Crop Management Effects on Pre-and Post-Anthesis Changes in Leaf Area Index and Leaf Area Duration and their Contribution to Grain Yield and Yield Components in Spring Cereals

Seasonal changes in leaf area index (LAI) and leaf area duration (LAD, i.e. LAI integrated over cumulated degree days) have a marked effect on crop productivity. Three case experiments were conducted at Suitia (60°11′N) and Viikki (60°13′N) Experimental Farms, University of Helsinki, Finland, to evaluate the possibilities of accelerating pre-an thesis expansion of leaf area and modifying pre- and post-anthesis LAD in spring cereals through crop management. Effects of time of incorporation of a green manure crop residue into the soil [conventional tillage (autumn ploughing and seed bed preparation in the spring), conservation tillage (sole spring tillage) with and without a green manure crop, common vetch (Vicia saliva I.)]and N fertilizer rate (0, 50, 100kg N ha^?1) on LAI and pre- and post-anthesis LAD in wheat (Triticum aestivum L.) were studied in exp I; green manuring (common vetch) and N fertilizer rate (0,40, 70,110,150kg N ha^?1) in barley (Hordeum vulgare L.), oat (Avena sativa L.), and wheat in exp II; and foliar application of chlormequat chloride (CCC) and ethephon in oat lines (dwarf, naked, modern, landrace) differing in canopy structure in exp III. Time of incorporation of the green manure crop residues into the soil (exp I), green manuring (exp II), N fertilizer rate (exps I and II), and selection for crop growth type (exp III), but not CCC and ethephon, modified LAI and LAD in spring cereals by affecting the rate of pre-anthesis expansion and post-anthesis reduction in leaf area rather than by markedly prolonging the growth period. High rates of N fertilizer accelerated expansion of leaf area, especially prior to stem elongation, and resulted in high pre-anthesis LAD due to enhanced tiller growth (exps I and II) and more tillers per main shoot (exp I). Green manuring increased leaf expansion from the tillering stage most when combined with high N rate, and especially in barley (exp II), but no such effects were found in exp I. Use of a high N fertilizer rate (exps I and II) and green manuring (exp II) also resulted in high post-anthesis LAD. Such modifications enabled higher rates of grain- and head-filling, and in exp I contributed to increased head weight and grain yield. Selection for inherent differences in growth type provided an additional possibility for manipulation of canopy structure and yield formation.     

燕麦产量形成生理机制研究进展

燕麦是我国北方重要的粮饲兼用作物。低产是制约燕麦产业健康稳定发展的主要问题。本文从燕麦小穗多花多粒特性、小穗不孕性和抗倒伏性能等角度分析了燕麦产量形成的主要特征;并从产量构成因素、光合生产性能和源库关系等方面系统梳理和总结了燕麦产量形成的生理机制研究进展,比较了皮燕麦和裸燕麦产量形成的生理学差异,提出了提高燕麦产量的技术途径。     

不同施氮量对裸燕麦产量品质及叶面硒肥效率的影响

为研究N肥对于裸燕麦产量和品质及硒吸收的影响,从而为冀北坝上裸燕麦高产优质富硒栽培技术提供一定的理论指导。以裸燕麦品种‘坝莜1号’为试验材料,分别在三叶期和拔节期施6个不同量的尿素,并且所有处理在三叶期和拔节期2 个时期、抽穗期和成熟前10 天2 个时期分别喷施相同量的2个型号硒肥。成熟期田间取样,室内测定裸燕麦的经济性状、产量构成、子实产量和生物产量。采用半微量凯氏定氮法测定籽粒粗蛋白含量;采用索氏提取法测定籽粒粗脂肪含量;利用酸水解法测定籽粒粗淀粉含量;利用原子荧光光度计测定籽粒硒含量。随着施N量的增加,裸燕麦的生育期有逐渐延长的趋势,裸燕麦的小穗数、穗粒重、穗数、穗粒数、籽实产量和生物产量以及籽实粗蛋白含量都有先增加后降低的趋势。施N肥增加了裸燕麦对硒肥的吸收,两年均是在三叶期施尿素210 kg/hm2拔节期施尿素240 kg/hm2时籽粒硒含量最高;N肥对于裸燕麦的穗长、粗淀粉、粗脂肪含量没有显著影响(P＞0.05);两年对于裸燕麦的株高和千粒重影响不同,2013 年不同处理对于裸燕麦的株高和千粒重影响都不显著,而2014年有增加的作用。     

