| Mechanical transplanting rice can improve rice production efficiency and decrease labor cost,which is the major direction of the development of rice cultivation in China.To solve the problems of the low degree of mechanization of rice cultivation in Chengdu Plain,slow development and unsuitable evaluation systems of varieties breeding for mechanical production,and to accelerate the research and integration of the key technology of high yield and high efficiency cultivation of mechanical transplanting rice,two experiments were carried out in Chongzhou and Meishan during 2015 and 2016 rice growing seasons to study the establishment of high-yielding populations and its physiological ecology characteristics of bowl mechanical transplanting rice.(1)The experiment in 2015 was to study the effects of seedling age and transplant density with hybrid rice cultivars F you 498 as material and carpet mechanical transplanting rice as the control.Split-plot design with two seedling ages(25 days after sowing and 40 days after sowing)as main plot and six treatments of mechanical transplanting methods combined with densities(bowl mechanical transplanting with high density,bowl mechanical transplanting with medium density,bowl mechanical transplanting with low density,carpet mechanical transplanting with high density,carpet mechanical transplanting with medium density,carpet mechanical transplanting with low density)as subplot in this experiment.(2)Based on the research of the suitable seedling age and density under bowl mechanical transplanting rice in 2015,we studied the most suitable integration between hybrid cultivars of different thousand grain weight and densities in 2016.The experiment was laid out in split-plot design with three hybrid cultivars with different thousand grain weight(Chuannong you huazhan,26 g(VI);F you 498,29 g(V2)and Yixiang you 211.5,32 g(V3))as main plot and four seeding rates(30 g per tray,40 g per tray,50 g per tray and 60 g per tray)as subplot.The experiments was designed to study the effects of cultivars,seeding rates,seedling age and densities on the quality of rice seedling and rice populations,the nitrogen absorption and utilization and the mechanism for establishing high-yielding populations of bowl mechanical transplanting rice,which is of great significance to the formation and production of large-scale mechanical transplanting rice production.The main results are as follows:1.Effects of different cultivation measures on grain yield and its components of bowl mechanical transplanting rice.There had significant influences on grain yield,the number of grains per panicle,total spikelets number and seed-setting rate affected by cultivars,seeding rates,seedling age and densities in bowl mechanical transplanting rice.Besides,there was no significant effect on 1000-grain weight except for cultivars.The number of effective panicles increased with the increases of transplanting densities or seeding rates.33 cm of line spacing combined 14.5 to 15.5 cm of row spacing of bowl mechanical transplanting rice had the advantage of total spikelets number and seed-setting rate in 25 day-seedling age,which had the highest grain yield than that of other treatments.Especially when the row spacing was 15.5 cm,which could give full play to the advantages of the plant type of hybrid rice in the study area and improve the photosynthetic biomass production to reach the highest yield of 12.74 t per hectare.Compared to the same seedling age of carpet mechanical transplanting rice and 40-day seedling age of bowl mechanical transplanting rice,the grain yield of the treatment of 33 cm of line spacing combined 15.5 cm of row spacing of bowl mechanical transplanting rice increased by 9.54%and 12.98%,respectively.The indexes of population quality deteriorated and the number of effective panicles decreased with the increment of seedling age and the reduction of transplant densities,which was the major factor for the lower grain yield.In the views of cultivars with different 1000-grain weight,the grain yield of F you 498 was better.When the seeding rate was 50 g per tray,the grain yield of F you 498 could reach as high as 12.24 t per hectare,which is 15.47%and 8.32%higher than that of Chuannong you huazhan and Yixiangyou 2115,respectively.The highest grain yield of different cultivars varied due to the varietal characteristic and yield potential of cultivars.By means of optimized calculation,Chuannong you huazhan,F you 498 and Yixiangyou 2115 could obtain its highest yield of 10.6 t per hectare,12.0 t per hectare and 11.0 t per hectare when its seeding rates were 43.0 g per tray,46.0 g per tray and 53.0 g per tray,respectively.Although the grain yield and its components varied by cultivars,the optimal seeding rate showed increased with the increases in 1000-grain weight of cultivars and the optimum seeding rate was 4 grains per hill.Young seedling age(25 days after sowing)with the row spacing of 14.5 to 15.5 cm could achieve the higher grain yield by ensuring the reasonable of the number of effective panicle and number of grains per panicle,and the higher seed-setting rate and 1000-grain weight in bowl mechanical transplanting rice.2.Effects of different cultivation measures on the quality of rice seedlings and seedling growth of bowl mechanical transplanting rice.The seedling age,seeding rates and the methods of raising rice seedlings had the significant effect on the quality of rice seedlings.The seedling quality of bowl mechanical transplanting was superior to that of carpet mechanical transplanting in the same seedling age conditions.The plant height and stem base width of rice seedlings,dry matter of 100 seedlings and dry matter per unit plant height showed increased while the green leaf number,leaf age,uniformity and rooting ability of rice seedlings decreased with the increment of seedling age and the reduction of seeding rate.The leaf age,stem base width,green leaf number,root number,rooting ability and dry matter per unit plant height of rice seedlings in bowl mechanical transplanting