Mechanized Seed Production of Xinhunyou No.6 through Mixed Seeding of Parents’Seeds

Dewen ZHANG，Jinlong Nl，Wanlin WANG，Dahu Nl，Qianjin YANG，Wei ZHANG

Rice Research Institute，Anhui Academy of Agricultural Sciences，Hefei 230031，China

Mechanized Seed Production of Xinhunyou No.6 through Mixed Seeding of Parents’Seeds

Dewen ZHANG*，Jinlong Nl，Wanlin WANG，Dahu Nl，Qianjin YANG，Wei ZHANG

Rice Research Institute，Anhui Academy of Agricultural Sciences，Hefei 230031，China

Hybrid rice Xinhunyou No.6 could be cultivated by mixing male and female parents and performing seedling raising followed by transplanting，mechanical planting or mechanical direct seeding according to the production methods of commercial rice.During flowering stage，leaf cutting，application of"920"and pollination were conducted；after pollination，bentazon with a certain concentration was sprayed to kill the male parent；and the hybrid rice was harvested mechanically.Before storage，color separation was performed to remove little remaining male parent，thereby achieving whole-process mechanization of hybrid rice seed production.This study introduced mechanized seed production of Xinhunyou No.6 through mixedseeding from the aspects including mechanical direct seeding，seeding raising followed by transplanting and mechanical planting.

Xinhunyou No.6；Bentazone-sensitive；Brown marker；Mechanization；Seed production

The potential of yield increase in hybrid rice has been acknowledged worldwide and made a significant contribution to food safety.However，the seed production area of hybrid rice as well as promotion area has been reduced with the increase of seed production cost of hybrid rice in recent years.How to reduce the seed production cost of hybrid rice to thereby remove the market bottleneck of hybrid rice popularization is a urgent problem to be solved.The realization of mechanization of hybrid rice seed production［1］is an effective method for solving this problem［2］.

Xinhunyou No.6（XinanS/2E06）is a new hybrid rice combination bred by Rice Research Institute，Anhui Academy of Agricultural Sciences，which involves the steps of directing a bentazone-sensitive gene into a restoring line and directing a brown marker gene into a sterile line.The two parents of the combination have near durations from seeding to heading，thus enabling simultaneous seeding.Meantime，the male parent 2E06 contains the bentazone-sensitive gene，and could be killed after pollination；and the female parent has dark brown husk which is different with the male parent，and after mechanized harvest，remaining parent could be removed by color separation，thereby realizing whole-process mechanization from seeding to harvest［3］.Xinhunyou No.6 has the advantages of simple seed production process，less seed production cost，and high seed production yield，and is of great significance to promotion of hybrid rice popularization and guarantee of national food safety.

Production Target and Technical Route

Production target

The target yield of mechanized seed production was 4 500 kg/hm2，which was higher than conventional seed production yield by 30%.In addi-tion，the dosage of hormone was reduced by 30%，and the labor cost was reduced by more than 2 400 Yuan/hm2.

Yield components

Male parent:the number of effective panicles was 30 000/hm2，and the number of spikelets per panicle was 170；and Female parent:the number of effective panicles was 2 400 000 hm2，the number of spikelets per panicle was 170，the number of filled grain per panicle was 90，the setting percentage was above 50%，and the kilograin weight was above 26 g.

Technical route

The male parent and female parent of the combination were mixed at a certain ratio；seedlings raisingplus transplanting，mechanical planting or mechanical direct seeding was conducted；when heading began，“920”was applied to relieve stems from being wrapped by leaves；and when entering heading stage，bentazon was sprayed once every two days，3 times in total，to ensure that the male parent was killed.After the female parent was ripe，harvest was conducted mechanically.Color separation was carried out before storage to remove remaining male parent.

Combination Selection

Combination selection

“2E06”containing bentazon-sensitive（lethal）gene was selected as the male parent of the seed production combination，to ensure that the male parent could be killed after pollination in heading stage by spraying the herbicide；and “Xinan S” containing brown marker gene was selected as female gene.After harvesting，remaining female parent was removed by color separation.

Seed quality

Quality of parent seeds was controlled according to GB4404.1.In order to improve seedlingsurvival rate and uniformity and rice seedlings，it was necessary to conduct accurate seed selection before seeding as well as seed sterilization with strong chlorine.

