Critical Yield Factors for Achieving High Grain Yield in Early-Season Rice Grown under Mechanical Transplanting Conditions

Double-season rice cropping systems occupy a large portion of the rice production area in southern China. Because the problem of insufficient labor, mechanical transplanting (in contrast to the manual transplanting) was become more attractive in double-season rice system. However, the decisive yield factors which resulting in high grain yield of early-season rice are unclear under mechanical-transplanted conditions. In present study, the field experiments were conducted in the early season in 2017 and repeated in 2018 in Santang Town, Hunan Province, China. Ten early season rice cultivars (Zhuliangyou 819, Lingliangyou 268, Lingliangyou 104, Luliangyou 996, Xiangzaoxian 24, Xiangzaoxian 32, Xiangzaoxian 45, Xiangzaoxian 42, Zhongjiazao 17, and Zhongzao 39) were used as materials in this study. The difference in grain yield and closelyrelated agronomic and physiological traits of ten tested cultivars were compared. The range of yields (t ha^–1 at 86% dry matter) in 2017 was 6.2 to 8.7 (mean 7.8) and in 2018 was 6.5 to 8.4 (mean 7.8). Grain weight and pre-heading biomass accumulation had potent significant positive correlations with the grain yield. The greater pre-heading biomass accumulation was major attributed to higher apparent radiation use efficiency. Our results suggested that early-season rice cultivars to achieve the high grain yield in mechanical-transplanted conditions depends on apparent radiation use efficiency in the pre-heading period and higher grain weight.     

机插水稻高产栽培关键技术的适宜值

在大田栽培条件下,以武香粳14为材料,对机插水稻的育秧、移栽、肥料运筹等高产栽培技术适宜值进行研究.结果表明,芽谷播量以每盘（1624 cm²）150～180g为最佳;壮秧剂处理的秧苗质量与机插质量均好于其它复合肥处理,复合肥处理苗床的用量以N∶P₂O₅∶K₂O=10∶10∶5及150 g·m^-2复合肥较好;双膜育秧的秧苗须在播后21 d内机插大田;小棵密植（取秧面积1.26 cm²、株距11.7 cm、行距30 cm）有利于提高机插水稻的个体质量及群体水平;大田施N量为315 kg·hm^-2、基蘖肥∶穗肥=6∶4的处理产量最高.单位面积总颖花量的显著提高是机插水稻产量增加的主要原因.     

Smash ridge tillage strongly influence soil functionality,physiology and rice yield

The practice of smash-ridging on dry land crop cultivation has shown much promise. However, the mechanism how does soil functionality and root traits can affect rice yield under smash ridge tillage with reduced nitrogen fertilization have not yet been explored. To fill this knowledge gap, we used three tillage methods—smash-ridging 40 cm (S40), smash-ridging 20 cm (S20), and traditional turn-over plowing 20 cm (T)—and two rice varieties (hybrid rice and conventional rice) and measured soil quality, root traits, rice yield and their correlation analysis at different growth stages. Soil physical and chemical properties were significantly improved by smash-ridging, including improvements in root morphological and physiological traits during three growth stages compared with T. S40 had the highest leaf area index (LAI), plant height (PH), and biomass accumulation (BA). Increment in biomass and panicle number (PN) resulted in higher grain yield (GY) of 6.9–9.4% compared with T. Correlation analysis revealed that root total absorption area (RTAA), root active absorption area (RAA), and root area ratio (RAR) were strongly correlated with soil quality. Root injury flow (RIF) and root biomass accumulation (RBA) were strongly correlated with LAI and above-ground plant biomass accumulation (AGBA). Conclusively, S40 is a promising option for improving soil quality, root traits, and consequently GY.     

Mapping Quantitative Trait Loci Associated with Toot Traits Using Sequencing-Based Genotyping Chromosome Segment Substitution Lines Derived from 9311 and Nipponbare in Rice (Oryza sativa L.)

