Temperature-driven yield variation of super hybrid rice across ecological regions: mitigation by nitrogen management and genotype selection.

Different mechanisms underlying the yield advantage of ordinary hybrid and super hybrid rice over inbred rice under low and moderate N input conditions

Analysis on Dry Matter Production Characteristics of Super Hybrid Rice

In order to find foundations of high-yield cultivation in super hybrid rice(SHR), we modeled on dynamics of population indices. A field experiment with two super hybrid rice cultivars(Zhunliangyou 527, Q you 6) and control(II you 838) was conducted in 2011 and 2012, and dry matter accumulation(DMA) and leaf area index(LAI) were measured. The dynamic equations of DMA and relative leaf area index(RLAI) were established and the dynamic characteristics of crop growth rate(CGR),relative growth rate(RGR), leaf area duration(LAD), net assimilation rate(NAR), and specific leaf area(LAR) were analyzed based on the equations. The DMA and its proportion to the total biomass at rapid growth stage were significantly higher than those of Control. In the process of time after transplanting, the tendency of CGR was expressed in a single peak curve, and CGR of two SHR was higher than that of control in rapid growth stage. The RGR of Zhunliangyou 527 was higher than that of control from 23d after transplanting to mature period. As compared with the RGR of control, the RGR of Q you 6 was lower before 43 d after transplanting, higher from 43 d to 113 d after transplanting, and not much difference from 113 d after transplanting to maturity. A significant correlation was observed between gross LAD and LAD at rapid growth stage, and also between gross LAD and duration of LAI at rapid growth stage. Compared with Control, the RGR of SHR showed faster increasing and decreasing, and its peak value was higher. A single peak curve was available for the dynamic changes of NAR with its most high value from 43 d to 53 d after transplanting. The LAR of two SHR decreased fast from 23 d to 43 d after transplanting, moderately from 73 d to mature stage, and slowly from 43 d to 73 d after transplanting stage. The LAR of two SHR was higher in rapid growth stage than that of control.

High radiation use efficiency improves yield in the recently developed elite hybrid rice Y-liangyou 900

Continued drought during the late growth stage of super hybrid rice (SHR) markedly reduces yield, and management practices that use water more efficiently can contribute greatly to high and stable yields from SHR. The absolute temperature differences (ATDs) between the rice plant and the atmosphere and between the soil and the atmosphere are believed to be important determinants of grain yield. However, it has not previously been determined whether these ATDs have any effect on SHR yields under water-saving cultivation. A two-year field experiment involving two SHR varieties, Liangyoupeijiu (LYPJ) and Y-Liangyou 9000 (YLY900), evaluated the effects of reducing water supply from mid-booting to maturity on grain yield, canopy relative humidity (CRH), leaf area index (LAI), and ATDs between the ambient temperature and the leaf surface, panicles, canopy, and soil. Grain yield increased significantly under shallow water irrigation (SW), by 8.84% (YLY900) and 12.26% (LYPJ), but decreased significantly under mild water stress (MS, -20 to -30 kPa), by 14.36% (YLY900) and 9.47% (LYPJ), as well as severe water stress (SS, -40 to -50 kPa), by 35.06% (YLY900) and 28.74% (LYPJ). As water supply decreased, so did the CRH and the ATDs, with significant decreases under MS and SS. The temperature differences were significantly and positively correlated with grain yield (P < 0.01) in both cultivars. LAI was increased under SW conditions, but was significantly decreased under MS and SS. Our study suggests that the dual goal of saving water while maintaining high yield can be achieved by applying SW irrigation from mid-booting to maturity and by adopting cultivation measures that maintain high CRH and high plant-atmosphere and soil-atmosphere ATDs in order to alleviate water stress. YLY900 has a higher yield potential than LYPJ under SW conditions, suggesting that its wide cultivation may help achieve this dual goal.

Good progress has been made in the super hybrid rice (Oryza sativa L.) breeding in China. However, rice yield not only depends on the genetic characteristics but also on the agronomic practices. No-tillage and direct seeding (NTDS) is a simplified cultivation technology that greatly simplifies both land preparation and crop establishment. Aiming to determine the grain yield performance of super hybrid rice under NTDS and to identify critical factors that determine grain yield, field experiments were conducted in Nanxian, Hunan Province, China in 2009 and 2010. Two super hybrid cultivars, Liangyoupeijiu and Y-liangyou 1, were grown under conventional tillage and transplanting (CTTP) and NTDS. Grain yield, yield components, biomass production, crop growth rate and biomass accumulation during sowing to heading (HD) and HD to maturity were measured for each cultivar. There was no difference in grain yield under NTDS and CTTP. However, grain yield differed with cultivar and year. Y-liangyou 1 produced 4 % higher grain yield than Liangyoupeijiu in 2009, whereas in 2010 both cultivars yielded similarly. Grain yields of both cultivars were higher in 2009 than in 2010. Higher grain yield of Y-liangyou 1 in 2009 was associated with higher spikelet filling (spikelet filling percentage and grain weight), which resulted from higher biomass production. Crop growth rate after HD was critical for biomass production by the super hybrid rice. We suggest that increasing the crop growth rate after HD is an effective approach to increase grain yield of super hybrid rice under NTDS.

