外源茉莉酸甲酯缓解盐对水稻种子萌发的抑制作用

在100 mmol/L NaC l胁迫下,经蒸馏水吸胀处理的LHN(耐盐)和IR26(盐敏感)水稻种子的发芽势、发芽率和发芽指数均较对照下降,LHN分别下降12.2%、12.5%和3.12,IR26分别下降46.6%、33.6%和9.42,IR26下降的幅度大于LHN.吸胀后,不同质量浓度(2、1、5×10-2、5×10-4和5×10-6mg/L)的外源茉莉酸甲酯(M e-Ja)对LHN和IR26在盐胁迫下发芽势、发芽率和发芽指数影响不同.以相对盐害率判断,质量浓度为2和5×10-6mg/L的Me-Ja对LHN在盐胁迫下萌发的促进作用不显著,质量浓度为5×10-2和5×10-4mg/L的M e-Ja表现为促进作用,质量浓度为5×10-2mg/L的M e-Ja促进作用最大;而对于IR26在盐胁迫下的萌发,5种质量浓度的M e-Ja的都具有显著的促进作用,且质量浓度为5×10-4mg/L的促进作用最大.     

Phosphorus saturation in soils and groundwaters

On average, crops require about 30 kg ha⁻¹ y⁻¹ of P in humid regions. in some regions fertilizer and manure are applied in amounts that exceed this. the surplus of P in agricultural areas is about 20-45 kg ha⁻¹ y⁻¹. This implies an accumulation of P. the surplus of P estimated from the balance of agricultural soils of industrialized countries in Europe in the last four decades is between 800 and more than 1500 kg ha⁻¹ although this distribution is not even. Phosphorus accumulation is more than one order of magnitude higher than average in areas with intensive livestock farming. Consequently, The application of high levels of manure exceed the capacity of the soil to store P. This implies that P saturation May, pose a problem. Indeed, about half of the Dutch sandy soils (approximately 300 000 ha) are currently considered to be saturated with P, meaning that there is a hazard of P leaching to groundwaters in the future. Assuming current phosphate application rates, phosphate leaching is a distinct possibility over a period of decades to a century. Vulnerable areas are soils with high inputs, low sorption capacities for P, high water-tables and a low retention time for water. the possible consequence is a time-delayed increase of eutrophication of surface waters (lakes, rivers and the sea) caused by a diffuse load of P in the few next decades. Modelling the influence of different agricultural strategies shows that accumulation of P would not increase further only if the use of P increases by an amount that compensates for the increased inputs. It is proposed to change the current support system of agriculture by installing a system of financial incentives and taxes which seek to promote nutrient balances for each farm.     

盐胁迫对羽衣甘蓝种子萌发的影响

为探明盐胁迫对羽衣甘蓝种子萌发特性的影响,明确种子萌发期对盐胁迫的耐受能力,本试验以羽衣甘蓝种子为试验材料,研究不同浓度的NaCL（0、40、80、120、160、200mmol/l）和NaHCO（3 0、20、30、40、50、60mmol/l）对种子萌发胁迫的作用。结果表明:1、2 种盐胁迫处理下,羽衣甘蓝种子的发芽率、发芽势、发芽指数和活力指数等指标均随着盐浓度的升高逐渐降低;2、高浓度的NaHCO³盐溶液对羽衣甘蓝种子的胚根、胚芽的生长抑制较NaCL 盐溶液显著;3、2 种盐     

One-time fertilization at first flowering improves lint yield and dry matter partitioning in late planted short-season cotton

Cotton producers have substantially reduced their inputs(labor, nutrients, and management) mainly by adopting a shortseason cropping management that is characterized by late sowing, high density, and reduced fertilization with one-time application at the first bloom stage without lint yield reduction. However, it has been hypothesized that one-time fertilization at an earlier growth stage could be a more effective and economic management practice. A two-year field experiment was conducted by applying five fertilizer one-time fertilization at 0(FT1), 5(FT2), 10(FT3), 15(FT4), and 20(FT5) days after the first flower appeared in the field and one three-split fertilizer application taken as the conventional control(FT6), making six treatments altogether. Cotton growth period, biomass accumulation, yield, and its formation were quantified. The results showed that the one-time fertilization did not affect the cotton growth progress as compared to FT6, however, the total crop cycles for FT3–FT5 were 3 days shorter. FT1 produced the highest cotton lint yield(1 396 kg ha–1), which was similar to the FT6 but higher than the other treatments, and could be attributed to more bolls per unit area and higher lint percentage. Cotton yield was positively correlated with cotton plant biomass accumulated. FT1 had both the highest average(VT)(193.7 kg ha–1 d–1) and the highest maximum(VM)(220.9 kg ha–1 d–1) rates during the fast biomass accumulation period. These results suggest that one-time fertilizer application at the first flower stage might be an adjustment that is more effective than at first bloom, and allowed for easier decision making for application date due to non counting of plants with flowers is needed.     