Identification of quantitative trait loci (QTLs) associated with rice root morphology provides useful information for avoiding drought stress and maintaining yield production under the irrigation condition. In this study, a set of chromosome segment substitution lines derived from 9311 as the recipient and Nipponbare as donor, were used to analysis root morphology. By combining the resequencing-based bin-map with a multiple linear regression analysis, QTL identification was conducted on root number (RN), total root length (TRL), root dry weight (RDW), maximum root length (MRL), root thickness (RTH), total absorption area (TAA) and root vitality (RV), using the CSSL population grown under hydroponic conditions. A total of thirty-eight QTLs were identified: six for TRL, six for RDW, eight for the MRL, four for RTH, seven for RN, two for TAA, and five for RV. Phenotypic effect variance explained by these QTLs ranged from 2.23% to 37.08%, and four single QTLs had more than 10% phenotypic explanations on three root traits. We also detected the correlations between grain yield (GY) and root traits, and found that TRL, RTH and MRL had significantly positive correlations with GY. However, TRL, RDW and MRL had significantly positive correlations with biomass yield (BY). Several QTLs identified in our population were co-localized with some loci for grain yield or biomass. This information may be immediately exploited for improving rice water and fertilizer use efficiency for molecular breeding of root system architectures.     

播种深度对夏玉米幼苗性状和根系特性的影响

选用郑单958(ZD958)和先玉335(XY335)为试验材料,在砂培和大田条件下设置3、5、7和9 cm 4个播种深度,并在大田条件下以不同播种深度混播作为对照(CK),研究播种深度对夏玉米幼苗性状和根系特性的影响.结果表明： 随着播种深度的增加,夏玉米的出苗率下降,出苗时间延长.ZD958和XY335播深9 cm的出苗率较3 cm的分别降低9.4%和11.8%,出苗时间较3 cm的均延长1.5 d.随着播种深度的增加,幼苗长度及幼苗整齐度显著降低,中胚轴长度显著增加,胚芽鞘长度差异不显著;初生胚根长度逐渐减小,次生胚根总长度逐渐增加,总根长度差异不显著;幼苗与中胚轴的总干质量增加,总根干质量差异不显著.随播种深度的增加,种子萌发时幼苗各部位可溶性糖含量增加,营养物质消耗量增加,幼苗根系生长速度增加,根系活力降低,总节根数及节根层数增加.播深增加后出苗率及幼苗活力的降低导致收获穗数的显著降低,最终影响产量形成.此外,播深一致有利于群体整齐度的提高和群体性状的改善,从而提高产量.     

不同生育时期水分有限亏缺对冬小麦产量及其构成因素的影响

利用温室盆栽试验研究了施Ｎ与不施Ｎ（施肥）条件下不同生育阶段水分有限亏缺对冬小麦产量及其构成因素的影响。结果表明,在小麦苗期、拔节期、灌浆期进行水分亏缺胁迫处理。对其经济学产量,生物学产量,每盆有效穗数、每穗粒数、千粒重等影响达显著或极显著水平。苗期和灌浆期为水分亏缺不敏感期,拔节期为亏缺敏感期。在施底肥条件下拔节期水分亏缺使每穗粒数、千粒重显著减少,或低于对照水平。从补偿角度看,苗期是生物学产量     

Seedling vigour and the early growth of transplanted rice (Oryza sativa)