Continued drought during the late growth stage of super hybrid rice (SHR) markedly reduces yield, and management practices that use water more efficiently can contribute greatly to high and stable yields from SHR. The absolute temperature differences (ATDs) between the rice plant and the atmosphere and between the soil and the atmosphere are believed to be important determinants of grain yield. However, it has not previously been determined whether these ATDs have any effect on SHR yields under water-saving cultivation. A two-year field experiment involving two SHR varieties, Liangyoupeijiu (LYPJ) and Y-Liangyou 9000 (YLY900), evaluated the effects of reducing water supply from mid-booting to maturity on grain yield, canopy relative humidity (CRH), leaf area index (LAI), and ATDs between the ambient temperature and the leaf surface, panicles, canopy, and soil. Grain yield increased significantly under shallow water irrigation (SW), by 8.84% (YLY900) and 12.26% (LYPJ), but decreased significantly under mild water stress (MS, −20 to −30 kPa), by 14.36% (YLY900) and 9.47% (LYPJ), as well as severe water stress (SS, −40 to −50 kPa), by 35.06% (YLY900) and 28.74% (LYPJ). As water supply decreased, so did the CRH and the ATDs, with significant decreases under MS and SS. The temperature differences were significantly and positively correlated with grain yield (P < 0.01) in both cultivars. LAI was increased under SW conditions, but was significantly decreased under MS and SS. Our study suggests that the dual goal of saving water while maintaining high yield can be achieved by applying SW irrigation from mid-booting to maturity and by adopting cultivation measures that maintain high CRH and high plant–atmosphere and soil–atmosphere ATDs in order to alleviate water stress. YLY900 has a higher yield potential than LYPJ under SW conditions, suggesting that its wide cultivation may help achieve this dual goal.

Relationship Between Grain Yield and Yield Components in Super Hybrid Rice

In order to provide the scientific basis and technical support for the selection of suitable cultivars and high-yielding cultivation in double cropping systems, we selected indica-japonica hybrid rice, japonica hybrid rice, japonica conventional rice and indica hybrid rice in double-cropping rice areas(Shanggao of Jiangxi) in the middle reaches of the Yangtze River to analyze the differences of yield and its components, development of stem and tiller number, development of leaf area and its composition, photosynthetic potential, dry matter accumulation, crop growth rate and net assimilation rate of rice cultivars with different types systematically using wet nursery and big seedlings transplanting under high-yielding cultivation condition. Results showed that the yields of different types of late rice cultivars in double cropping systems all demonstrated indica-japonica hybrid rice ja-ponica hybrid rice japonica conventional rice indica hybrid rice very significantly. Establishing enough total spikelets through adequate panicles and large spikelets per panicle, and keeping a sustainable seed-setting rate and 1000-grain weight on the basic way to obtain the highest yield for indica-japonica hybrid rice. Compared with japonica hybrid rice, japonica conventional rice and indica hybrid rice, indica-japonica hybrid rice showed fewer tillers at the early growth stage, achieved expected number of stems and tillers at the critical leaf age for productive tiller, and had lower number of peak tiller at the jointing stage. Then, the indica-japonica hybrid population had a steady decline in number of tillers with a higher productive tillers rate(about 73.19%). The leaf area index of indica-japonica hybrid rice population was lower at the early growth stage, with the maximum leaf area index of about 7.93 at booting, and kept more than 3.85 at maturity, whose leaf area index, the ratio of effective leaf area, ratio of effective leaf area in top three leaves and ratio of grain to leaf were significantly higher than those of japonica hybrid rice, japonica conventional rice and indica hybrid rice population at heading. The dry matter accumulation of indica-japonica hybrid rice was comparable to that of japonica hybrid rice, japonica conventional rice and indica hybrid rice population at the critical leaf age for productive tiller and at the jointing stage, increased greater after jointing, and was higher at booting, heading, milky stage and maturity. The proportion of total biomass accumulation was higher at the middle and late growth stage. The photosynthetic potential, crop growth rate and net assimilation rate were smaller at the early stage and higher at the middle and late stages.

