| Precision sparse sowing is an important measure to solve the problem of poor seedling quality and low quality of machine transplanting.To explore the effects and machanisms of sowing rate,planting density and seedling age on rice population quality,yield formation and planting cost of precision strip sowing in hybrid rice transplanting.Two experiments were designed in the Modern Agricultural Research Base of Sichuan Agricultural University,Chongzhou,Chengdu,and the Haowei Rice Cooperative Experimental Base in Dongpo District,Meishan City from 2021 to 2022,using indica hybrid rice Yixiangyou 2115 as material,both of which were two-factor split plot experiments.Experiment 1 was the sowing rate and planting density test.The main plot consisted of four sowing rates: 30g/ plate(S1),45g/ plate(S2),60g/ plate(S3)and 75g/plate(S4).The sub plot consisted of three planting densities: the row spacing of machine planting was 30 cm,and the plant spacing was 16cm(D1),18cm(D2)and 21cm(D3),respectively.Experiment 2 was sowing rate and seedling age test.The main plot had 5sowing rates: 30g/ plate(S1),45g/ plate(S2),60g/ plate(S3),75g/ plate(S4)and 85g/plate(S5),and the sub plot had 3 seedling ages: 24d(Y1),32d(Y2),and 40d(Y3);The machine planting density is selected as the optimal result of Experiment 1(D1).The effects of "rate-density-seedling age" treatment on mechanical planting quality,photosynthetic matter production,yield formation and economic benefits were systematically studied,which provided theoretical and practical basis for the formation of precision sparse sowing technology of hybrid rice in Sichuan.The main results are as follows:1.Effects of different sowing rate and seedling age on seedling qualitySowing rate had significant effect on various indicators of seedling quality.In experiment 1,with the increase of sowing rate,seedling rate,quality to height ratio,leaf age and plant height all showed a decreasing trend.Compared with the highest sowing rate treatment(75g/ plate,S4),seedling rate of 60g/ plate(S3)treatment decreased by 9.83%,quality to height decreased by 6.78%,leaf age decreased by 4.31% and plant height decreased by 3.04%,Making it was the least reduced treatment.The root binding force and blanket forming ability were increased,and the blanket forming ability under 45g/ plate(S2)and 60g/plate(S3)treatments had reached the "general" level,basically meeting the requirements of machine operation.In experiment 2,the interaction between sowing rate and seedling age affected the seedling qualities,and the influence of seeding rate on seedling quality is roughly consistent with that of experiment 1,but the range of change is not the same.The main influencing factor is seedling age.From the perspective of seedling age,leaf age,plant height and root consolidation force all show an increasing trend with the extension of seedling age under the same seeding amount while the seedling rate shows a decreasing trend.Among them,compared with the treatment with the maximum age(40d,Y3),the seedling rate of the shortest seedling age(Y1)had decreased by 13.01%;the root binding force of 30g/ plate(S1)and 45g/ plate(S2)in 24 d seedling age(Y1)showed "poor",which could not meet the requirements for machine installation;In other treatments,the root binding force reached "average" or "good" levels,which met the machine requirements.Under the interaction of two factors,considering the influence of indicators such as seedling rate,the treatment with 60g/ plate(S3)seeding quantity and 24 d short seedling age(Y1)had better seedling quality.2.The influence of different sowing rate and seedling age on the quality of mechanical transplantingIn experiment 1 and experiment 2,the influence trend of seeding rate on the quality of machine transplanting was basically consistent.With the seeding rate incraesed,the uniformity of machine transplanting and the rate of seedling leakage showed a decreasing trend.In experiment 1,compared with the treatment of the highest sowing rate(S4,75g/plate)and the treatment of the lowest sowing rate(S1,30g/ plate),the machine transplanting uniformity of S4 was reduced by 15.25%.In experiment 2,compared with the treatment of the highest sowing rate(S5,75g/ plate)and the treatment of the lowest sowing rate(S1,30g/ plate),the highest sowing rate(S5,85g/ plate)was reduced by17.70% in machine transplanting uniformity,and the seedling leakage rate was reduced by63.29% in experiment 1 and 70.23% in experiment 2.The rate of seedling injury and seedling drift were higher in lower and higher sowing rate treatments.The number of basic seedlings in each hole increased.Compared with the treatment of the highest seeding rate(S5,85g/ plate)and the lowest seeding rate(S1,30g/ plate),the number of basic seedlings in the treatment of the highest seeding rate(S4,75g/ plate)in experiment 1 increased by113.18%and in experiment 2 the highest seeding rate(S5,85g/ plate)increased by134.61%.From the perspective of seedling age,under the condition of the same sowing rate,with the seedling age increased,the rate of seedling injury and seedling drift both showed an increasing trend,and the change regularity of seedling leakage rate between different treatments was not strong.In terms of the mechanical transplanting uniformity,the mechanical transplanting uniformity of short seedling age was better.In general,under the premise of considering cost effect and meeting the requirements of seedling loading,the treatment of Y1 seedling age(24d)with sowing quantity S3(60g/ plate)had the best uniformity and quality of mechanical transplanting.3.Effects of planting density and seedling age on population quality of rice under different sowing rateIn