Effects of post-silking water deficit on the leaf photosynthesis and senescence of waxy maize

Waxy maize is widely cultivated under rainfed conditions and frequently suffers water shortage during the late growth stage. In this study, a pot trial was conducted to examine the effects of post-silking drought on leaf photosynthesis and senescence and its influence on grain yield. Two waxy maize hybrids, Suyunuo 5(SYN5) and Yunuo 7(YN7), were grown under the control and drought(soil moisture content was 70–80% and 50–60%, respectively) conditions after silking in 2016 and 2017. The decrease in yield was 11.1 and 15.4% for YN7 and SYN5, respectively, owing to the decreased grain weight and number. Post-silking dry matter accumulation was reduced by 27.2% in YN7 and 26.3% in SYN5. The contribution rate of pre-silking photoassimilates transferred to grain yield was increased by 15.6% in YN7 and 10.2% in SYN5, respectively. Post-silking drought increased the malondialdehyde content, but decreased the contents of water, soluble protein, chlorophyll, and carotenoid in the leaves. The weakened activities of enzymes involved in photosynthesis(ribulose-1,5-bisphosphate carboxylase and phosphoenolpyruvate carboxylase) and antioxidant system(catalase, superoxide dismutase and peroxidase) reduced the photosynthetic rate(P_n) and accelerated leaf senescence. The correlation results indicated that reduced Pn and catalase activity and increased malondialdehyde content under drought conditions induced the decrease of post-silking photoassimilates deposition, ultimately resulted in the grain yield loss.     

富硒区茶树鲜叶中硒累积与土壤因子的相关性分析

茶树是富硒植物,饮用富硒茶是一种安全、有效的补硒途径之一。茶叶的硒含量受多种环境因素影响,但有关富硒茶区茶树硒积累特性及主要影响因子的研究还鲜有报道。以高硒茶区湖北恩施、陕西安康不同地点生产茶园成龄茶树和根际土壤为研究对象,结合土壤及植物样品全硒含量等多种指标,明确了根际土壤硒含量对茶树硒分布特性的影响,分析了富硒区土壤pH、硒含量等9个重要土壤特性相关因子的数值分布规律。通过对186组具有代表性的土壤样品和附生茶树新梢组织检测数据进行分组和整体相关性分析,证实了富硒区茶叶全硒含量与土壤硒含量之间存在极显著相关（相关系数r=0.59,P<0.01）,揭示了茶叶全硒含量与土壤有机质含量、水解性氮、锌含量以及茶叶中硫、锌含量的显著相关,同时对安康和恩施地区的土壤和茶叶硒含量相关因素进行了深入分析。提出了茶叶硒含量对土壤有机质含量、硫含量、硒含量和锌含量的数学模型,模型拟合优度为0.512 6,达极显著水平（P<0.01）。     

