氮肥与种植密度对春玉米产量及抗倒伏性能的调控效应

【目的】适宜的密度与氮肥运筹是提高玉米抗倒伏能力、保证高产稳产和提高生产效益的重要措施。探讨不同施氮量与种植密度对春玉米产量及抗倒伏性能的影响,以期为山西春玉米的高产高效栽培及籽粒机收的发展提供理论支撑。【方法】于2018和2019年在山西晋中进行玉米田间试验,供试玉米品种为‘郑单958’。设置4个施氮水平:0、120、180、240 kg/hm^(2) (N0、N1、N2、N3);3个种植密度:60000、75000、90000株/hm^(2)(D1、D2、D3)。调查玉米吐丝期茎秆农艺性状,生理成熟期穗位以下茎秆生物学、力学性状及倒伏率,并测定产量。【结果】随着种植密度和施氮量的增加,玉米产量呈先增加后降低的趋势。在D2密度下达到最高值,两年平均产量为13792 kg/hm^(2),较D1和D3密度下分别增加了4.8%和8.3%。与N0相比,N1、N2和N3处理分别增产24.3%、26.7%和23.9%。N3处理对穗粒数与千粒重无显著影响,但产量低于N1和N2处理。增密导致玉米茎秆变细,株高、穗位上升,玉米第3~6节长粗比增加,穿刺强度、抗压强度、抗弯折力等茎秆力学特性变差。D2和D3密度下两年玉米平均倒伏率较D1分别升高了1.33、3.73个百分点。N1、N2、N3处理两年玉米平均倒伏率较N0分别增加了2.50、3.25、4.80个百分点。适当增氮有利于消减因密度增加导致的生物学、力学特性变差,D2和D3密度下,N2处理第3~6节穿刺强度、抗压强度和抗弯折力维持在较高水平,显著高于N3处理。【结论】合理的氮肥用量可改善因密度增加导致的茎秆细弱、玉米茎秆力学特性变差问题,降低倒伏风险,因而增加产量。在山西中部春玉米种植区,种植密度为75000株/hm^(2)、施氮量180 kg/hm^(2),是玉米产量、茎秆力学特性及抗倒性能和谐的密度肥料组合。

聚乙烯地膜降解过程与机理研究进展

为探讨聚乙烯地膜的降解过程及影响因素,从聚乙烯材料的分子结构与特性入手,结合国内外最新研究进展,系统论述了聚乙烯分子的降解过程、产物、机理与作用因素。文章指出聚乙烯分子较高的结晶度与相对分子质量、较强的疏水性与分子间作用力是导致其难以降解的主要因素;其中,聚乙烯分子间共价键的氧化断裂是整个降解过程的限速反应。环境中较强的光能、热能、机械作用力等能够促进聚乙烯分子键的氧化断裂,使聚乙烯分子非结晶区及小型结晶区域解聚成亲水性低聚物或小分子,并最终在微生物作用下完全分解为CO_2、H_2O、CH_4、生物质等微生物代谢产物。深入系统开展聚乙烯分子降解机理的系统研究,不仅可以科学评价残留地膜对环境的影响,而且能够指导聚乙烯地膜配方改进,降低聚乙烯地膜残留污染。

肥密因子对旱地豇豆产量效应分析

[目的]探索山西旱地条件下豇豆栽培的高产措施。[方法]以中豇1号为研究对象,选取密度、氮肥、磷肥和钾肥为试验因素,按照二次通用旋转组合设计统计分析方法建立回归模型,分析种植密度和不同肥料配比对中豇1号产量的影响。[结果]各因子对豇豆产量的影响达到显著水平,且变化趋势均呈开口向下的抛物线,影响顺序由高到低依次为K肥、P肥、N肥、密度;要获得1 875 kg/hm2的产量,种植密度、氮肥、磷肥和钾肥的最优取值范围为:种植密度为120 465～128 295株/hm2,施N 40.49～54.66 kg/hm2,施P2O542.92～56.24 kg/hm2,施K2O 57.91～65.93 kg/hm2。[结论]该研究为豇豆大面积种植提供理论依据。

Nitrogen uptake and transfer in broad bean and garlic strip intercropping systems

Utilization and transfer of nitrogen （N）in a strip intercropping system of garlic （Allium safivum L.） and broad bean （Vicia faba L.） have been investigated rarely. The objectives of this study were to quantify N uptake and utilization by intercropped broad bean and garlic and determine the magnitude of N transfer from broad bean to garlic. Field and pot trials were carried out in the Erhai Lake Basin in China using ^15N tracer applied to the soil or injected into broad bean plants. Strip intercropping of garlic and broad bean increased N absorption （47.2%） compared with sole crop broad bean （31.9%） or sole crop garlic （40.7%） and reduced soil residual N. Nearly 15% of 15N injected into petioles of broad bean intercropped with garlic was recovered in garlic at harvest, suggesting that N could be transferred from broad bean to strip intercropped garlic. The findings provide a basis for evaluating legumes＇ role in optimizing N fertilization when intercropped with non-legumes.