江淮地区燕麦籽粒产量与农艺性状的相关性及通径分析

为了研究江淮地区燕麦籽粒生产的影响因素,选取了13个皮燕麦种质和7个裸燕麦种质,对其12个主要农艺性状和籽粒产量进行了相关性分析和通径分析。结果表明,12个农艺性状与皮燕麦籽粒产量的相关性大小依次为分蘖数>茎叶比>株高>茎粗>千粒重>穗长>旗叶宽>轮层数>小花数>穗鲜重>旗叶长>小穗数;对逐步回归分析筛选出的6个农艺性状和皮燕麦籽粒产量做通径分析,其直接效应依次为茎粗>分蘖数>茎叶比>穗长>株高>千粒重,株高和千粒重为负效应。农艺性状与裸燕麦籽粒产量相关性依次为小花数>旗叶长>小穗数>茎粗>穗长>分蘖数>穗鲜重>株高>轮层数>旗叶宽>茎叶比>千粒重;进行通径分析后,直接效应大小为穗鲜重>穗长>茎粗>小穗数>小花数>旗叶长>分蘖数,旗叶长和分蘖数为负效应。综合考虑,皮燕麦籽粒丰产的关键在于增加单株分蘖数;裸燕麦的生产过程中则要选择小穗性状优良、小花数适中的品种。     

Response of Yield Attributes of Isogenic Tall, Semidwarf, and Doubledwarf Winter Wheats to Nitrogen Fertilizer and Seeding Rates

Relationships between grain yield attributes and response to agronomic practices of dwarf and tall genotypes in the major U.S. wheat region were investigated. Isogenic tall, semidwarf, and doubledwarf (Norin 10/5/Pawnee) 'Pawnee' winter wheat ( Triticum aestivum L.) lines were planted in a split-split-plot design with nitrogen fertilizer rates of 0, 50, and 100 kg ha⁻¹ as main plots and seeding rates of 30, 60, and 90 kg ha⁻¹ as subplots in four replications at Hutchinson and Manhattan, Kansas, during 1980–1981. There was no evidence that dwarf lines responded better than the tall line to nitrogen fertilizer; however, percentage fertile spikelets, spike length, harvest index, and kernel number per spike of the semidwarf line were favored by high nitrogen rates. Grain yield was more responsive to seeding rate in the doubledwarf line than in the other lines, and test weight and spike number per unit area were more responsive to seeding rate in one or both dwarf lines than in the tall line. Grain yield of each genotype depended highly on the predominant yield attributes — usually spike number per unit area and/or kernel weight — at one or both locations.     

Growth and Yield Response of Facultative Wheat to Winter Sowing, Freezing Sowing and Spring Sowing at Different Seeding Rates

Growth and yield of wheat are affected by environmental conditions and can be regulated by sowing time and seeding rate. In this study, three sowing times [winter sowing (first week of September), freezing sowing (last week of October) and spring sowing (last week of April)] at seven seeding rates (325, 375, 425, 475, 525, 575 and 625 seeds m^?2) were investigated during the 2002–03 and 2003–04 seasons, in Erzurum (Turkey) dryland conditions, using Kirik facultative wheat. A split‐plot design was used, with sowing times as main plots and seeding rates randomized as subplots. There was a significant year × sowing time interaction for grain yield and kernels per spike. Winter‐sown wheat produced a significantly higher leaf area index, leaf area duration, spikes per square metre, kernel weight and grain yield than freezing‐ and spring‐sown wheat. The optimum time of sowing was winter for the facultative cv. Kirik. Grain yields at freezing and spring sowing were low, which was largely the result of hastened crop development and high temperatures during and after anthesis. Increasing seeding rate up to 525 seeds m^?2 increased the spikes per square metre at harvest, resulting in increased grain yield. Seeding rate, however, was not as important as sowing time in maximizing grain yield. Changes in spikes per square metre were the major contributors to the grain‐yield differences observed among sowing times and seeding rates. Yield increases from higher seeding rates were greater at freezing and spring sowing. We recommended that a seeding rate of 525 seeds m^?2 be chosen for winter sowing, and 575 seeds m^?2 for freezing and spring sowing.     

