机插条件下低氮密植栽培对“早晚兼用”双季稻产量和氮素吸收利用的影响

为了缓解长江中下游双季稻区机插双季稻生育期不配套的矛盾,2014—2015年早晚两季均以常规早稻品种中嘉早17为材料,在大田栽培条件下研究机插密度(36.4、28.6、19.0穴m–2)与施氮量(0、110~140、176~189 kg N hm–2)对机插双季稻产量及氮肥利用率的影响。结果表明:采用"早晚兼用"机插双季稻栽培模式有利于早、晚2季周年高产,以"高密+高氮"处理产量最高,2年分别达到16.94 t hm–2和16.99 t hm–2,但与"高密+低氮"处理的产量差异不显著;氮肥利用率随氮肥用量增加而下降,随栽插密度增加而提高,以"高密+低氮"处理最高,2年4季分别为62.77%、55.75%、65.82%、64.37%,比"高密+高氮"处理分别提高12.11%、9.01%、8.49%、2.14%;"高密+低氮"处理与"低密+高氮"处理相比,群体干物质积累量及辐射利用率均有一定的优势。由此可见,在此模式下适当增加机插密度,减少氮肥用量,既可实现高产,又能显著提高氮素利用率。采用"早晚兼用"品种搭配模式,低氮、密植栽培可作为长江中下游双季稻区机插双季稻生产的关键技术。     

Spatial variability of salt-affected soils in the middle Ebro Valley (Spain) and implications in plant breeding for increased productivity

Barley breeding programs have empirically selected for improving grain yield and quality. The objective of this study was to quantify genetic gains in yield in 2-rowed malting barley cultivars released from 1944to 1998 in Argentina, identifying the major physiological traits responsible for them. For this purpose, a field experiment was conducted in absence of biotic and abiotic stressful factors and with lodging being prevented mechanically. Until the 1970's,potential yield was maintained nearly constant at 5.25 mg ha^-1 and since then it increased at a rate of 41 kg ha^-1 year^-1. That bi-linear trend was closely related to the trend of averaged yields obtained by farmers. The contribution made by breeding yield potential to the total yield gains achieved by farmers was estimated in c. One third. Neither time to heading nor time to maturity were systematically modified by breeding. However, the partitioning of the developmental time was modified: time to achieve both maximum number of floret primordia and length of the jointing –heading period were increased with the year of release of the cultivars. The main component associated with yield was the number of grains per m², due to variations in number of spikes per m².Total and vegetative biomass at maturity increased with the year of release of the cultivars, at a rate of 45 and 19 kg ha^-1 year^-1, while both harvest index and stem height remained virtually unmodified. Differences in biomass at heading among cultivars were related to the improvement on the abilities to capture more radiation. This revised version was published online in August 2006 with corrections to the Cover Date.     

西北绿洲灌区水氮耦合对燕麦品种陇燕3号耗水特性及产量的影响

灌水和施肥,尤其是施氮肥,是调控作物生长和增加产量的两大重要技术措施,其互作是燕麦高产高效栽培中重要因素。2014—2015年连续2个生长季,在甘肃河西绿洲灌区的田间试验设3个定额灌溉和3个施氮(纯氮)水平,研究水氮耦合对陇燕3号农田0~150 cm土层耗水量、棵间蒸发、产量及水分利用效率的影响。3个灌溉处理的灌水量分别为270 mm(I_1)、337.5 mm(I_2)和405 mm(I_3),3个施氮水平分别为90 kg hm~(–2)(N_1)、120 kg hm~(–2)(N_2)和150 kg hm~(–2)(N_3)。从播种到成熟,燕麦阶段耗水强度呈先增后减趋势,抽穗至灌浆是最大耗水期,且同一施氮水平下,阶段耗水强度随灌水量增大而显著增加。在全生育期内,棵间蒸发量(E)及土壤水分蒸发量占总蒸发量的比例(E/ET)表现先降后升趋势,且相同施氮量下,拔节至灌浆期随灌水量的增大而增大,而灌浆至成熟期则随灌水量的增大而减小。相同施氮量下,燕麦产量随灌水量增加而显著增加,水分利用效率却随灌水量增加而降低。产量N_3I_3最高(5466.0~5727.5 kg hm~(–2)),N_3I_2次之(5428.5~5678.5 kg hm~(–2)),N_1I_1最低(4504.5~4804.3 kg hm~(–2));水分利用效率N_3I_2最大(12.11~12.82 kg mm~(–1) hm~(–2)),N_3I_1次之(12.04~12.63 kg mm~(–1) hm~(–2)),N_1I_3最小(9.79~10.58 kg mm~(–1) hm~(–2))。由此表明,水氮耦合对燕麦水分利用及产量具有显著互作效应。施氮量150 kg hm~(–2)、灌溉定额337.5 mm是西北绿洲灌区燕麦种植较佳的节水、高产水氮管理模式。     