Previous studies suggest that the positive response of transplanted rice (Oryza sativa L.) to nursery fertiliser application was due to increased seedling vigour or possibly to increased nutrient content. This paper presents results of two glasshouse experiments designed to test the hypothesis that seedling vigour was responsible for the response of transplanted seedlings to nursery treatments. The aim of the present study was to explore the concept of seedling vigour of transplanted rice and to determine what plant attributes conferred vigour on the seedlings. Seedling vigour treatments were established by subjecting seedlings to short-term submergence (0, 1 and 2 days/week) in one experiment and to leaf clipping or root pruning and water stress in another to determine their effect on plant growth after transplanting. Submerging seedlings increased plant height but depressed shoot and root dry matter and root:shoot ratio of the seedling at 28 days after sowing. After transplanting these seedlings, prior submergence depressed shoot dry matter at 40 days. Nursery nutrient application increased plant height, increased root and shoot dry matter, but generally decreased root:shoot ratio. Pruning up to 60% of the roots at transplanting decreased shoot and root dry matter, P concentration in leaves at panicle initiation (PI) and straw dry matter and grain yield at maturity. By contrast, pruning 30% of leaves depressed shoot and root dry matter by 30% at PI, and root dry matter and straw and grain yield by 20% at maturity. The combined effects of leaf clipping and root pruning on shoot, root and straw dry matter were largely additive. It is concluded that the response of rice yield to nursery treatments is largely due to increased seedling vigour and can be effected by a range of nutritional as well as non-nutritional treatments of seedlings that increase seedling dry matter, nutrient content, and nutrient concentration. Impairment of leaf growth and to a lesser extent root growth in the nursery depressed seedling vigour after transplanting. However, rather than increasing stress tolerance, seedling vigour was more beneficial when post transplant growth was not limited by nutrient or water stresses.     

Root Morphology Was Improved in a Late-Stage Vigor Super Rice Cultivar

This study aimed to test the hypothesis that root morphology might be improved and consequently contributing to superior post-heading shoot growth and grain yield in late-stage vigor super rice. A pot experiment was carried out to compare yield attributes, shoot growth and physiological properties and root morphological traits between a late-stage vigor super rice cultivar (Y-liangyou 087) and an elite rice cultivar (Teyou 838). Grain yield and total shoot biomass were 7–9% higher in Y-liangyou 087 than in Teyou 838. Y-liangyou 087 had 60–64% higher post-heading shoot growth rate and biomass production than Teyou 838. Average relative chlorophyll concentration and net photosynthetic rate in flag leaves were 7–11% higher in Y-liangyou 087 than in Teyou 838 during heading to 25 days after heading. Y-liangyou 087 had 41% higher post-heading shoot N uptake but 17–25% lower root biomass and root-shoot ratio at heading and maturity than Teyou 838. Specific root length and length and surface area of fine roots were higher in Y-liangyou 087 than in Teyou 838 at heading and maturity by more than 15%. These results indicated that root-shoot relationships were well balanced during post-heading phase in the late-stage vigor super rice cultivar Y-liangyou 087 by improving root morphology including avoiding a too great root biomass and developing a large fine root system.     

Drought tolerance in rice: morphological and molecular genetic consideration

Rice is one of the most important food crop drastically affected by drought in lowland rice ecosystem. Dissecting out the traits of importance and genomic regions influencing the response of drought tolerance and yield traits on grain yield will aid the breeders to know the genetic mechanism of drought tolerance of rice leads to the development of drought tolerant varieties. Grain yield and its components on drought situation of recombinant inbred population (IR 58821/IR 52561) were investigated under lowland managed stress situation in 2003 and 2004 by given importance to the relative water content. Water deficit resulted in significant effect on phenology and grain yield. Best lines were selected for further varietal development programme. Variability studies showed the traits viz., days to 70% relative water content, leaf rolling, leaf drying, harvest index, biomass yield and grain yield offer high scope for improvement for drought tolerance by way of simple selection technique. Correlation and path analysis indicated that, to harness high yielding combined with drought tolerance breeders should give selection pressure on relative water content, panicle length, grains per panicle, harvest index, biomass yield, root/shoot ratio and root length in positive direction, and low scores of leaf rolling, leaf drying and drought recovery rate. Analysis of quantitative trait loci for drought tolerance, yield and its components allowed the identification of 38 regions associated with both drought tolerant and yield traits. Out of these, 18 were closely linked with DNA markers could be used for marker assisted selection in breeding for drought tolerance in rice. Pleiotropism and G × E effects interaction were noticed in some of the traits. Parent IR 58821 contributed favorable alleles for the entire drought related and most of the yield component traits. Identification of traits of importance and their nature of relationship by morphological and molecular level under lowland condition will be useful to improve drought tolerance of rice.     

