Effects of Machine-transplanted Density on Yield and Yield Formation of Lingliangyou104

Guang YANG，Jiana CHEN，Chenjian FU，Yuanzhu YANG*，Yingbin ZOU**.Hunan Ava Seed Academy of Sciences，Changsha 409，China；.College of Agriculture，HNAU，Changsha 408，PRC，China

Effects of Machine-transplanted Density on Yield and Yield Formation of Lingliangyou104

Guang YANG1，Jiana CHEN1，Chenjian FU2，Yuanzhu YANG1*，Yingbin ZOU2**
1.Hunan Ava Seed Academy of Sciences，Changsha 410119，China；
2.College of Agriculture，HNAU，Changsha 410128，PRC，China

IIn order to ascertain the suitable machine-transplanted density of Lingliangyou104 in Hunan，a field experiment was conducted in Mingyue Village of Lukou Town of Changsha County in 2013，and the effects of three machine-transplanted densities （D1:333 000 holes/hm2；D2:250 000 holes/hm2；D3:175 000 holes/hm2）on yield and yield formation of Lingliangyou104 were studied.The results indicated that the yield of Lingliangyou104 showed an increase tendency with the increasing of machine-transplanted density；the highest yield of Lingliangyou104 showed in D1 by 9.66 t/hm2，it increased by 12.2%and 22.4%compared with D2 and D3，respectively. Under high machine-transplanted density，Lingliangyou104 performed with more effective panicles，large index of leaf area，high probability of intercepting light radiation by canopy，and strong leaf photosynthetic capacity，thus increasing amount of dry matter production and high yield.

Machine-transplanted seedling；Density；Yield

W ith social and economic development and rural labor transferring to other industries and fields，rice planting has evolved from traditional manual transplanting to labor and cost-saving methods.For example，mechanized transplanting is one of the planting ways.Compared with traditional way，mechanized transplanting takes advantages，such as labor，time，and farmland saving，as well as yield and benefits increasing［1-4］.Nevertheless，as for transplanting of hybrid rice，it is necessary to make adjustments on mechanized transplanting technology suitable for conventional japonica varieties，in order to guarantee it can be adapted to hybrid rice characters and farming systems of planting areas［2］.

A rational planting density is important for rice cultivation with high yielding and good quality，which would not only coordinate population with individual rice growth by building rational population structure，but also improve efficiency of light energy utilization and prevent rice diseases［5-10］.It is a hot is sue to investigate transplanting density of hybrid rice in China，given the difference among regional climate conditions，cultivated varieties，soil fertility and fertilizer levels，the density should be adjusted according to circumstances to improve mechanized transplanting technology for hybrid rice.In this research，Lingliangyou104 was used to explore the differences of photosynthetic capacities，dry matter accumulation，and yield structure under different transplanting density，as well as characteristics of high-yielding cultivation，in order to provide references for its promotion in Hunan province and similar regions.

Materials and Methods

Materials and sites

The materials was Lingliangyou104，atwo-line Indica hybrid rice derived from the combination of Xiangling750S and Hua104，cultured by Hunan Research Academy of YahuaSeeds.The field experiment was conducted in Lukou town，Changsha county，Hunan province（28°24′54″N，113°12′52″E）.Furthermore，the preceding crop in the experimental field was rice.

Experiment design

The test designed three densities，including D1 （333 000 holes/hm2），D2（250 000 holes/hm2），and D3（175 000 holes/hm2）.Randomized block design with three replications was used，with the plot was 30 m2.N fertilizer was applied at 150 kg/hm2，divided into 50% base fertilizer applied before transplanting，40%tillering fertilizer applied 7 d after transplanting，and 10%additional fertilizer applied in differentiation phase of ear.P fertilizer（P2O5）was all applied at 56 kg/hm2as base fertilizer. K fertilizer（K2O）was applied at 105 kg/hm2，classified into base fertilizer at 50%and additional fertilizer at 50%. Seedlings were cultivated as per mechanized transplanting with specialized seedling cultivation with soft trays and sludge.Seeds were sown on March 27 and transplanted on April 13 with a riding-style paddy rice transplanter（2ZGQ-7D25）at 4-5 plants per hole.After transplanting，the seedlings were irrigated on time and it is notable that the irrigation frequency should be guaranteed but each irrigation should be at a small amount from seedling reviving to earring.When total seedling reached 80%-90%of predicted number，dewatering should be conducted for 7-8 d.During earring period，seedlings were irrigated in a small amount，followed by alternate wet/dry irrigation，but watering should be stopped 7 d before rice ripening.Other field managements were the same as local method.