Transfer of Grain Legume Nitrogen within a Crop Rotation Containing Winter Wheat and Winter Barley

In a crop rotation trial, conducted from 1985 to 1988 at TU-Munich's research station in Roggenstein, the transfer of grain legume nitrogen was evaluated in crop rotations containing fababeans and dry peas as well as oats (reference crop) and winter wheat and winter barley as following crops. The results obtained can be summarized as follows: Dinitrogen fixation by fababeans ranged from 165 to 240 kg N ha¹, whereas N₂-fixation by peas amounted from 215 to 246 kg N ha^?1. In all seasons the calculated N-balance where only grain was removed was positive, with a net gain being on average 106 (peas) and 84 (fababeans) kg N ha^?1. After the harvest of peas 202 kg N ha^?1 remained on the field on average over seasons (158 kg N ha^?1 in the above ground biomass and 44 kg N ha^?1 as NO₃-N in 0–90 cm depth). As compared to peas, fababeans left 41 kg N ha^?1 less due to smaller amounts of nitrogen in the straw. After oats very small amounts of residual nitrogen (33 kg N ha^?1) were detected. After the harvest of grain legumes always a very high nitrogen mineralization was observed during autumn especially after peas due to a close C/N-relationship and higher amounts of nitrogen in the straw as compared to fababeans. In comparison with fababeans, N-mineralization after the cultivation of oats remained lower by more than 50%. During winter, seepage water regularly led to a considerable decrease of soil NO₃-N content. The N-leaching losses were especially high after cultivation of peas (80 kg N ha ^?1) and considerably lower after fababeans (50 kg N ha^?1) and oats (20 kg N ha^?1). As compared to oats, a higher NO₃-N content in soil was determined at the beginning of the growing period after preceding grain legumes. Therefore, winter wheat yielded highest after preceding peas (68 dt ha^?1) and fababeans (60 dt ha^?1) and lowest after preceding oats (42 dt ha^?1). The cultivation of grain legumes had no measurable effect on yield formation of the third crop winter barley in either of the growing seasons.     

水稻品种氮肥群体最高生产力及其增长规律

在提出氮肥群体最高生产力概念的前提下, 以长江中下游地区有代表性的50个早熟晚粳品种(系)为供试材料, 比较研究品种间氮肥群体最高生产力的差异及其与产量构成因素、株型和氮肥农学利用率的关系。结果表明: (1)在基础地力产量为6 t hm^-2的沙壤土上, 50个早熟晚粳品种氮肥群体最高生产力对应的施氮量主要集中在225~300 kg hm^-2, 各品种的氮肥群体最高生产力因种而异, 变动在7.42~11.02 t hm^-2, 差异显著。(2)氮肥群体最高生产力与群体颖花量呈显著正相关(r = 0.865), 生产力处于顶层与高层水平品种的颖花量极显著高于中层、低层品种, 而颖花量的增加主要体现在每穗粒数的极显著增加。(3)氮肥群体最高生产力随高效叶面积与单穗重增加而增长, 顶层和高层水平品种的基本株型性状均显著优于中层和低层水平品种, 主要表现为株高105~110 cm, 基部节间粗0.65 cm左右, 高效叶面积大(高效LAI大于5), 穗型较大。(4)品种间理论氮肥群体最高生产力随对应施氮量增加而增长, 但相同对应施氮量下, 品种生产力亦有一定差异。(5)筛选出6个氮肥群体最高生产力(≥10.5 t hm^-2)与氮肥农学利用率均较高且协调统一的品种。     