Morphological alteration caused by brassinosteroid insensitivity increases the biomass and grain production of rice

The rice (Oryza sativa) dwarf mutant d61 phenotype is caused by loss of function of a rice BRASSINOSTEROID INSENSITIVE1 ortholog, OsBRI1. We have identified nine d61 alleles, the weakest of which, d61-7, confers agronomically important traits such as semidwarf stature and erect leaves. Because erect-leaf habit is considered to increase light capture for photosynthesis, we compared the biomass and grain production of wild-type and d61-7 rice. The biomass of wild type was 38% higher than that of d61-7 at harvest under conventional planting density because of the dwarfism of d61-7. However, the biomass of d61-7 was 35% higher than that of wild type at high planting density. The grain yield of wild type reached a maximum at middensity, but the yield of d61-7 continued to increase with planting density. These results indicate that d61-7 produces biomass more effectively than wild type, and consequently more effectively assimilates the biomass in reproductive organ development at high planting density. However, the small grain size of d61-7 counters any increase in grain yield, leading to the same grain yield as that of wild type even at high density. We therefore produced transgenic rice with partial suppression of endogenous OsBRI1 expression to obtain the erect-leaf phenotype without grain changes. The estimated grain yield of these transformants was about 30% higher than that of wild type at high density. These results demonstrate the feasibility of generating erect-leaf plants by modifying the expression of the brassinosteroid receptor gene in transgenic rice plants.     

耕作播种方式对稻茬小麦根系发育、土壤水分和硝态氮含量的影响

2016—2018年,以深旋耕播种模式为对照,研究了浅旋耕播种和免耕带旋播种模式对稻茬小麦根系发育、土壤水分和硝态氮含量的影响。结果表明: 孕穗期以前免耕带旋播种和浅旋耕播种处理耕层土壤含水量高于深旋耕播种处理,而硝态氮含量低于深旋耕播种处理。拔节和开花期根重密度和根表面积密度处理间差异不显著。2016—2017年,3种耕播方式的产量和地上部分氮吸收量无显著差异;2017—2018年,免耕带旋播种和浅旋耕播种处理的产量较深旋耕播种分别增加10.9%和10.5%,地上部分氮吸收量分别增加17.5%和12.0%。与深旋耕播种和浅旋耕播种处理相比,免耕带旋播种处理播种效率高、断垄率低。综上,免耕带旋播种处理可提高稻茬小麦的播种质量,增强土壤保墒能力,降低氮淋溶风险,促进产量和环境效益的协同提升。     

稻鸭共生系统中鸭品种对水稻生长特性的影响

鸭子品种间的差异对稻鸭共生系统中水稻的生长特性可能有重要影响.为了探究鸭子品种对水稻生长特性的影响,选取水鸭(SY)、洋鸭(YY)和绿头鸭(LTY)3个常见鸭品种作为处理,以水稻常规单作(CK)为对照,采用随机区组设计的方法进行田间小区试验,研究其对水稻根部、茎部、叶部性状及水稻产量的影响.结果 表明:YY和LTY处理...     

Potential for Marker-Assisted Simultaneous Improvement of Grain and Biomass Yield in Triticale

Triticale is a promising crop for agricultural biomass production but breeding has until now mainly focused on grain yield. Here, we evaluated the potential of marker-assisted simultaneous improvement of grain yield and biomass yield. To this end, we employed a large triticale doubled haploid population with 647 individuals derived from four families that were phenotyped for grain yield and biomass yield, as well as thousand-kernel weight, tiller density, and plant height in multi-environment field trials. Employing an association mapping approach, we identified quantitative trait loci (QTL) for all the five traits. The phenotypic correlation between grain yield and biomass yield was low, and we detected only one overlapping QTL suggesting different genetic architectures underlying both traits. Our results indicate that a marker-based selection for either grain yield or biomass yield does not adversely affect the other traits. Furthermore, an improvement of the multiplicative yield traits can to some extent also be achieved by selection for QTL identified for the component traits. Taken together, our results suggest that marker-assisted breeding can assist the establishment of dual-purpose triticale cultivars with high grain and biomass yield.     

