Do combined applications of crop residues and inorganic fertilizer lower emission of N2O from soil?

Emissions of N₂O were measured following addition of ¹⁵N‐labelled residues of tropical plant species [Vigna unguiculata (cowpea), Mucuna pruriens and Leucaena leucocephala] to a Ferric Luvisol from Ghana at a rate of 100 mg N/kg soil under controlled environment conditions. Residues were also applied in different ratio combinations with inorganic N fertilizer, at a total rate of 100 mg N/kg soil. N₂O emissions were increased after addition of residues, and further increased with combined (ratio) applications of residues and inorganic N fertilizer. However, ¹⁵N‐N₂O production was low and short‐lived in all treatments, suggesting that most of the measured N₂O‐N was derived from the applied fertilizer or native soil mineral N pools. There was no consistent trend in magnitude of emissions with increasing proportion of inorganic fertilizer in the application. The positive interactive effect between residue‐ and fertilizer‐N sources was most pronounced in the 25:75 Leucaena:fertilizer and cowpea:fertilizer treatments where 1082 and 1130 mg N₂O‐N/g residue were emitted over 30 days. N₂O (log_e) emission from all residue amended treatments was positively correlated with the residue C:N ratio, and negatively correlated with residue polyphenol content, polyphenol:N ratio and (lignin + polyphenol):N ratio, indicating the role of residue chemical composition in regulating emissions even when combined with inorganic fertilizer. The positive interactive effect in our treatments suggests that it is unlikely that combined applications of residues and inorganic fertilizer can lower N₂O emissions unless the residue is of very low quality promoting strong immobilisation of soil mineral N.     

不同pH条件下接种菌根真菌对柑橘砧木苗生长及光合效应的影响

本文以枳橙（Citrus sinensis (L.) Osbeck譸oncirus trifoliate (L.)）为试验材料,利用盆栽试验,研究不同pH条件下接种丛枝菌根(Arbuscular mycorrhiza)真菌摩西球囊霉(Glomus mosseae)对柑橘砧木枳橙苗的生长及植株光合效应的影响。试验选定3个pH范围（pH 5.5~6.5, 6.5~7.5, 7.5~8.5）和接种摩西球囊霉为试验因子,共设6个处理组合,以不同pH条件下未接种摩西球囊霉为对照。采用单株小区,随机区组排列,重复10次。结果表明,接种摩西球囊霉能有效地侵染枳橙植株,菌根侵染率65%以上。试验还发现,处理植株的菌根侵染率和株高、生物量干重均显著高于对照植株,同时,接种AM真菌显著增加了植株叶片叶绿素含量,并显著提高处理植株光合作用速率和蒸腾速率。研究结果表明,接种AM真菌增强了宿主植物对土壤酸碱度的适应性,在酸性和碱性土壤上均能显著提高柑橘的光合效应。     

Spatiotemporal Distribution of Two Euschistus spp. Stink Bugs (Hemiptera: Pentatomidae) in Southeastern Farmscapes

Stink bugs (Hemiptera: Pentatomidae) are ubiquitous, cryptic, phytophagous pests that are found in many crops. In agroecosystems, individuals disperse from adjacent noncrop hosts and tend to aggregate or cluster within fields. In this study, we characterized the distribution of Euschistus servus (Say) and Euschistus tristigmus (Say) (Hemiptera: Pentatomidae) over 2 yr at three southeastern United States farmscapes. Stink bugs were captured in pheromone-baited traps, and Spatial Analysis by Distance Indices (SADIE) used to identify the location of significant aggregations by habitat type and season. Euschistus servus adults were more likely to be captured in pecan orchards, cotton, other crops, or unmanaged habitats than in woodland habitats. Significant aggregations of E. servus were detected in a variety of habitats including pecan, corn, cotton, peanut, and tobacco, as well as fallow and hay fields, pastures, and hedgerows. Fewer adult E. tristigmus were captured than E. servus adults, and E. tristigmus adults were typically trapped and aggregated in woodland habitats. The resulting data provide an important understanding regarding the seasonal movement and relative abundance levels of stink bug populations, which are critical to the development of integrated pest management strategies.     

Impact of cash crop cultivation on household income and migration decisions: Evidence from low-income regions in China

This study examines the impact of cash crop cultivation on household income and migration decisions, using survey data collected from low-income regions in China. Given farmers decide themselves whether to cultivate cash crops, an endogenous treatment regression model that accounts for potential selection bias issue is used to analyze the data. The empirical results show that cash crop cultivation exerts a positive and statistically significant impact on household income, but it does not affect household migration decisions significantly. The disaggregated analyses reveal that cash crop cultivation significantly increases farm income but decreases off-farm income.     