Measured items and methods

Surveying on tillering The tillers of 10 plants in every plot was recorded every 5 d until full heading stage.

Dry matter and leaf area Six plants were sampled from every plot at middle tillering stage，booting stage，full heading stage，15 d after full heading，and ripening stage，respectively.Leaf length and width，leaf area （leaf length×leaf width×0.75），and leaf area index were evaluated.Before full heading，ground part of rice was harvested divided into stem and leaf，and after full heading，divided into stem，leaf，and ear.Weight of dry matter，and compute photosynthetic potential［9］and net assimilation rate［10］were measure after the treatment with 105℃30 min and dried at 70℃ until to get a constant weight.

Radiation interception rate of rice canopy At middle tillering stage，booting stage，full heading stage，and 15 d after full heading，photosynthetically active radiation，in and outside of rice canopy，was measured during 11:00-14:00 with canopy analysis system （Sunscan）.Totaling 4 sites in two directions were measured in every plot.With canopy bottom and external radiation ratio as light transmittance rate，the interception rate can be concluded as follows:Interception rate=1-Light transmittance rate.

Yield and yield components At rice ripening stage，5 m2plantswas harvested in every plot and dried with moisture content of 14%to measure yield.Meanwhile，30 plants were surveyed of the number of productive panicle per plant，and the number of spikelet per panicle，setting rate and thousand-grain weight were measured from 10 plant.

Data analysis

The test data were settled with Microsoft Excel 2003，followed by variance analysis with DPS V3.01 and comparisons of statistical significance with LSD 0.05.

Results and Analysis

Yield and yield components

As shown in Table 1，transplanting density had significant effects on yield and productive panicles of Liangliangyou104，and insignificant differences on thousand-grain weight and setting percentage. D1 Treatment yielded highest with 9.66 t/hm2，increasing by 12.2%and 22.4%compared with D2 and D3 treatment.It can be concluded from analysis on yield components that D1 took advantages in terms of the number of productive panicle，which was 28.1%and 50.7% higher compared with D2 and D3.

Tillering

Tillering dynamic rule and the days get to tillering-peak stage were coincide in different transplanting densities treatment（Fig.1）.As growth period advanced，tillers changed from increasing to decreasing.For instance，tillering achieved the peak at 39-44 d after transplanting and was the highest of D1 at 684.44 per m2，increasing by 21.8%and 63.1%compared with D2 and D3.

Table 1 Effects of different transplanting densities on yield and yield components of Lingliangyou No.104

Production of dry matter

Transplanting density had considerable effects on dry matter of Lingliangyou104 （Table 2）.Considering from different stages，transplanting density had little effects on dry matterin early growth stage，showing insignificant differences among treatments.After full heading stage，D1 treatment has the highest dry matter production （686.9 g/m2），significantly higher than that of D3.In general，total dry matter in D1 was 23.3%and 47.6%higher compared with D2 and D3，with significant differences among treatments.

Table 2 Effects of different transplanting densities on dry matter production of Lingliangyou No.104

Leaf area index and radiation interception rate of canopy

Leaf area index Leaf area index of rice dynamic changed from increasing to decreasing since tillering stage to the 15 d after full heading stage，and reached the highest value during booting to full heading stage （Fig.2）.Leaf area indices were 9，7 and 6 in D1，D2 and D3，respectively.Leaf area indices of D1 treatment was all the highest in the same period，and showed highest difference with that of D2 and D3 after full heading stage，which laid foundation for dry matter accumulation in later period of D1 treatment.