低氮密植栽培对超级稻产量和氮素利用率的影响

为了研究低氮密植栽培对水稻分蘖发生及成穗率、干物质积累及其转化、氮素利用率和产量的影响,2012—2013年以超级稻Y两优1号为材料,在湖南长沙和海南澄迈进行了施氮量(75、150、225 kg N hm–2)与栽插密度(68、40、27、19穴m–2),每穴苗数(单、双、三本穴–1)与栽插密度(40、27、19、14穴m–2)的大田栽培试验。结果表明,在基本苗数相同或相近的条件下,减苗增密在齐穗期和成熟期的干物质量及产量分别比增苗减密高10.5%、5.2%和2.9%,有效穗数对产量的贡献最大,达到显著水平;在低氮密植条件下,有效分蘖期缩短6 d左右,分蘖成穗率、表观转化率、氮肥偏生产力和氮素籽粒生产效率分别提高10.9%、21.0%、150.6%和19.6%。在施氮量为75 kg N hm–2的密植(40~68穴m–2)条件下,齐穗期和成熟期的干物质量及长沙点产量分别比中、高氮(150~225 kg N hm–2)常规密度(19~27穴m–2)低3.2%、7.5%和1.2%,但差异不显著,而澄迈点产量在2012年和2013年分别比之低5.2%和高9.1%,且差异均达显著水平。在施氮量为150 kg N hm–2的密植条件下,成熟期干物质量比高氮常规密度低1.7%,但齐穗期干物质量和产量比高氮常规密度高10.3%和3.3%。因此,超级稻采用低氮密植栽培,在100~150 kg N hm–2和40穴m–2条件下提早了够苗期,增加了有效穗数,提高了分蘖成穗率和结实率,加之齐穗期适宜的干物质积累和较高的表观转化率,有利于高产的形成和氮肥利用率的提高。     

不同年代中籼水稻品种的产量与氮肥利用效率

本研究旨在探明中籼水稻在品种改良过程中产量与氮肥利用效率的变化特点。以江苏省近70年来不同年代在生产上广泛应用的12个代表性中籼水稻品种(含杂交稻组合)为材料,依据应用年代将其分为20世纪40—50年代、60—70年代、80—90年代和2000年以后4个类型,设置0 N(全生育期不施氮)、MN(全生育期施氮210 kg hm–2)和HN(全生育期施氮300 kg hm–2)3个施氮量处理,研究其产量、氮肥利用效率及其生理特性。结果表明,随品种应用年代的演进,不同年代中籼水稻品种的产量和氮肥利用效率均获得较大提高。2000年以后的品种(超级稻)产量和氮肥利用效率较高,根系性状和叶片光合特性以及氮代谢相关酶活性强是其重要生理基础。超级稻抽穗后根系氧化力和剑叶光合速率下降的幅度较大可能是导致超级稻结实率较低的一个重要原因。提高灌浆中后期超级稻的根系氧化力和剑叶光合速率,有望提高超级稻的结实率。     

Genotypic Variation of Gas Exchange Parameters and Leaf Stable Carbon and Nitrogen Isotopes in Ten Quinoa Cultivars Grown under Drought