Response of carbon footprint to plastic film mulch application in spring maize production and mitigation strategy

Producing more food with a lower environmental cost is one of the most crucial challenges worldwide. Plastic mulching has developed as one of the most dominant practices to improve crop yields, however its impacts on greenhouse gas(GHG) emissions during the production life cycle of a crop are still unclear. The objective of this work is to quantify the impacts of plastic film on GHG emissions and to reduce GHG emissions with innovative agronomic practices. Carbon footprint per unit of area(CFa), per unit of maize grain yield(CFy), and per unit of economic output(CFe) were evaluated for three maize cultivation systems: a no mulch system, a conventional plastic mulching system(PM) and a biennial plastic mulching pattern, namely a ’one film for 2 years’ system(PM2), during 2015–2018 in a maize field located on the Loess Plateau of China. The results suggested that PM induced a 24% improvement in maize yields during the four experimental years compared to a no-mulch treatment(NM). However, PM dramatically increased the CFa by 69%, 59% of which was created by the input of the plastic film material, and 10% was created by increases in the soil N2O emissions. The yield improvements from PM could not offset the increases in CFa, and CFy and CFe were both increased by 36%. Shifting from PM to PM2 did not reduce crop yields, but it led to a 21% reduction in CFa and 23% reductions in CFy and CFe due to the reduced input amount of plastic film, decreased soil N2O emissions, and less diesel oil used for tillage. Compared to NM, CFy and CFe were only 5% higher in PM2. This study highlights the necessity of reducing the amount of plastic film input in the development of low-carbon agriculture and shifting from conventional PM cultivation to PM2 could be an efficient option for mitigating GHG emissions while sustaining high crop yields in plastic mulched fields.

Silicon-on-Insulator 2×2 Symmetric Optical Switch Based on Total Internal Reflection

Based on the large cross-section single-mode rib waveguide condition,the total internal reflection and the free-carrier plasma dispersion effect,a silicon-on-insulator(SOI)2×2 symmetric optical waveguide switch with a transverse injection structure has been proposed and fabricated,in which the SOI technique utilizes silicon and silicon dioxide thermal bonding and back-polishing.The device performance is measured at the wavelength of 1.3μm.It shows that the crosstalk and insertion loss are less than -18.1 and 4.8 dB,respectively,at an injection current of 60mA,and response time is 110 ns.

Double-Injection Bifurcation Optical Active Switch Integrated on Silicon-on-Insulator for 1.3μm Operation

Based on the double-injection effect,the dual-mode interference principle and the free-carrier plasma dispersion effect,a double-injection bifurcation optical active switch integrated on silicon-on-insulator has been proposed and fabricated.Its insertion loss and crosstalk are measured to be less than 5.32 and -14.4dB,respectively,at wavelength 1.3μm and the total switching current 90mA.Response time is about 180ns.

SiGe Optical Waveguide Modulators Based on the Plasma Dispersion Effect

Based on plasma dispersion of Si_(1-x)Ge_(x),the single mode waveguide modulators consisting of Si_(1-x)Ge_(x)/Si and Si/Si_(1-x)Ge_(x)/Si which were grown by molecular beam epitaxy have been fabricated.For Si_(1-x)Ge_(x)/Si structure,the switch current and insertion loss at wavelength 1.3 fiin are 36 mA and 2.8 dB,respectively.The switching response time is 40 ns.

不同收获期对玉米子粒机械收获质量及产量的影响

以山西子粒机收主推的4个品种金科玉3306、迪卡517、中地88、DF607为研究对象,生理成熟后设置不同收获期,研究玉米不同收获期对子粒机械收获质量(子粒破碎率、含杂率、落粒率、落穗率、总损失率)及产量的影响。结果表明,子粒收获质量中含杂率、总损失率分别为1.57%、1.75%,均满足《玉米收获机械(GB/T21962-2020)》标准要求;破碎率为5.46%,是子粒机械收获质量的主要问题,不同收获期对机收产量影响不显著。含水率随着收获期的推迟而降低,含水率高是导致破碎率高的主要因素。结合两年不同收获期,通过拟合方程可以得出,含水率与破碎率呈二次曲线关系,当含水率在19.0%~24.3%时,破碎率低于5%。根据不同收获期子粒含水率的变化规律,该区域子粒机械收获以10月15~20日为宜。供试玉米品种中迪卡517、金科玉3306表现较好。