机插稻传统的土育秧不仅消耗资源，而且费时费力。因此，对于水稻轻简高效育秧而言，串联式水卷苗等无土育秧方法养分管理的改善和优化是必要的。本研究以控释肥（CRF）-释放周期为3个月的树脂包衣复合肥（PCCF-3M）作为育秧肥(SF)，并且设置5种不同用量：SF-0，SF-10，SF-20，SF-30，SF-40，以基质育秧作为对照（CK）。在所有SF处理中，施用20g/盘SF（SF-20）的处理效果最好，秧苗素质和机插质量均与CK相当。相反，较低施用量（SF-0和SF-10）导致秧苗氮含量低并抑制地上部生长；较高施用量导致毒害（丙二醛含量增加）并抑制根系生长。与CK相比，SF-20处理增加了穗数（5.6-7.0%）和产量（4.3-5.3%），这可能与被根系盘住的剩余SF移栽后促进秧苗分蘖生长有关。此外，SF-20处理降低了秧块重量（53.1%）和育秧成本（23.5%）并提高了利润，这表明该处理是轻简和经济的。综上所述，SF-20处理是一种促进水稻秧苗生长和提高移栽效率的经济和有效的方式。据我们所知，本研究第一次在水稻无土育秧基础上明确最适的CRF用量。

本试验探讨了7种不同类型缓控释肥一次性施用对水稻产量及群体特征的影响。在研究肥料氮素（N）释放特征的基础上，于2018和2019年进行盆栽试验，以常规分次施肥（CK，基穗比为1:1）为对照，对水稻叶片SPAD值、产量及其构成、茎蘖动态和干物质积累进行研究。结果表明：不同类型缓控释肥的氮素释放特征差异显著。树脂包衣尿素（PCU）表现为控释模式，整个生育期持续释放氮素；硫包衣尿素（SCU）表现为缓释模式，中后期氮素释放不足；脲酶抑制剂尿素（AHA）和脲甲醛（UF）表现为速释模式，前期爆发性释放，中后期无释放，但其供肥能力可持续到抽穗期。PCU延缓了高峰苗期，与CK相比，干物质积累、叶片SPAD值无显著差异，同时由于整个生育阶段氮素的持续释放，每穗粒数、结实率和千粒重增加，从而提高水稻产量；SCU由于后期氮供应不足，总颖花量低，水稻产量降低，但差异不显著；AHA和UF易受环境因素的影响，对产量的影响不一致。本试验结果表明，在盆栽等量施氮条件下，供肥能力强、有效持续时间长的肥料类型更有利于水稻后期干物质积累，提高产量。

提高水稻单产是实现粮食安全的关键。化肥，尤其是氮肥的使用，对水稻增产起到历史性作用。然而，氮肥管理不善，尤其是施肥量过大，带来了稻米品质恶化、产量不稳定、环境恶化等问题。因此，如何在不影响水稻产量和品质的前提下，提高氮肥利用率，减少氮肥投入，已成为世界各国科学家高度关注的问题。

水稻优质高效精确施肥，最核心的是根据品种特点提高氮肥利用率，同时提高稻米品质。提高氮肥利用率的途径主要有以下三个方面：一是选育氮高效的水稻品种，二是氮肥的精确管理，三是应用新型肥料和高效施肥方法。

为此，Journal of Integrative Agriculture (《农业科学学报》(英文)，JIA) 于2020年3月底积极筹备“High quality and high efficiency fertilization of rice”专题，邀请来自南京农业大学、华中农业大学、扬州大学、四川农业大学、安徽农业大学、河南农业大学、美国德州农工大学等研究团队进行撰稿。通过对水稻氮素高效利用的理论及方法的实验，相关团队从水稻的氮高效品种选育、氮肥精确管理以及新型肥料和高效施肥方法等方面进行了深入研究。

