Effects of the potassium application rate on lipid synthesis and eating quality of two rice cultivars

Lipid content has an important effect on rice eating quality, but the effects of fertilizer application rate on the lipid synthesis and eating quality of rice are not well understood. Potassium (K) has a strong influence on rice quality and the requirement for K fertilizer in rice is greater than for nitrogen (N) and phosphorus (P) fertilizers. To investigate the effects of K fertilizer on the lipid synthesis and eating quality of rice, we used Nanjing 9108 (NJ9108, japonica) and IR72 (indica) rice as experimental materials and four K levels: K0 (0 kg ha^–1), K1 (90 kg ha^–1), K2 (135 kg ha^–1) and K3 (180 kg ha^–1). The results showed that the lipid content, free fatty acid (FFA) content, unsaturated fatty acid (UFA) content, malonyl-CoA (MCA) content, phosphatidic acid (PA) content, lipid synthesis-related enzyme activities and eating quality first increased and then decreased with increasing K in both cultivars. The maximum values were obtained under K2. However, the saturated fatty acid (SFA) content showed the opposite trend. No significant differences were found in pyruvate (PYR) content among the K treatments. The protein and oxaloacetic acid (OAA) contents and phosphoenolpyruvate carboxylase (PEPCase) activity of NJ9108 first decreased and then increased with increasing K, and the minimum values were obtained under K2; while IR72 showed the opposite trend and the maximum values were obtained under K1. Overall, increasing K optimized the fatty acid components and increased the lipid content and eating quality of rice by enhancing lipid synthesis-related enzyme activities and regulating substrate competition for lipid and protein synthesis. The optimal K application rate for lipid synthesis, eating quality and grain yield was 135 kg ha^–1 for both cultivars.     

不同秧苗素质和移栽密度条件下臭氧胁迫对水稻光合作用、物质生产和产量的影响

近地层臭氧浓度升高使水稻生长受抑进而使产量下降,但这种影响是否因不同栽培条件而异尚不清楚.2011年依托先进的稻田臭氧FACE( Free Air gas Concentration Enrichment)技术平台,以汕优63为供试材料,臭氧设置大气臭氧浓度(Ambient)和高臭氧浓度(比Ambient高50％),秧苗素质设置弱苗(移栽时无分蘖)和壮苗(移栽时带两个分蘖),移栽密度设置低密度(16穴/m2)、中密度(24穴/m2)和高密度(32穴/m2),研究不同秧苗素质和移栽密度条件下臭氧胁迫对水稻生长和产量的影响.结果表明:高浓度臭氧使水稻结实期叶片SPAD值、净光合速率、气孔导度和蒸腾速率明显下降,但胞间CO2浓度和叶温无显著变化.高浓度臭氧对水稻拔节前物质生产量没有影响,但使拔节至抽穗期、抽穗至成熟期物质生产量平均分别降低13％和29％,进而使成熟期生物产量和籽粒产量均显著下降.方差分析表明,臭氧与秧苗素质间没有互作效应,但臭氧与移栽密度的互作对最终产量的影响达显著水平.以上结果表明,臭氧胁迫使水稻生长后期光合受阻,导致物质生产和产量显著下降;适当增加移栽密度可能会减少臭氧胁迫下水稻产量的损失.     

Effects of planting methods on yield and quality of different types of japonica rice in northern Jiangsu plain,China

Mechanical transplanting with carpet seedlings (MC) and mechanical direct seeding (MD) are newly developed planting methods, which increase in popularity and planted area each year. Knowing the difference for yield and rice quality under different planting methods is of great importance for the development of high quality and yield cultivation techniques under mechanical conditions. Therefore, three kinds of japonica rice including hybrid japonica rice, inbreed japonica rice, and soft rice were adopted as materials. And the differences in the quality of processing, appearance, cooking and eating quality, nutrition, and the rapid viscosity analyzer (RVA) profile were studied to reveal the effects of planting methods on yield and quality of different types of japonica rice. Results showed that the milled rice and head rice rates under MC was significantly higher than those under MD, and the processing quality of inbreed japonica rice was the most stable. Compared with MC, length/width ratio of rice under MD was significantly increased, and chalkiness rate, size, and degree were significantly decreased. The protein content under MD was lower than that under MC. MC showed higher peak viscosity and breakdown value than MD. The taste value was the greatest for soft rice, followed by inbreed japonica rice, and then by japonica hybrid rice, with no significant differences resulting from planting methods. Compared with MC, MD significantly improved the appearance quality, though processing quality and nutritional quality were decreased. And there was no significant difference in cooking and eating quality between MC and MD. Under different planting methods, the appearance quality of inbreed japonica rice changed the most and the processing quality was the most stable. The nutritional, cooking and eating quality of soft rice changed the least. Therefore, according to the different planting methods and market needs, selecting the appropriate rice varieties can reduce the risks in rice production and achieve good rice quality.     

