Yield losses on wheat crops associated to the previous winter crop: Impact of agronomic practices based on on-farm analysis

Wheat is one of the most important cultivated cereals worldwide. In Uruguay, the area increased from 153.000 ha to 453.000 ha between 2004 and 2012, nowadays representing 80% of the total winter crops area. As the high area of the crop, is common planting wheat in a field with wheat as previous winter crop (“wheat after wheat”). This practice leads to a high inoculum pressure of necrotrophic pathogens which guarantees disease inoculation mainly of Pyrenophora tritici-repentis (tan spot—TS) and Zymoseptoria tritici (septoria leaf blotch—SLB). There is strong evidence that integrated crop management practices such as nitrogen (N) fertilization, genetic resistance to leaf diseases and fungicides could mitigate yield losses associated with monoculture. However, the impacts of integrated technologies based on actual field data have not been reported before. We based our study in an on-farm wheat yield and management database to assess the previous winter crop effect on wheat yield under no-till systems. This database corresponds to a set of farmers grouped in CREA (Consorcio Regional de Experimentación Agrícola). A complete database of 1292 no-till wheat fields was analyzed. The effect of previous winter crop on yield and the impact of different technologies were estimated based on two approaches: (i) yield quartile analysis and (ii) yield frontier analysis. The crop rotation had a significant impact on yield. The practice of growing “wheat after wheat” was associated with a yield loss of ca 500 kg ha⁻¹. The selection of a diseases resistant cultivar under “wheat after wheat” fields increases yields in ≈700 kg ha⁻¹. The percentage of fields with an efficiency higher than 80% improved from 49 to 77% when a resistant cultivar to TS and SLB was selected, and when N fertilizer was applied earlier and in higher rates. Unexpectedly, only 18% of the “wheat after wheat” fields are applying these two technologies in scenarios under high inoculum pressure. This study, based in on-farm data, highlights the relevance of integrated disease management, and remarks the potential of this approach to minimize the interference of foliar diseases in fields with high inoculum pressure of stubble-borne pathogens.     

Effect of Foliar Application of Iron on Seasonal Changes of Minerals Composition in Petioles and Berries of Halwani Lebanon and Kamali Grape Cultivars （Vitis vinifera L,）

A field experiment was conducted in 2009 and 2010 growing seasons, to study the effect of foliar application of iron-chelated ＂Fe-EDTA＂ at concentration 0, 100 and 200 mg/L on the seasonal dynamic of mineral composition of N, P, K, Fe and Zn in petioles and berries of Halwani Lebanon and Kamali grape cultivars, grown on a calcareous soil in Mosul region, Iraq. The results revealed that the foliar application of 200 mg Fe/L caused a significant increase of N, P, K, Fe and Zn concentrations in petioles and berries compared with the control for both seasons. Additionally, the N, P, K, Fe and Zn concentration in petioles were high at the beginning of the growth season, whereas, decrease towards in the end of the growth season in both cultivars and seasons. While the N, P, K, Fe and Zn in berry content was increased towards from berry set to veraison and ripening stage in both cultivars and seasons. So there are various element contents in the cultivars.     

根外追肥对新疆杨叶片内叶绿素含量及保护酶活性的影响

试验研究了根外追肥对新疆杨叶片内叶绿素含量及保护酶活性的影响规律,以期为确定最佳的尿素根外追肥浓度提供理论依据。结果表明:根外追肥可以提高新疆杨叶片内的叶绿素含量,随着喷施尿素浓度的增加而升高,浓度为2.10%以上时显著高于对照;POD活性在浓度为2.10%以上时显著高于对照,其他浓度与对照之间无显著差异;SOD活性仅10月份2.10%浓度处理显著高于对照,其余浓度处理与对照之间无显著差异;PPO活性在7月份表现为随着尿素浓度的增加而降低的变化,8~10月份2.10%浓度处理显著高于对照。综合分析认为,根外追施尿素浓度以2.10%为宜。     

感染玉米矮花叶病毒后玉米叶片细胞超微结构的变化

 利用透射电镜对感染玉米矮花叶病毒山东分离物 (MDMV SD)的不同抗性玉米叶片细胞超微结构进行了观察。结果表明 ,与健康植株相比 ,无论是在抗病品种鲁玉 16还是在感病的自交系鲁原 92细胞中 ,MDMV SD与玉米植株之间的互作都可以导致寄主发生明显的细胞病理学变化。但是 ,在抗病和感病植株中叶片细胞超微结构的变化存在明显差异。在抗病植株细胞中 ,虽然叶绿体、线粒体等主要细胞器的结构损伤较轻 ,但线粒体和过氧化物酶体的数量明显增多 ,细胞质中有风轮体、束状体和片层聚集体 3种内含体 ,存在于细胞质中的病     

The Effects of Foliar Fertilization on Pest Control of Cowpea

研究了经不同叶面肥处理后,豇豆白粉病、锈病、豆野螟的发生情况,测定了多酚氧化酶(PPO)、产量指标,结果表明,合理施肥能够提高植物对有害生物的抗性,增加产量,保证品质。综合各方面因素,各种施肥措施中以施海藻有机肥效果较好。     

Translocation and recovery of 15N-labelled N derived from foliar uptake of 15NH3 by rice (Oryza sativa L.) cultivars