Climate Condition

The daily average temperature was 24-30℃，and the temperature was 28-32℃ during flowering time； the relative humidity was 70%-90%；and during daytime，there was no three-day continuous rain，and the weather was breezeless or breeze.

Seedling Management

Mechanical direct seeding

Mechanical dry direct seeding

Fine soil preparation The paddy fields，which were on the lee side facing the sun and naturally separated with other paddy fields，were selected as the direct seeding fields for seed production by mixed seeding，with the four sides separated from rice not less than 500 m.Fine soil preparation were conducted until the soil was crushed and leveled.The purposes of soil tillage were deep ploughing，crushed soil，preservation of soil moisture and weeding，and a depth of 18-20 cm was proper.

Rational fertilization Pure N 150-210 kg/hm2（urea 330-450 kg/hm2），P2O575-105 kg/hm2（calcium superphosphate 750 kg/hm2）and K2O 120 kg/hm2（KCl 225 kg/hm2）were applied；organic fertilizer was applied as more as possible as the base fertilizer，the practical amount of which was calculated according to applied fertilizer types（such as different kinds of compound fertilizers，ammonium carbonate，urea and diammonium phosphate）and effective components contained therein at different locations.Among them，70%of P，K and N fertilizers were applied as the base fertilizer before rotary tillage；25%of the N fertilizer was applied in booting stage combined with irrigation；and the rest 5%was applied in heading stage followed by irrigation.

Seeding The male and female parents of Xinhunyou No.6 were mixed according to a weight ratio of 1:5（according to the tillering ability of the two parents and number of grains per panicle，to maintain the ratio between the numbers of spikelets per panicle of the two parents at about 1:4）.Before seeding，seeds were soaked for 2-3 h，then cleaned，and added with dry-cultivation nurse at a ratio of 1:3 to perform seed dressing followed by airing. The seeding quantity was 45-60 kg/hm2（dry seeds before seed dressing），and the depth of seeding was 3-5 cm.In case of drought weather，irrigation was performed after seeding to protect seedlings.

Weed control Spraying was carried out per hectare by adding water 750 kg into 20%butachlor+oxadiazon EC 2 250-3 750 ml，after seeding before emergence of seedling，or the herbicide could be mixed with 1 800-2 000 kg of fine wet soil，and this two methods were conducted before weeds came up out of the ground and under the condition of wet soil；after emergence of seedling，weeds in 1-2 leaf stage were killed by spraying the mixture of 20%bensulfuron-methyl·butachlor wettable powder 3 000 g and water 750-900 kg per hectare；in the stage of 4 leaves and 1 central leaf，spraying was carried out with the mixture of 10%Qianjin 1 500 ml and water 750-900 kg according to seeding condition；and after 5 leaf stage，it was necessary to increase the amount of applied chemicals properly.

Mechanical water direct seeding

Field preparation The selection of field was the same as"Fine soil preparation".

Soil preparation:soil preparation wasperformedaccording to such standards as flat cropland（with height differences not greater than 1 cun，no weeds and stubbles），mature mud（precipitated，not hard）and shallow water（no land exposed to air）.

Rational fertilization:Fertilization was carried out according to"Rational fertilization".

Ditching and bed formation:the bed width was about 3 m，the ditches had a width of about 20-50 cm and depth of 8-10 cm，and leveling was performed with a rake.Drainage was performed 2 h before seeding.

Seeding Since the utilization rate of seeds by water direct seeding was relatively low，it was necessary to improve seeding rate，to ensure sufficient basic seedlings.The seeding rate was 45-60 kg/hm2.It was necessary to weigh seeds and perform seeding uniformly according to rows in batches.

Water and fertilizer management

There was no water on border faces after seeding，and if the border faces cracked after emergence of seedling，running water was introduced and drained.In 2.5 leaf stage，shallow water was introduced，topdressing wasperformed with urea112.5-150kg/hm2，and in the 6th stage of young panicle differentiation，the panicle-spikelet fertilizer could be applied according to growth of seedlings.Field drainage was performed in time to prevent lodging of the female parent，generally at the time when a certain panicle number was reached，with the requirements of dense cracks at the boundary of field and exposure of white roots on field surface.

Application of paclobutrazol In order to effectively control lodging and increase tillers，paclobutrazolwas sprayed in 1.5-2 leaf stage in an amount of 375-450 g/hm2with the requirements of no water on border faces and one-time uniform spraying.

