持措施配置等工作提供科学依据.     

用模糊综合评判法预测马尾松毛虫幼虫高峰期发生量

为了提高马尾松毛虫一代、二代幼虫高峰期发生量预报的准确性,为有效防治马尾松毛虫提供科学依据,本文运用模糊综合评判的6个数学模型预测安徽省潜山县马尾松毛虫一代、二代幼虫高峰期的发生量,验证预报1989年、1994年、2002年和2017年一代马尾松毛虫幼虫高峰期发生量,预报结果分别为2级、4级、2级和1级,与实况级别完全吻合,预报结果准确。预报1989年、1994年、2002年和2017年二代马尾松毛虫幼虫高峰期发生量,预报结果依次是4级、5级、2级和1级。同样与实况级别全部相同。预报的准确率为100%,模糊综合评判法是一个运算简便、准确性高的预报方法。     

密度与环境因子对蒙古黄芪育苗影响研究

为了明确育苗时密度与环境因子对蒙古黄芪生长特征影响,本试验以蒙古黄芪为研究对象,通过单因素田间随机区组试验,测定蒙古黄芪株高、茎粗、根粗和根长4个指标。结果表明,密度对蒙古黄芪影响最大,其次是湿度,最后是光照和电导率。密度与蒙古黄芪株高、茎粗、根粗呈现负相关性,与根长呈正相关性(P<0.05),密度为400株/m ²时,株高、茎粗及根粗最大,密度为1000株/m ²时根长最大。     

Short time effects of biological and inter-row subsoiling on yield of potatoes grown on a loamy sand,and on soil penetration resistance,root growth and nitrogen uptake

Soil compaction, especially subsoil compaction, in agricultural fields has increased due to widespread use of heavy machines and intensification of vehicular traffic. Subsoil compaction changes the relative distribution of roots between soil layers and may restrict root development to the upper part of the soil profile, limiting water and mineral availability. This study investigated the direct effects of inter-row subsoiling, biological subsoiling and a combination of these two methods on soil penetration resistance, root length density, nitrogen uptake and yield. In field experiments with potatoes in 2013 and 2014, inter-row subsoiling (subsoiler) and biological subsoiling (preceding crops) were studied as two potential methods to reduce soil penetration resistance. Inter-row subsoiling was carried out post planting and the preceding crops were established one year, or in one case two years, prior to planting. Soil resistance was determined with a penetrometer three weeks after the potatoes were planted and root length density was measured after soil core sampling 2 months after emergence. Nitrogen uptake was determined in haulm (at haulm killing) and tubers (at harvest). Inter-row subsoiling had the greatest effect on soil penetration resistance, whereas biological subsoiling showed no effects. Root length density (RDL) in the combined treatment was higher than in the separate inter-row and biological subsoiling treatments and the control, whereas for the separate inter-row and biological subsoiling treatments, RLD was higher than in the control. Nitrogen uptake increased with inter-row subsoiling and was significantly higher than in the biological subsoiling and control treatments. However, in these experiments with a good supply of nutrients and water, no yield differences between any treatments were observed.     

AM80-0.2Sr-1.5Ca镁合金高温压缩过程动态再结晶模拟

在Gleeble-1500热压缩实验机上对AM80-0.2Sr-1.5Ca镁合金进行高温压缩实验，得到了该合金在温度为300~450 ℃、应变速率为0.01~1 s-1条件下的流变应力曲线.结合改进的Laasraoui-Jonas（L-J）位错密度模型和Kock-Mecking（K-M）位错密度模型，获得AM80-0.2Sr-1.5Ca镁合金在改进的L-J位错密度模型中的应变硬化参数和应变软化参数，建立该合金的动态再结晶模型.利用DEFORM-3D软件，实现了对AM80-0.2Sr-1.5Ca镁合金在450 ℃热压缩实验时微观组织演变和位错密度变化过程的有限元模拟，并与实际热压缩实验微观组织进行对比.研究结果表明：在相同的温度和应变量下，应变速率较低时，AM80-0.2Sr-1.5Ca镁合金组织粗大且晶粒分布不均，随着应变速率增大，再结晶组织细小均匀模拟与实验结果一致，说明求解的应变硬化参数和应变软化参数准确，所建立的动态再结晶模型能准确预测该合金高温压缩过程动态再结晶过程.     