Effects of Seeding Rate on Growth Duration and Accumulation and Partitioning of Dry matter in Oats

Crop management influences considerably the three components of grain yield, growth duration, growth rate, and harvest index (HI). Effects of seeding rate on these yield components in oats ( Avena sativa L.) was assessed in field experiments at the Viikki Experimental Farm, University of Helsinki, Finland (60°13'N) in 1991 and 1992. Three Finnish oat genotypes were evaluated; a long-strawed landrace cultivar, a moderately long-strawed modern cultivar, and a semi-dwarf breeding line. The following traits were measured: grain yield, days from sowing to yellow ripeness, number of tillers on main shoot, phytomass, vegetative phytomass, and their growth rates (PGR and VGR, respectively), panicle weight and its filling rate (PFR), HI, leaf area index (LAI), and at intervals, dry-matter accumulation in leaves and straw.
Increases in seeding rate significantly decreased growth duration and PGR of individual plants but increased PGR on a ground area basis. Seeding rate did not, however, affect HI. When seeding rate was increased from 200 seeds m⁻² to 500 seeds m⁻², reductions in vegetative phytomass, panicle weight, VGR, and PFR for individual plants ranged between 20 and 40 %, depending on genotype. At ≥600 seeds m⁻² differences in these components between seeding rates were modest. However, PGR, VGR, and PFR per unit ground area increased with increasing seeding rates up to 600–700 seeds m⁻². Moreover, the higher the seeding rate, the higher the peak LAI (2.7 maximum) and the earlier the canopy closure. Hence, our results showed that a seeding rate of 600–700 seeds m⁻², which resulted in uniculm growth habit, is advantageous in terms of grain yield at high latitudes due to higher biomass accumulation and subsequently greater interception of PAR.     

两种灌溉方式下保水剂用量对裸燕麦产量和品质的影响

保水剂和滴灌是两种节水措施,在小麦、玉米和番茄上广泛应用。燕麦是一种对水分敏感的作物,籽粒产量和品质受水分影响较大,目前这方面研究较少。本文在大田条件下,采用裂区设计,研究了传统灌溉和滴灌两种灌溉方式下4个保水剂用量(0、30、60和90 kg hm^-2)对裸燕麦白燕8号籽粒产量、籽粒品质、籽粒矿质元素含量和饲草品质的影响。结果表明,传统灌溉处理的籽粒产量比滴灌处理高14.78 %,粗蛋白、粗脂肪和β-葡聚糖含量比滴灌处理分别降低1.22%、2.73%和3.36%,差异显著(P < 0.05)。滴灌处理下籽粒中钙、镁、钾、锌、铁含量均显著高于传统灌溉,锰含量差异不显著。滴灌处理的相对饲用价值为122.38%~135.67%,显著高于传统灌溉(118.75%~134.44%)。保水剂用量对裸燕麦籽粒产量有显著影响,滴灌条件下施用保水剂比不施保水剂增产2.95%~12.14%,传统灌溉条件下施用保水剂比不施保水剂增产1.1%~5.0%。60 kg hm^-2保水剂有利于裸燕麦大多数品质性状的提高,以及矿质元素的吸收利用。     

The Influence of Row Spacing and Seeding Rate on Seed Yield and Yield Components of Forage Turnip (Brassica rapa L.)

