磷硒配施对郑麦9023硒吸收及土壤硒形态转化的影响

为给通过合理施用磷肥来提高冬小麦籽粒硒含量提供参考依据,以冬小麦品种郑麦9023为供试材料进行盆栽试验,设置3个磷水平(0、80、160mg·kg~(-1),分别表示为P_0、P_(80)和P_(160))和2个硒水平(0和1mg·kg~(-1),分别表示为Se_0和Se_1),共6个处理。结果表明,在Se_0水平下,籽粒产量随着施磷量的增加而逐渐提高,而在Se_1水平下,籽粒产量随着施磷量的增加呈先增加后降低的趋势,在P_(80)处理下籽粒产量最高。在Se_1水平下,施磷显著增加了小麦各器官以及整株硒累积量,但是施磷降低了硒从颖壳向籽粒中的迁移系数,显著降低了各器官的硒含量。施硒可提高土壤各形态硒的含量,提高水溶态和可交换态硒的比例。在Se_0水平下施磷可以提高土壤水溶态硒、可交换态硒、铁锰氧化物结合态硒所占总硒的比例;而在Se_1水平下,施磷增加了土壤水溶态硒、有机物硫化物结合态硒、残渣态硒的含量及比例,但是降低了可交换态硒、铁锰氧化物结合态硒的含量及比例。因此,适宜的磷硒配施可通过影响土壤中各种形态硒的转化过程,促进土壤硒向水溶态硒的转化,提高土壤硒的有效性,进而促进郑麦9023对土壤硒的吸收累积,达到增产的效果。     

施硒对冬小麦产量及硒吸收转运的影响

为探明施硒(Se)对冬小麦产量及Se吸收转运的影响规律,采用盆栽试验,研究了北方石灰性潮土中5种施Se量对冬小麦产量、Se吸收及分布的影响。结果表明,随着施Se量的增加,冬小麦籽粒产量、成穗数和穗粒数均呈先增加后降低的趋势,其中,Se0.5、Se1处理的籽粒产量和各产量构成要素均高于Se0处理,最大值均出现在Se0.5处理。施Se显著增加了冬小麦各部位的Se含量、Se累积量以及植株总Se累积量;施Se增加了Se元素从颖壳向籽粒的迁移系数,降低了Se元素从地下部向地上部、茎叶向颖壳的迁移系数;施Se增加了Se在冬小麦籽粒中的占比,降低了Se在颖壳、茎叶中的占比。Se0.5、Se1较Se0处理,增加了冬小麦籽粒产量、籽粒Se含量、籽粒Se累积量及籽粒Se的占比。     

全程深施肥对水稻产量形成及稻米品质的影响

以超级稻东农423为试验材料,设全程深施肥、全层施肥、表层施肥及无肥4个处理,研究水稻生长发育的动态变化,包括分蘖消长、叶绿素含量、叶面积指数和干物质积累量动态变化,并对产量及其构成因素、稻米蛋白质含量、直链淀粉含量和味度值进行了比较。结果表明：1）全程深施肥方法能够促使水稻生育前期平稳生长,后期优势生长,延长有效分蘖期,增加有效分蘖数,提高叶绿素含量、叶面积指数和干物质积累量;2）各处理的产量和稻米蛋白质含量间均达极显著水平,并呈现全程深施＞全层施＞表施＞无肥的趋势;各处理的直链淀粉含量、味度值之间均达极显著水平,并呈现无肥＞表施＞全层施＞全程深施的趋势;3）全程深施肥能够提高水稻的产量、穗数、每穗粒数和蛋白质含量,却降低了结实率、千粒重、稻米直链淀粉含量及味度值。     

