Search Results (9)

The transplanting of over-aged seedlings is an important adaptive strategy for rice cultivation during the monsoon season in the coastal areas of Bangladesh. This study aimed to identify promising hybrid rice varieties that can be transplanted as over-aged seedlings in the south-central tidal coastal ecosystem of Bangladesh. Three elite hybrid varieties, namely, AZ7006, Dhani Gold, and INH-16019, along with a popular local cultivar, Moulata (as the control), were used in this field study, and seedlings at two different ages (e.g., 50- and 60-day-old) were transplanted. The results showed that Dhani Gold had the highest grain yield (5.47 t/ha) with the maximum number of tillers (17) and effective tillers (15) per hill for the 50-day-old seedlings as compared with the 60-day-old seedlings. In addition, the hybrid variety INH-16019 also yielded 5.20 t/ha grain with the highest number of spikelets/panicle (191), filled grains/panicle (174), and unfilled grains/panicle (17) for 50-day-old seedlings. However, the local cultivar, Moulata, had the highest plant height (149 cm), required the maximum time for 50% flowering (75 days after transplanting, DAT) and harvesting (104 DAT), and also produced the lowest number of spikelets/panicle (114) and filled grains/panicle (108), leading to the lowest grain yield (3.57 t/ha) considering both ages of the seedlings. Our data further revealed the significant influence of seedling age (50- and 60-day-old seedlings) on the straw yield. Interestingly, this study revealed that the hybrid variety Dhani Gold showed a remarkable decrease in straw yield (by 36%) but obtained the highest (56.3%) harvest index when transplanted as very over-aged (e.g., 60-day-old) seedlings. Moreover, we recorded a higher grain nitrogen content in the hybrid varieties than in the local cultivar, Moulata. Among the hybrids, AZ7006 showed the highest nitrogen content (1.72%), which was statistically similar to INH-16019 (1.67%) and Dhani Gold (1.57%) for 50-day-old seedlings. Importantly, the grain yield of Dhani Gold was 50% higher than Moulata for 50-day-old seedlings, and the benefit–cost ratio of Dhani Gold was also the highest (1.34) for the same seedling age. Hence, the over-aged Dhani Gold hybrid rice seedlings would be a good choice for increasing Aman rice productivity during the monsoon season in the south-central coastal ecosystem of Bangladesh. Full article

Perennial rice has recently garnered global attention due to its potential to save on seeds and labor costs and its high production efficiency. The “mid-season rice–ratoon forage” mode is a new planting system that has emerged in recent years. However, detailed information is still lacking on the regenerative characteristics, grain and ratoon forage yields, and forage nutrient content of perennial rice under different planting densities, nitrogen (N) rates, stubble heights, and water management practices. Four experiments with perennial rice were conducted in Sichuan Province, Southwest China, from 2017 to 2022. The results show that the rice grain and ratoon forage yields were significantly affected by year, planting density, and N. The grain yield was 28.18% and 60.81% lower in 2018F and 2019F, respectively, than in 2017F; similarly, the ratoon forage yield was 29.01% and 52.74% lower in 2018S and 2019S, respectively, than in 2017S. The low grain yield was mainly associated with lower numbers of spikelets per panicle and panicles per m², which resulted from a lower regrowth rate, and the low ratoon forage yield was mainly attributed to the lower regrowth rate. The rice grain and ratoon forage yields increased with an increase in the N rate and planting density. The ratoon forage was found to be rich in crude protein, crude fat, crude fiber, calcium, nitrogen, phosphorus, potassium, and other nutrients. Moreover, the content of these nutrients increased significantly with an increase in the N rate. The regrowth rate and maximum tillers showed trends of first increasing and then decreasing with an increase in the stubble height under dry and wet alternation irrigation during the winter season. When the relative soil moisture decreased to below 80% during the winter season, the regrowth rate and seedling development index could reach more than 99% and 84%, respectively. Our results suggest that integrating N, water, and other management practices (including the combination of a 150 kg ha⁻¹ N rate, 18.0 hills per m², 10–20 cm rice stubble height, and alternating dry and wet irrigation during the winter season) is a feasible approach for achieving high grain and ratoon forage yields in perennial rice systems. Full article