were higher than those of carpet mechanical transplanting.The optimum transplanting seedling age was 25 days after sowing.There had significant difference among the seedling quality of different cultivars.The missing hill rate was larger in the field than that in trays.Besides,Chuannong you huazhan had the lowest missing hill rate both in the field or the trays while Yixiangyou 2115 had the highest missing hill rate.Meanwhile,the numbers of survived seedling per hill of all cultivars showed increased but the percentage of seedling emergence,the missing hill rate of the tray or the field decreased with increasing the seeding rate.With the consideration of grain yield,seedling quality and the numbers of survived seedling,4 grains per hill should be ensured despite of the varied cultivars with different 1000-grain weight.2 or 3 survived plants per hill could guarantee the basic seedlings above 45 ×104 per hectare,and then the missing hill rate should be controlled below 15%and the plant height of transplanting should be lower to 20 cm,and the leaf age and green leaf number should be higher to 3.5,which could have the potential to establish high-yielding population of mechanical transplanting rice.3.Effects of different cultivation measures on population quality of bowl mechanical transplanting rice.There had the significant regulatory effects of cultivars,seeding rates,seedling age and planting densities on population quality of rice during the major growth stage.The tillers number of population,leaf area index(LAI),the apparent translocation amount and ratio of leaf and stem-sheath of single stem,biomass of single stem and populations,stages of dry matter accumulation,population growth ratio,root growth,photosynthetic potential and the net assimilation rate after heading stage of 25-day seedling age were superior to those of 40-day seedling age under the same transplanting density of bowl mechanical transplanting rice.However,the tillers number of population,LAI and the attenuation rate of the main growth stage,dry matter of population,photosynthetic potential,dry matter accumulation before heading stage,population growth ratio and the net assimilation rate before heading stage showed increased with the increases of planting densities in the same seedling age under bowl mechanical transplanting rice.Furthermore,dry matter accumulation after heading stage,population growth ratio and the net assimilation rate after heading stage of 25-day seedling age in bowl mechanical transplanting rice showed increased first and then decreased with increasing the planting densities.Those indexes of population quality of carpet mechanical transplanting showed deteriorated by increasing the planting densities.All the indexes of population quality of bowl mechanical transplanting were superior to that of carpet mechanical transplanting.For the same rice cultivars,the tillers number,LAI,attenuation rate of LAI,photosynthetic potential and dry matter after jointing stage showed increased while the apparent translocation amount and ratio of leaf and stem-sheath of single stem,dry matter of single stem at the major growth stages and the net assimilation rate before heading stage showed decreased with the seeding rates increased.Among all the cultivars,the photosynthetic biomass production of F you 498 showed the best and had the highest population quality.Based on the above information,we proposed the quantifying quality indicators of the population of high quality for high-yielding bowl mechanical transplanting rice in Chengdu Plain.4.Effects of different cultivation measures on nitrogen utilization of bowl mechanical transplanting rice.The nitrogen absorption and stages of nitrogen accumulation of rice growth stages,the nitrogen absorption rate from heading stage to maturity stage,the nitrogen translocation amount of stem and leaf,the nitrogen increment of panicle,nitrogen partial productivity,root dry matter after jointing stage and grain yield of 25-day seedling age were superior to those of 40-day seedling age.Compared with carpet mechanical transplanting rice,bowl mechanical transplanting rice could improve the root growth of rice at every growth stages,enlarge the nitrogen accumulation and absorption rate,and increase the nitrogen redistribution amount from vegetative organs to grains under the same seedling age conditions.Especially,the treatment of 25-day seedling age combined with the row spacing of 15.5 cm was superior to other treatments,which was the optimum combination of seedling age and planting density in this study.There had the significant influence of cultivars and seeding rates on nitrogen utilization of the main rice growing stage.The nitrogen absorption amount of the major growth stage,the nitrogen absorption rate before jointing stage,nitrogen accumulation of stem at heading stage and nitrogen accumulation of leaf at maturity stage and nitrogen increment of panicle showed increased with the increases of the seeding rate.Correlation analysis indicated that there was a significant positive correlation(r=0.47**～0.83**)between root dry matter during the major growth stage and grain yield and nitrogen absorption and utilization,and a significant negative correlation(t=-0.52**～0.79**)between root shoot ratio at heading stage and maturity stage and grain yield and nitrogen absorption and utilization under the integration of mechanical transplanting methods and planting densities.However,a significant positive correlation(r=0.44**～0.81**)between the nitrogen translocation amount of leaf from heading stage to maturity stage and nitrogen harvest index and root dry matter at the main rice growing stage was observed in different seeding rates.Finally,rice cultivar F you 498,combined with optimal planting density(33 cm of line spacing and 15.5 cm of row spacing)and seeding rate(46 to 52 g per tray),could optimize the relationship of individuals and populations to improve the harmonious development of each other and finally enhance the nitrogen absorption and utilization. |
PDF Full Text Request