叶面喷施硒酸钠对不同小麦品种(系)籽粒硒及其他矿质元素含量的影响

为了解叶面喷施硒酸钠对不同小麦品种(系)籽粒硒含量及其他矿质元素的影响,对114个不同小麦品种(系)进行叶面喷施硒酸钠,试验设4个梯度,分别为0 mg·kg~(-1)(CK)、100 mg·kg~(-1)(Se10)、200mg·kg~(-1)(Se20)、300mg·kg~(-1)(Se30),利用离子发射光谱-原子吸收仪测定了籽粒硒、钙、镁、铜、铁、锰、锌、硫含量。结果表明,叶面喷施硒酸钠可以提高小麦籽粒的硒含量,增幅因品种(系)而异;CK、Se10、Se20及Se30处理下,籽粒的总硒含量分别为1.54、5.70、10.01和13.10mg·kg~(-1)。籽粒中不同矿物质元素对叶面喷施硒酸钠的响应不同;籽粒中硒与其他元素的积累既有协同也有拮抗作用,因元素种类、小麦品种(系)和施硒量而异。总体而言,高浓度硒处理降低了籽粒中钙、镁、铜、铁、锰和硫的含量,但提高了锌的含量。     

测土配方施肥对水稻生长发育及产量形成的影响

以当地优质稻南粳5718和糯稻99-25为供试材料,根据试验地土壤养分状况,采取减氮增磷增钾的措施,即在基肥中减少氮肥,增加磷钾肥,并在追肥中降低氮肥投入,来研究测土配方施肥技术对当地水稻增产的途径和方法。结果表明,测土配方施肥技术能够通过促进水稻分蘖,提高成穗数,其中南粳5718高峰苗较常规施肥处理增加8.02%,有效茎蘖数增加5.26%,穗数增加4.89%;糯稻99-25高峰苗较常规施肥处理增加10.12%,有效茎蘖数增加4.32%,穗数增加2.34%。测土配方施肥可以提高抽穗期的叶面积指数(增幅19.47%),强化水稻的光合能力。在不影响穗粒数和结实率的情况下,测土配方施肥可以增加水稻千粒质量,从而最终提高产量。     

晚播条件下施氮量对稻茬小麦氮素吸收及产量的影响

为给安徽省江淮稻麦轮作区域晚播稻茬小麦高产栽培的氮肥合理施用提供依据,选用当地主栽品种扬麦18和皖垦麦076为试验材料,设置5个施氮水平(0、90、180、270和360 kg·hm~(-2)),分析施氮量对晚播小麦氮素积累与分配、糖氮比、氮素同化酶活性及产量的影响。结果表明,增施氮肥能显著提高小麦各器官的氮积累量以及营养器官花前贮存氮素转运量、转运效率和转运氮素对籽粒氮素的贡献率,氮素收获指数随着施氮量的增加而降低。随施氮量的增加,小麦各生育时期不同器官的糖氮比值显著降低。小麦的氮素分配比例在生育前期以叶片最高,成熟期籽粒中氮素分配比例显著高于其余部位,而小麦的可溶性糖分配比例在生育前期以茎鞘最高,成熟期籽粒较高。在0～270 kg·hm~(-2)施氮量范围内,增施氮肥后,两个小麦品种的硝酸还原酶、谷氨酰胺合成酶和谷氨酸合成酶活性均显著提高,穗数、穗粒数和籽粒产量均明显增加。继续增加施氮量至360kg·hm~(-2)时,氮素同化酶活性和产量无显著变化,说明施氮过多对小麦氮素同化和产量无益。土壤氮贡献率、氮肥农学利用效率和氮素偏生产力均随施氮量增加而降低。推荐江淮区域稻茬小麦晚播条件下适宜施氮量为180～270kg·hm~(-2)偏下限,可兼顾高产及氮素高效吸收和利用。     

Effect of pre-emergence herbicides and timing of soil saturation on the control of six major rice weeds and their phytotoxic effects on rice seedlings

