Study On High-yield Formation Rules And Quantitative Cultivation Of Machine-transplanted Double Rice

Mechanical transplanting for rice have become increasingly attractive in recent years in China because of the transfer of rural labor force and the development of family farms and rural cooperatives.While limited information is available on the high-yield formation rules and quantitative cultivation of machine-transplanted double rice.Therefore,some field experiments were conducted in Jiangxi Province in 2013–2015 to determine characteristics and leaf-age-model parameters of high-yield cultivars,high yield group formation rules and quantitative indices,safe production dates,index of strong and healthy rice seedling,parameters of basic population formulae and row-spacing,and nitrogen management technology of machine-transplanted double rice.Then it could provide theoretical and technical basis for high yield cultivation of machine-transplanted double rice.The main results were showed as following:Part 1 Characteristics and leaf-age-model parameters of high-yield cultivars of machine-transplanted double riceFor machine-transplanted early rice,the average leaf numbers of main stem(N)was10.7–12.2,with change amplitude of 10–13,elongated internode number(n)of 4,and the stage of tiller equal panicle was N-n+1.For machine-transplanted late rice,the N,change amplitude,n and stage of tiller equal panicle were 14.4–15.2,14–16,5,and N-n,respectively.High-yield cultivars of machine-transplanted double rice were characterized by medium tillering ability,high earing rate,powerful abilities of dry matter per stem and high leaf area inde(LAI)in mid and latter stages,large number of spikelets and high daily production.While some differences were existed between early rice and late rice.For machine-transplanted early rice,it was about 110–113 d of growth duration,75–79kg/hm~2/d of daily yield,115-135 spikelets per panicle,and big weight of grain(26–28 g for1000-grains).For machine-transplanted late rice,it was about 115–120 d of growth duration,78–82 kg/hm~2/d of daily yield,large number of the grains(130–150 spikelets per panicle),and 25–28 g for 1000-grains.Part 2 High yield group formation rule of machine-transplanted double riceWith the increase of yield level,the panicles,grains per panicle and total spikelets all increased significantly.While there was no significant difference in filled grain percentage and 1000-grain-weight.Between the total spikelets and grain yield,there existed a significant positive linear correlation.The basic characteristics of high-yield machine-transplanted double rice were enriching the amount of total spikelets by obtaining more and bigger panicles and keeping normal filled grain percentage and1000-grain-weight.High-yield group showed earlier and stabler growth at the early growth stage,achieved expected number of tiller at leaf age N-n+1 and N-n for early rice and late rice,and had appropriate number of peak tiller at the jointing stage,then increased the percentage of productive tiller and panicles number.Also,high-yield group had the characteristics of powerful abilities of dry matter,N absorption as well as high LAI at middle and late growth stages,and well coordination of grains to leaf area.Therefore,achieveing appropriate matter accumulation and nutrient absorption at the early growth stage,improving population growth rate at middle and late growth stages,and coordinating source-sink and yield structures were critical to yield formation of high-yield machine-transplanted double rice.Part 3 Quantitative indices of high yield group of machine-transplanted double rice at main growth stageDuring the studies on high yield group formation rule,the quantitative indices of high yield group of machine-transplanted double rice at main growth stage were also discussed.The main results were showed as following:1.The stage of tiller equal panicleFor machine-transplanted early rice,tillers number per hectare was 3.40–3.70 million,LAI was 1.4–1.6 and dry matter accumulation was 920–1080 kg/hm~2.For machine-transplanted late rice,tillers number per hectare was 3.45–3.80 million,LAI was 1.7–2.1 and dry matter accumulation was 1050–1300 kg/hm~2.2.Panicle initiation?stageFor machine-transplanted early rice,tillers number per hectare was 5.10–5.75 million,LAI was 3.2–3.7 and dry matter accumulation was 2200–2550 kg/hm~2.For machine-transplanted late rice,tillers number per hectare was 5.45–6.35 million,LAI was 4.8–5.4 and dry matter accumulation was 4000–4400 kg/hm~2.3.Heading stageFor machine-transplanted early rice,the effective number of panicle per hectare was3.35–3.65 million,430–485 million per hectare for the number of total spikelets,6.2–6.7for LAI,0.68–0.77 grain/cm~2 for grain-leaf area ratio,8220–9420 kg/hm~2 for dry matter accumulation.For machine-transplanted late rice,the effective number of panicle per hectare was3.35–3.70 million,430-500 million per hectare for the number of total spikelets,6.5–7.4for LAI,0.63–0.72 grain/cm~2 for grain-leaf area ratio,10100–11000 kg/hm~2 for dry matter accumulation.4.Mature stageFor machine-transplanted early rice,LAI was 3.5–4.0,dry matter accumulation after heading was 5650–6230 kg/hm~2 and 14250–14750 kg/hm~2 in the total.For machine-transplanted late rice,LAI was 3.4–4.2,dry matter accumulation after heading was 6200–6500 kg/hm~2 and 16050–16800 kg/hm~2 in the total.Part 4 Quantitative cultivation of Machine-transplanted Double Rice1.Safe production dates of double rice in Jiangxi ProvinceThe safe production dates and heat-light resources changed obviously between the first 15 years(1984—1998)and the second 15 years(1999—2013),and there exist certain differences among different regions.Compared with the first 15-year period,the safe sowing dates and transplanting dates of early rice in the second 15-year period were ahead of time.For late rice,the safe maturity dates were delayed obviously,while those of full heading delayed unobviously.Finally,the safe production season for double rice were extended significantly.The change characteristics of heat-light resources during the safe production season were temperature increasing obviously,accumulated temperature adding remarkably,and sunshine hours changing unobviously.According to the security of production and high use efficiency of heat-light resources,the current climate change is favorable to the development of