Effects of nitrogen application rate and hill density on rice yield and nitrogen utilization in sodic saline–alkaline paddy fields

Soil salinity and alkalinity can inhibit crop growth and reduce yield,and this has become a global environmental concern.Combined changes in nitrogen (N) application and hill density can improve rice yields in sodic saline–alkaline paddy fields and protect the environment.We investigated the interactive effects of N application rate and hill density on rice yield and N accumulation,translocation and utilization in two field experiments during 2018 and 2019 in sodic saline–alkaline paddy fields.Five N application rates (0 (control),90,120,150,and 180 kg N ha~(-1) (N0–N4),respectively) and three hill densities(achieved by altering the distance between hills,in rows spaced 30 cm apart:16.5 cm (D1),13.3 cm (D2) and 10 cm (D3))were utilized in a split-plot design with three replicates.Nitrogen application rate and hill density significantly affected grain yield.The mathematical model of quadratic saturated D-optimal design showed that with an N application rate in the range of 0–180 kg N ha~(-1),the highest yield was obtained at 142.61 kg N ha~(-1) which matched with a planting density of 33.3×10~4 ha~(-1).Higher grain yield was mainly attributed to the increase in panicles m~(–2).Nitrogen application rate and hill density significantly affected N accumulation in the aboveground parts of rice plants and showed a highly significant positive correlation with grain yield at maturity.From full heading to maturity,the average N loss rate of the aboveground parts of rice plants in N4 was 70.21% higher than that of N3.This is one of the reasons why the yield of N4 treatment is lower than that of the N3 treatment.Nitrogen accumulation rates in the aboveground parts under treatment N3 (150 kg N ha~(-1)) were 81.68 and 106.07% higher in 2018 and 2019,respectively,than those in the control.The N translocation and N translocation contribution rates increased with the increase in the N application rate and hill density,whereas N productivity of dry matter and grain first increased and then decreased with the increase in N application rate and hill density.Agronomic N-use efficiency decreased with an increase in N application rate,whereas hill density did not significantly affect it.Nitrogen productivity of dry matter and grain,and agronomic N-use efficiency,were negatively correlated with grain yield.Thus,rice yield in sodic saline–alkaline paddy fields can be improved by combined changes in the N application rate and hill density to promote aboveground N accumulation.Our study provides novel evidence regarding optimal N application rates and hill densities for sodic saline–alkaline rice paddies.     

宽窄行种植对水稻生长发育及产量的影响

以松-122水稻品种为试材,通过田间小区试验,对水稻在不同宽窄行配置下的生长发育及产量形成进行了研究.结果表明:70 cm-20 cm宽窄行距配置使水稻的分蘖数、穗数、粒重降低,导致产量减少;50 cm-20 cm宽窄行距配置对水稻形态发育和产量形成无明显影响,可提高插秧效率,改善田间环境.     

行距配置对春玉米群体冠层环境与光合特性的影响

以紧凑型玉米品种郑单958为试验材料,在密度75 000株·hm-2条件下,采用3种行距配置模式(110~0cm双株紧靠、82.5~27.5cm大垄双行和55~55cm等行距型),比较研究玉米群体冠层微环境、光合特性和产量的变化特征。结果表明,行距配置显著改变了群体冠层中光、CO2、温度和湿度等冠层微环境,合理行距配置(82.5~27.5cm)的植株上部叶片较为直立,下部叶片平展,群体内光分布较为合理,CO2分布更为均匀,花后叶绿素相对含量、LAI均高于其他2个处理,且高值持续期较长,生育后期下降缓慢,最大光合速率和表观量子效率较高,光能利用率和水分利用率亦优于其他2个处理。从产量和产量构成因素来看,大垄双行种植模式的平均产量最高,分别较双株紧靠和等行距种植模式高3.33%和2.08%,穗粒数和千粒质量的显著增加是产量较高的主要原因。     