Genotypic variations in leaf gas exchange and grain yield were analysed in 10 highland‐adapted quinoa cultivars grown in the field under drought conditions. Trials took place in an arid mountain region of the Northwest of Argentina (Encalilla, Amaicha del Valle, 22°31′S, 65°59′W). Significant changes in leaf gas exchange and grain yield among cultivars were observed. Our data demonstrate that leaf stomatal conductance to water vapour (g_s) is a major determinant of net CO₂ assimilation (A_n) because quinoa cultivars with inherently higher g_s were capable of keeping higher photosynthesis rate. Aboveground dry mass and grain yield significantly varied among cultivars. Significant variations also occurred in chlorophyll, N and P content, photosynthetic nitrogen‐use efficiency (PNUE), specific leaf area (SLA), intrinsic water‐use efficiency (_iWUE) and carboxylation capacity (A_n/C_i). Many cultivars gave promissory grain yields with values higher than 2000 kg ha^?1, reaching for Sayaña cultivar 3855 kg ha^?1. Overall, these data indicate that cultivars, which showed higher photosynthesis and conductances, were also generally more productive. Carbon isotope discrimination (Δ) was positively correlated with the grain yield and negatively with _iWUE, but δ¹⁵N did not show significant correlations. This study provides a reliable measure of specific responses of quinoa cultivars to drought and it may be valuable in breeding programmes.     

Yield Responsiveness in Two- and Six-Rowed Barley Grown in Contrasting Nitrogen Environments

Two‐ and six‐rowed barley with different intrinsic ability to produce tillers and kernels per ear, would differ in responsiveness to nitrogen availability with environmental improvements. Two field experiments were carried out to elucidate how nitrogen supply (N₄₀ and N₁₅₀) affects yield and its components in two‐ and six‐rowed barley. High nitrogen increased aboveground dry matter at anthesis, by improving cumulative solar radiation intercepted by the crop, determining an increased dry‐matter production at maturity without changes in harvest index. In both barley types, variations in grain yield were explained by changes in kernels per unit land area rather than by differences in the average kernel weight. However, changes in the number of kernels were due to variations in the number of ears per m² in two‐rowed barley and the number of kernels per ear in six‐rowed barley. Ears per unit area showed a greater responsiveness in two‐ than in six‐rowed barley due to a higher nitrogen supply treatment, associated with their intrinsic higher tillering capacity, while the number of kernels per ear was more responsive in six‐ than in two‐rowed types. The fact that responses to nitrogen by the number of kernels per unit land area in two‐ and six‐rowed barley is better explained by different yield sub‐components, allows the speculation that the critical period for yield determination would differ between barley types.     

氮肥后移对玉米间作豌豆耗水特性的调控效应

针对水资源不足严重制约干旱灌区间作发展,间作中以氮调水理论研究的薄弱,生产实践中缺乏氮肥运筹同步提高间作产量和水分利用效率的措施等问题。2012-2013年,以河西走廊规模化应用的玉米间作豌豆为研究对象,在总施氮量相同且基肥和孕穗肥分别占10%和50%条件下,设氮肥后移30% (N₁,拔节肥0+花粒肥40%)、氮肥后移15% (N₂,拔节肥15%+花粒肥25%)、传统制度(N₃,拔节肥30%+花粒肥10%) 3个施氮处理,探讨氮肥后移对间作产量和水分利用效率(WUE)的影响,以期为禾豆间作优化施氮制度、提高产量和水分利用效率提供理论依据。结果表明,氮肥后移对玉米间作豌豆总耗水量(ET)影响不显著,但降低了棵间蒸发量(E)和棵间蒸发量占总耗水量的比例(E/ET);与传统施氮处理相比,氮肥后移15%使玉米间作豌豆的E和E/ET降低6%和4%,氮肥后移30%使玉米间作豌豆的E和E/ET均降低2%。在间作系统中,豌豆带、玉米带的棵间蒸发量分别为329 mm、232 mm,表明豌豆带的无效耗水显著高于玉米带。氮肥后移15%间作的混合籽粒产量、WUE较传统施氮间作分别高出6%、5%,氮肥后移30%间作混合籽粒产量、WUE较传统施氮间作分别提高3%、2%。因此,玉米间作豌豆结合氮肥后移15%,即豌豆开花结荚期(玉米拔节期)追施氮肥67.5 kg hm^-2、玉米大喇叭口期追施氮肥225 kg hm^-2、玉米花后15 d追施氮肥112.5 kg hm^-2,可作为绿洲灌区玉米间作豌豆增产和提高WUE的农艺措施之一。     