In Northeast China’s black soil rice cropping area, nitrogen (N) application is lower than in the south, yet excessive N fertilizer use persists, particularly in base fertilizers. This study aimed to assess the impact of reduced N and increased planting density on rice yields and photosynthetic matter production. From 2019 to 2020, a field split-plot experiment was conducted with two N rates (conventional N, CN: 120 kg ha−1 and reduced basal N, RN: 108 kg ha−1) and two planting densities (D1: 33.3 × 104 hills ha−1 and D2: 27.8 × 104 hills ha−1) using the rice varieties Kongyu131 (KY131) and Kendao24 (KD24). The results showed that RN increased the effective panicle formation rate but decreased the tiller numbers, dry matter accumulation, stems/sheaths transport capacity, leaf photosynthetic capacity, and yield by 2.67% compared to CN. D1 significantly boosted the dry matter accumulation, stems/sheaths transport, effective panicles, grains per square meter, and yield by 8.26% compared to D2. Interaction analysis revealed that RN under D2 conditions reduced the effective panicle percentage, harvest index, filled grain number, leaf area index (LAI), crop growth rate (CGR), and net assimilation rate (NAR) but increased the seed setting rate and 1000-grain weight. Under D1, RN reduced the LAI, CGR, and NAR at the tillering and heading stages but increased the NAR post-heading. Compared to CND2, RND1 increased the biomass, stems/sheaths transport, LAI, CGR, NAR, seed setting rate, 1000-grain weight, panicle numbers, and filled grains per square meter, compensating for the lower harvest index and effective panicle rate, achieving a 5.36% yield increase. KD24 outperformed KY131 in yield improvement. In summary, using 108 kg ha−1 with a planting density of 33.3 × 104 hills ha−1 promotes tillering, enhances photosynthetic substance production stems/sheaths dry matter transport, and increases rice yields.

Adding organic matter to soil proved an efficient strategy for restoring soil fertility and improving crop dry matter – an indicator of yield potential. In this regard, evaluating the sources of organic matter (OM) (control, poultry manure [PM], farmyard manure [FYM], compost, and mungbean residues [MR]) to provide 120 kg N ha-1 and effective microbes (EM) (0, 100, 200, and 300 L ton-1 of OM) as 2% solution proceeded in field conditions during 2017–2019. The sowing of wheat seeds (cv. Pirsabak 2015) at 120 kg ha-1 took place in the field using RCB design with four replications. Results showed that PM/FYM had delayed the phenology and improved the biomass-related parameters, dry matter (DM) accumulation, and crop growth rate (CGR) more than compost and MR. However, the results were more pronounced when applied with 300 L EM ton-1 of OM from the PM. The maximum DM (55%) accumulation in plant parts occurred beyond 100 days after sowing (DAS). A marked increase in DM and CGR beyond 60 DAS and a reduction in CGR beyond 120 DAS appeared irrespective of treatments. In the case of EM, the 300 L ton-1 revealed superior in terms of growth, DM accumulation, CGR, and delayed phenology. Structural equation modeling suggested that DM production gained a direct effect from crop phenology (46.1%) and crop stand (30.4%) but no indirect effect from crop growth (24.8%). In conclusion, the 300 L EM ton-1 of OM applied to PM or FYM had improved the crop stand, development, and DM production in wheat.

The field experiments were conducted during the rainy (kharif) seasons of 2019 and 2020 at crop research centre (CRC) of Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut, Uttar Pradesh to study the effect of seedling density and micronutrient application on growth, physiological parameters and yield of basmati rice (Oryza sativa L). Three planting densities, viz. 1 seedling per hill, 2 seedlings per hill and 3 seedlings per hill and 5 foliar application of micronutrient [MN0-control; MN1, B @0.04% and Fe @0.1% at maximum tillering (MT) stage; MN2, B @0.04% and Fe @0.1% at panicle initiation (PI) stage; MN3, Fe @0.1% at maximum tillering stage (MT) and B @0.04% at panicle initiation (PI) stage and MN4, B @0.04% and Fe @0.1% at maximum tillering (MT) and panicle initiation (PI) stages] were tested in a split plot design, keeping as main plots and sub plots, respectively with 3 replications. The growth, physiological traits and yield of basmati rice were significantly influenced by varying planting density and micronutrients application through leaves, as indicated by the outcomes of the experiments. Growth and physiological parameters such as dry matter accumulation, leaf area index, plant height, chlorophyll content, crop growth rate and relative growth rate increased through the application of boron and iron, being highest in foliar spray of 0.04% B and 0.1% Fe at both the stages (MT and PI). Of the different seedling densities, 3 seedlings per hill resulted in significantly higher grain yield (5.0 and 5.1 t/ha) during 1st and 2nd year, respectively. In both the years, the highest grain and straw yield were observed by using 3 seedlings per hill along with a foliar application of 0.04% B and 0.1% Fe during the MT and PI stages.