The study evaluated the effects of pre-emergence herbicides and their rates [oxadiazon (0.5 and 1 kg ai ha⁻¹), pendimethalin (1 and 2 kg ai ha⁻¹), and pretilachlor with safener (0.6 kg ai ha⁻¹)], and time of soil saturation establishment after herbicide application [1, 3, 5, and 7 days after spray (DAS)] in controlling the six major rice weeds, and their phytotoxic effects on rice seedling growth. All herbicides provided 100% control of Echinochloa colona, Echinochloa crus-galli, Leptochloa chinensis, Cyperus iria, and Amaranthus spinosus. Murdannia nudiflora was 100% controlled by oxadiazon and pretilachlor with safener, but poorly controlled (22–75%) by pendimethalin. Pendimethalin at 2 kg ai ha⁻¹ was more effective than at 1 kg ai ha⁻¹ in reducing the biomass of the stem, leaf, and root of M. nudiflora irrespective of timing of soil saturation. Rice plant height was reduced to a maximum (77–96%) by pendimethalin at 2.0 kg ai ha⁻¹ followed by oxadiazon at 1.0 kg ai ha⁻¹ (38–70%) compared to the non-treated control. In contrast, the tallest rice plants were observed in the non-treated control and those treated with pretilachlor with safener which had 80–100% rice plant survival. The lowest rice plant survival of 0, 6, 7, and 16% was found in the soil applied with pendimethalin at 2 kg ai ha⁻¹ and saturated at 1, 3, 5, and 7 DAS, respectively, which was followed by oxadiazon at 1 kg ai ha⁻¹. All herbicides except pretilachlor with safener reduced SPAD values with early soil saturation, which improved with delay in soil saturation timing. Pendimethalin at 2 kg ai ha⁻¹ reduced the SPAD values of rice plants by 100–164% relative to the non-treated control and produced the highest phytotoxicity symptoms. Pendimethalin also reduced rice shoot biomass more than oxadiazon, which was compounded by early soil saturation after herbicide application. Pretilachlor with safener was the only herbicide that exhibited low phytotoxic symptoms on rice plants and did not reduce leaf, stem, root, and shoot biomass of rice. Percent reduction in rice leaf, stem, root, and shoot biomass by the different herbicides was in the order of pendimethalin 2 > oxadiazon 1 > pendimethalin 1 > oxadiazon 0.5 > pretilachlor with safener 0.6 kg ai ha⁻¹. Each herbicide treatment reduced rice growth parameters as soil saturation was delayed in the order of 1 DAS > 3 DAS > 5 DAS > 7 DAS. The study suggests that soil water content and herbicide rates are important factors in influencing herbicide phytotoxicity in rice. The application of herbicides should be avoided when the soil is too wet, and irrigation should be delayed at least one week after herbicide application.     

硒酸钠施用对小麦的富硒效应及其残效

为明确外源硒酸盐对小麦各器官硒含量的影响以及硒酸盐的残效,通过两年连续盆栽试验,设置了0、0.02、0.04、0.08、0.16 mg·kg^-1五个施硒水平,第一年施硒,第二年不施硒且在原土中继续种小麦,测定和分析了两年小麦不同器官（叶、茎、籽粒和颖壳）和土壤硒含量及产量和生物量。结果表明,施硒当季能够增加小麦产量及地上部生物量,显著提高各器官硒含量,各器官硒含量与施硒量均呈显著的线性正相关。器官中叶片对硒的富集能力最强,其次为籽粒、茎和颖壳。小麦不同器官硒强化指数大小与富集系数表现一致,施硒量每增加1 mg·pot^-1,叶片、籽粒、茎、颖壳的硒含量分别增加8.9、6.2、4.6和3.6 mg·kg^-1。外源硒酸盐具有残效,尤其在硒施用量较高时,小麦对外源硒的利用率两年均随施硒量的增加而增加,当季硒的利用率最高值为33.7%,两年累积利用率最高值为34.7%。施硒在第二年对小麦各器官硒的含量、土壤硒含量仍有显著的增加效应,尤其在施硒量较高时,但其对小麦硒含量的影响大于对土壤有效硒、总硒含量的影响。在农业生产应用中应选择适宜的施硒用量,关注硒肥的后效,实现高效安全的小麦硒强化。     