Chemical weeding Generally，a comprehensive control measure of agricultural control assisted by chemical agents was taken.The agricultural measures were promoting early emergence of seedling，early tillering and early closing of the crop combined with soil preparation for killing weeds，and after the young plants grew tidily，weed emergence was controlled by establishing a water layer.Chemical control often adopted the method of applying a herbicide without bentazon according to weed situation in fieldtwice，beforeseeding or after seeding before emergence of seedling and after emergence of seedling.

Control of pests and diseases in seeding stage For the control of pests and diseases，it was necessary to pay attention to the control of Lissorhoptrus oryzophilus and thrips，with Kuaishaling generally after emergence of seedling，and the control of sheath blight，borers and rice planthoppers，among which sheath blight could be controlled with Jinggang mycin wettable powder，borers could be controlled with fipronil，triazophos，etc.，and rice planthoppers could be controlled with imidacloprid.

Seedlings raising plus transplanting

Dry seedling raising

Seedbed selection Rice fields with fertility above the average and convenient drainage and irrigation on the lee side facing the sun beneficial to crop growth were selected.The ratio of rice seedbed to the field was about 1:2.

Seedbed preparation and fertilization In last autumn and winter，organic matters including pulverized stalks and shells （pulverized rice straws，bran，rapeseed hulls，dry branches and fallen leaves without pathogens）3-5 kg，fermented farm manure 3 kg，and calcium superphosphate 0.25 kg were applied per m2. The fertilizers were applied in batches into whole plough layer with a depth of 15-20 cm，and soil water was kept properly.If soil fertility was not improved in autumn and winter，it was necessary to utilize compost and fermented shit before winter，and they were applied 20-30 d before seeding in an amount according to above standard，and flattened by ploughing and harrowing.

Borders with a border width of 1.2-1.4 m，a ditch width of 35-40 cm and a ditch depth of 25 cm were formed with the requirements of loose elastic crushed soil with good water absorption capacity，flat border faces，no broken stones and no weeds.Fertilization was performed 15-20 d before seeding according to urea 50 g，calcium superphosphate 100 g and potassium chloride 20 perm2of seedbed，and ploughing wasperformed for 2-3 times to mix the fertilizers with the 10-15 cm soil layer.The fertilization before seeding also could adopt thefertilizerspecial for rice in an amount of 40 kg/hm2.In addition，it was advised to avoid application of chemical fertilizers in 5 d before seeding.The application of growth promoting hormone in upland rice nursery according to product instruction could simplify fertilization operation and achieve a good effect.

Quality of raised seedlings At the seeding age of 30-40 d，in 6-8 leaf stage，individual plant had 1-3 large tillers，and the seedlings were upright，strong and green，with many short roots，free of pests and diseases.

Seeding time Seeding was carried out in Hefei on May 20，to ensure that heading began in early or middle August.

Seeding rate The sowing quantity of mixed parent seeds for the seed production field was 22.5 kg/hm2.The seeding rate for net seedbed was 50-75 g/m2.

Pregermination of seedling by presoaking The seeds of male and female parents were mixed at a ratio of 1:5 and dried in the sun before soaking of seeds.After winnowing，the seeds were soaked with 1:500 strong chlorine for 24 h，cleaned with clear water and then soaked in clear water for 24 h，and pregerminatoin of seedling was conducted at 28℃ followed by sowing.In addition，the seeds also could be soaked in antibacterial agent 402，whose concentration was 400-500 times generally.The seeds was soaked until they were transparent，and flushed to no extraneous odor to perform pregerminatoin of seedling. After the husks were broken and kernels were exposed，the seeds were spread for cooling.

Seeding The seedbed was sprayed with 50%fenaminosulf 2.5 g/m2mixed with water 1.5 kg，to sterilize soil；and watering was performed repeatedly until water began to leak from soil. Seeding were performed quantitatively according to border.After seeding，a layer of sieved soil without fertilizer was covered on seeds，and border faces were wetted with water and covered with films or straws to keep water.

Seedling management Before emergence of seedling，water perseverations was important，a sealing or covered state was kept substantially，and the temperature within films was no greater than 35℃.The films were removed gradually in 1.5-2.5 leaf stage to reduce the temperature. There was no need to water seedbeds generally，but if it was observed that seedlings had no water drops thereon in the morning and was slightly rolled in the noon，it was necessary to perform watering at dusk thoroughly.In case of rain，the seedbed was covered with films or subjected to drainage by ditching deeply.