不同培养方法及培养密度对绵羊腔前卵泡发育的影响

通过对绵羊腔前卵泡培养方法的研究,能够探索出适宜绵羊腔前卵泡生长发育的培养条件,以及为进一步揭示绵羊卵泡生长发育的规律奠定一些基础。试验一通过使用微滴法和琼脂培养基法培养腔前卵泡,观察其对绵羊腔前卵泡生长的影响;试验二通过绵羊腔前卵泡单独培养与群体培养,探讨不同培养密度对绵羊腔前卵泡生长的影响。试验结果显示,使用微滴法与琼脂培养基法培养的绵羊腔前卵泡,在培养3天时,卵泡直径增加值和存活率差异均不显著(P0.05);但培养6天时,琼脂培养基法培养的腔前卵泡的直径增加值和存活率均极显著高于微滴法培养的腔前卵泡(P0.01);在使用琼脂培养基培养的条件下,对绵羊腔前卵泡进行单独培养和群体培养,在培养的6天时间内二者卵泡直径增加值和存活率差异均不显著(P0.05)。试验结果表明,琼脂培养基法是较为适宜的绵羊腔前卵泡体外培养方法;培养密度对绵羊腔前卵泡体外培养并无显著影响。     

Dense planting with less basal nitrogen fertilization might benefit rice cropping for high yield with less environmental impacts

Dense planting and less basal nitrogen (N) fertilization have been recommended to further increase rice (Oryza sativa L.) grain yield and N use efficiency (NUE), respectively. The objective of this study was to evaluate the integrative impacts of dense planting with reduced basal N application (DR) on rice yield, NUE and greenhouse gas (GHG) emissions. Field experiments with one conventional sparse planting (CK) and four treatments of dense planting (increased seedlings per hill) with less basal N application were conducted in northeast China from 2012 to 2013. In addition, a two-factor experiment was conducted to isolate the effect of planting density and basal N rate on CH₄ emission in 2013. Our results show that an increase in planting density by about 50% with a correspondingly reduction in basal N rate by about 30% (DR1 and DR2) enhanced NUE by 14.3–50.6% and rice grain yield by 0.5–7.4% over CK. Meanwhile, DR1 and DR2 reduced GWP by 6.4–12.6% and yield-scaled GWP by 7.0–17.0% over CK. According to the two-factor experiment, soil CH₄ production and oxidation and CH₄ emission were not affected by planting density. However, reduced basal N rate decreased CH₄ emission due to it significantly reduced soil CH₄ production with a smaller reduction in soil CH₄ oxidation. The above results indicate that moderate dense planting with less basal N application might be an environment friendly mode for rice cropping for high yield and NUE with less GHG emissions.     

Culture of Eriocheir sinensis Larvae in Ponds in Greenhouse

A total of 15 pools were selected from a greenhouse, and they were randomly and evenly divided into three groups. In each group, one stocking density of Eriocheir sinensis was arranged. The results showed that after 45-d culture, the crab number per kilogram reached about 300 with survival rate of about 20%; the initial stocking density had significantly effect on the body size of E. sinensis on sel , instead on the survival rate of E. sinensis larvae. Therefore, it is feasible to conduct the culture of E. sinensis larvae in a pool in greenhouse.     

不同种植密度对夏玉米品种株型及产量性状的影响

为了阐述不同玉米品种株型及产量性状对密度响应，以目前生产上广泛种植的6个品种（‘郑单958’、‘先玉335’、‘伟科702’、‘浚单20’、‘金海5号’、‘利民33’）为材料，研究4个种植密度(60000、90000、112500、127500株/hm2)下不同品种株型和产量性状的变化。结果表明：6个品种棒三叶面积及茎粗系数均随着密度增加而减小，但减小幅度在不同品种或不同叶位存在差异。产量构成因素如穗长、穗粗、穗行数、行粒数、穗粒数和千粒重随着密度增加而减小。4个种植密度中，‘金海5号’、‘伟科702’、‘郑单958’在密度为90000株/hm2时产量为最高；其他3个品种随密度增加，产量降低。回归分析发现在10个已知影响玉米产量因素中，穗粒数对产量的直接影响最大，其次为行粒数。此结果为玉米品种选育和生产上高效栽培提供理论依据。