Effects of three types of soil amendments on yield and soil nitrogen balance of maize-wheat rotation system in the Hetao Irrigation Area,China

Excessive fertilization combined with unreasonable irrigation in farmland of the Hetao Irrigation Area (HIR), China, has resulted in a large amount of nitrogen (N) losses and agricultural non-point source pollution. Application of soil amendments has become one of the important strategies for reducing N losses of farmland. However, there is still no systematic study on the effects of various soil amendments on N losses in the HIR. In this study, three types of soil amendments (biochar, bentonite and polyacrylamide) were applied in a maize-wheat rotation system in the HIR during 2015-2017. Yields of maize and wheat, soil NH₃ volatilization, N₂O emission and NO₃^- leaching were determined and soil N balance was estimated. The results showed that applications of biochar, bentonite and polyacrylamide significantly increased yields of maize by 9.2%, 14.3% and 13.3%, respectively, and wheat by 9.2%, 16.6% and 12.3%, respectively, compared with the control (fertilization alone). Applications of biochar, bentonite and polyacrylamide significantly reduced soil N leaching by 23.1%, 35.5% and 27.1%, soil NH₃-N volatilization by 34.8%, 52.7% and 37.8%, and soil N surplus by 23.9%, 37.4% and 30.6%, respectively. Applications of bentonite and polyacrylamide significantly reduced N₂O-N emissions from soil by 37.3% and 35.8%, respectively, compared with the control. Compared with application of biochar, applications of bentonite and polyacrylamide increased yields of maize and wheat by 5.1% and 3.5%, respectively. Our results suggest that soil amendments (bentonite and polyacrylamide) can play important roles in reducing N losses and increasing yield for the maize-wheat rotation system in the HIR, China.     

间作模式下小麦联合收获机清选装置CFD-DEM气固耦合仿真与试验验证

为了提高间作模式下小麦联合收获机清选性能，研究旋风分离筒内流场和颗粒的运动状态，探索分离筒的最佳工作参数组合，运用离散元法和计算流体力学耦合的方法分析了气流与颗粒的相互作用，以喂入速度、吸杂压强、筒体高度、下椎体角度为试验因素对清选过程进行了仿真正交试验，对最佳清选参数组合完成了田间试验验证。结果表明:气流在分离筒内形成内、外旋涡，内漩涡的运动使短茎秆进入吸杂管道，籽粒在外旋涡的作用下滑落到集粮盘；仿真试验的最佳参数组合为喂入速度12 m·s^-1吸杂压强-1 800 Pa、筒体高度350 mm、下椎体的角度65°，得到的清洁率和损失率分别为92.18%和1.99%，与田间试验的误差分别为2.947%和7.428%。     

冬小麦生物量及氮积累量的植被指数动态模型研究

利用遥感技术实时监测小麦生长状况,依据监测结果适时促控,可提高产量。本研究以高产小麦品种周麦27为试验材料,在不同试验地点设置了水氮耦合的大田试验,筛选出了适宜监测冬小麦地上部氮积累量和生物量的植被指数,并构建了不同产量水平下优选植被指数的动态模型。结果表明,(1)不同的水氮耦合模式显著影响小麦冠层光谱变化,在350～700nm和750～900nm表现相反的反应特征;(2)对2个农学生长指标反应敏感且兼容性好的植被指数主要有修正型红边比率(mRER)、土壤调整植被指数[SAVI(825,735)]、红边叶绿素指数(CI_(red-edge))和归一化差异光谱指数(NDSI),其与产量间相关性较好的时期为拔节至灌浆中期;(3)双Logistic模型可以很好地拟合植被指数的动态变化,高产和超高产水平下拟合精度较高(R~20.82),而低产水平下相对较低(R~2=0.608～0.736)。比较而言,CI_(red-edge)和SAVI (825, 735)用于评价小麦长势较为适宜。研究结果对作物因地定产、以苗管理、分类促控具有重要意义。     

Drought and heat stress reduce yield and alter carbon rhizodeposition of different wheat genotypes