我们希望本专题的研究成果有助于读者了解水稻先进优质高效施肥理论及技术，为进一步保障中国乃至世界的粮食安全与农业环境可持续发展提供经验借鉴、理论依据与技术支撑。

为探究机插条件下不同水稻品种倒伏差异的主要因素及其对氮肥的响应，2017年和2018年在江苏丹阳（长江中下游代表性区域）开展了两年重复的田间试验，以22个杂交籼稻、22个常规粳稻以及2个籼粳杂交稻3种类型水稻为材料，设置3个氮肥水平(0、150、300 kg ha^-1)，采用毯苗机插的移栽方式，从倒伏相关的力学指标、形态学指标以及物质转运等方面进行系统研究。不同类型水稻产量的差异表现为常规粳稻<杂交籼稻<籼粳杂交稻。杂交稻（杂交籼稻、籼粳杂交稻）的倒伏指数(LI)高于常规粳稻源于其较高的株高，籼粳杂交稻较低的茎鞘物质表观输出率导致其LI显著低于杂交籼稻。杂交籼稻品种间倒伏指数较大的差异主要来源于茎鞘物质表观输出率，株型紧凑的品种茎鞘物质表观输出率低，因而具有较强的抗倒伏能力；常规粳稻品种间的差异则是由断面模数(Z)即茎粗造成的。籼粳杂交稻或常规粳稻的倒伏指数在氮肥处理间的变异相对较小，高氮水平下均没有发生倒伏，这是由于其叶倾角较小且在高氮条件下变化不大；而杂交籼稻不同品种LI和倒伏率对氮肥的响应存在较大的差异，株型紧凑的品种耐高氮。因而，紧凑株型品种适宜作为机插条件下的抗倒耐氮型品种。

Understanding the characteristics of rice productivity is of great importance for achieving high yield formation.  However, such traits have not yet been studied for different ages of hydroponically grown long-mat rice seedlings (HLMS), which constitutes a new method of seedling cultivation.  Field experiments were conducted to evaluate the effects of seedling age on the growth stage, photosynthesis characteristics, dry matter production, and yield of HLMS.  A conventional japonica rice cultivar (Wuyunjing 24) and an indica hybrid rice cultivar (6 Liangyou 9368) were used as test materials.  The results showed that the whole phase was shortened by 13–15 days for young seedlings (13-day-old) compared with old seedlings (27-day-old), which occurred because the growth process accelerated with the transplantation of young seedlings.  As seedling age increased, the dry matter weight of stems of individual plants and of the population increased at the transplanting stage but decreased at the maturity stage (MS).  Compared with that of 27-day-old seedlings, the average ratio of panicle weight to total plant dry weight of 13-day-old seedlings during a 2-year period increased by 3.71% for Wuyunjing 24 and by 3.78% for 6 Liangyou 9368 at the MS.  Moreover, as seedling age increased, the leaf area index and photosynthetic potential decreased for both cultivars, and the photosynthetic rate markedly decreased at the heading stage (HS).  With the exception of that of Wuyunjing 24 from the jointing stage to the HS in 2014, the crop growth rate was higher for young seedlings than for old seedlings.  Grain yield significantly decreased with seedling age, but no significant difference was detected between the 13- and 20-day-old seedlings for either cultivar.  Therefore, equilibrious and high biological yield formation, vigorous growth in the late stages, and high photosynthetic production capacity are important characteristics and causes of the efficient and sustainable output of photosynthetic systems and for achieving high yield formation in young transplanted seedlings (13–20-day-old).

This study was conducted to investigate the effects of soilless substrates of hydroponically grown long-mat seedlings (HLMS) on seedling quality and field growth characteristics of transplanted super japonica rice.  A widely grown conventional super japonica rice cultivar (Wuyunjing 23) was selected as the test material.  The effect of HLMS on seedling quality, mechanical transplantation quality, field growth characteristics, yield, and benefit-cost ratio were compared with seedlings grown in organic substrates and traditional nutritive soil, which was selected as the control.  Root number, root twisting power and root activity of seedlings cultivated by HLMS were decreased compared to that of the organic substrates and control.  However, seedling root length as well as aboveground growth were increased compared to the organic substrates and control seedlings.  In the HLMS, the content of gibberellin acid (GA₃) decreased while abscisic acid (ABA) content increased compared to that of the organic substrates and control seedlings.  During the early stages after transplanting, the re-greening of HLMS was delayed compared to that of the organic substrates and control seedlings.  Nevertheless, there were no significant differences in tiller dynamics and crop yield among the HLMS, organic substrates and control treatments.  The effects of HLMS on seedling production were similar to those of the organic substrates and traditional nutritive soil in the present study, suggesting that HLMS have the potential to replace traditional nutritive soil in seedling production without decreasing crop yield.  Finally, it is important to reduce organic substrates and topsoil dependence during rice seedling production and worthwhile to consider HLMS popularization and its application on a larger scale.