The effects of four row spacings (17.5, 35.0, 52.5 and 70.0 cm) and five seeding rates (50, 100, 200, 400 and 800 viable seeds m^?2) on seed yield and some yield components of forage turnip (Brassica rapa L.) were evaluated under rainfed conditions in Bursa, Turkey in the 1998–1999 and 1999–2000 growing seasons. Plant height, stem diameter, pods/terminal raceme, total pods/plant, seeds/pod and primary branches/plant were measured individually. The number of plants per unit area was counted and the lodging rate of the plots was scored. The seed yield and 1000‐seed weight were also determined. Row spacing and seeding rate significantly affected most yield components measured. The number of plants per unit area increased with increasing seeding rate and decreasing row spacing. Plant height was not greatly influenced by row spacing and seeding rate, but higher seeding rates reduced the number of primary branches and the stem diameter. The number of pods/main stem was affected by row spacing and but not by the seeding rate. Also, the number of seeds per pod was not affected by either the row spacing or the seeding rate. In contrast, the number of pods per plant clearly increased with increasing row spacing, but decreased with increasing seeding rate. The plots seeded at narrow row spacings and at high seeding rates were more sensitive to lodging. Seeding rate had no significant effect on seed yield in both years. Seed yield was similar at all seeding rates, averaging 1151 kg ha^?1. However, row spacing was associated with seed yield. The highest seed yield (1409 kg ha^?1) was obtained for the 35.0‐cm row spacing and 200 seeds m^?2 seeding rate combination without serious lodging problems.     

Agronomic Optimum Seeding Rate for Irrigated Maize in Texas is Concomitant to Growing Season Mean Daily Minimum Temperature

Our study was conducted to determine agronomic optimum seeding rates (AOSR) for irrigated maize under a range of agroecological conditions in Texas. Environmental factors that affect irrigated maize production vary considerably across Texas. This variability imposes region‐specific limitations on statewide maize seeding rate recommendations. Our research examined the efficiency of varying seeding rates on irrigated maize grain yields in five USEPA Level IV Ecoregions that comprise most of the irrigated maize‐producing area of Texas. The selected sites span a distance of 1200 km from south to north Texas and elevations from 20 to 1218 m above mean sea level. We conducted the study over three growing seasons from 2005 through 2007 in two Level IV Ecoregions of the High Plains of North Texas (N), one in the East Central Plains (E), one in the Southern Plains and one in Western Gulf Coastal Plains of South Texas (S). We observed that maximum grain yields and AOSR to achieve maximum maize grain yields vary considerably among ecoregions. In South Texas, we observed grain yield response rates of 125–129, 151 kg 1000 seeds^?1 in E and 163–199 kg 1000 seeds^?1 in N. We show that growing season average daily minimum air temperature (T_MIN) explains most of this variation (r² = 0.98, P‐value < 0.01) and conclude that seeding rate efficiency is concomitant to T_MIN. Maximum grain yields (GY_MAX) determined with seeding rate response analysis also varied among ecoregions and with T_MIN from south to north Texas, from a low of 8.3 Mg ha^?1 in S to a high of 18.4 Mg ha^?1 in N (r² = 0.59, P‐value < 0.01). We conclude that development of agronomic management models by Level IV Ecoregions of Texas combined with site‐specific T_MIN climatological data serve as a valid template for delivering robust and agroecozone‐specific irrigated maize seeding rate recommendations in Texas.     

Altitude,temperature, and N Management effects on yield and yield components of contrasting lowland rice cultivars

Nitrogen (N) is one of the main nutrients that drive rice grain yield and is intensely managed especially in lowlands under irrigated conditions. A set of experiments was conducted in mid- and high-altitude sites in Rwanda to investigate the response of five genotypes under different sowing dates and different N management. Genotype grain yields were higher and more stable at mid-altitude across sowing dates. N rates strongly affected grain yield at mid-altitude (p < .0001), but not at high altitude. Postponing basal N had positive effects on yield and yield components in both sites, with more pronounced effects at high altitude. Increasing N rate beyond 120 kg/ha led to a decrease in percentage of panicles per tiller and spikelet fertility and a decrease in grain yield due to excessive tillers at both high altitude and mid-altitude. Thus, basal N application should be recommended at high altitude and the increase in N rate up to 120 kg/ha at mid-altitude. A strict observation of recommended planting date should be followed at high altitude, and the use of cold-tolerant genotypes is encouraged.     