In 1 leaf stage，the seedbed was sprayed with 15%paclobutrazol 0.3 g/m2mixed with water 150 g uniformly. Dressing at weaning stage was conducted by spraying urea 10g/m2mixed with water 2.5 kg，followed by washing seedlings.If growth promoting hormone in upland rice nursery was applied before seeding，it was not necessary to apply paclobutrazol and to per-form dressing at weaning stage.Application of Songjiafei was conducted 3-4 d before transplanting by spraying urea 10 g/m2followed by washing seedlings.

Wet-bed seedling raising

Seedbed preparation Rice fields with fertility above the average and convenient drainage and irrigation on the lee side facing the sun beneficial to crop growth were selected.It was necessary to apply adequate base fertilizer（mainly containing fermented shed manure，people and animal excreta and various cake fertilizers）.Fermented organic fertilizer 7 500 kg/hm2，urea 225 kg/hm2，calcium superphosphate 600 kg/hm2and potassium chloride 150 kg/hm2were applied，carbofuran was used as the surface fertilizer in an amount of 30 kg/hm2，and sterilization was performed with chemicals，to create a good nutrition environment for seedling growth.Ploughing was performed after fertilization followed by water introduction and harrowing，to from an integral seedbed with a bed width of 1.5 m，a ditch width of 25 cm and a ditch depth of 20 cm.The bed face was stood for 6-12 h for seeding. Seedling board should be flat with good ventilation，drainage and irrigation conditions.The ratio of seedbed to field was of 1:10.

Seeding quality At the seeding age of 30-40 d，in 6-8 leaf stage，individual plant had 1-3 large tillers，and the seedlings were upright，strong and green，with many short roots，free of pests and diseases.

Seeding time Seeding was carried out in Hefei on May 20，to ensure that heading began in early and middle August.

Seeding rate Seeding rate:the sowing quantity of mixed parent seeds for the seed production field was 22.5 kg/hm2.The seeding rate fornet seedbed was 180-225 kg/hm2.

Method:the seedbed was sprayed with 50%fenaminosulf 2.5 g/m2mixed with water 1.5 kg，to sterilize soil；watering was performed repeatedly until water began to leak from soil. Seeding were performed quantitatively according to border. The seeds sankafter seeding，a layer of sieved soil without fertilizer was covered on seeds，and border faces were wetted with water and covered with films or straws to keep water.

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Seeding Quantitative seeding were performed according to border uniformly by sowing at first and supplementing then.The seeds sank and had three sides against mud after seeding.The seeds were covered with rice hull ash or wheat hulls after seeding.

Seedling bed management Before the stage of 2 leaves and 1 central leaf，seedlings were in heterotrophy stage，without the need of fertilization. Until 3 leaf stage，dressing at weaning stage were conducted skillfully taking fertility and the base fertilizer into consideration.Generally，1:3 diluted people and animal manure can be applied in an amount of 2 250-3 750 kg/hm2. Urea as the tiller accelerating fertilizer was heavily applied in male and female parent seedbed in an amount of 120-180 kg/hm2.After introducing water into the seedbed 3-4 d before transplanting，urea as Songjiafei was applied in an amount of 45-60 kg/hm2. Ditch irrigation was performed to keep wet without water on the border face in 2 leaf stage，and a shallow water layer was kept after 3 leaf stage.

Control of diseases，insect pests and weeds High-efficiency farm chemicals could be used according to conditions in the field 5-7 d before transplanting. The specific control measures were the same as above.

Field preparation and planting

Field selection The paddy fields，which were on the lee side facing the sun and naturally separated with other paddy fields，were selected as the fields for seed production bymixed seeding，with the four sides separated from rice not less than 500 m.

Base fertilizer The base fertilizer could be applied before plowing，and the surface fertilizer were applied after leveling by harrowing.The base fertilizer included fermented farm manure 15 000 kg/hm2or cake fertilizer 750 kg/hm2，urea 150 kg/hm2，calcium superphosphate 600 kg/hm2，potassium chloride 112.5 kg/hm2and zinc sulfate 7.5 kg/hm2.

Soil preparation After the harvest of previous crop such as rapeseed and wheat，soil was subjected to ploughing under dry conditions immediately with a depth of 15 cm，and dried in the sun for 3-4 d.Harrowing was performed after water was introduced，according to such standards as uniformly-mixed soil and fertilizers，crushed soil，mature mud （precipitated），height differences not greater than 3 cm，and no weeds and stubbles exposed.