Simulation of Potential Production and Optimum Population Quantitative Indices for the Second Hybrid Rice

The article established the HDRICE model by modifying the structure of the ORYZA1 model and revising its parameters by field experiments. The HDRICE model consists of the modules of morphological development of rice, daily dry matter accumulation and partitioning, daily CO₂ assimilation of the canopy, leaf area, and tiller development. The model preferably simulated the dynamic rice development because of the thorough integration of the effects of temperature and light on the rates of rice development, photosynthesis, respiration, and other ecophysiological processes. In addition, this model has attainable grain yield in the test experiment that showed the potential yield of cultivar Xieyou 46 ranged from 11 to 13 tons ha⁻¹. Besides, the model was used to optimize the combinations of the transplanting date, seedling age and density for cultivar Xieyou 46 at Jinhua area, and the population quantitative indices to attain the potential yield such as maximum stems, effective panicles, filled grain number/leaf area, and so on. The result showed that the combination of transplanting date on July 25, seedling age of 35 days and base seedling density of 1.33×10⁶ha⁻¹ is the optimum combination for the second hybrid rice production in Jinhua County, China. And the maximum stems, the effective panicles, the filled grain per panicle, the peak of optimum LAI, LAI in later filling stage, and the filled grain number/leaf were 6.03×10⁶ha, 3.99×10⁶ha, 119.2, 8.59, 5–6, and 0.64, respectively.     

Comparison of grain yield and quality of different types of japonica rice cultivars in the northern Jiangsu plain,China

In recent years, an increasing number of different types of japonica rice cultivars have been released in the southern rice region of China. The grain yield and quality of these new cultivars showed significant differences in large scale planting. However, the causes of the differences remain little known. Therefore, three typical types of japonica rice cultivars were used in this study to investigate their grain yield and quality. A scanning calorimeter(DSC), X-ray powder diffractometer(XRD), rapid viscosity analyzer(RVA) and taste analyzer were used to evaluate the cooking and eating properties. The results showed that the yield of non-soft hybrid japonica rice cultivars was significantly higher than that of non-soft inbred japonica rice cultivars and soft inbred japonica rice cultivars. Soft inbred japonica rice cultivars had a low amylose content and moderate protein content, which are the main reasons for the superior cooking and eating quality. In addition, the relative crystallinity of soft inbred japonica rice cultivars was significantly higher than that of non-soft inbred and non-soft hybrid japonica rice cultivars, which is considered the major factor resulting in higher transition temperature and gelatinization enthalpy(ΔHgel). Non-soft hybrid japonica rice cultivars had a higher number of large starch granules than soft inbred and non-soft inbred japonica rice cultivars. The setback value(SB) and breakdown value(BD), indirectly reflecting the cooking and eating quality of the three types of japonica rice cultivars, also confirmed that soft inbred japonica rice cultivars with a low SB value and a high BD value had better palatability than the other two types. This study provides guidance for future plantation of different types of japonica rice cultivars in large rice-producing areas.     

不同农艺措施对机插水稻产量的影响

[目的]统计分析机插水稻产量形成的特点,研究机插密度和肥料运筹对机插水稻产量的影响,以优化机插水稻农艺配套措施。[方法]分别设置3种机插秧规格和3种氮肥作基蘖肥与穗肥配比田间试验,考察产量及其构成差异。[结果]结果表明,机插水稻增产增收明显,单产在5737.5~10315.7 kg/hm2时,产量与总颖花量及每穗实粒数呈极显著正相关,与千粒重呈显著正相关。适宜的机插规格应掌握在11.7~13.3 cm×30.0 cm,基本苗75万~105万/hm2。土壤肥力中等,单产要求在9000 kg/hm2以上时,投入总氮(纯)应为270~300 kg/hm2,N∶P2O5∶K2O为1.0∶0.3∶0.5,氮素基蘖肥与穗肥比例宜为5∶5或6∶4。[结论]机插水稻高产栽培策略适宜走建立适中群体、抬升后期肥料运筹比重、提高成穗率、主攻大穗、增加千粒重之路,穗数型增产与穗重型增产相结合。     