the two-year experiment,the sowing rate,planting density and seedling age had significant or extremely significant effects on dry matter accumulation,population leaf area index(LAI),photosynthetic potential,SPAD,net photosynthetic rate(Pn value)and other indicators,and the interaction effect was significant.In experiment 1,with the increase of seeding rate,dry matter accumulation of rice population firstly decreased and then increased;LAI and photosynthetic potential both increased with the increase of seeding rate,while SPAD and Pn values decreased.Under the same sowing rate,with the decrease of planting density,stem sheath dry weight at full head and mature stage decreased.The dry weight at mature stage and dry matter accumulation after full head decreased,stem sheath output rate increased,and stem sheath material conversion rate increased first and then decreased.The values of LAI,efficient LAI,photosynthetic potential,SPAD and Pn in each growth period showed an increasing trend with the increase of planting density.In experiment 2,with the increase of seeding rate,the dry matter accumulation of rice population firstly decreased and then increased;LAI,efficient LAI,photosynthetic potential and SPAD of rice population in each growth period all increased with the increase of seeding rate,and Pn value firstly increased and then decreased.Under the condition of the same seeding amount,dry matter weight,LAI,efficient LAI,photosynthetic potential,SPAD and Pn values of population at each growth stage showed a decreasing trend with the extension of seedling age.4.Effects of planting density and seedling age on rice yield and component factorsIn the two-year experiment,the effects of sowing amount,planting density and seedling age on yield and its component factors were significant or extremely significant.In Experiment 1,with the increase of sowing rate,the effective panicle,grain number per panicle and yield of machine-inserted rice showed an increasing trend,while the1000-grain weight and seed setting rate had no significant difference.Under the same sowing rate,with the decrease of planting density,the effective panicle showed a downward trend,and the number of grains per panicle showed an upward trend.In the sowing rate of 30g/ plate and 45g/ plate,the grain yield gradually decreased with the decrease of planting density,while in the sowing rate of 60g/ plate and 75g/ plate,the yield showed an overall increase trend.In experiment 2,with the increase of sowing rate,the effective panicle,grain number per panicle and yield of machine-inserted rice showed an overall increasing trend.Compared with experiment 1,the seed setting rate and 1000-grain weight were significantly increased.With the same seeding rate,the number of grains per panicle and yield decreased with the increase of seedling age,and the yield of 24 d seedling age had the highest in different seeding rate.In conclusion,from the perspective of sowing rate,experiment 1 had the highest yield in the treatment of sowing rate of 75g/ plate combined with 30cm×18cm planting density,but compared with the treatment of lower sowing rate of 45g/ plate combined with 30cm×16cm(D1)planting density,the yield only decreased by 2.5%.From the perspective of seedling age,in experiment 2,the treatment with 24d(Y1)seedling age and 75g/ plate had the highest yield,compared with experiment 2,the yield of the lower sowing rate of 60g/plate dropped only 4.73%.Therefore,on the basis of considering cost saving effect,the treatment combination with sowing rate 45-60g/ plate,and planting density of 30 cm ×16cm and age of 24 d seedling would have better performance.5.Analysis of economic benefits of rice production under sowing rate,planting density and different seedling agesEconomic output value and cost profit rate were significantly different in each treatment of the two experiments.Economic output value gradually increased with the increase of sowing rate in experiment 1,while the change regularity was not obvious in experiment 2.The maximum value of economic output value in experiment 1 was at the sowing rate of 75g/ plate and the planting density of 30 cm × 16 cm.However,the maximum cost profit rate was at the sowing rate of 60g/ plate and planting density of 30cm×16cm.Compared with the two treatments,the economic output value of the former was only 0.22% higher than that of the latter,but the economic profit rate was reduced by10.05% and the cost profit rate was reduced by 13.79%.In experiment 2,the maximum economic value was obtained when the sowing rate was 75g/ plate with 24 d seedling age;however,the maximum cost-profit value occurred when the sowing rate was 60g/ plate with 24 d seedling age;the value was 50.16%.Compared with the two treatments,the economic output value of the former was only 1.17% higher than that of the latter,but the economic benefit was reduced by 3.31% and the cost profit rate was reduced by 6.52%.Therefore,to obtain higher economic benefits,choose the processor with sowing rate of60g/ plate and 24 d seedling age with 30cm×16cm planting density would have the highest economic output value and cost profit margin.In summary,based on the effects of sowing rate,seedling age and planting density on the growth,yield and economic benefits of machine-inserted rice,the key techniques of precision sparse sowing of hybrid rice in Sichuan rice area were put forward: It is more advantageous for machine transplanting to select sowing rate of 60g/ plate,24 d seedling age and planting density of 30cm×16cm to play the potential of hybrid rice production,achieve stable yield and increase,and obtain higher economic benefits. |
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