不同施氮量对烤烟干物质积累的影响

在不同的施氮水平下，对湘东烟区烤烟干物质的积累规律进行了初步的研究。结果表明，在每公顷施纯氮127．5kg的水平下，根、茎、叶干物质积累量较高，到圆顶时分别为78．20，74．66和128．48g，相对增长量分别是不施氮处理的4．33，2．967和1．355倍，相对增长速度分别为2．060，1．819，2．198g／d，说明在当地的气候条件下，在每公顷施127．5kg纯氮的条件下，撂烟有较高的生物学产量。     

氮肥运筹技术对淮稻9号群体质量的效应研究

适量增施氮肥能促进淮稻9号分蘖和个体发育,有利于高产群体的形成,增加抽穗期至成熟期的干物质积累量,穗多穗大产量高。增加前期施氮比例可有效增加淮稻9号单位面积有效穗数。     

Effects of transition season management on soil N dynamics and system N balances in rice–wheat rotations of Nepal

In the low-input rice–wheat production systems of Nepal, the N nutrition of both crops is largely based on the supply from soil pools. Declining yield trends call for management interventions aiming at the avoidance of native soil N losses. A field study was conducted at two sites in the lowland and the upper mid-hills of Nepal with contrasting temperature regimes and durations of the dry-to-wet season transition period between the harvest of wheat and the transplanting of lowland rice. Technical options included the return of the straw of the preceding wheat crop, the cultivation of short-cycled crops during the transition season, and combinations of both. Dynamics of soil N_min, nitrate leaching, nitrous oxide emissions, and crop N uptake were studied throughout the year between 2004 and 2005 and partial N balances of the cropping systems were established. In the traditional system (bare fallow between wheat and rice) a large accumulation of soil nitrate N and its subsequent disappearance upon soil saturation occurred during the transition season. This nitrate loss was associated with nitrate leaching (6.3 and 12.8 kg ha⁻¹ at the low and high altitude sites, respectively) and peaks of nitrous oxide emissions (120 and 480 mg m⁻² h⁻¹ at the low and high altitude sites, respectively). Incorporation of wheat straw at 3 Mg ha⁻¹ and/or cultivation of a nitrate catch crop during the transition season significantly reduced the build up of soil nitrate and subsequent N losses at the low altitude site. At the high altitude site, cumulative grain yields increased from 2.35 Mg ha⁻¹ with bare fallow during the transition season to 3.44 Mg ha⁻¹ when wheat straw was incorporated. At the low altitude site, the cumulative yield significantly increased from 2.85 Mg ha⁻¹ (bare fallow) to between 3.63 and 6.63 Mg ha⁻¹, depending on the transition season option applied. Irrespective of the site and the land use option applied during the transition season, systems N balances remained largely negative, ranging from −37 to −84 kg N ha⁻¹. We conclude that despite reduced N losses and increased grain yields the proposed options need to be complemented with additional N inputs to sustain long-term productivity.     

水氮措施影响夏玉米氮素利用的叶绿素荧光特性研究

以产量差异显著的两个夏玉米品种德单5号和郑单958为材料,设不同灌溉和施肥水平,开展水氮互作对玉米产量、氮素利用和叶绿素荧光特性的影响研究。结果表明,在不同灌溉处理下,增施氮肥显著提高营养器官氮素转运量,降低氮素转运效率,N3(180 kg/hm²)、N4(225 kg/hm²)处理间无显著差异。增施氮肥也显著提高了各灌溉条件下两个品种吐丝期穗位叶F_v/F_m和F_v/F_o,当氮肥施用量增加至N3(180 kg/hm²)后增肥效果不显著。因此,大喇叭口期和吐丝散粉期分别灌溉37.5 mm配合180 kg/hm²的施氮量有利于提高叶绿素荧光参数F_v/F_m和F_v/F_o,促进夏玉米植株氮素转运,提高氮肥利用效率。此外,F_v/F_m和F_v/F_o均与植株氮...     

基于高光谱特征参数的冬小麦氮营养指数估算

为了实现快速高精度获取冬小麦氮营养指数的高光谱监测技术,利用美国SVC HR-1024I型野外光谱辐射仪对2017-2019年关中地区的冬小麦进行遥感监测,获取“三边”参数、任意两波段光谱指数和植被指数,通过相关性分析和逐步回归分析方法筛选冬小麦氮营养指数的敏感光谱参数,结合偏最小二乘回归(PLSR)、随机森林算法(RFR)、支持向量机回归(SVR)和梯度增强回归(GBDT)建立冬小麦氮营养指数模型,并对模型估算精度进行验证。结果表明,从拔节期到灌浆期,各时期的氮营养指数与任意两波段光谱指数均呈极显著相关,其中拔节期氮营养指数与任意两波段光谱指数相关性均高于其他时期,且基于一阶导数光谱的归一化光谱指数和比值光谱指数与氮营养指数的相关系数最大,为0.66。拔节期基于梯度增强回归的冬小麦氮营养指数预测模型的决定系数(r²)和均方根误差(RMSE)分别为0.96和0.05,模型验证的r²、RMSE和相对预测偏差(RPD)分别为0.95、0.12和2.12,模型预测精度最高。因此,拔节期基于梯度增强回归的冬小麦氮营养指数估算模型可用于冬小麦氮营养监测...     