Effects of varying nitrogen fertilization on crop yield and grain quality of emmer grown in a typical Mediterranean environment in central Italy

Experiments were carried out to study the effects of N fertilizer rates and timing of application on the yield and grain quality of a rainfed emmer crop (Triticum dicoccum Shübler) under Mediterranean conditions. The following parameters were analyzed: hulled and net grain yield, hulled index, spikes m^?2, spikelets per spike, kernels m^?2, thousand-kernel weight, biomass, plant height, lodging, grain protein and ash content. In the first experiment, different N rates (30, 60 and 90 kg N ha^?1 plus a control not fertilized) were split at three phenological stages (seeding 20%, tillering 40% and stem elongation 40%). In the second experiment, three N doses (30, 60 and 90 kg N ha^?1) were applied to three crop stages (seeding, tillering and stem elongation). In the third experiment, the rate of 90 kg N ha^?1 was distributed in different amounts (90-0-0, 0-90-0, 0-0-90, 45-45-0, 45-0-45, 0-45-45, 30-30-30) at the three mentioned crop stages. Increasing N rates resulted in higher hulled and net grain yield, as well as protein content. Fertilization (from 60 to 90 kg N ha^?1) applied to tillering maximized hulled and net grain yield. Fertilization (90 kg N ha^?1) applied to stem elongation gave the highest grain protein content (%) while splitting application (30 kg N ha^?1 each) at three phenological stages maximized protein yield per hectare. Application of half or one-third of 90 kg N ha^?1 to stem elongation improved grain protein content in comparison with applications at sowing, or at both sowing and tillering. The main factor determining higher yields with increasing N rates in this emmer crop was the number of kernels m^?2. None of the yield components accounted for differences in grain yield when timing and splitting application were varied.     

Is the Companion Crop Harmless to Alfalfa Establishment in the Highlands of East Anatolia?

This study documented the effects of barley companion crop seeding rate and cutting stage on alfalfa establishment in a highland area. Alfalfa was established with barley at seeding rates of 0, 60, 120 and 180 kg ha^?1 and cut at the milk‐dough and ripe grain stages. In most cases, hay yield and composition of herbage were affected by companion crop seeding rate and cutting stage. Total hay yield increased from 3294 to 5131 kg ha^?1 when the companion crop seeding rate was increased from 0 to 180 kg ha^?1 at the milk‐dough stage. Legume and weed growth was suppressed by the companion crop during establishment, but using a barley companion crop decreased alfalfa plant losses in the seeding year. Few residual effects of barley were seen on hay yield in the subsequent year, but residual effects of companion crop treatments on weed suppression continued in all clippings of the second year. The results suggest that alfalfa should be sown with a barley companion crop in highland areas with adequate moisture. The seeding rate for barley is about the same as that for barley grown alone, and the companion crop could be harvested for hay or grain in the establishment year.     

Yield Formation in Mediterranean durum wheats under two contrasting water regimes based on path-coefficient analysis

The components of grain yield are altered by adverse growing conditions as the effects of certain environmental factors on crop growth and yield differ depending upon the developmental stages when these conditions occur. Path-coefficient analysis was used to investigate the main processes influencing grain yield and its formation under Mediterranean conditions. Twenty-five durum wheat genotypes, consisting of four Spanish commercial varieties and 21 inbred lines from the ICARDA durum wheat breeding program, were grown during 1997 and 1998 under both rainfed and irrigated conditions in southern Spain. {P}ath-coefficient analysis revealed that under favourable conditions grain yield depended in equal proportion on the three primary yield components (i.e. spikes m⁻², grains spike⁻¹, and mean grain weight), whereas in the rainfed experiments, variations in grain yield were due mainly to spikes m⁻² and to a lesser extent to grains spike⁻¹. Compensatory effects were almost absent under irrigated treatments; however, under water shortage, spikes m⁻² exerted a negative influence on grain spike⁻¹ due mainly to a negative interrelationship between tiller production and apical development. These compensatory effects could partially explain the restricted success in durum wheat breeding observed in water-limited environments of the Mediterranean region. Under rainfed conditions the number of spikes m⁻² depended mainly on the ability for tiller production, whereas in the irrigated experiments the final number of spikes was determined mostly by tiller survival.     