Changes over time in the adaptation of barley releases in north-eastern Spain

The objective of this study was to characterize grain yield and adaptation of barley cultivars released in recent decades in north-eastern Spain. Ten six-rowed and 10 two-rowed barley genotypes were grown in eight environments. Mean yields varied among environments between 1.7 and 5.8 tha^?1. New releases showed higher mean yields and were specifically adapted to nonlimiting growing conditions. The average genetic advances were estimated as 40.7 and 32.9 kg ha^?1 years^?1 for two- and six-rowed genotypes, respectively, in the four most productive environments. Old genotypes, with lower overall grain yields, were specifically adapted to the poorer sites. A negative genetic gain, estimated as -14.8kg ha^?1 years^?1. was reorded for six-rowed culiivars in the four poorest sites. No significant association was observed between heading date and year of release. Variations in carbon isotope discrimination (Δ) were examined to assess whether changes in adaptation could be partially explained by shifts in the genoiypic transpiration efficiency (TE) over time, in the most favourable environments, new releases showed the highest grain yields and carbon isotope discrimination values (Δ). By contrast, older cultivars had constitutively? lower Δs and therefore higher TEs. These results suggest a genetic association between low TE and yield potential and specific adaptation to stress-free conditions so that selection for yield under favourable conditions could have resulted in an indirect downward genetic shift in the TE of modern cultivars.     

公顷产10000kg小麦氮素和干物质积累与分配特性

以泰山23和济麦22为试验品种,通过连续2年的田间试验,对单产高达10 000 kg hm^-2的小麦进行了施氮量和氮素吸收转运和分配特性的研究。在2006-2007年生长季,随着施氮量的增加,小麦籽粒产量先增加后降低,施纯氮240 kg hm^-2 (N240)和270 kg hm^-2(N270)处理的产量分别达9 954.73 kg hm^-2和10 647.02 kg hm^-2,比不施氮肥处理(N0)分别增加11.20%和18.93%。与N0处理相比,施氮处理显著增加了小麦植株氮素积累量、籽粒氮素积累量和开花后营养器官氮素向籽粒的转运量;随着施氮量的增加,成熟期小麦植株氮素积累量呈先增后降趋势,以N270处理最高;开花后营养器官氮素向小麦籽粒转运量和转运率先升后降,转运量以N270处理最大,为213.78 kg hm^-2;而转运率以N240处理最高,为67.98%。随施氮量的增加,小麦成熟期各器官干物质积累量、花后营养器官干物质再分配量和再分配率先增后降,均以N270处理最高;开花后干物质积累对籽粒的贡献率亦呈先增后降的趋势,以N240处理最高。2005-2006年的试验结果呈相同变化趋势。在本试验条件下,小麦产量水平达10 000 kg hm^-2时的适宜施氮量为240~270 kg hm^-2,可供生产中参考。     