大豆作为前作植物对油菜根肿病发生的影响

为了解前作大豆对后茬油菜根肿病的影响,采用大田轮作试验和实时荧光定量PCR检测法,研究大豆、白菜、油菜分别作为前作,调查后茬油菜根肿病的发生和土壤中休眠孢子含量,比较分析了不同前作的根系分泌物对休眠孢子萌发的影响,结果表明前作大豆,后茬油菜根肿病的发病率和病情指数分别为34.00%和19.26、土壤休眠孢子含量为1.45×106个/克土壤,显著低于前作为油菜、白菜和撂荒对照的相应量。大豆、油菜和白菜根系分泌物均可刺激根肿菌休眠孢子萌发。与根肿菌休眠孢子共培6 d后,大豆根系分泌物培养的休眠孢子萌发率为29.82%,显著高于白菜（15.52%）、油菜根系分泌物（14.83%）和营养液（6.48%）培养下的萌发率。据此推测,前作种植大豆,后茬油菜根肿病发生和危害减轻,原因应与大豆根系分泌物刺激根肿菌休眠孢子萌发,产生的游动孢子因缺少寄主植物而死亡,导致诱发病害的初侵染源（土壤中休眠孢子含量）减少有关。     

基于SIMDual_Kc模型估算非充分灌水条件下冬小麦蒸散量

为研究关中冬小麦植株蒸腾和土壤蒸发规律,利用2 a冬小麦小区控水试验实测数据,率定和验证了双作物系数SIMDual_Kc模型在关中地区的适用性.用大型称重式蒸渗仪的实测蒸散量值(或水量平衡法计算值)与模型模拟值进行对比.结果表明:SIMDualKc模型可较准确地模拟关中不同水分条件下冬小麦蒸散量,且模拟精度较高.模型估算的平均绝对误差为0.643 3 mm/d.模型估算的冬小麦初期、中期和后期的基础作物系数分别为0.35,1.30,0.20.另外,模型还可以较准确地估算不同水分供应条件下的土壤水分胁迫系数、土壤蒸发量和植株蒸散量.冬小麦整个生育期,土壤蒸发主要发生在作物生育前期,中期较低,后期略微增大;植株蒸腾主要发生在作物快速生长期和生长中期,整个生育期中呈先增大后减小的趋势.     

植物染色体重排在作物遗传改良中的应用研究进展

染色体重排是一种可能导致DNA片段丢失、重复、易位和倒位的机制,从而改变基因组结构,为创造新的变异性状提供可能。植物染色体重排事件的准确鉴定有助于更深入地理解植物基因组的结构、功能及它们在植物演化和作物育种中的作用。该文深入探讨了植物染色体重排的基本概念,介绍了植物染色体重排的自然发生和人工诱导的技术方法,阐述了植物染色体重排的细胞生物学、分子遗传学和高通量测序鉴定方法。同时,系统总结了植物染色体重排技术在作物遗传育种中的应用,结合具体实践,着重强调了染色体重排技术在提高农作物的遗传多样性、改良农作物的重要性状、增强农作物的环境适应性等方面极具优越性。然而,目前染色体重排的发生概率较低,技术上仍存在挑战,需要更多精准的工具和策略来实现染色体片段的精准定位和重排。通过全面了解染色体重排及其相关技术,研究人员和育种家可以更好地利用植物基因组,为全球粮食安全和环境可持续发展提供创新解决方案。相关研究不仅为深入认识植物基因组提供新途径,也为未来创新作物育种奠定坚实基础。通过挖掘植物基因组的多样性和可塑性,染色体重排技术有望为培育高产、优质、多抗的农作物新品种提供更多可能性,对解决全球日益严峻的...     

Early flower initiation allows ample manipulation of flowering time in cherimoya (Annona cherimola Mill.)

Flower initiation date and readiness to flowering in buds of different age were studied in ‘Fino de Jete’ cherimoya (Annona cherimola) cultivar in order to establish the limits for the manipulation of its flowering date. Flower initiation was analyzed by light and scanning electron microscopy (SEM) collecting axillary buds from May to the following February, whereas the bud readiness to produce perfect flowers was determined by forcing buds of different age to sprout by means of leaf removal and tipping the new growth. SEM images confirm that cherimoya buds are differentiated into flowers almost a year before blooming. In this regard, axillary buds have already formed the sepals when the subtending leaf has just begun unfolding (week 0), while the petals are clearly visible in 1-week-old buds. Sectioning of paraffin-embedded buds illustrate that cherimoya buds are in fact a bud complex that 1 week after its inception comprises 4–5 buds of different size of which the two largest ones are reproductive, while the 2–3 smallest buds often remain undifferentiated at that time. The high capacity of flowering expressed by young buds that have been forced to grow proves that cherimoya meristems are early competent for flowering. No differences in fertility or in the time needed to reach anthesis after leaf removal were found among buds of different ages. Node position had no effect on bud break and flowering potential. The early flower initiation in cherimoya deduced from this work opens a wide temporal window for the experimental manipulation of flowering and harvest dates in this crop.