不同供氮水平多花黑麦草化感抑草作用与资源竞争分析

[目的]为了判断黑麦草与猪殃殃的化感作用与资源竞争关系。[方法]运用化感一竞争分离法,通过盆栽混播不同比例的供、受体植株,测定受体植株干重的变化规律,以探讨黑麦草对猪殃殃杂草的化感作用或资源竞争的关系。[结果]当黑麦草和猪殃殃混播比例较大时（供受体混播比例为12：10）,会由竞争作用转为化感作用;而在氮素胁迫条件下,两者的关系均会加强,在氮水平为10kg／667m2时,化感作用最强,随着氮水平的加大,抑制作用减弱,竞争作用逐渐加强。[结论]明确黑麦草与猪殃殃的资源竞争与化感作用的关系,为黑麦草化感抑草作用研究提供理论依据。     

添加生物炭的水芹湿地对农村低污染水的净化研究

为研究生物炭对湿地处理污水的效果,以种植水芹的湿地系统为对象,通过盆栽试验研究了添加1%和5%煅烧温度为500℃和700℃的两种生物炭对低污染水的净化作用及其对水芹生长的影响。结果表明:加入1%煅烧温度为700℃和500℃生物炭的水芹盆中,系统表面水TN浓度均值在4.05~4.18 mg·L~(-1),低于不加生物炭对照组。煅烧温度为500℃,添加量为1%的生物炭处理组的氨挥发损失总量为96.07 kg·hm~(-2),显著提高;而煅烧温度为700℃,添加量为1%的处理组的氨挥发损失总量(43.02 kg·hm~(-2))与对照相当,其植株地上部分生物量和养分累积量较大,且该种生物炭对土壤养分有一定的固持作用,具有较好的正面效应。通过生物炭和水芹湿地系统的耦合,筛选出了较优的生物炭类型,其在净化污水的同时降低了对环境的负面影响,有效利用了污水中的氮、磷等养分资源,从而为设计农村低污染水的生态修复工程提供了基础数据和技术支撑。     

Distribution of Leaf Color and Nitrogen Nutrition Diagnosis in Rice Plant

Greenness and nitrogen content of each leaf on main stem of different japonica and indica ricevarieties under different nitrogen levels were investigated. Results showed that the fourth leaf from the top ex-hibited active changes with the change of plant nitrogen status. When the plant nitrogen content was low, itscolor and nitrogen content were obviously lower than those of the three top leaves. With the increase of plantnitrogen content, the color and nitrogen content of the fourth leaf increased quickly, and the differences ofcolor and nitrogen content between the fourth leaf and the three top leaves decreased. So, the fourth leaf wasan ideal indication of plant nutrition status. In addition, color difference between the fourth and the third leaffrom the top was highly related to the plant nitrogen content regardless of the variety and development stage.Therefore, color difference between the fourth and the third leaf could be widely used for diagnosis of plantnutrition. Results also indicated that the minimized color difference between the fourth and the third leaf at the criticaleffective tillering, the emergence of the second leaf from the top, and the heading was the symbol of high yield. Plantnitrogen content of 27 g kg-1 DW for japonica rice and 25 g kg-1 DW for indica were the critical nitrogen concentrations.     

淹水土壤中氮素运移与转化试验及其数值模拟

在室内试验的基础上,建立了淹水土壤中NH₄⁺—N和NO₃^-运移转化的耦合数学模型,并对表施于水层中的氮肥(碳铵:NH₄HCO₃)在饱和土中运移与转化过程进行了数值模拟。结果表明:该试验条件下NH₄⁺—N的硝化作用主要发生于土壤表层1cm左右的范围内。     

Time-course of nitrogen fixation in two bambara groundnut (Vigna subterranea L. Verdc.) cultivars

TheA-value method, involving the application of a higher¹⁵N rate to a reference non-N₂-fixing plant, was used to assess the magnitude of N₂ fixation in two bambara groundnut cultivars at four growth stages [vegetative, 0–47 days after planting (DAP); early pod-filling, 47–99 DAP; mid-pod-filling, 99–120 DAP; physiological maturity, 120–148 DAP). The cultivars were Ex-Ada, a bunchy type, and CS-88-11, a slightly spreading type. They were grown on a loamy sand. Uninoculated Ex-Ada and CS-88-11 were used as reference plants to measure the N₂ fixed in the inoculated bambara groundnuts. In this greenhouse study, soil was the major source of N in bambara groundnuts during vegetative growth, and during this period it accounted for over 80% of the N accumulaed in the plants. However, N₂ fixation became the major source of plant N during reproductive growth. There were significant differences between the two cultivars in the ability to fix N₂, and at physiological maturity, almost 75% of the N in CS-88-11 was derived from the atmosphere compared to 55% in Ex-Ada. Also, the total N fixed in CS-88-11 at physiological maturity was almost double that in Ex-Ada. Our data indicate that the higher N₂ fixation in CS-88-11 was due to two factors, a higher intensity of N₂ fixation and a longer active period of N₂ fixation. The results also suggest that bambara groundnut genotypes could be selected for higher N₂ fixation in farining systems.