To optimize both grain yield and quality of low-glutelin rice cultivars under N-fertilizer strategies, two-year field experiments involving three low-glutelin rice cultivars (W1240, W1721, W025) and an ordinary rice cultivar (H9405) with five N treatments were carried out to determine the effects of N application rate and genotype on protein fractions contents and Glutelin/Prolamin ratio (Glu/Pro). The difference of protein fraction concentrations affected by N application rate existed in genotypes. Ordinary rice cultivar had a larger increase in glutlein concentration affected by N application rate than low-glutelin rice cultivars did. Glutelin in H9405 had a increase of 30.6 and 41.0% under the N4 treatment (360 kg N ha–1) when compared with N0 treatment (no fertilizer N) in 2010 and 2011 respectively, while all the low-glutelin rice cultivars showed relatively smaller increases for two years. Variance analysis showed no significant effect of N application rate on glutelin in W1240 and W025 while the effects on albumin, globulin and prolamin were significant in low-glutelin rice. What’s more, N treatment had no significant influence on Glu/Pro ratios in low-glutelin rice cultivars while a significant increase in Glu/Pro ratio was observed in ordinary rice cultivar. So low-gultelin rice cultivars showed a different pattern from ordinary rice cultivars when influenced by N application rate.

Lodging is an important factor limiting rice yield and quality by bending or breaking stem in japonica rice (Oryza sativa L.) production. The objectives of this study were to determine the mechanism of lodging resistance in japonica rice as affected by carbohydrate components, especially its related arrangement in culm tissue and response to top-dressing nitrogen (N) fertilizer. Field experiments were conducted in Danyang County, Jiangsu Province, China, by using two japonica rice varieties Wuyunjing 23 (lodging-resistance variety) and W3668 (lodging-susceptible variety) with three top-dressing N fertilizer rates (0, 135 and 270 kg N ha^–1) in 2013 and 2014. Lodging related physical parameters, morphological characteristics and stem carbohydrate components were investigated at 30 d after full heading stage. Results showed that with increasing N fertilizer rates, the lodging rate and lodging index increased rapidly primarily due to significant reduction of breaking strength in two japonica rice varieties. Correlation analysis revealed that breaking strength was significantly and positively correlated with bending stress, but negatively correlated with section modulus, except for significant correlation at W3668 in 2014. Higher stem plumpness status and structural carbohydrate contents significantly enhanced stem stiffness, despite of lower non-structural carbohydrate. With higher N fertilizer rate, the culm wall thickness was almost identical, and culm diameter increased slightly. The structural carbohydrates, especially for lignin content in culm, reduced significantly under high N rate. Further histochemical staining analysis revealed that high N treatments decreased the lignin deposition rapidly in the sclerenchyma cells of mechanical tissue, large vascular bundle and small vascular bundle region, which were consistent with reduction of bending stress, especially for W3668 and thus, resulted in poor stem strength and higher lodging index. These results suggested that structural carbohydrate plays a vital role for improving stem strength in japonica rice. N rate decreased lodging resistance primarily due to poor stem stiffness, by reducing structural carbohydrate content and lignin deposition in the secondary cell wall of lower internode culm tissue.

This study aims to investigate the variation in occurrence of white-belly rice kernel (WBRK) and white-core rice kernel (WCRK) among different positions within a panicle. Twenty-four M4 mutants involved in four panicle types, namely the compact, intermediate, loose, and chicken foot panicle were used. They derived from a japonica rice cultivar Wuyujing 3. Considerable differences in morphological characters existed among the four types of panicle, especially in panicle length, the secondary branch number and ratio of grain number to total branch length. Marked differences were found in WBRK and WCRK among different positions within a panicle for all types of panicle. In general, grains located on the primary rachis and top rachis branches had higher WBRK and WCRK percentage than those on the secondary rachis and bottom rachis branches. WCRK exhibited larger variation among grain positions than WBRK did. Moreover, there was a significant difference in WCRK/WBRK among grain positions within a panicle, with primary rachis and top rachis branches having higher values than the secondary and bottom rachis. In addition, panicle type showed no significant effect on the pattern of WBRK and WCRK occurrence within a panicle. The results indicated the difference in mechanism of WBRK and WCRK formation in grain position within a panicle, and are valuable for breeding and agronomic practices aimed at lowering chalky grain rate.