底墒与磷肥互作对春小麦产量形成的影响

研究了浇底墒水和施磷肥对春小麦产量形成的影响.实验设4个处理对照(CK);耕作层施磷(P);浇30 nm底墒水(W);施磷加浇30mm底墒水(PW).测定土壤含水量、根系生物量、地上生物量和测产等.结果表明,WP处理根重和中下层分配比例均较高.与W处理相比,WP处理利用底墒并没有增加,但水分利用效率和产量均增加.决定产量的主要因素是小麦早期小穗和小花形成的数量和质量.W和WP两个浇底墒水的处理,其土壤水分利用量平均为34.6 mm,略高于所浇的底墒水的量(30 mm).CK、P、W、WP等4个处理的籽粒产量分别为91 7.7,1191.1,2516.5,2734.1 kg/hrm2,水分利用效率分别为0.186,0.192,0.172,0.207 g/(mm.m2).     

Effectiveness of Sesbania rostrata and Phaseolus calcaratus as green manure for upland rice grown in acidic soil

Two field experiments on green manuring were conducted under upland acidic soil (pH = 4.35) conditions with the following objectives: (1) to determine the influence of inoculation site, P fertilization, and liming on the biomass production, N content, N accumulation, and N availability of S. rostrata grown in an acidic soil, (2) to compare the effectiveness of S. rostrata, P. calcaratus and urea as N sources for upland rice as affected by liming and N source-sowing time combination, and (3) to assess the effect of liming and N source-sowing time combination on % Ndff (N derived from the fertilizer), % Ndfs (N derived from soil), % FNU (fertilizer N utilization), and FNY or fertilizer N yield (kg N ha^–1) of upland rice grown in acidic soil. At 2 weeks after incorporating S. rostrata (95 days after lime application), liming significantly increased N availability by more than 2-fold suggesting that the decomposition of S. rostrata by soil microflora was stimulated by lime. Liming, phosphorus application, and inoculation site improved significantly the dry biomass production, N content and N accumulation of S. rostrata; thus, enhancing its green manuring potential. Regardless of liming, S. rostrata whether applied at 0 week or 2 weeks before sowing was superior to urea in improving grain and straw yields. P. calcaratus when applied at 2 weeks before sowing also produced higher grain yield than urea. Immediate sowing of upland rice after green manure incorporation did not affect negatively the growth and development of upland rice; hence, farmers could save at least 2 weeks in their cropping calendar. N source-sowing time combination had a highly significant influence on % Ndff, % Ndfs, % FNU, N uptake, and fertilizer N yield of upland rice. However, only N uptake was influenced significantly by liming. The rice plant obtained significantly higher % Ndfs from the soils treated with green manure than those treated with urea regardless of liming. The % FNU and % Ndff from the green manures were 11-37% and 9-25%, respectively. These values are much lower than those obtained under continuously flooded soil conditions possibly because of the differences in the organic matter decomposer populations and N loss mechanisms between sloping upland conditions and continuously flooded conditions.     

From Flooded to Aerobic Conditions in Rice Cultivation: Consequences for Zinc Uptake

Scarcity of water causes a shift from flooded to aerobic conditions for rice production in zinc deficient areas in Northern China. This shift alters soil conditions that affect zinc availability to the crop. This paper concerns the effect of aerobic compared to flooded conditions on crop biomass production, grain yield and zinc content. A field experiment was done with six rice genotypes (Oryza sativa L.) grown on a calcareous soil, both with (23 kg Zn ha⁻¹) and without Zn fertilization. Sampling was conducted at tillering and physiological mature stage. Zn concentration in the shoots was significantly lower at both stages in plants grown in the aerobic field. At maturity, Zn uptake, biomass production, grain yield and Zn-harvest index [grain Zn/(shoot + grain Zn)] were lower under aerobic cultivation. Rice genotypes including aerobic rice and lowland rice differ in degree of response to low Zn supply. A twofold difference was found among aerobic genotypes in grain yield and Zn uptake. Also Zn-harvest index varied significantly. Zn application affected neither grain yield nor grain Zn content, although it significantly improved biomass production in both systems in most genotypes. These results demonstrate that introduction of aerobic rice systems on calcareous soils may increase Zn deficiency problems.     