A field experiment was conducted to study the effect of bio priming levels and nitrogen management practices on dry biomass accumulation of wheat and crop growth indices during two consecutive rabi seasons of year 2020-21 and 2021-22. The experiment was laid out in randomized block design (Factorial) consisting of factor I bio priming with two levels viz. P0 (without bio priming) and P1 (with bio priming) and factor II nitrogen management with seven levels viz. N0 (Control), N1 (90 kg N ha-1 through urea), N2 (63 kg N ha-1 through urea + 27 kg N ha-1 through FYM), N3 (120 kg N ha-1 through urea), N4 (84 kg N ha-1 through urea + 36 kg N ha-1 through FYM), N5 (150 kg N ha-1 through urea) and N6 (105 kg N ha-1 through urea + 45 kg N ha-1 through FYM). The results showed that level P1 recorded significantly higher shoot dry matter accumulation (280.15 and 295.07 g running m-1) and root dry matter accumulation (186.77 and 196.71 g running m-1) during both the years of study at harvest stage while crop growth rate was found significant for second experimental year only in the growth period of 90 days after sowing- At harvest (9.49 g m-2 day-1). As for relative growth rate during interval of 90 DAS- At harvest, P0 recorded higher value (0.00688 and 0.00728 g g-1 day-1) although found at par with level P1 during both the years of study. Application of N6 proved superiority in shoot dry matter accumulation (284.26 and 302.24 g running m-1) and root dry matter accumulation (189.51 and 201.49 g m-1 row length) during both the years and was statistically at par with level N5 during both the experimental years except for crop growth rate which was found significant (9.68 g m-2 day-1) only in the second year of experiment for the growth stage interval of 90 DAS- At harvest. The relative growth rate for 90 DAS- At harvest interval got the highest significant maximum value with N0 (0.00732 and 0.00735 g g-1 day-1) although found at par with other levels of nitrogen management during both the years.

Succeeding in breeding super hybrid rice has been considered as a great progress in rice production in China. This on-farm study was conducted with Minirhizotron techniques to identify dynamic root morphological traits and distribution (0–30 cm) under different nitrogen treatments. Five elite super hybrid rice cultivars, Liangyoupeijiu (LYPJ), Yliangyou 1(YLY1), Yliangyou 2(YLY2), Yliangyou 900(YLY900) and Super 1000(S1000), were grown at four N levels: 0 kg ha−1 (N1), 210 kg ha−1 (N2), 300 kg ha−1 (N3) and 390 kg ha−1 (N4) in 2015 and 2016. Results showed these cultivars had greater root traits and higher grain yield under N3. Total root number (TRN) and total root length (TRL) of these cultivars reached maximum at 55 days after transplanting (DAT). The new released cultivars YLY900 and S1000 were featured with an improved root system among these cultivars. The percentage of root number on 10–20 cm soil was over 50% compared with other soil layer. A significant positive correlation was found between grain yield and both TRN and TRL at 10–20 cm soil layer (P < 0.01). Given this situation, the grain yield of super rice cultivars could be further improved by increasing the proportion of roots at 10–20 cm soil layer under suitable nitrogen management.

The present field experiment was carried out during pre-kharif season (February to May) for two consecutive years of 2024 and 2025 at Baruipur Experimental Farm, University of Calcutta, West Bengal, India to evaluate the replacement potential of neem-coated prilled urea (NCPU) with nano-urea in sesame (var. Suprava, CUMS-17). The randomized block design included 10 nitrogen management treatments, combining varied proportions of soil-applied NCPU with foliar nano-urea (4% N) or 2% urea sprays. Growth, yield attributes, and seed yield were recorded and statistically analyzed. Results showed significant effects of nitrogen management on plant height, dry matter accumulation (DMA), crop growth rate (CGR, 30–60 DAS), capsules plant-¹, seeds capsule-¹, and seed yield. The highest plant height (143.71 cm), DMA (609.28 g m-2), CGR (8.28 g m-2 day-¹), capsules plant-¹ (69.47), and seed yield (1.09 t ha-¹) were achieved with 100% RDN through split NCPU application. This was statistically at par with (75% NCPU+nano-urea spray at 45 DAS; yield: 1.07 t ha-¹), suggesting that partial soil-applied N replacement with nano-urea was feasible without yield loss. The study concluded that integrating 75% RDN via NCPU with a single nano-urea spray could sustain yields comparable to full NCPU application, offering a resource-efficient, sustainable nitrogen management option for sesame in West Bengals’s pre-kharif season.