麦/油-稻轮作下秸秆还田与氮肥管理对直播杂交稻氮素利用特征的影响

【目的】探明秸秆还田和氮肥管理对麦/油后直播杂交稻氮素积累、转运、氮肥利用效率及籽粒产量的影响。【方法】选用优质三系杂交稻宜香优2115,采用二因素裂区设计,麦、油茬田同步开展试验,处理完全一致。主区为麦/油秸秆全量翻埋还田(M₁)和秸秆不还田(对照,M₀),副区设4个氮肥管理,即不施氮对照(N₀)、m_基肥∶m_分蘖肥∶m_促花肥∶m_保花肥比例分别为1∶0∶0∶0(N₁)、3∶3∶2∶2(N₂)、2∶2∶3∶3(N₃),测定了直播杂交稻主要生育时期各器官的氮素积累量及籽粒产量。【结果】结果表明,两种轮作方式下,氮肥管理对直播杂交稻主要生育时期的氮素积累、齐穗后茎鞘、叶片的氮素转运及稻株氮素利用效率均存在显著或极显著的调控效应。秸秆还田显著提高麦/油茬杂交稻中后期的氮素积累量、茎鞘和叶片的氮素转运量以及氮肥利用效率,其中,氮肥农学利用率、氮肥偏生产力和氮肥表观利用率较秸秆不还田分别提高了34.96%/28.76%、2.52%/2.61%和31.91%/22.30%。同时,油菜秸秆还田下直播杂交稻各生育时期氮素积累和产量较麦秆还田表现更好,籽粒产量提高481 kg/hm²(5.22%)。M₁N₂处理、M₀N₃处理下,直播杂交稻各阶段的氮素积累速率明显加大,促进结实期茎鞘和叶片的氮素向穗部转运,成熟期稻株氮素积累量优势明显且有较高的氮素利用效率(麦/油茬稻氮肥农学利用率、偏生产力和表观利用率分别达17.87 kg∙kg^-1/17.85 kg∙kg^-1、67.27 kg∙kg^-1/71.28 kg∙kg^-1、74.93%/75.05%),最终实现高产。【结论】在麦/油-稻轮作下秸秆全量还田,配合N₂氮肥管理,可有效提高直播杂交稻氮素吸收、利用效率,增加籽粒产量,尤以油菜秸杆还田的效果更好。     

干旱区平原水库坝后排水沟对下游农田土壤水盐运移的影响

干旱区平原水库的渗漏会抬高坝后农田地下水位,使土壤发生盐渍化,许多土地因此减产甚至弃耕。坝后设置排水沟是一种有效控制农田地下水位的措施。本研究采用排水沟调控坝后农田的地下水位,并利用HYDRUS模拟出在不同地下水位和深度的条件下土壤含水率与含盐量的变化情况,将实测数据与模拟数据相互对比,检验出模拟值的可靠度。研究结果表明:地下水位通过排水沟从1 m降到3 m,表层含盐量相差1.49～33.19 g·L~(-1),因此排水沟遏制地下水位越深,水盐运移越不明显,次生盐渍化越不容易发生,反之,则容易发生土壤盐渍化;地下水位相同时,土体种植植物可以降低含水率和含盐量,其中含水率最大变化为6.33%,含盐量仅相差0.08～4.56 g·L~(-1)左右,而且随着土层深度增加其影响的程度也逐渐减小。设置排水沟是解决坝后农田土壤盐渍化的较好方式。     

Challenges for the sustainable use of water and land resources under a changing climate and increasing salinization in the Jizzakh irrigation zone of Uzbekistan

Jizzakh Province in Uzbekistan is one of the largest irrigated areas in Central Asia without natural drainage.In combination with aridity,climate change and extensive irrigation practices,this has led to the widespread salinization of agricultural land.The aim of this study was to identify opportunities to improve the reclamation status of the irrigated area and how best to effectively use the water resources in Jizzakh Province based on investigations conducted between 1995 and 2016.A database of field measurements of groundwater levels,mineralization and soil salinity conducted by the provincial Hydro-Geological Reclamation Expeditions was used in the study.The total groundwater mineralization was determined using a portable electric conductometer(Progress 1T)and the chloride concentration was determined using the Mohr method.The soil salinity analyses were conducted by applying two different methods:(1)the extraction and assessment of the soluble salt content,and(2)using an SM-138 conductivity sensor applied to a 1:1 mixture of soil sample and water.The analyses of the monitoring results and the salt balance in the"irrigation water–soil–drainage water"system clearly demonstrated that the condition of the irrigated land in the province was not significantly improved.Under these conditions,the stability of crop yields is achieved mainly through the use of large volumes of fertilizer.However,excess amounts of mineral fertilizers can also cause the salinization of soils.The average groundwater salinization value in most of the irrigated land(75.3%)fluctuated between 1.1 and 5.0 g/L,while the values were less than 1.0 g/L in 13.1%of the land and in the range of 5.1–10.0 g/L in 10.5%of the land.During the period of 1995–2016 the salinization level of the irrigated land in Jizzakh Province increased slightly and the area could be divided into the following classes:no salinity(17.7%of the total area),low salinity(51.3%),moderate salinity(29.0%),and high salinity(2.0%).Detailed studies of the salt balance in irrigated land,the impact of climate change,increased fertilizer use,and repeated remediation leaching on the groundwater level and mineralization should be conducted in the future,due to the possibility of accelerated salinization,fertility decline,and reduced yields of agricultural crops.