不同锌效率基因型水稻籽粒中矿质元素的原位微区分布研究

 采用同步辐射（SRXRF）结合ICP MS研究了足Zn条件下不同锌效率水稻籽粒中Zn及其他矿质元素的微区分布特征。结果表明SRXRF技术可高效分析水稻籽粒锌等矿质元素的微区分布特征。水稻籽粒中K和Ca元素的分布特征与其余4种元素相关不显著,而Zn、Fe、Cu、Mn元素的含量分布相互间则显著相关;水稻籽粒中K含量最高,移动性也最强,精米中K含量可达颖壳的52.6%~90.6%,而Ca在颖壳中含量最高。其余矿质元素含量最高值均出现在糊粉层;Zn、Fe等元素主要集中在水稻籽粒的胚及糊粉层等外层功能组织,在胚乳中由外向里呈递减趋势。此外,锌高效基因型IR8192在水稻籽粒各部位的Zn含量均低于锌低效基因型二九丰。可见,与锌低效品种相比,锌高效品种仅在低Zn水平下表现出更高的锌吸能力及利用效率,在足Zn条件下并无籽粒富锌特征。     

Selenium Alleviates Carbohydrate Metabolism and Nutrient Composition in Arsenic Stressed Rice Plants

This study reported the influence of selenium (Se) on carbohydrate composition and some related enzymes and nutrient compositions of arsenic (As) stressed rice plants. Rice plants of cultivar PR126 were grown on soil amended with As in a range of 25–100 μmol/kg with and without 0.5 or 1.0 mg/kg Se. Total soluble sugars (TSS) and reducing sugars (RS) increased in leaves of As stressed plants at the tillering and grain filling stages whereas sucrose and starch contents showed the reverse trend. Se supplementation to As stressed plants further increased TSS and RS, and enhanced sucrose phosphate synthase activity in rice leaves, thus improving sucrose content and the tolerance to As stress of the plants. Se alone or in combination with As resulted in lower As accumulation in rice husk and grains, and the highest reduction was observed in Se applied at 1.0 mg/kg compared to the corresponding As treatments alone. As may limit the accumulations of Na, Mg, K, Ca, Fe, Zn and Mn in rice grains, which are essential for humans. Binary application of different combinations of As and Se protected the plants against As and increased the mineral content in rice grains. Addition of Se in As treated soil significantly alleviated As stress by enhancing grain yields compared to the corresponding As treatment. It is concluded that Se induced amelioration of the toxic impact of As in rice either by modulating carbohydrate composition and/or nutrient uptake is one of the mechanisms to alleviate As stress in plants.     

锌、硒种肥配施对裸燕麦产量及矿质元素含量的影响

为了明确锌、硒种肥配施对裸燕麦产量及矿质元素含量的影响,以裸燕麦品种燕科1号为材料,田间试验设置锌肥、硒肥、锌肥和硒肥配施及对照4个处理,分析了燕麦籽粒产量及其构成因素、籽粒中矿质元素Ca、Mg、Fe、Mn、Cu、Zn、Se的含量以及Zn、Se的累积量。结果表明,与对照相比,种施锌肥、硒肥以及锌肥和硒肥配施可以显著提高燕麦生物学产量。锌肥和硒肥配施时,燕麦籽粒比对照增产2.8%,但不同处理间差异不显著。随着生育进程的推进,不同处理Zn、Se累积量均呈现逐渐增加的变化趋势。与对照相比,单独施用锌肥、锌硒肥配施可以显著提高燕麦全株Zn的积累量,分别提高了30.2%和37.1%;单独施用硒肥、锌硒肥配施可以显著提高全株Se的积累量,分别提高了95.3%和110.6%。不同施肥处理均可提高成熟期籽粒中Zn、Se含量,锌肥、硒肥、锌肥和硒肥配施时籽粒中Zn含量分别比对照提高了30.5%、13.9%和31.5%,Se含量分别提高了41.7%、175.6%和239.4%。不同处理间成熟期籽粒中Ca、Mg、Fe、Mn、Cu含量的差异不显著。说明通过种施锌肥、硒肥、以及锌肥和硒配施在不影响产量的条件下可以达到提高燕麦籽粒中Zn、Se含量的目的。     