Planting Transplanting was performed in late May in rotational rape fieldand in early and middle June in rational wheat field as early as possible.The row spacing and plant spacing were 20-27 cm and 13-17 cm，respectively，with a planting density of 240 000-270 000 holes/hm2，and seedlings was planted uniformly，shallowly，stably and linearly in the manner of planting one plant in one hole.One operation row wasleft every 6 m，and the basic seedlings were1 200 000-1 500 000/hm2.

Mechanical planting

Machine selection A walking type transplanter with a row spacing of 30 cm was selected.

Vigorous seedling indexes At the seeding age of 17-18d，in 3.5-3.8 leaf stage，seedlings had a height of 12-17 cm，were green in color，and grew uniformly，with about 3.5 leaves，free of pests and diseases.The base of stem was thick and elastic.The roots wound firmly，carrying soil with a thickness of 2.0-2.5 cm，and individual plant had more than 10 white roots. The density of mature seedlings was 1.5-3.0 plant/cm2.

Seedling raising technique

Seedbed preparation The fields with separated drainage and irrigation andconvenientmanagementwere selected as the base for seedling raising.

Plastic film and tray Soft tray:plastic trays with the specification of 58-28 cm were prepared at 375-450 trays per hectare.

Agricultural film:the seeding bed needed the agriculture film with a width of 1.4 m in amount of 4 200 m/hm2（i.e.，the seedling bed supplying seedlings for the field subjected tomechanical planting needed the agriculture film with a width of 1.4 m in amount of 51 m/hm2）.

Nutrient soil preparation Bed soil（nutrient soil）selection:the most suitable bed soil was vegetable garden soil，dry farmland soil（the soil taking from grassland and the wheat field sprayed with herbicide in the right season was not suitable）and rice field soil subjected to autumn plowing，winter ploughing and spring harrowing. The topsoil of plough layer was pulverized and sieved until the particle size was not greater than 5 mm and the particles with a particle size of 0.2-0.4 cm accounted for 60%of all the particles.During pulverization，if thesoil slices was too dry resulted，particle size after pulverization was too small，i.e.，the granular structure was destroyed，resulting in after seeding poor air permeability which was not good for germination，while too wet soil slices increased the difficulty of pulverization.

Dosage:qualified nutrient soil was prepared in an amount of 1 200-1 500 kg per hectare of field.Soil fertility build-up:in early February，fertilization was performed on the field where the nutrient soil was obtained with people and animal excreta or a fermented miscellaneous fertilizer 30 000 kg/hm2and a high-content compound fertilizer 375 kg/hm2；and after 2-3 times of continuous rotary tillage，the mature topsoil was sieved，and the sieved nutrient soil 100 kg was mixed with a rice seedling nutrient agent 1 kg.

Seeding board fabrication Seedling board specification:the border face was 1.4 m in width，the middle ditches had a width of 0.25 m and a depth of 0.15 m，and the ditches around the border had a width of 0.3 m and a depth of 0.25 m.

Seedling board quality:water was introduced 10-15 d before seeding，followed by ploughing，harrowing and ditching. After the formation of seedling boards，drainage was performed to harden the surfaces of the seedling boards；and leveling was conducted 2 d before seeding，and the boards were compacted sufficiently，with the requirement of solid，flat，smooth and straight board surface.

Area ofseedling boards:the seedling bed was designed according to the ratio of seedling boards to field of 1:100.

Seeding and seedling raising The treatment of seeds was the same as above，i.e.，seeds were subjected to cleaning with clear water， and pregermination till kernels were exposed.The sowing quantity was 45 kg/hm2.

Tray and soil laying:two trays were placed in parallel closely without void，with bottoms closely abutted on seedling board.Soil was then laid with a thickness of 2-2.5 cm and flattened with a smooth wood plate.

Ditch irrigation:ditch irrigation was performed to supply adequate basic water.

Seeding:Seeding was performed according to 150-160 g（germinated rice seeds）per tray，equivalent to 125-130 g of dry seeds（the amount at a germination rate of 90%，which increased or decreased by 2 g corresponding to increase or decrease of germination rate of 1 percentage）.