Drought and high temperature are major environmental stress factors threatening wheat production during grain filling stage resulting in substantial yield losses. Four wheat genotypes (Suntop, IAW2013, Scout and 249) were planted under two temperature levels (25 and 30°C) and two water levels (15% and 25% soil moisture content). Wheat yield, leaf δ¹³C, plant rhizodeposition, shoot biomass and root traits were examined. Low moisture (drought stress) and high temperature (heat stress) decreased the grain yield of all wheat genotypes, in particular 249, while combined drought and temperature stresses had the most pronounced negative effect on plant biomass and grain yield. Decreasing soil water availability decreased the allocation of plant‐derived C to soil organic carbon (SOC) and to microbial biomass through rhizodeposition. Leaf δ¹³C decreased with increased yield, suggesting that higher yielding genotypes were less water stressed and allocated less C to SOC and microbial biomass through rhizodeposition. Wheat genotypes with lower root/shoot ratios and thinner roots were more efficient at assimilating C to the grain, while genotypes with higher root/shoot ratios and thicker roots allocated more C belowground through rhizodeposition at the expense of producing higher yield. Therefore, improving these traits for enhanced C allocation to wheat grain under variable environmental conditions needs to be considered.     

Agronomic performance of winter wheat grown under highly divergent soil moisture conditions in rainfed and water‐managed environments

Even in the temperate climates of Europe, increasing early season drought and rising air temperature are presenting new challenges to farmers and wheat breeders. Sixteen winter wheat (Triticum aestivum L.) genotypes consisting of three hybrids, six line cultivars and two breeding lines from Germany as well as five line cultivars from France, Austria, Slovakia, Hungary and the Ukraine (referred to as “exotic” lines) have been included in this study. The genetic materials were evaluated over three growing seasons under a range of soil moisture regimes at the three North German sites Braunschweig (irrigated and drought‐stressed), Warmse (rainfed) and Söllingen (rainfed). The average grain yields in the twelve growth environments (water regime × season combinations) ranged from 6.1 to 13.5 t ha^?1. The exotic lines showed little evidence of specific phenological adaptation to drought although they are frequently faced with water scarcity in their countries of origin. The hybrids and German lines exhibited higher regression coefficients (b_i) to environmental means than the exotic lines, indicating particular adaptation to favourable growing conditions. The phenotypical correlations of grain yield between the various environments were high, ranging for instance from 0.6 to 0.8 for the irrigated and drought‐stressed environments at Braunschweig. It is thus expected that in the foreseeable future continued selection aiming at high yield potential will suffice as a means to counter the expected increase in droughts.     

基于无人机多光谱遥感的冬小麦叶绿素含量反演及监测

旨在实现冬小麦各生育期叶绿素含量的准确估测,探究其时空变化规律。利用无人机获取冬小麦越冬期、返青期、拔节期、孕穗期和灌浆期的高分辨率多光谱图像,同时采集地面SPAD数据。选取三类光谱参数建立反演模型,优选出各生育期的最佳预测模型,并定量监测试验区冬小麦叶绿素含量时间变化和空间分布。结果表明：原始波段模型和波段倒数对数模型分别为越冬期及其他生育期叶绿素含量预测的最佳模型,拟合精度R²>0.59;时空分布上,灌浆期前试验区冬小麦叶绿素含量呈南北高、中部低特点,灌浆期则呈北高南低的趋势,叶绿素含量从越冬期到拔节期逐步增加,拔节期到孕穗期开始降低,孕穗期到灌浆期则大幅度降低。本研究建立的倒数对数预测模型,精度较高,且适用于返青到灌浆的4个生育期,对于试验区冬小麦叶绿素含量有较好的时空监测效果。     