Genetic gains in Nordic spring barley breeding over sixty years

Accurate assessments of genetic gains ensuing from plant breeding for the most important agronomic characteristics in Nordic spring barley (Hordeum vulgareL.) are not available. Hence this research was aimed to determine the rate of genetic improvement in the Nordic barley breeding pool. This study included 90, 2-row spring barley cultivars released (1942–1988) and29, 6-row spring barley cultivars released(1930–1991) adopted by Nordic farmers that were tested in four Nordic locations for three consecutive years. Relative genetic gain owing to plant breeding was 13% in2-row barley and 34% in 6-row barley for grain yield. The absolute gain for this characteristic was 13 ± 3 kg ha^-1 year ^-1 in 2-row barley, and22 ± 3 kg ha^-1 year^-1 in6-row barley. Improved yield was achieved in Nordic barley by reducing plant height(0.20 ± 0.04 cm year^-1 for 2-rowbarley and 0.16 ± 0.06 cm year^-1for 6-row cultivars), thereby reducing significantly lodging (0.5 ± 0.1%year^-1 and 0.4 ± 0.1year^-1), and increasing significantly the harvest index (0.0008 ± 0.0002year^-1 and 0.0018 ± 0.0002year^-1). Additionally, in 2-row spring barley cultivars resistance to powdery mildew (0.19 ± 0.08% year^-1)and thousand-kernel weight (0.07 ±0.03 g year^-1) were also significantly enhanced, whereas hectoliter weight was improved (0.06 ± 0.02 kg year^-1)in 6-row barley cultivars in the period investigated. This revised version was published online in August 2006 with corrections to the Cover Date.     

不同施氮水平对超高产夏玉米氮磷钾积累与分配的影响

为探明不同施氮水平下玉米超高产(≥13 500 kg hm^-2)群体氮磷钾积累及分配规律,通过苏玉20、浚单20两品种3年不同氮肥运筹方案的试验,实现了籽粒最高产量14 753 kg hm^-2的目标。结果表明：(1)随着生育进程,两品种氮磷钾在植株、籽粒中积累逐渐增大,在叶片、茎秆、叶鞘中呈先单峰变化趋势,叶片氮钾峰值在大口期,磷峰值在开花期。增大灌浆期植株氮积累量及叶片氮转移率,促使成熟期籽粒氮磷较大积累量,利于超高产玉米群体的形成。(2)籽粒产量、1 kg氮生产籽粒量、氮肥的农学效率、氮素利用率、植株(及叶片、茎秆、叶鞘、籽粒等器官)氮磷钾含量在450 kg hm^-2施氮水平时达到最大值,其值(苏玉20)分别为14753 kg hm^-2、44.0 kg、19.24%、38.63%、335.4 kg hm^-2、178.2 kg hm^-2、230.7 kg hm^-2,过高过低施氮均使氮磷钾积累量及产量下降。(3)由两品种产量与施氮水平的回归方程,确定了超高产时的最佳施氮量、超高产施氮水平和最佳施氮范围,苏玉20分别为457.0 kg hm^-2、418.3~495.7 kg hm^-2、418.5~495.4 kg hm^-2;浚单20分别为452.7 kg hm^-2(最佳施氮量)、410.8~494.6 kg hm^-2 (最佳施氮范围)。     

公顷产10000kg小麦氮素和干物质积累与分配特性

以泰山23和济麦22为试验品种,通过连续2年的田间试验,对单产高达10 000 kg hm^-2的小麦进行了施氮量和氮素吸收转运和分配特性的研究。在2006—2007年生长季,随着施氮量的增加,小麦籽粒产量先增加后降低,施纯氮240 kg hm^-2 (N240)和270 kg hm^-2(N270)处理的产量分别达9 954.73 kg hm^-2和10 647.02 kg hm^-2,比不施氮肥处理(N0)分别增加11.20%和18.93%。与N0处理相比,施氮处理显著增加了小麦植株氮素积累量、籽粒氮素积累量和开花后营养器官氮素向籽粒的转运量;随着施氮量的增加,成熟期小麦植株氮素积累量呈先增后降趋势,以N270处理最高;开花后营养器官氮素向小麦籽粒转运量和转运率先升后降,转运量以N270处理最大,为213.78 kg hm^-2;而转运率以N240处理最高,为67.98%。随施氮量的增加,小麦成熟期各器官干物质积累量、花后营养器官干物质再分配量和再分配率先增后降,均以N270处理最高;开花后干物质积累对籽粒的贡献率亦呈先增后降的趋势,以N240处理最高。2005—2006年的试验结果呈相同变化趋势。在本试验条件下,小麦产量水平达10 000 kg hm^-2时的适宜施氮量为240~270 kg hm^-2,可供生产中参考。     