Coverage with soil，sealing with films and coverage with straws:the soil thickness was 0.3-0.5 cm，with the requirement of totally covering seeds. On the surfaces of the soft trays，one reed or other stalk was placed every 30 cm longitudinally along the seedling board （to prevent sprouts from rotting due to oxygen deficit，in case of rain before film uncovering which resulted in the condition of the agricultural films closely abutting on tray surfaces），and the agricultural films were covered on the trays with peripheries sealed.A layer of thin rice straws was covered on the films （to preventyoung seedlings from scalding by sunshine in the noon），capable of sunshading and reducing the temperature，thereby ensuring that the temperature within the films was controlled at 30-38℃.Afterwards，irrigation was carried out by introducing water flush with ditch top，and drainage was performed after all the seedling boards were wet，to thereby facilitate temperature control，moisture preservation and seedling growth promotion.Before the seedlings grew tidily，a water gap was formed to prevent submersion of seedling boards which might cause oxygen deficit and rotten sprouts.

Film uncovering and seedling training:films were uncovered 3-4 d after seeding when the seedlings grew tidily at dusk of a sunny day or at 8:00-9:00 a.m.of a rainy day，and irrigation was carried out by introducing water flush with ditch top，to supplement water in trays.

Water management of seedling field Before film uncovering，the tray surfaces were kept wet by supply water in case of lack of water；after film uncovering and before 2 leaf stage，irrigation was carried out by introducing water flush with ditch top to keep the tray surface wet and soil in the trays contained enough water under the condition of air permeable，to thereby facilitating root winding；and water in the ditches was kept at the level half of the ditch depth 3-4 d before transplanting to restrain the growth of seedlings，to thereby facilitate mechanical planting.

Topdressing of seedling field At the stage of 1 leaf and 1 central leaf，urea was applied in an amount of 60-90 kg/hm2in a uniform form or by mixing with water 15 000 kg/hm2.The Songjiafei was applied 3-4 d before seedlings were pulled outofthe seedling bed，with the caution that the dosage of urea was less than 75 kg/hm2.

Pest control Chloethrips oryzae（Wil.），rice planthopper，sheath blight，rice blast in seedlings and so on were controlled according to occurrence conditions.

Transplanting

Field preparation Soil preparation: soil preparation was performed according to such standards as flat cropland （with heightdifferences not greater than 1 cun，no weeds and stubbles），mature mud（precipitated，not hard）and shallow water（no land exposed to air）.

Application of sufficient base fertilizer:before ploughing under dry conditions，fertilization was performed as following:the organic fertilizer 15 000 kg/hm2，returned straw 1 500 kg/hm2，ammonium bicarbonate 300 kg/hm2，and a compound fertilizer （15%N，15%P and 15%K）225 kg/hm2.

Mechanized transplanting Planting was conducted according to a row spacing of 30 cm and a plant spacing 12 cm at a density of 270 000 holes/hm2，each hole was plantedwith 34 seedlings，and there were 10 200 000 basic seedlings.The mechanical planting depth was 1.52 cm，and the shallow the better.

Field management

Target Tillering began 5-7 d after planting and was vigorous 13-15 d after planting，and the effective tillersreached an expected target 20-25 d after planting；the ratio of the highest stem tiller number to panicle number was 1:1.2-1.3；in full heading stage，crops were closed with growth，and single stem had 4-5 leaves；and during harvest，the plants had green stalks and yellow grains.

Fertilization management The field with medium fertility was applied with total pure nitrogen amount 180-210 kg/hm2，P2O575-90 kg/hm2and K2O 165-195 kg/hm2.In the nitrogen fertilizers，the basic fertilizer accounted for 50%-60%，the tillering fertilizer accounted for 20%，and the paniclespikelet fertilizer accounted for 20%-30%；all the phosphate fertilizer was all used as the basic fertilizer；and in the case of the potassium fertilizer，the ratio of the basic fertilizer to the paniclespikelet fertilizer was 6:4.

The tillering fertilizer was applied using urea 75-112.5 kg/hm2，which also could be used as the surface fertilizer in case of dry nursery plus planting. In jointing stage，urea was applied according to seedling condition and weather condition in an amount of 60-75 kg/hm2（middle panicle type variety）.In booting stage （young panicle having a length of 1-2 cm），fertilization wasperformedwith urea75-90 kg/hm2and potassium chloride 75 kg/hm2.In low-fertility field，a leaf fertilizer or growth regulator could be sprayed in heading stage.