遮阴对冀中南优质强筋小麦形态和品质的影响

选用4个适于冀中南种植的优质强筋小麦进行花后遮阴处理,测定了株高和旗叶形态特征、千粒重以及品质性状,研究不同遮阴条件下这些主要形态特征和品质性状的变化。结果表明：与对照(S0)相比,25%遮阴(S1)增加小麦株高,50%遮阴(S2)株高增幅低于S1,藳优2018甚至低于S0；不同品种旗叶对遮阴处理响应不同,师栾02-1和石优20通过增加叶片长度增加旗叶叶面积,藳优5766叶片厚度降低,藳优2018无显著变化；遮阴造成千粒重降低,蛋白含量、沉降值和湿面筋含量品质指标增加,但是面筋指数下降；遮阴对面团流变学特性影响在品种间存在较大差异,遮阴提高石优20和藳优5766的面团形成时间、稳定时间、拉伸能量和最大拉伸阻力,但是降低师栾02-1的面团形成时间、稳定时间、拉伸面积和最大拉伸阻力,降低藳优2018面团形成时间、稳定时间和最大拉伸阻力,却增加拉伸面积。优质强筋小麦品质对遮阴的响应有共同点,但也存在品种间差异, 可能是遮阴降低小麦光合速率导致光合产物合成和运输受阻,蛋白含量的相对提高使得不同小麦在遮阴处理中有共性的反应,例如4个小麦品种的蛋白含量和湿面筋含量都增加,同时品种间籽粒的蛋白组成不同,可能是导致粉质参数和拉伸参数存在差异的重要原因。     

农机作业服务能提升小麦生产技术效率吗?——基于2007—2017年省级面板数据的实证分析

为了解农机作业服务的作用效果，基于中国15 个小麦主产省(自治区)2007—2017年面板数据，采用随机前沿生产函数对小麦生产技术效率进行估算，并运用Tobit模型分析影响小麦生产技术效率的因素，研究农机服务对技术效率的影响并解释其作用机制。结果表明:2007—2017年小麦生产技术效率逐年递增，各省间存在显著差异，且起点低的省份技术效率增长速度明显快于领先的省份，区域间不平衡逐步缩小；农机投入对小麦技术效率有显著正向影响，主要通过替代效应、技术效应及分工效应等路径优化小麦生产要素配置，获得小麦技术效率的提高。基于研究结论，提出建议如下:规范农机服务市场，健全农机社会化服务体系；优化农机补偿机制，提升政策作用的时效性。     

不同育成年份冬小麦苗期根冠生物量分配

为探讨品种更替过程中小麦苗期根冠生物量分配的演变趋势,以历年来黄淮海麦区大面积推广种植的22个冬小麦品种为研究对象,采用砂培的方法进行幼苗培养,分析小麦种子萌发后不同时间根、冠生长及生物量分配的变化规律。结果表明:冬小麦种子萌发后第3天幼苗根数在品种间无显著差异,第9天、第15天随着品种更替的进行呈现出显著下降的趋势,现代品种初生根数目显著低于早期品种。在第3天、第9天、第15天,小麦苗期幼苗生长随品种更替呈现不同的变化趋势,芽长显著下降,但根长无显著差异。可见,冬小麦苗期芽干质量在品种改良过程中未发生明显变化,而根干质量和根冠比呈现出显著下降的趋势,冬小麦苗期现代品种地上部分分配到更多的生物量。     

小麦赤霉病生防菌DZSG23的抗病机制

课题组前期从健康杜仲叶片中分离得到1株内生细菌枯草芽孢杆菌DZSG23,此菌可以较好地防控小麦赤霉病。为明确芽孢杆菌DZSG23在小麦中的定殖与强化抗病机制研究,利用抗生素标记法分析了DZSG23菌体在小麦组织中的定殖情况,采用荧光定量PCR技术检测不同生育期小麦穗部PR-1、AOS、ACOI等基因的表达水平变化。结果表明,DZSG23可在苗期小麦植株和小麦穗表面稳定定殖;DZSG23浇灌接种苗期小麦后的第34天,DZSG23在苗期小麦植株的根、茎和叶中的定殖量分别达到1.437×10⁶ CFU·g^-1、3.285×10³ CFU·g^-1和2.377×10³ CFU·g^-1;DZSG23喷施小麦穗表面15 d后,穗表面菌群密度仍可达7.146×10³ CFU·g^-1。此外,诱导系统抗性(ISR)信号通路研究表明,拮抗菌DZSG23可以诱导PR-1和AOS基因的上调表达,表明拮抗菌DZSG23引入小麦后可诱导小麦的水杨酸(SA)和茉莉酸(JA)信号通路,增强其抗病性。