Silicon fertilization modulates 2-acetyl-1-pyrroline content,yield formation and grain quality of aromatic rice

Present study aimed to assess silicon (Si) mediated yield, grain quality and regulations in 2-acetyl-1-pyrroline accumulation (2-AP) in aromatic rice. Four different levels of Si at 15, 30, 45 and 60 mg kg⁻¹ were applied to two aromatic rice cultivars i.e., Nongxiang 18 and Meixiangzhan 2, while pots without Si were served as control (CK). Results revealed that Si fertilization improved 2-AP, Si and proline contents in leaves and grains as well as activities of proline dehydrogenase (PRODH) and net photosynthetic rates (Pn) (in leaves) while interfered with total N contents in leaves and grains. Moreover, leaves N and proline contents, and net photosynthetic rates (Pn) were decreased with plant age i.e., tillering > flowering > maturity while PRODH activities and Si contents were highest at flowering and maturity stages, respectively and minimum at tillering stage. Furthermore, growth, yield and quality components were also improved by Si application but results were not consistent regarding grain quality for both rice cultivars. Further, Si contents in leaves have significant positive relations (r = 0.3974, P < 0.05) with grain 2-AP contents at flowering stage. Hence, Si proved better for both rice cultivars whereas 2-AP contents were higher for Meixiangzhan 2 than Nongxiang 18.     

Effects on rice plant morphology and physiology of water and associated management practices of the system of rice intensification and their implications for crop performance

Field experiments were conducted in Bhubaneswar, Orissa, India, during the dry season (January–May) in 2008 and 2009 to investigate whether practices of the System of Rice Intensification (SRI), including alternate wetting and drying (AWD) during the vegetative stage of plant growth, could improve rice plants’ morphology and physiology and what would be their impact on resulting crop performance, compared with currently recommended scientific management practices (SMP), including continuous flooding (CF) of paddies. With SRI practices, grain yield was increased by 48% in these trials at the same time, there was an average water saving of 22% compared with inundated SMP rice. Water productivity with AWD-SRI management practices was almost doubled (0.68 g l⁻¹) compared to CF-SMP (0.36 g l⁻¹). Significant improvements were observed in the morphology of SRI plants in terms of root growth, plant/culm height, tiller number per hill, tiller perimeter, leaf size and number, leaf area index (LAI), specific leaf weight (SLW), and open canopy structure. These phenotypic improvements of the AWD-SRI crop were accompanied by physiological changes: greater xylem exudation rate, crop growth rate, mean leaf elongation rate (LER), and higher light interception by the canopy compared to rice plants grown under CF-SMP. SRI plants showed delayed leaf senescence and greater light utilization, and they maintained higher photosynthetic rates during reproductive and grain-filling stages. This was responsible for improvement in yield-contributing characteristics and higher grain yield than from flooded rice with SMP. We conclude that SRI practices with AWD improve rice plants’ morphology, and this benefits physiological processes that result in higher grain yield and water productivity.     

Selectivity and weed control efficacy of pre- and post-emergence applications of clomazone in Southern Brazil

During the 2006/07 and 2008/09 growing seasons in Southern Brazil, we evaluated crop selectivity and weed control efficacy of clomazone on rice when applied alone or in a mixture with other pre- and post-emergence herbicides (BRS Querência variety). All herbicide treatments caused some degree of rice injury during both years; however, in no case was the injury still visible 21 days after application. Rice injuries were observed when application rates exceeded the recommended dose, and particularly when the herbicide was applied pre-emergence. Density reduction and panicle sterility served as measures of rice injury. Echinochloa crus-galli was the primary weed; it reduced rice yields by approximately 50% compared treated plots. In both growing seasons, clomazone herbicide (400 g ai ha⁻¹) controlled the weed 87.0%–99.6%, and it provided 8.06 t ha⁻¹ to 9.44 t ha⁻¹ of rice yield.     