大粒裸燕麦与普通栽培燕麦主要营养成分的比较

对《中国燕麦品种资源目录》一、二册中的大粒裸燕麦与普通栽培燕麦的蛋白质、脂肪和亚油酸含量的化验结果进行了统计分析。结果表明,大粒裸燕麦的蛋白质含量平均为15.53%,脂肪含量为6.35%,亚油酸含量为42.44%,均比普通栽培燕麦的13.74%,6.23%,40.20%高。大粒裸燕麦的主要营养成分高于普通栽培燕麦。     

CO2浓度升高和施氮对冬小麦花前贮存碳氮转运的影响

为探讨大气CO₂浓度升高对冬小麦花前贮存碳氮转运的影响及氮素营养的调节作用,以小偃22和小偃6号为材料,于2007—2009连续2个生长季,利用开顶式气室进行盆栽试验,对背景CO₂浓度(375 μL L^-1)和高CO₂浓度(2007—2008年度680 μL L^-1, 2008—2009年度750 μL L^-1)条件下不同施氮处理的干物质和氮素在籽粒、花前地上部中的累积以及花后营养器官的转运进行了评价。2007—2008年度设4个施氮水平,分别是0、0.1、0.2和0.3 g kg^-1土; 2008—2009年度设3个施氮水平,分别是0、0.15和0.30 g kg^-1土。结果表明,施氮和CO₂浓度升高促进了干物质和氮素在籽粒和花前营养器官的积累,增加了花前营养器官和地上部贮存干物质和氮素向籽粒的转运量,适量施氮提高了CO₂浓度升高对花前营养器官干物质和氮素累积以及花后向籽粒转运的正向效应。与背景CO₂浓度相比,高CO₂浓度提高了花前营养器官和地上部干物质对籽粒产量的贡献率和转运率,但CO₂浓度升高对花前氮素的贡献率和转运率的影响因年份和品种而异。CO₂浓度升高后,2007—2008年度各营养器官和地上部,以及2008—2009年度茎鞘和穗的氮素贡献率和转运率均增加,但2008—2009年度2个品种叶片和地上部氮素贡献率在施氮时均显著降低,小偃22叶片和地上部氮素转运率在各施氮水平下以及小偃6号地上部氮素转运率在0.13 g kg^-1土施氮水平下均明显增加。适量施氮也在大多数情况下增强了CO₂浓度升高对营养器官干物质和氮素的贡献率和转运率的正向效应。说明CO₂浓度升高后小麦产量和氮素积累增加与其促进花前干物质和氮素积累及花后向籽粒的转运密切相关。     

Effect of Ethephon Spraying at Three Developmental Stages of Barley Planted in Arid and Semiarid Mediterranean Locations

To determine the effects of ethephon [(2‐chloroethyl) phosphonic acid] on yield and yield components of rainfed barley in arid (150 mm rainfall) and semiarid (346 mm) regions, the present study was conducted during the growing seasons of 1999–2001. Ethephon was applied at the tillering, stem elongation and flowering stages. Acomparison of the effect of ethephon on rainfed and irrigated barley performed at the semiarid location in the following season confirmed the results. Ethephon decreased grain yield when sprayed at tillering and stem elongation compared with the later flowering stage for both the arid and semiarid locations. All arid‐location barley plants had lower grain yields than the semiarid‐location plants. There was a reduction in spikes m^?2 in the tillering and stem elongation stage sprayings compared to the control for both locations. In the semiarid and arid locations no difference in earliness (50 % heading) was observed between spraying times but ethephon always delayed heading. All arid‐location plants were earlier than semiarid‐location plants. However, when ethephon was used with supplementary irrigation it was found to increase grain yield, spikes m^?2 and earliness.     