machine-transplanted double rice in Jiangxi Province.Monitoring data showed that,there exist certain deviations between practical production dates and safe production dates,though the practical production dates were adjusted correspondingly in recent years.So the safe production dates under 80%guarantee rate over the past 30 years were obtained by each meteorological stations.The safe sowing dates of machine-transplanted early rice of different ecology regions from north to south,are 23~rdd March,21~stt March,16~thh March,respectively.Those of safe transplanting dates are20~thh April,16~thh April,13~thh April,respectively.For late rice,the safe full heading dates of different ecology regions from north to south,are 14~thh Septemper,15~thh Septemper,18~thh September,respectively;and the safe maturity dates are 22~ndd October,25~thh October,31~stt October,respectively.2.Index of strong and healthy rice seedling of machine-transplanted double riceIn our current study,field experiments such as seedling matrix,sowing density and transplanting seeding age were conducted to determine the effects of seedlings cultivation measures on seedling characteristics,mechanized quality and grain yield.Based on those experiments,the index of strong and healthy rice seedling of machine-transplanted double rice was obtained.The results showed that,under the condition of mixed matrix treatment and dry rice-nursery,a suitable sowing density and transplanting seeding age could be conducive to improving seedling characteristics,mechanized quality and grain yield.For machine-transplanted early rice,the transplanting seeding age should be controlled within 24 d,suitable sowing density was 2.0–2.5 grain/cm~2 and 2.5–3.0grain/cm~2 for hybrid rice and inbred rice,respectively.Index of strong and healthy rice seedling:about 3.0–3.6 of leaf age,14–17 cm of seedling height,more than 2.7 mm of stem base wide,more then 9 of shirane number,more than 30 mg of dry weight per plant,above 5.0 of strong seedling index,more than 75%of seeding rate planting percent,under2.7(inbred rice)and 2.0(hybrid rice)of the leaf age without tillering and above 7 of field root number per plant.For machine-transplanted late rice,the transplanting seeding age should be controlled within 21 d,suitable sowing density was about 2.0 grain/cm~2.Index of strong and healthy rice seedling:about 3.5–4.5 of leaf age,15–18 cm of seedling height,more than 3.2 mm of stem base wide,more then 13 of shirane number,more than 40 mg of dry weight per plant,above 9.0 of strong seedling index,more than 80%of seeding rate planting percent,under0.8 of the leaf age without tillering and above 13 of field root number per plant.3.Parameters of basic population formulae and row-spacing of machine-transplanted double riceCompared with the traditional“9 inches”transplanter,the new“7 inches”transplanter was conducive to improving yield for acquiring more panicles and total spikelets.Under the condition of row spacing in 25 cm,the proper row spacing for early rice was 12–14 cm and while for late rice was about 14 cm.For machine-transplanted early rice,the primary tillers initiated mainly from leaf 3 to leaf 6 on main stems with leaves 4 and 5 being the superior positions for tiller initiation and panicle formation.Secondary tillers initiated mainly in 1/3?2/3?1/4,but could not form panicles.The panicle number per seedling was 3.1 and 2.2 for hybrid rice and inbred rice,respectively.Panicles on both main stems and tillers of superior leaf positions showed better properties and higher productivity,thus making greater contributions to the yield.For hybrid rice mechanically transplanted at the stage with 3–4 leaves,the leaf age without tillering(bn)was 1.7–1.8,with the correction factor(a)of-1.2–-1.1 and the percentage of productive tillers(r)of 0.75.For inbred rice,the bn,a,and r were 2.5–2.7,-1.3–-1.1,and0.7,respectively.For machine-transplanted late rice,the primary tillers initiated mainly from leaf 3 to leaf 7 on main stems with leaves 3,4,5 and 6 being the superior positions for tiller initiation and panicle formation.Secondary tillers emerged from 3/0 to 5/0,such as 1/3,2/3,3/3,1/4,2/4,1/5,but panicles formed mainly in 1/3 and 1/4.The panicles earbeared mainly from primary tillers,and a few of secondary tillers could form panicles.The panicle number per plant was 4.5 or so for late hybrid rice in mechanical transplanting.Appropriate number of panicles per stem especially tillers of superior leaf positions is the premise of high-yield cultivation,which particularly increases the grain yield,not only the panicle numbers,branch numbers,the grain numbers,setting percentage,the grain weights,and the spike weights,but also for more harmonious yield factors.For late hybrid rice mechanically transplanted at the stage with 4–5 leaves,the leaf age without tillering(bn)was 0.7–0.8,with the adjusting factor(a)of 0.6 and the percentage of productive tillers(r)of 0.8 or so.The population calculated from basic population formulae was set as the middle population,one population of the higher and the lower were set respectively,and the yield and yield structure of these different basic population were compared.The results showed that the yield structure of the middle population was most harmonious as a whole and grain yield was the highest among the three treatments.The reserch primarily validated the correctness of basic population formulae and its parameters of machine-transplanted double rice.4.Nitrogen management technology of machine-transplanted double riceModerate amount of nitrogen fertilizer can increase effective panicle number and grain number per panicle,thereby increase spikelet number.For machine-transplanted double rice,the optimal nitrogen application amount was 180 kg/hm~2 for eaily rice and 195kg/hm~2 for late rice,while maintaining high utilization rate of nitrogen absorption and yield.Ratio and period of nitrogen application had significant influences on yield and nitrogen absorption.The optimal ratios of nitrogen application were 8?2 to 7?3 for early rice,and 7?3 for late rice.Appropriate time for top application of nitrogen was 7 days after transplanting and the stage of the second leaf to top shooting out.The optimal ratios and time of nitrogen application can optimize the quality of group and increase effective panicle number and grain number per panicle,while maintaining high utilization rate of nitrogen absorption.