The objective of this study was to determine the morphology mechanism of nitrogen (N) fertilizer rates and ratio on lodging resistance through analying its effects among lodging index (LI), lodging-related morphological traits and physical strength in basal internodes by comparing japonica and indica super rice cultivars. Field experiments, with three nitrogen levels (0, 150 and 300 kg ha-1) and two ratios of basal to topdressing (8:2 and 5:5) with two super rice cultivars (Yliangyou 2 and Wuyunjing 23), were conducted in the Baolin Farm, Danyang Country, Jiangsu Province, China, in 2011 and 2012. Effects of N fertilizer rates and ratios on morphology of whole plant, morphology traits in basal internodes and culm’s physical strength parameters were investigated at 20 d after full heading stage. LI of Yliangyou 2 was significant greater than that of Wuyunjing 23 due to larger bending moment by whole plant (WP) with higher plant height and gravity center height. With higher volume of N fertilizer, LI of two super rice cultivars was increased conspicuously. However, no significant effect was detected with increase of panicle fertilizer ratio. The size of breaking strength (M) in basal internodes was the key factor determining LI among N fertilizer treatments. Correlation analysis revealed that M value was positively related bending stress (BS) of Wuyunjing 23 and section modulus (Z) of Yliangyou 2, respectively. The higher N fertilizer levels induced reduction of BS of Wuyunjing 23 due to weak culm and leaf sheath plumpness status and reduced Z of Yliangyou 2 owning to small diameter and culm wall thickness, consequently, influencing their M indirectly. These results suggested that breaking strength was the key factor influencing LI with increase of N fertilizer levels. However, the lodging-related morphology mechanism was different with genotypes. Culm wall thickness and diameter in basal internodes of indica super rice and culm and leaf sheath plumpness status of japonica super rice influenced breaking strength, as well as lodging index, respectively.

Nitric oxide (NO) is a gaseous signaling molecule in plants that plays a key role in mediating a wide range of physiological processes and responses to biotic and abiotic stresses. The present study was conducted to investigate the effects of the exogenous application of sodium nitroprusside (SNP), an NO donor, on cadmium (Cd)-induced oxidative stress and Cd uptake in rice plants. Rice plants were exposed to Cd stress (0.2 mmol L-1 CdCl2) and different concentrations of SNP (0.05, 0.1, 0.2, and 0.4 mmol L-1). A SNP concentration of 0.1 mmol L-1 (SNP10) significantly reduced the Cd-induced decrease in shoot and root dry weights and leaf chlorophyll concentrations. The addition of NO also reduced the malondialdehyde (MDA), hydrogen peroxide (H2O2) and ascorbic acid (ASA) concentrations. However, the reduction in glutathione (GSH) concentration was inhibited by NO treatment. Moreover, NO prevented the Cd-induced increase in antioxidative enzyme activity. The amount of Cd accumulation in rice plants was also influenced by the addition of NO. The NO supplied by the SNP enhanced the Cd tolerance of the rice by increasing the Cd uptake by the roots and decreasing the Cd accumulation by the shoots. However, the application of potassium ferrocyanide (Cd+Fe) or sodium nitrate and nitrite (Cd+N) (without NO release), did not exhibit the effects of the SNP. Furthermore, the effects of the SNP were reversed by the addition of hemoglobin (an NO scavenger). Our results suggested that exogenous NO was involved in the resistance of rice to Cdtoxicity.

Northeast of China and Jiangsu Province are major production areas of japonica rice in China. Rice from northeast of China is well-known for its good-eating and appearance quality, and that from Jiangsu Province is viewed as inferior. However, little is known concerning the difference in physicochemical and sensory properties of rice between the major two production areas. Analysis of 16 commercial rice samples showed marked differences in physicochemical properties, including chalky grain rate, contents of amylose and protein and pasting properties between the two main areas. Northeastern rice contained more shortchain amylopectin as compared with Jiangsu rice. However, Jiangsu rice is comparable to northeastern rice in terms of sensory quality including overall acceptability and textural properties of springiness, stickiness and hardness as evaluated by trained panel. Our results indicated the limitation of conventional index of physicochemical properties, and suggested the necessity of identification of new factors controlling rice sensory property. In addition, the taste analyzer from Japan demonstrates limitation in distinguishing the differences between northeastern and Jiangsu rice, and therefore needs localization to fit China.