Water management Planting was performed with shallow water，which was naturally evaporated totally 4-5 d after planting，water was introduced again，and the return green fertilizer was applied followed by hand weeding and airing.Irrigation was then conducted and a shallow water layer with a depth of 2-3 cm was kept to promote tillering.When the total tiller number reached 90%of the anticipated panicle number，water was drained to slightly dry the field for multiple times，and if the growth was vigorous afterre-irrigation，drying was performed over and over again until jointing stage.A shallow water layer with a depth of 3 cm was kept 5-15 d before heading and 5-15 d after heading，before and after this，a wet condition and interrupted irrigation were kept，and such dry and wet alternated status was kept until yellow ripeness.Water supply was stopped 7 d before ripe.

Control of diseases and pests

Control principle The principle was prevention first and integrated control. The combination of resistant varieties was selected，sterilization was performed，and control of diseases and pests in nursery stage was strengthened by sowing with agricultural chemicals；it was necessary to avoid overfertilization，too-high seedling density，lodging or delayed senescence；consecutive irrigation and long-term deep irrigation were strictly prohibited；natural enemy protection and killing of weeds around field were paid attention to；and observation and prediction of diseases and pests were strengthened to apply agricultural chemicals at proper time in the manner of general control.General control were emphasized and strictly conducted in middle and late July and middle and late August according to NY/T5117.

Control ofdiseases and pests In tillering stage （from the end of June till early July）:when the rice planthopper presented a population density of 1 000 planthoppers per 100 hills and the rice leaf folder showed a density of 100 larvae per 100 hills，spraying was conducted with 8 000 unit of B.t powder 1 125 g/hm2or a B. t and monosultap mixed preparation（such as 51%Teshaming）plus 25% buprofezin powder 900 g/hm2mixed with water 600 kg uniformly.When center disease plants infected by leaf blight appeared，spraying was performed with 20%Yekuning1 500 g/hm2uniformly to control in time.

Booting stage-filling stage:whenthe rice leaf folder showed a density of 60 larvae per 100 hills，the rice planthopper presented a population density of 1 500 planthoppers per 100 hills，the diseased hill rate of leaf blight was 30%，and it was predicted that Chilosuppressalis was at the peak period of egg hatching，spraying was conducted with 40%chlorpyrifos EC 1 500 ml/hm2plus 90%monosultap 1 050 g/hm2plus 20%imidacloprid 60 g/hm2（effective dosage）plus 10%Zhenling EW 1 800 ml/hm2mixed with water 600 kg uniformly，and rice false smut was prevented 5-7 d before break period with Wenquning EC.For seed production field，more attention was paid to the control of rice kernel smut and rice false smut which were treated once more after a week in case of outbreak in last year.

Weeding A water layer with a depth of 5 cm was kept in the field 4-5 d after transplanting，to prevent weeds. The specific control measures were shown in the appendix A.

Application of“920”

In heading stage of the female parent（10%headed），spraying was carried out with“920”30 g/hm2mixed with water 30 kg；and in the morning of the third day，spraying was carried out again with “920”30 g/hm2mixed with water 450 kg.

Bentazon application

At the period when 50%of the male parent headed，the mixture of 48%bentazon 2 250 ml/hm2and water 675 kg was sprayed with a Gongnong15 type sprayer uniformly in a manner of fixed border with fixed quantity （or together with the application of “920”at the second time）. Bentazon was sprayed at the third day timely according to the dosage and usage of last time［4］.

Supplementary pollination

Pollination was conducted using ropes with plastic tubes，at the full blooming time of the female parent in the morning once every half hour everyday under normal weather，2-3 times in total for each day.If the weather was rough，the pollination time could be changed.Especially after rain，it was necessary to conduct pollination in time when most spikelets bloomed.

Removal of extraneous plants for ensuring purity

In seedling stage and before applying “920”，the field was examined row by row to remove various headed extraneous plants followed by hormone application.During pollination，examination was performed at flowering time by specially-assigned personrow by row to remove left extraneous plant.Before harvest，Removal of extraneous plants was performed carefully again.

Table 1 Cost comparisonYuan/hm2

Table 2 Benefit analysis Yuan/hm2

Harvest

Harvest was conducted at the end of yellow ripeness.Threshingand drying were performed in time with the cautions of not drying grains on sandgravel pavements，bituminous pavements and so onand avoiding sun exposure of thin layer spread on cement field.The dried grains were stored in time until the water content satisfied the standard.