行距配置氨基酸水溶肥与甜菜碱对机收夏玉米生理效应与收获指数的影响

为解决黄淮海夏直播玉米成熟期短、脱水慢、栽培密度高（≥7.5×10⁴株/hm²）导致的冠层光温利用率低等因素造成的减产问题,以籽粒机收夏玉米‘迪卡517’为试验材料,利用2种生长调节物质与行距模式配置的综合效应,分析其对玉米叶面积指数、单株干物质积累量、灌浆速率及脱水速率的影响,以期为该地区机收夏玉米生产用调节剂的选择及种植模式优化利用提供理论依据。结果表明,7.5×10⁴株/hm²密度下氨基酸水溶肥处理,无论等行距或宽窄行模式,均能以较小的叶面积指数、较低的单株干物质积累量,在授粉15天后随着高效的灌浆速率获得较高的收获指数及产量,相对于等行距模式差异不显著的脱水速率,宽窄行模式有利于将高效的籽粒脱水峰值提前至授粉后35天,且灌浆周期提前至花后45天,但收获期籽粒含水率仍不低于32%;而甜菜碱处理受宽窄行模式影响,生物产能过大,虽然产量较对照显著增加,仍显著低于氨基酸水溶肥处理。建议黄淮海鲁中地区夏玉米‘迪卡517’推广70 cm+50 cm宽窄行栽培模式,6叶期喷施富锌氨基酸水溶肥提高收获指数与产量,若要实现籽粒机收,需通过延缓收获期来完成籽粒含水率不大于26%的脱水指标。     

8寸插秧机在双季稻区的应用及配套农艺技术研究

为了研究不同行距插秧机对双季稻产量的影响及配套农艺技术,以11个早晚稻品种为材料,设置8寸和9寸两个机插行距,系统测定不同处理的机插质量和产量。结果表明：8寸插秧机的机插质量高,作业性能稳定;8寸插秧机较9寸插秧机,早稻增产347.30 kg/hm2,增产率达5.49%,晚稻增产579.54 kg/hm2,增产率达9.12%。基于试验支持研究和已有相关研究成果,制定了适应8寸插秧机的配套农艺技术。     

Combined effect of shading time and nitrogen level on grain filling and grain quality in japonica super rice

There is limited information about the combined effect of shading time and nitrogen(N) on grain filling and quality of rice. Therefore, two japonica super rice cultivars, Nanjing 44 and Ningjing 3, were used to study the effect of shading time and N level on the characteristics of rice panicle and grain filling as well as the corresponding yield and quality. At a low N level(150 kg N ha~(–1), 150 N), grain yield decreased(by 21.07–26.07%) under the treatment of 20 days of shading before heading(BH) compared with the no shading(NS) treatment. These decreases occurred because of shortened panicle length, decreased number of primary and secondary branches, as well as the grain number and weight per panicle. At 150 N, in the treatment of 20 days of shading after heading(AH), grain yield also decreased(by 9.46–10.60%) due to the lower grain weight per panicle. The interaction of shading and N level had a significant effect on the number of primary and secondary branches. A high level of N(300 kg N ha~(–1), 300 N) could offset the negative effect of shading on the number of secondary branches and grain weight per panicle, and consequently increased the grain yield in both shading treatments. In superior grains, compared with 150 N NS, the time to reach 99% of the grain weight(T_(99)) was shortened by 1.6 to 1.7 days, and the grain weight was decreased by 4.18–5.91% in 150 N BH. In 150 N AH, the grain weight was 13.39–13.92% lower than that in 150 N NS due to the slow mean and the maximum grain-filling rate(GR_(mean )and GR_(max)). In inferior grains, grain weight and GR_(mean) had a tendency of 150 N NS150 N BH150 N AH. Under shaded conditions, 300 N decreased the grain weight due to lower GR_(mean) both in superior and inferior grains. Compared with 150 N NS, the milling and appearance qualities as well as eating and cooking quality were all decreased in 150 N BH and 150 N AH. Shading with the high level of 300 N improved the milling quality and decreased the number of chalky rice kernels, but the eating and cooking quality was reduced with increased chalky area and overall chalkiness. Therefore, in the case of short term shading, appropriate N fertilizer could be used to improve the yield and milling quality of rice, but limited application of N fertilizer is recommended to achieve good eating and cooking quality of rice.     