不同覆盖方式和施氮量对糜子光合特性及产量性状的影响

于2011-2013年以榆糜2号为试验材料, 采用双因素裂区设计, 以覆盖栽培方式为主因素, 氮肥应用水平为副因素,调查分析不同栽培方式和施氮量下糜子光合指标及产量性状的变化。结果表明, 与传统不覆盖和不施肥相比, 覆盖和施氮均显著提高糜子开花至成熟阶段旗叶的叶绿素含量、净光合速率(P_n)、气孔导度(G_s)和蒸腾速率(T_r), 同时显著降低胞间CO₂浓度(C_i), 光合改善效果以“W”垄覆地膜+垄间覆秸秆和180 kg·hm^–2氮肥施用量最为显著。覆盖和氮肥均显著提高糜子开花期和成熟期干物质积累量、干物质在各器官中的分配量, 降低糜子花前营养器官贮藏同化物转运量及其对籽粒的贡献率, 而提高了糜子花后同化物在籽粒中的分配量及其对籽粒的贡献率。覆盖显著提高糜子产量、千粒重、穗粒数和穗长, 其调控效应以“W”垄覆地膜+垄间覆秸秆较好;随施氮量的提高, 糜子产量和千粒重先升后降, 而穗粒数和穗长持续增加, 适宜的氮肥施用量为135~145 kghm^–2。因此, 建议黄土高原糜子最佳栽培措施为“W”垄覆地膜+垄间覆秸秆的二元覆盖集水保水系统结合135~145 kghm^–2氮肥用量。     

水稻产量对氮肥响应的品种间差异及其与根系形态生理的关系

以籼稻天优华占、两优培九和粳稻陵香优18、宁粳1号为材料,研究了水稻产量对氮肥的响应。结果表明,水稻产量对施氮量的反应存在明显的品种间差异。上述4个水稻品种在获得最高产量(10.1~10.3 t hm^-2)时,天优华占和陵香优18所需施氮量为242.5~255.5 kg hm^-2,明显低于两优培九和宁粳1号的327.3~328.0 kg hm^-2。天优华占和陵香优18的氮肥农学利用率和氮肥偏生产力均明显高于两优培九和宁粳1号,表明天优华占和陵香优18产量对氮肥的反应较两优培九和宁粳1号敏感。在高产(10.5~10.9 t hm^-2)条件下,天优华占和陵香优18主要生育期根系的重量、长度和总吸收表面积低于两优培九和宁粳1号,而根系活跃吸收表面积及其占总吸收表面积的比例、根系伤流量以及根系活力则显著高于两优培九和宁粳1号。上述结果表明,通过栽培措施调控或选用根系活跃吸收表面积、根系伤流量和根系活力高的水稻品种将更有利于降低水稻施氮量和提高产量及氮肥利用效率。     

Effect of Different Preceding Crops and Crop Rotations on Yield of Winter Oil-seed Rape (Brassica napus L.)

To determine the effect of different preceding crops and crop rotations on the grain yield of oil-seed rape, a long-term rotation experiment was conducted at the Hohenschulen experimental station in Kiel, NW Germany. Additional factors included the nitrogen fertilization and the fungicide application. The results reported herein are based upon the harvest years 1988 to 1993. Averaged over the different rotations and husbandry treatments, the grain yields in the 6 experimental years varied between 2.71 t ha^?1 and 3.99 t ha^?1. In contrast, the effect of the different husbandry treatments was smaller and non significant. Averaged over 6 years, only the fungicide application caused small yield increase of 0.2 t ha^?1. The highest grain yields of 3.77 t ha^?1 or 3.65 t ha^?1 occurred when oil-seed rape was directly following peas. Low yields between 3.15 tha^?1 and 3.33 tha^?1 were obtained when oil-seed rape was grown after oilseed rape. The lowest grain yield of 3.13 t ha^?1 was produced with oil-seed rape grown in monoculture only. In rotations with oil-seed rape following a preceding cereal crop (wheat or barley), the grain yields averaged between 3.22 tha^?1 in a two course rotation and up to 3.44 tha^?1 in a four course rotation. In general, the yields of oil-seed rape increase with the length of the rotation and the length of the break between two oilseed rape crops. The yield component number of seeds per m² was affected by the previous cropping accordingly, whereas the thousand seed weight did not respond to the cropping history. Based upon disease assessments in the first years of this experiment, we argue that an increase in the incidence of fungal diseases has considerably contributed to the yield decrease of oil-seed rape in short rotations.     