不同栽培措施集成对稻茬小麦产量、农艺及光合特性的影响

为探究不同栽培措施集成对稻茬小麦产量及农艺和光合特性的影响,以小麦品种扬麦16和扬麦20为材料,设置氮空白、当地常规(对照)、减氮、减密减氮、施有机肥、施蚓粪6种栽培措施处理,对不同栽培措施下稻茬小麦产量、干物质积累与转运、冠层光合特性等进行了分析。结果表明,两个品种的产量在不同栽培措施下均表现为施有机肥>施蚓粪>减密减氮>当地常规>减氮>氮空白。与对照相比,两个品种的平均产量在减密减氮、施有机肥和施蚓粪栽培处理下分别提高了7.45%、22.33%和11.02%,而这主要得益于穗数、穗粒数与千粒重的同步提高。各栽培措施处理均显著增加了小麦茎蘖成穗率、拔节期至成熟期的干物质积累量、干物质向籽粒中的分配量及其对籽粒产量的贡献率,提高了开花期的叶面积、比叶重、叶片氮含量和拔节期至成熟期旗叶的净光合速率、蒸腾速率、气孔导度,降低了开花期的株高、叶角、透光率以及拔节期至成熟期的冠层温度。综合来看,在江苏稻茬麦区,扬麦16和扬麦20均在基本苗192×10株·hm^-2、施氮量216 kg·hm^-2和有机肥施用量1 800 kg·hm^-2条件下可以获得较好的群体质量和冠层光合特性,进而实现高产。     

Growth and yield formation of rice (Oryza sativa L.) in the water-saving ground cover rice production system (GCRPS)

A new water-saving ‘Ground Cover Rice Production System’ (GCRPS) was evaluated in 2001 and 2002 near Beijing, North China. Using GCRPS, lowland rice was cultivated without a standing water layer during the entire growth period and plots were irrigated when soil water tension was below 15 kPa (approximately 90% water holding capacity). In order to prevent soil evaporation, the soil surface was covered with 14 μm thick plastic film (GCRPS_Plastic) or mulched with straw (GCRPS_Straw). In a third GCRPS treatment the soil was left uncovered (GCRPS_Bare). These treatments were compared with lowland rice cultivated under traditional paddy conditions (Paddy control). In an additional treatment with bare soil, one aerobic rice variety was cultivated. Compared to Paddy control, only 32–54% of irrigation water was applied in GCRPS treatments. Plants in GCRPS were smaller, developed fewer panicles and had a smaller leaf area index compared to Paddy control. Yield was significantly less in GCRPS_Bare and GCRPS_Straw compared to Paddy control in both years, while yield in GCRPS_Plastic was only 8% less than the Paddy control yield in 2002. Water-use efficiency (WUE, gram grain yield per litre water input) in GCRPS_Plastic was higher (0.35) than in Paddy control (0.23). Grain yield was highly significantly correlated with maximum leaf area index and leaf area index duration. Among yield components, the number of productive tillers had the greatest positive effect on yield, while the number of grains per panicle, thousand-grain weight and harvest index remained almost unaffected. Under uncovered condition, the aerobic rice variety had a significantly higher harvest index (HI), yield, and WUE compared to the lowland rice variety (GCRPS_Bare). The experiment demonstrates that GCRPS has potential to save substantial amounts of water at relatively minor yield penalties, if stress factors such as low soil temperature, water deficit, and nutrient deficiencies during the vegetative growth stage are avoided by suitable management practices.     

杂交水稻不同器官重金属铅浓度与累积量

以生长于盆钵中的两系杂交稻和三系杂交稻共6个组合为试验材料,设置土壤铅(Pb)浓度为500mg/kg和不加Pb土壤(对照)两个处理,测定水稻植株不同器官Pb的浓度和累积量。结果表明,Pb处理降低了两优培九、103S/郑粳2号、丰优香占和汕优63的产量,主要是每穗粒数减少,对其余组合的产量无显著影响;不同基因型水稻植株对Pb吸收与积累存在差异,以103S/郑粳2号和两优培九累积量最多,K优818累积量最少;水稻植株不同器官Pb的浓度和累积量的大小顺序为根>茎鞘>叶片。籽粒不同部位Pb的浓度大小顺序为糠层>颖壳>精米,精米中Pb累积量仅为谷粒的25%左右,精米中Pb的浓度以103S/郑粳2号最高,K优818最低;在抽穗期和成熟期,同一器官Pb浓度与累积量呈显著或极显著正相关,但不同器官之间的相关不显著。对不同杂交稻组合植株中Pb浓度和累积量差异的原因进行了讨论。     