Light interception and radiation use efficiency response to tridimensional uniform sowing in winter wheat

Improving radiation use efficiency(RUE) of the canopy is necessary to increase wheat(Triticum aestivum) production. Tridimensional uniform sowing(U) technology has previously been used to construct a uniformly distributed population structure that increases RUE. In this study, we used tridimensional uniform sowing to create a wheat canopy within which light was spread evenly to increase RUE. This study was done during 2014–2016 in the Shunyi District, Beijing, China. The soil type was sandy loam. Wheat was grown in two sowing patterns:(1) tridimensional uniform sowing(U);(2) conventional drilling(D). Four planting densities were used: 1.8, 2.7, 3.6, and 4.5 million plants ha–1. Several indices were measured to compare the wheat canopies: photosynthetic active radiation intercepted by the canopy(IPAR), leaf area index(LAI), leaf mass per unit area(LMA), canopy extinction coefficient(K), and RUE. In two sowing patterns, the K values decreased with increasing planting density, but the K values of U were lower than that of D. LMA and IPAR were higher for U than for D, whereas LAI was nearly the same for both sowing patterns. IPAR and LAI increased with increasing density under the same sowing pattern. However, the difference in IPAR and LAI between the 3.6 and 4.5 million plants ha–1 treatments was not significant for both sowing patterns. Therefore, LAI within the same planting density was not affected by sowing pattern. RUE was the largest for the U mode with a planting density of 3.6 million plants ha–1 treatment. For the D sowing pattern, the lowest planting density(1.8 million plants ha–1) resulted in the highest yield. Light radiation interception was minimal for the D mode with a planting density of 1.8 million plants ha–1 treatment, but the highest RUE and highest yield were observed under this condition. For the U sowing pattern, IPAR increased with increasing planting density, but yield and RUE were the highest with a planting density of 3.6 million plants ha–1. These results indicated that the optimal planting density for improving the canopy light environment differed between the sowing patterns. The effect of sowing pattern×planting density interaction on grain yield, yield components, RUE, IPAR, and LMA was significant(P0.05). Correlation analysis indicated that there is a positive significant correlation between grain yield and RUE(r=0.880, P0.01), LMA(r=0.613, P0.05), and spike number(r=0.624, P0.05). These results demonstrated that the tridimensional uniform sowing technique, particularly at a planting density of 3.6 million plants ha–1, can effectively increase light interception and utilization and unit leaf area. This leads to the production of more photosynthetic products that in turn lead to significantly increased spike number(P0.05), kernel number, grain weight, and an overall increase in yield.     

耕作和育秧方式对机插水稻群体质量和产量的影响

用3因素裂区设计,研究了耕作方式、品种和育秧方式对机插稻群体质量和产量的影响.结果表明,免耕机插栽插质量整体差于常规翻耕机插,群体质量与常规翻耕机插差异不大,产量低于常规翻耕机插.塑料软盘育秧与钵形毯状育秧对水稻生长和产量的影响较小,生产上可因地制宜选用.     

秧龄与宽窄行移栽对单季晚粳常优1号产量的影响

[目的]为水稻超高产栽培提供相关技术依据。[方法]以杂交粳稻常优1号为研究对象,研究秧龄与行距配置对水稻群体、产量及其构成因素的影响。[结果]小苗移栽可促进水稻及早分蘖,形成大穗,且群体干物质积累快,从而提高产量;宽窄行栽培由于窄行水稻植株间过早产生竞争,不利于水稻群体的早发,从而导致减产。[结论]小苗移栽有利于水稻高产,宽窄行不利于水稻生长。     