基于ORYZA2000模型的北京地区旱稻适宜播种期分析

确定适宜播种期是制定合理的作物栽培管理方案的关键内容之一。在作物模型ORYZA2000有效性验证的基础上,以北京地区为例,利用该模型结合长期历史气候资料,对确定旱稻适宜播种期做了初步研究。结果表明：在不考虑水分因子条件下,北京地区旱稻297安全播期的范围较广,多年平均为3月26日-6月4日;受温度升高的影响,最早播期有提前趋势,而最晚播种期有延后趋势。在同一年份内,播期不同旱稻的产量也有一定的变化,呈现为先升高而后降低的趋势。播期过早或过晚导致生育期平均温度偏低是影响穗干物质累积且造成减产的主要原因,在适宜的播期范围内才能获得高产。以90%-100%当年最高产量潜力作为适宜播期的产量指标,确定北京地区旱稻297的适宜播期变化在5月11日-5月19日之间,相应的产量变化在6689-7257 kg/hm2范围内。研究方法可为其他地区旱稻的播期研究提供借鉴。     

高产水稻品种及种植方式对稻田甲烷排放的影响

采用大田试验研究了不同水稻品种（早稻：超级稻“陆两优996”和常规稻“创丰1号”;晚稻：T优259）及不同种植方式（直播和移栽）对稻田甲烷排放通量的影响.结果表明：早稻晒田前甲烷排放量占排放总量的52%～73%,排水晒田减少了甲烷排放通量;晚稻生育前期甲烷排放量占生长期间甲烷排放总量的70%.早稻直播方式的甲烷排放通量均值低于移栽种植方式,但甲烷排放总量大于移栽种植方式;晚稻直播方式的甲烷排放通量均值与排放总量都大于移栽种植方式.早、晚稻直播方式的单位稻谷甲烷排放量与移栽种植方式间均存在显著差异,早稻中超级稻和常规稻直播方式的单位稻谷甲烷排放量分别比移栽方式高4.84和3.48 g·kg^-1稻谷,常规稻的甲烷排放量高于超级稻;晚稻直播方式的单位稻谷甲烷排放量比移栽方式高6.67 g·kg^-1稻谷.相同面积、相同时间不同种植方式的稻田甲烷排放量、单位经济产量甲烷排放量表现为：早稻：常规稻直播＞常规稻移栽＞超级稻直播＞超级稻移栽;晚稻：直播＞移栽.     

窄行匀播对晚播冬小麦群体环境、个体性状和物质生产的影响

为了明确行距和行内种子分布形式对华北平原晚播冬小麦群体生长的影响,以济麦22为试验材料,在晚播条件下设置3种行距(10、15、20 cm)和2种行内种子分布形式[随机分布(R)和均匀分布(A)]处理,考察了不同处理冬小麦的冠层结构与环境特征、个体性状、生物量累积及产量性能。结果表明:在相同播种量下较小行距比较大行距、种子均匀分布比非均匀分布群体叶面积较大,冠层下部漏光较少,温度较低且相对湿度较高;缩小行距或增加行内种子分布均匀度使群体内个体间植株性状差异缩小,穗层分布趋向均匀,花后物质积累量增加,穗粒重增加,最终产量提高。10 cm行距的产量高于15 cm行距、显著高于20 cm行距;在15 cm和20 cm行距下植株均匀分布处理产量显著高于非均匀分布处理的产量。综合研究认为,窄行匀播是华北平原干旱缺水地区提高晚播小麦群体产量的有效措施。