Foliar uptake of ¹⁵NH₃ applied at two growth stages (tillering and anthesis) and the subsequent ¹⁵N-labelled vegetative-N distribution in different plant components at maturity was investigated in three rice cultivars, IR-6, NIAB-6 and Bas-385. Rice plants absorbed 22–30% and 18–24% of the ¹⁵NH₃ applied at tillering and anthesis stages, respectively. Of the total ¹⁵NH₃ absorbed at tillering stage, IR-6 and Bas-385 showed higher recovery (71%) in different plant components at maturity as compared to NIAB-6 (48% recovery). At maturity, percent recovery of the ¹⁵NH₃ absorbed at anthesis stage was almost comparable in different cultivars, but it was lower (46–55%) than that absorbed at the tillering stage. Recovery of the absorbed ¹⁵NH₃-N in the soil was negligible and ranged from 0.3–1%. At maturity, the cultivars IR-6 and Bas-385 showed a higher loss (45–53%) of ¹⁵NH₃ absorbed at anthesis than at the tillering stage (29% loss), whereas for NIAB-6, the corresponding figures were comparable for the two growth stages (tillering, 51% loss; anthesis, 49% loss). Results indicated a variable potential of the tested rice cultivars for foliar uptake of atmospheric ¹⁵NH₃ and distribution of ¹⁵N-labelled vegetative-N in different plant components.     

The challenges of maintaining wheat productivity: pests, diseases, and potential epidemics

Knowing pests and diseases that may cause injuries and are likely to affect plant health and quality is critical to minimizing the gap between attainable yield and actual yield. In this paper, we highlight concepts and strategies aimed at controlling major biotic constraints affecting wheat in intensive production systems and present emerging challenges, with a special attention to the developing world. Disease epidemics result from the combination of inoculum, favorable environment, and host susceptibility. Changes in cropping systems as a result of adoption of conservation agriculture may have serious implications. Necrotrophic pathogens such as those responsible for tan spot or septorias are likely to emerge, and Fusarium head blight may increase. However, resistance breeding combined with rotations, timely sowing, and irrigation or even fungicide utilization, if affordable, are part of integrated crop management practices that can minimize losses. In South Asia, the effect of spot blotch, a devastating foliar disease caused by Cochliobolus sativus, can be minimized by reducing physiological stress through timely sowing and adequate use of fertilizers, which demonstrates the complex relationships among crop physiology, disease resistance, and yield. Although some root rots that induce premature death of tillers in cooler high-yielding humid environments can be important, the dryland crown rot (Fusarium spp.), common root rot (C. sativus), and the cereal nematode (Heterodera spp. and Pratylenchus spp.) should not be ignored. These are all known to be much more damaging under suboptimal moisture (rainfed or supplementary irrigation), particularly where plant growth is stressed. Climate change is likely to modify the wheat disease spectrum in some regions, and pathogens or pests considered unimportant today may turn out to be potential new threats in future.     

喷施不同纳米硅肥对红苋菜增产效果研究

[目的]研究不同纳米硅肥对红苋菜增产效果的影响。[方法]以制备的纳米二氧化硅、纳米硅藻土和纳米膨润土为硅肥,叶面喷施于盆栽红苋菜植株,测定红苋菜的增产效果。[结果]喷施上述3种纳米硅肥(Si O2浓度0.09%)后,苋菜鲜重和干重明显增加,分别比对照提高了11.20%、20.37%、31.49%。硅肥提高苋菜的产量,在矿石材料纳米硅藻土、纳米膨润土中存在Ca、Mg、Fe等中微量元素,对苋菜生长具有促进作用,茎粗增加,叶绿素含量提高。硅肥增强了光合作用、促进作物生长。[结论]该研究中,Si、Fe与材料的纳米结构多因素协同作用促进了苋菜生长,提高了肥料的利用率。     

叶面喷施不同配比氮、钾元素对富士苹果叶片性状及果实品质的影响

研究采用两因素三水平叶面喷肥不同比例的N/K试验,为苹果生产合理施肥提供参考。试验选用尿素和氯化钾对7年生红富士进行叶面喷肥,采用两因素三水平,2 因素为尿素 (C) 和氯化钾 (K) ,尿素与氯化钾各设置3个水平浓度〕,试验共设置9 个处理,设置3 次重复,测定叶片和果实相关指标。叶施氮肥、钾肥均可促进果实产量、单果重、果型指数,叶施氮肥增加了果实可滴定酸含量,叶施钾肥对果实硬度、色泽、可溶性固形物有促进作用,当喷施氮肥浓度大于等于2.5 g·L^-2时对果实硬度、色泽、可溶性固形物有抑制作用;氮钾配施对叶绿素含量影响不显著,对类胡萝卜素影响显著,氮肥与钾肥均可以促进叶比重、叶绿素含量、叶面积、百叶重。喷施适宜浓度氮肥钾肥对苹果产提质均具有促进作用,但浓度过大则会产生负效应。当喷施氮肥浓度小于等于2.5 g·L^-2,喷施钾肥浓度小于或等于1.82 g·L^-2时,苹果产量和品质均随着钾肥浓度的增加而提高;而当氮肥喷施浓度大于2.5 g·L^-2小于5 g·L^-2时,喷施钾肥浓度大于1.82 g·L^-2小于5 g·L^-2时,则会抑制苹果叶片生长,降低果实品质。氮钾肥用量过多,不仅增加了经济投入,而且对提高苹果产量与品质不利。     

生育期间喷施氮肥对优质强筋小麦品种龙麦26品质性状的影响

通过黑龙江省两个生态区四个试验点的小区试验,分析了生育期间叶面喷施氮肥对优质强筋小麦龙麦26品质性状的影响。结果表明,叶面喷施氮肥对多数品质性状具有改善作用。对延伸性等品质指标有正向影响;对最大抗延阻力、形成时间、稳定时间、吸水率、评价值、沉淀值、蛋白质、单位蛋白质含量形成的湿面筋影响大小及方向因地点而异;对湿面筋的影响不大。本试验的三个处理比较,开花期喷施氮肥及三叶期与开花期两期喷施氮肥对多数品质性状有较大的正向影响。