减氮对机插杂交籼稻产量和稻米品质的影响

【目的】研究减氮对机插杂交籼稻产量和稻米品质的影响,为机插杂交籼稻合理减氮提供理论依据。【方法】以杂交籼稻品种宜香优2115和F优498为试验材料,基于品种高产栽培施氮量（180 kg/ha,CK）,在贵州贵阳和湄潭2个试验点,研究不同减氮量[减氮30 kg/ha（N_-30）、减氮60 kg/ha（N_-60）和不施氮（N₀）]对机插杂交籼稻产量、加工品质、外观品质、营养品质和蒸煮食味品质的影响。【结果】在贵阳和湄潭试验点,减氮后机插杂交籼稻产量和稻米品质变化趋势基本一致,即随着减氮程度的增加,机插杂交籼稻群体颖花量和实际产量均逐渐降低,稻谷加工品质（糙米率、精米率和整精米率）表现为先增加后降低,稻米外观品质（垩白粒率和垩白度）和蛋白质含量逐渐降低,而稻米蒸煮食味品质（胶稠度和直链淀粉含量）均逐渐增加,综合食味值评分提高。与CK相比,减氮后机插杂交籼稻群体颖花量和实际产量分别降低4.43%~35.08%和1.76%~38.77%,垩白粒率、垩白度和蛋白质分别降低2.08%~29.58%、3.57%~45.33%和3.10%~21.37%,胶稠度、直链淀粉含量和食味值分别提高3.89%~49.28%、0.52%~13.24%和0.25%~5.67%;同一减氮处理下两试验点稻谷加工品质变化趋势略有不同,但整体上差异较小。相关分析结果表明,实际产量与群体颖花量呈极显著正相关（P<0.01,下同）,且实际产量和群体颖花量与稻米蒸煮食味品质（胶稠度、碱消值和食味值）大多呈显著（P<0.05,下同）或极显著负相关,与稻米加工品质（糙米率、精米率）、外观品质（垩白粒率、垩白度）和蛋白质含量呈显著或极显著正相关。【结论】适宜的减氮量（N_-30）能改善稻谷加工品质、稻米外观品质和蒸煮食味品质,且产量仍能维持在9.80 t/ha以上,协同实现机插杂交籼稻稳产和优质;而过量减氮（N_-60和N₀处理）虽能提高稻米外观品质和蒸煮食味品质,但稻谷加工品质有变劣趋势,且产量显著降低,难以实现机插杂交籼稻高产稳产。     

播期和密度对超级稻天优3301产量形成的影响

以超级杂交稻天优3301为材料,在大田中采用双因素裂区设计,研究播期和移栽密度对天优3301产量及构成因素的影响.结果表明,播期对单位面积穗数、穗粒数、结实率、千粒重及产量均有显著影响,移栽密度对产量及其构成因素的影响也显著.移栽密度主要影响穗数,随着移栽密度的增加,单位面积有效穗数显著增多,穗粒数下降,而结实率和千粒重相对稳定.在建阳及闽西北地区,超级杂交稻天优3301的适宜播期为5月20～30日,适宜栽插密度为25.0万丛·hm-2,在此条件下可形成足够穗数和穗粒数,从而获得较高的产量.     

Effects of mechanized deep placement of nitrogen fertilizer rate and type on rice yield and nitrogen use efficiency in Chuanxi Plain,China