A process model for explaining genotypic and environmental variation in growth and yield of rice based on measured plant N accumulation

The objective of this study was to develop a mechanistic model for simulating the genotypic and environmental variation in rice growth and yield based on measured plant N accumulation. The model calibrations and evaluations were conducted for rice growth and yield data obtained from a cross-locational experiment on 9 genotypes at 7 climatically different locations in Asia. The rough dry grain yield measured in the experiment ranged from 71 to 1044 g m⁻² over the genotypes and locations. An entire process model was developed by integrating sub-models for simulating the processes of leaf area index development, partitioning of nitrogen within plant organs, vegetative biomass growth, spikelet number determination, and yield. The entire process model considered down-regulation of photosynthesis caused by limited capacity for end-product utilization in growing sink organs by representing canopy photosynthetic rate as a function of sugar content per unit leaf nitrogen content. The model well explained the observed genotypic and environmental variation in the dynamics of above-ground biomass growth (for validation dataset, R² = 95), leaf area index development (R² = 0.82) and leaf N content (R² = 0.85), and spikelet number per unit area (R² = 0.67) and rough grain yield (R² = 0.66), simultaneously. The model calibrations for each sub-model and the entire process model against observed data identified 10 genotype-specific model parameters as important traits for determining genotypic differences in the growth attributes. Out of the 10 parameters, 5 were related to the processes of phenological development and spikelet sterility, considered to be major determinants of genotypic adaptability to climate. The other 5 parameters of stomatal conductance, radiation extinction coefficient, nitrogen use efficiency in spikelet differentiation, critical leaf N causing senescence, and potential single grain mass had significant influence on the yield potential of genotypes under given climate conditions.     

Nitrogen and Potassium Fertility Impacts on Aggregate Sheath Spot Disease and Yields of Rice

Abstract

Aggregate sheath spot (AgSS), a disease caused by Rhizoctonia oryzae-sativae, is one of the major rice (Oryza sativa L.) diseases in California. A three year study was initiated in 1998 to evaluate the effect of nitrogen (N) and potassium (K) fertility on the severity of AgSS. A field with a history of AgSS was divided in two: in one the straw was incorporated and in the other the straw was removed. Rice was fertilized annually with five rates of N ranging from 0 to 200 kg ha-¹ (main plot) and six rates of K ranging from 0 to 125 kg ha-¹ (sub-plot). Soil K levels in both fields declined over time and by the third year, soil K was below the critical level of 60 μg K g-¹ soil in both fields. There was a grain yield response to K fertilizer in all 3 years in the field where straw was removed and in the third year when straw was incorporated. Where there was a significant response to K fertilization, yields increased by 560 kg ha-¹. In all fields and years there was a significant yield response to N fertilizer. AgSS severity decreased with increasing N and K fertilizer rates and leaf N and K concentrations at panicle initiation. Furthermore, the leaf N concentration required for maximum rice yields was lower than the leaf N concentration which resulted in the lowest severity of AgSS .     

不同硒肥对水稻产量和籽粒中硒含量的影响

以Y两优302为材料,在大田栽培条件下设置3种硒肥试验,研究不同硒肥对水稻产量和籽粒中硒含量的影响。结果表明：施用硒肥对水稻产量没有明显影响,可提高水稻籽粒中的硒含量,不同硒肥作用效果不同。从综合经济效益来看,以齐穗后3d叶面喷施有机富硒肥500倍液50kg/667m^2效果最好,水稻籽粒中硒含量达0.067mg/kg,比对照增加0.043mg/kg,达极显著水平,生产的大米符合富硒米的国家标准。