Hill number per unit area and seedling number per hill are foundational agrotechnical factors shaping the growth and development of rice plants. This study aimed to determine the effects of decreasing the hill number per unit area combined with increasing the seedling number per hill on grain quality in hybrid rice. Field experiments were performed in Hengyang, Hunan Province, China, in 2022 and 2023 using the hybrid rice variety Huazheyou 261, as well as in Liuyang, Hunan Province, China, in 2023 using the hybrid rice varieties Yueyou 2646 and Zhenliangyouyuzhan. Treatments (combining hill number per unit area and seedling number per hill) encompassed a combination of 24 hills per m² and one seedling per hill (H24S1) and a combination of 14 hills per m² and three seedlings per hill (H14S3) in Hengyang, as well as a combination of 28 hills per m² and two seedlings per hill (H28S2) and a combination of 14 hills per m² and four seedlings per hill (H14S4) in Liuyang. There were no significant differences in the leaf area index at the heading stage, as well as no significant differences in canopy light transmittance during the grain-filling period between H24S1 and H14S3 in Hengyang, or between H28S2 and H14S4 in Liuyang. The differences in grain quality traits, including milling traits (brown, milled, and head rice rate), appearance traits (rice length, rice length-width ratio, chalky grain rate, and chalkiness degree), amylose and protein content, and pasting characteristics were also not significant between H24S1 and H14S3 in Hengyang, nor between H28S2 and H14S4 in Liuyang. This study indicates that the grain quality in hybrid rice is unaffected by decreasing the hill number per unit area integrated with increasing the seedling number per hill. Full article

Aulacaspis yasumatsui Takagi invaded Guam in 2003 and caused the widespread mortality of the indigenous Cycas micronesica K.D. Hill population. The regeneration of the surviving tree population continues to be constrained 20 years later, and a look at the changes in megastrobili traits may inform future conservation management decisions concerning regeneration. We quantified megastrobilus reproductive effort and output from 2001 to 2022 to address this need. The reproductive effort of each megastrobilus was immediately reduced by the invasion, as the number of megasporophylls declined by 29%, and the number of ovules declined by 73% in 2006. Reproductive output was also damaged, as the percent seed set declined by 56% and the number of seeds per strobilus declined by 88%. These fecundity metrics have shown few signs of recovery through 2022. Our results reveal that chronic A. yasumatsui infestations, combined with other invasive herbivore threats, have damaged the host C. micronesica population through a sustained reduction in ovule production and the percent seed set for each megastrobilus, thereby impairing regeneration. This plant response to the biotic threats is distinct from the ongoing mortality of mature trees and emerging seedlings. Conservation interventions may be required to foster a return to adequate regeneration during future attempts to aid C. micronesica recovery. Full article

Rice yields can only be achieved by selecting a high-quality population. Nitrogen rates and transplanting density play a significant role in determining population quality and yield. Field experiments were conducted in Heshan District, Hunan Province, China, to explore suitable nitrogen rates and appropriate transplanting densities for rice production in 2021 and 2022. In this study, three levels of nitrogen, e.g., N1, N2, and N3 (0, 150, and 210) kg ha⁻¹, and three transplanting densities, e.g., B1, B2, and B3 (1, 2, and 3) seedlings per hill were used to study their individual or combined effects on rice (Taiyou 390) population quality, yield, and yield components, nitrogen-related enzyme activities, and nitrogen absorption and utilization efficiency. The results showed that N2B3 had the highest yield, with an average yield of 9.30 t ha⁻¹ in two years, which was 3.7~49.6% higher than other treatments. This increase was attributed to higher dry matter accumulation (1538.22 g m⁻²) and effective panicle number (435.2 × 10⁴ ha⁻¹), influenced by increased nitrate reductase activity at the booting stage and glutamine synthase at the heading stage, along with maintenance of higher SPAD value and leaf area index. Nitrogen rates and transplanting densities significantly affected nitrogen use efficiency, with the contribution rate of nitrogen fertilizer to yield decreasing as nitrogen rates increased. However, N2B3 improved nitrogen use efficiency and stabilized rice yield by reducing nitrogen fertilizer application. This study suggested that N2B3 treatment could enhance rice yield by improving plant nitrogen use efficiency under low nitrogen supplementation. Full article

Sesame seeds are flat and oval, with poor mobility, easily blocking a seed tube and reducing seeding quality. An air-assisted seed-guiding device was designed for a hill-seeding centralized seed-metering device for sesame. The core of the seed-guiding device is a distribution manifold that could restrict the trajectory of seeds and make seeds move in the same direction as airflow. Six-factor three-level orthogonal tests were carried out using CFD–DEM coupling simulation to study the influence of the structure and operation parameters of the seed-guiding device on airflow field, seed transport, and seeding performance. The simulation results derived optimal parameters: the depth of the circular section of the seed slide was 2.62 mm, the length of the expansion and contraction section was 188 mm and the length of the contraction section was 20 mm, the seed tube diameter was 19 mm, the airflow velocity was 6.3 m/s, and the rotation speed of the roller was 25 r/min. Under the optimal parameters, the positive pressure required for the seed-guiding device was 256.77 Pa, the time of seeds passing through the seed-guiding device was 0.77 ± 0.02 s, and the velocity of seeds when they came out of the seed tubes was 2.24 ± 0.30 m/s. The qualified rate was 88.33% (2 ± 1 seeds/hill), and the miss-seeding rate was 5.00% (0 seeds/hill). Bench test showed that the qualified rate was 86.80%, and the miss-seeding rate was 6.00%. The seeding performance of the bench test was consistent with the simulation results. Field tests showed that the average number of seedlings per hill was 1.32. The seed-guiding device could meet the requirements of precision hill-seeding for sesame. This study provides a reference for design of a seed-guiding device of a centralized seed-metering device for sesame. Full article