氮肥施用量对不同紫甘薯品种产量和氮素效率的影响

选取紫甘薯品种浙紫1号、宁紫2号和紫菁2号,设置3个施氮处理,即0 (N0)、75 (N1)和150 (N2) kg hm^–2纯氮,于2013-2014年2个生长季在青岛农业大学现代农业科技示范园进行大田试验,研究不同氮肥用量对块根产量、干物质累积速率、氮素累积量及氮素效率的影响。结果表明,施用氮肥不同程度地降低了浙紫1号和紫菁2号的薯块产量,其中,浙紫1号的N1、N2处理分别较N0处理降低12.64%和13.32%,紫菁2号分别降低3.94%和29.06%;宁紫2号N1处理产量略高于N0处理,两年分别较N0处理提高8.5%和3.4%,而N2处理块根产量显著低于N0处理。茎蔓生物量和氮素累积量随着施氮量的增加而增加,而收获指数、氮素收获指数和氮素利用效率逐渐降低。第1年N1、N2处理的茎蔓干物质累积量分别较N0处理提高2.7%~20%和12.3%~36.4%,第2年分别提高12.6%~51.9%和28.7%~85.5%。相关分析表明,块根产量与氮素效率各指标均呈显著或极显著正相关;而茎蔓生物量与收获指数、氮素收获指数及氮肥利用效率均呈极显著负相关(r = –0.615^**, –0.704^**, –0.663^**)。肥沃土壤上施用氮肥会造成浙紫1号和紫菁2号的茎蔓旺长,光合产物向薯块转运比例降低,导致源库比例不协调,块根产量下降。宁紫2号对氮肥的需求相对较高,施用氮肥75 kg hm^–2时鲜薯产量提高,而施氮量过高时薯块产量降低。因此,紫甘薯在含氮量较高的肥沃土壤上种植时,对氮肥的需求量较低,茎蔓和薯块的协调生长是提高块根产量和氮素利用效率的保障。     

Effect of Post-Anthesis Water Stress on Accumulation of Dry Matter, Carbon and Nitrogen and Their Partitioning in Wheat Varieties Differing in Drought Tolerance

In four wheat ( Triticum aestivum L.) cultivars of tall (C306 and Narmada) and dwarf (HD2329 and Kundan) type, post-anthesis water stress affected the dry matter accumulation in plant parts with respect to main shoot controls. HD2329 among the dwarf types and Narmada 112 among the tall types were more adversely affected by stress, with greater reductions in their biomass and grain yield. Of the tolerant types, C306 (tall) showed a marginal reduction while Kundan (dwarf) had no reduction in these parameters as a result of stress. The results also indicated a varietal response to carbon and nitrogen accumulation and their partitioning in the main shoot when subjected to post-anthesis stress. In the susceptible dwarf cultivar HD2329, and in the susceptible tall cultivar Narmada 112, carbon and nitrogen contents were reduced in the grains of stressed main shoots. Of the tolerant cultivars, the dwarf type Kundan was not affected by stress, while the tall type C306 registered an increase in carbon content and its partitioning to grain.     

White lupine as a beneficial crop in Southern Europe. II. Nitrogen recovery in a legume–oat rotation and a continuous oat–oat

One experiment lasting for two years was carried out at Pegões (central Portugal) to estimate the impact of mature white lupine residue (Lupinus albus L.) on yield of fodder oat (Avena sativa L. cv. Sta. Eulalia) as the next crop in rotation, comparing with the continuous cultivation of cereal, under two tillage practices (conventional tillage and no-till) and fertilized with five mineral nitrogen (N) rates, with three replicates. Oat as a first crop in the rotation provided more N to the agro-ecosystem (63 kg N ha⁻¹) than did lupine (30–59 kg N ha⁻¹). This was at a cost of 100 kg of mineral N ha⁻¹, whereas lupine was grown without addition of N. A positive response of oat as a second crop was obtained per kg of lupine-N added to the system when compared with the continuous oat–oat. The cereal also responded positively to mineral N in the legume amended soil in contrast with the oat–oat sequence where no response was observed, partly due to the fast mineralization rate of lupine residue and a greater soil N immobilization in the continuous oat system. Each kg N ha⁻¹ added to the soil through the application of 73 kg DM ha⁻¹ mature lupine residue (above- and belowground material) increased by 72 kg DM ha⁻¹ the oat biomass produced as the second crop in rotation when 150 kg mineral N ha⁻¹ were split in the season, independent of tillage practice. Mature legume residue conserved in the no-tilled soil depressed the yield of succeeding cereal but less than the continuous oat–oat for both tillage practices, where the application of mineral N did not improve the crop response.