This paper investigates the yield and nitrogen use efficiency (NUE) of machine-transplanted rice cultivated using mechanized deep placement of N fertilizer in the rice–wheat rotation region of Chuanxi Plain, China. It provides theoretical support for N-saving and improves quality and production efficiency of machine-transplanted rice. Using a single-factor complete randomized block design in field experiments in 2018 and 2019, seven N-fertilization treatments were applied, with the fertilizer being surface broadcast and/or mechanically placed beside the seedlings at (5.5±0.5) cm soil depth when transplanting. The treatments were: N0, no N fertilizer; U1, 180 kg N ha^–1 as urea, surface broadcast manually before transplanting; U2, 108 kg N ha^–1 as urea, surface broadcast manually before transplanting, and 72 kg N ha^–1 as urea surface broadcast manually on the 10th d after transplanting, which is not only the local common fertilization method, but also the reference treatment; UD, 180 kg N ha^–1 as urea, mechanically deep-placed when transplanting; M1, 81.6 kg N ha^–1 as urea and 38.4 kg N ha^–1 as controlled-release urea (CRU), mechanically deep-placed when transplanting; M2, 102 kg N ha^–1 as urea and 48 kg N ha^–1 as CRU, mechanically deep-placed when transplanting; M3, 122.4 kg N ha^–1 as urea and 57.6 kg N ha^–1 as CRU, mechanically deep-placed when transplanting. The effects of the N fertilizer treatments on rice yield and NUE were consistent in the 2 yr. With a N application rate of 180 kg ha^–1, compared with U2, the N recovery efficiency (NRE), N agronomic use efficiency (NAE) and yield under the UD treatment were 20.6, 3.5 and 1.1% higher in 2018, and 4.6, 1.7 and 1.2% higher in 2019, respectively. Compared with urea alone (U1, U2 or UD), the NRE, NAE and yield achieved by M3 (combined application of urea and controlled-release urea) were higher by 9.2–73.3%, 18.6–61.5% and 6.5–16.5% (2018), and 22.2–65.2%, 25.6–75.0% and 5.9–13.9% (2019), respectively. Compared with M3, the lower-N treatments M1 and M2 significantly increased NRE by 4.0–7.8% in 2018 and 3.1–4.3% in 2019, respectively. Compared with urea surface application (U1 or U2), the yield under the M2 treatment was higher by 4.3–12.9% in 2018 and 3.6–10.1% in 2019, respectively. Compared with U2, the NRE and NAE under the M2 treatment was higher by 36.9 and 36.3% in 2018, and 33.2 and 37.4% in 2019, mainly because of higher N uptake. There was no significant difference in the concentration of nitrate in the top 0–20 cm soil under U1, U2 and M2 treatments during the full heading and maturity stages. During the full heading stage, U2 produced the highest concentration of nitrite in 0–20 cm and 20–40 cm soil among the N fertilizer treatments. In conclusion, mechanized deep placement of mixed urea and controlled-release urea (M2) at transplanting is a highly-efficient cultivation technology that enables increased yield of machine-transplanted rice and improved NUE, while reducing the amount of N-fertilization applied.     

机插密度对连作晚稻“甬优6号”产量的影响

[目的]研究机插密度对连作杂交晚稻"甬优6号"产量的影响,明确其合理的群体起点,为连作稻区晚季杂交稻机插技术的推广提供科学依据。[方法]根据插秧机设计的行株距规格,设栽插丛数为12万、15万、18万、21万和24万丛/hm25个处理,采用小区重复试验,对产量进行方差分析。[结果]随着机插密度的增加,单位面积最高苗数、有效穗增加,穗粒数减少,成穗率降低;机插密度过高或过低均不利于增产增效。[结论]"甬优6号"在温州地区作连作晚稻种植,机插密度以21万丛/hm2左右,每丛插2.5～3.5本较适宜。     

Comparison of agronomic performance between inter-sub-specific hybrid and inbred japonica rice under different mechanical transplanting methods

Mechanical transplanting has been applied to rice cultivation to save labor costs and ease labor shortages in Asian countries, especially in China. However, little information is available related to the characteristics of agronomic performance when comparing inter-sub-specific hybrid rice (IHR) and inbred japonica rice (IJR) under mechanical transplanting method. In 2013 and 2014, field experiments were conducted using IHR (Yongyou 2640) and IJR (Wuyunjing 24) under two cultivation patterns, that is, pot seedlings mechanically transplanted (PS) and carpet seedlings mechanically transplanted (CS). Grain yield, yield components, leaf area index (LAI), leaf area duration (LAD), aboveground biomass, crop growth rate (CGR), nitrogen (N) uptake, and N accumulation were investigated. When compared with CS, PS displayed significantly increased grain yield for both varieties because the larger sink size allowed higher N accumulation from panicle initiation to maturity. Moreover, total aboveground biomass under PS increased significantly compared with that under CS; that is, higher photosynthetic productivity resulted from a greater LAI and higher LAD during the grain filling stage. Higher N absorption capacity in the middle and late growth periods resulted in significantly enhanced total N uptake under PS. When compared with IJR for both treatments, IHR generated 75.2% more grain yield. However, the characteristics creating high yield of IHR were different from those of IJR. Greater aboveground biomass production as well as higher N uptake and accumulation created higher grain yield in IHR than in IJR. These results suggest higher yield could be achieved using PS with IHR, attributing to exploit both yield superiority and productive potential.