Because the current hybrid rice machine transplanting sowing quantity is too large and the high rate of missing hills or poor seedling quality during mechanical transplanting, the mechanized planting of hybrid rice is limited, which results in significant hindrance of large-scale planting of hybrid rice in China. In this study, a mixed sowing technology (replacement of a portion of hybrid rice seeds with conventional rice seeds) in seedling cultivation was adopted to determine the appropriate variety combinations and conventional rice sowing quantity using a variety combination experiment and sowing quantity experiments, respectively. The results of the variety combination experiment showed that combinations of Changyou 4 mixed with Nanjing 5055, and Yuanliangyou mixed with Yangdao 6 could reduce the sowing quantity of hybrid rice, improve the quality of machine transplanting, and not reduce the grain yield. The results of the conventional rice sowing quantity experiment showed that with the increase in conventional rice sowing quantity, the seedling quality, spikelet per panicle, and filled kernel percentage decreased, and the mechanical transplanting quality improved. Compared with pure sowing hybrid rice, the grain yield was not significantly different in the japonica rice treatment when the sowing quantity of Nanjing 5055 was more than 75 g/tray and Yangdao 6 was more than 60 g/tray. With the increase in conventional rice sowing quantity, the missing hill rate decreased significantly and the seedling density increased significantly, so that the panicle number was also improved, which might have compensated the reduction in seedling quality, spikelet per panicle, and filled kernel percentage. As a whole, 90 g Nanjing 5055 seeds mixed with 30 g Changyou 4 seeds per tray and 75 g Yangdao 6 seeds mixed with 30 g Yuanliangyou seeds per tray were suitable sowing quantities for mixed planting that could ensure strong seedlings and better mechanical transplanting quality, while reducing the cost (reduce the sowing quantity of hybrid rice and conventional rice) without reducing the grain yield. Full article

The number of seedlings per hill and the configuration of plant row spacing are important management measures to improve rice yield. In the present study, we evaluated the impact of various seedlings per hill (1, 3, 6, and 9 seedlings hill⁻¹) under four different rice verities (two conventional rice, two hybrid rice) on allometric characteristics, nitrogen use efficiency (NUE) and yield in 2020 at early and late season. Results showed that compared with nine seedlings per hill (wide row spacing), the number of effective panicles, yield, grain biomass allocation, grain-to-leaf ratio, grain nitrogen accumulation, nitrogen dry matter production efficiency (NDMPE), N harvest index (NHI) of 1 seedling per hill increased by 21.8%, 10.91%, 10.5%, 32.25%, 17.03%, 9.67%, 6.5%, respectively. With the increase of seedlings per hill and the expansion of row spacing, stem biomass (SB) and reproductive biomass (RB) increased with the increase of above-ground biomass, mainly showing the relationship of isometric growth. Leaf biomass (LB) increased with above-ground biomass, mainly showing the relationship of allometric growth. The results suggested that under the same basic seedlings, transplanting 1 seedling per hill and dense planting was the most beneficial to improve rice yield. Full article

Mutation technology has been applied more in recent decades to achieve novel products that are not commonly found in nature. An experiment was conducted to examine the effects of an N-methyl-N-nitrosourea (MNU) mutation on the growth, yield, and physicochemical properties of rice. Seeds of two rice cultivars (K1: DT84, and K3: Q5), along with their mutant lines (K2: mutated DT84, and K4: mutated Q5), were sown, and the established seedlings were transplanted to an open field. Ten hills per plot were randomly selected to evaluate growth parameters, yield, and components. Physicochemical attributes, including protein, amylose, and lipid contents, as well as taste score were measured by a quality tester device. The results showed that plant length, tiller number, and panicle length were higher in mutant lines than those of their cultivars. Furthermore, mutant lines took longer to reach heading and maturity stage. The highest panicle number, spikelet number, repined ratio, 1000 grain weight, 1000 brown rice weight, and grain yield were obtained in mutant lines, as compared to cultivars. The greatest grain yield was obtained in the K4 mutant line (11.6 t/ha), while the lowest was recorded in the K1 cultivar (7.7 t/ha). Lower amylose, protein, and lipid contents were observed in mutant lines compared to those in cultivars. The taste score, which increased from 67.7 to 73.7, was found to be correlated with lower amylose, protein, and lipid contents. The mutation approach increased the grain length but decreased the grain width of tested varieties. This study highlights and suggests the importance of MNU mutation in terms of rice yield improvement with preferable quality. Full article