Economic Benefit Analysis

Cost comparison

According to practical experiment appropriation expenditure of various seed production ways and market investigation，this study compared the production cost of multiple seed production ways，as shown in Table 1. From the point of consumption of means of production by the multiple seed production ways，mechanical dry direct seeding had the lowest cost of 6 333 Yuan/hm2，while conventional seed production showed the highest cost of 18 222 Yuan/hm2.

Benefit analysis

As shown in Table 2，the production values of seeds per unit area were calculated according to the theoretical yields of hybrid seeds （Table 1）produced by several seed production ways and the market price of hybrid rice seeds（40 Yuan/kg）.In comparison with conventional seed production，the economic benefit analysisshowed that the economic benefits of mixed seeding plus manual planting was the largest，and reached 63 852 Yuan/hm2.Therefore，it was advised to promote and popularize the way of mixed seeding plus manual planting for hybrid rice seed production.

［1］ZHANG DW（张德文），YANG QJ（杨前进），WANG SM（王士梅），et al.The production technology of seeds by mechanize of Hunzhi No.1（混制1号机械化混播制种技术规程）［J］.Chinese Agricultural Science Bulletin （中国农学通报），2008，24（10）:66-69.

［2］WANG WL（汪婉琳），ZHU QS（朱启升），WANG SM （王士梅），et al.A New breakthrough of mechanization hybrid rice seed production technology（杂交水稻机械化制种技术研究及组合选育进展）［J］.Journal of Anhui Agricultural Sciences（安徽农业科学），39（9）:5055-5056，5059.

［3］LIU YB（刘延斌），YANG YZ（杨远柱），LIU JF （刘 建丰 ），et al.Research progress of mechanization production of hybrid rice seed through parents’seeds mixed planting（杂交水稻亲本混播机械化制种研究进展）［J］.Crop Research（作物研究），2012，01:85-87.

［3］LIU YB（刘延斌），YANG YZ（杨远柱），LIU JF （刘 建 丰），et al.Research progress of mechanization production of hybrid rice seed through parents’seeds mixed planting（杂交水稻亲本混播机械化制种研究进展）［J］.Crop Research（作物研究），2012，01:85-87.

［4］ZHANG DW（张德文），CHEN DP（陈多璞），YANG QJ（杨前进），et al.Effect of spraying bentazon in different stages on seed production of Hunzhi No.1 （不同时期喷施苯达松对"混制1号"制种产量的影响）［J］.Journal of Anhui Agricultural Sciences （安徽农业科学），2007，35（11）:3212-3213，3215.

Responsible editor：Yingzhi GUANG

Responsible proofreader：Xiaoyan WU

杂交水稻新混优6号机械化混播制种技术

张德文*，倪金龙，汪婉琳，倪大虎，杨前进，张伟 （安徽省农科院水稻研究所，安徽合肥230031）

杂交水稻“新混优6号”可以将父母本种子按照一定的比例混合，按照商品水稻生产的方法，育秧移栽、机械插秧或机械直播等方法进行种植。开花时，割叶、喷施“920”，并赶粉，在母本授粉后，通过喷施一定浓度的苯达松杀死父本，并机械化收割。入库前通过色选技术去除少量残留的父本，从而达到杂交水稻制种的全程机械化。该文从机械直播、育秧移栽、机械插秧等几个方面分别介绍"新混优6号"机械化混播制种技术。

新混优6号；苯达松敏感；褐色标记；机械化；制种技术

安徽省农科院科技创新团队“杂交水稻机械化制种技术创新团队”（15C0108）安徽省农科院学科建设项目“适宜机械化混播制种的水稻种质资源创新”（14A0102）；科技部科技支撑计划“两系杂交水稻新品种选育及安全制种技术研究”（2012BAD07B01-3）。

张德文（1972-），男，安徽合肥人，副研究员，硕士，研究方向为水稻杂种优势利用研究，E-mail：zhangdewen0551@163.com。*通讯作者。

2015-08-25

Supported by Science and Technology Innovation Team of Anhui Academy of Agricultural Sciences （15C0108）；Subject Construction Project of Anhui Academy of Agricultural Sciences（14A0102）；Science and Technology Support Program of Ministry of Science and Technology（2012BAD07B01-3）.

*Corresponding author.E-mail:zhangdewen0551@163.com.

Received:August 25，2015 Accepted:November 29，2015

修回日期 2015-11-29