水氮耦合对固定道垄作栽培春小麦根长密度和产量的影响

固定道垄作(PRB)是在农田中设固定的机械行走道的一种垄作和沟灌栽培模式,是河西灌区春小麦取代传统平作和大水漫灌种植方式的一种新技术。为了明确PRB种植模式下合理的施氮水平和灌水量,2014—2015年连续2年采用二因素裂区设计,以3种灌溉定额(1200、2400和3600 m3 hm–2)为主区,以4种施氮水平(0、90、180和270kg hm–2)为副区,研究水氮耦合对小麦不同生育期的根长密度及最终产量的影响。随灌水量和施氮量的增加,根长密度呈现先增后降的变化趋势,且灌水量的效应大于施氮水平的效应;开花、灌浆和成熟期的根长密度与籽粒产量呈正相关。回归分析显示,根长密度最大值的水氮耦合条件是灌水量约2850 m3 hm–2、施氮量196~207 kg hm–2。中等灌水量(2400 m3 hm–2)条件下,小麦主要生育期根长密度显著增加,提高了根长密度在40~80 cm土层的分配比例,增加了水分利用效率和氮肥农学利用效率。综合评价小麦籽粒产量、水分利用率和氮肥农学利用效率,中等灌水量与中氮水平(180 kg hm–2)是所有处理中的最佳水氮耦合模式,可用于河西灌区春小麦PRB栽培模式。当加大灌水至3600m3 hm–2时,产量没有显著增加,水分利用效率和氮肥农学利用效率显著下降,其原因可能是高灌水量使小麦主要生育期的根长密度降低,且根长密度在0~40 cm土层的比例升高,在40~80 cm土层的比例下降。     

Assessment of soybean yield with altered water-related genetic improvement traits under climate change in Southern Brazil

Water deficit is a major factor responsible for soybean yield gap in Southern Brazil and tends to increase under climate change. An alternative to reduce such gap is to identify soybean cultivars with traits associated to drought tolerance. Thus, the aim of this study was to assess soybean adaptive traits to water deficit that can improve yield under current and future climates, providing guidelines for soybean cultivar breeding in Southern Brazil. The following soybean traits were manipulated in the CSM-CROPGRO-Soybean crop model: deeper root depth in the soil profile; maximum fraction of shoot dry matter diverted to root growth under water stress; early reduction of transpiration under mild stress; transpiration limited as a function of vapor pressure deficit; N₂ fixation drought tolerance; and sensitivity of grain filling period to water deficit. The yields were predicted for standard and altered traits using climate data for the current (1961–2014) and future (middle-century) scenarios. The traits with greater improvement in soybean yield were deeper rooting profile, with yield gains of ≈300 kg ha⁻¹, followed by transpiration limited as a function of vapor pressure deficit and less drought-induced shortening of the grain filling period. The maximum fraction of shoot dry matter diverted to root and N₂ fixation drought tolerance increased yield by less than 75 kg ha⁻¹, while early reduction of transpiration resulted in a small area of country showing gains. When these traits were combined, the simulations resulted in higher yield gains than using any single trait. These results show that traits associated with deeper and greater root profile in the soil, reducing transpiration under water deficit more than photosynthesis, creating tolerance of nitrogen fixation to drought, and reducing sensitivity of grain filling period to water deficit should be included in new soybean cultivars to improve soybean drought tolerance in Southern Brazil.