Radiation interception rate of canopy Radiation interception rate was growing with the increasing of transplanting density （Fig.3）.In the same period，D1 treatment has the highest canopy radiation interception rate，and the rate was72.28% ，90.36%，86.87%and 93.86%in middle tillering stage，booting stage，full heading stage and 15 d after full heading. The highest interception rate difference showed in middle of tillering stage，the rate of D1 was 11.67%and 25.91%higher than that of D2 and D3，respectively.However，as growth stage advanced，the differences among treatments is decreased.The rates in D1，D2 and D3 were 93.86%，85.69%and 85.35%at 15 d after full heading stage，respectively.

Photosynthetic potential and net assimilation rate

D1 treatment showed the highest photosynthetic potential from middle tillering to booting stage，which was 14.6%and 88.1%higher than that of D2 and D3，respectively.From booting to full heading stage，photosynthetic potential in D1 was 28.2%and 67.3% higher than with D2 and D3，respectively，with significant differences. From full heading to the 15t d after full heading stage，the photosynthetic potential also showed highest value in D1，which was 45.0%and 57.5%than D2 and D3，respectively.

The net assimilation rates all showed the highest value in D3 in different growth stages and showed significant differences from middle tillering to booting stage，and insignificant differences from booting to full heading stage and from full heading to the 15 d after full heading.

Table 3 Effects of different transplanting densities on photosynthetic potential and net assimilation rate of Lingliangyou No.104

Conclusions and Discussions

A rational transplanting density is an important cultivation measure for rice high yielding［11］.Given the low temperature，short vegetative growth stage，the period of productive tillering lasts short for early rice，it is necessary to guarantee transplanting density at transplanting with machines in order to improve the number of basic seedlings and productive panicles.The results in He et al.［12］showed that the density of mechanized transplanting of hybrid early rice should be set in the range of 208 300 to 277 800 holes/hm2and Wang et al.［13］believed that the densityshould be 238 100-277 800 holes/hm2. In this research，the maximum rice yield was achieved with density at 333 000 holes/hm2.On the other hand，with the decreasing of mechanized transplanting density，the number of spikelet per panicle and grain weight of Lingliangyou104 kept increasing，but the number of productive panicle，the number of basic seedling and the highest seedling number reduced，resulting in the declining of yield.It are inconsistent with the results of previous studies，the difference of rice cultivars and local climate could be the possible reasons.

The production of dry matter from earring to ripening stages is an important index for evaluating the quality of rice population［14］，which is under influence of the interception rate of canopy. On the other hand，leaf area index has effects on radiation interception capacity of canopy.In this research，the increasing of transplanting density significantly increases leaf area index and photosynthetic potential，so the production of dry matter enhanced dramatically，increasing rice yield，accordingly.

Nevertheless，it should be recognized that the curve result between transplanting density and yield was not concluded，so that it can not prove that the 333 000 holes/hm2is optimal density for Lingliangyou104 in Hunan. Nevertheless，333 000 holes/hm2can be taken as the center for density gradient setting in the further experiment. In addition， interannual changes should be well considered in order to determine the optimal transplanting density of Lingliangyou104 in Hunan Province.

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機(jī)插密度對(duì)陵兩優(yōu)104產(chǎn)量及產(chǎn)量形成的影響

楊 廣1，陳佳娜2，符辰建2，楊遠(yuǎn)柱1*，鄒應(yīng)斌2**
（1.湖南亞華種業(yè)科學(xué)研究院，湖南長(zhǎng)沙 410119；2.湖南農(nóng)業(yè)大學(xué)農(nóng)學(xué)院，湖南長(zhǎng)沙 410128）

為了探明陵兩優(yōu)104在湖南地區(qū)適宜的機(jī)插密度，于2013年在長(zhǎng)沙縣路口鎮(zhèn)明月村進(jìn)行了機(jī)插秧大田試驗(yàn)，研究了3種機(jī)插密度（33.3萬(wàn)、25.0萬(wàn)、17.5萬(wàn)穴/hm2）對(duì)陵兩優(yōu)104產(chǎn)量及產(chǎn)量形成的影響。結(jié)果表明：隨著機(jī)插密度的增加，陵兩優(yōu)104的產(chǎn)量呈增加趨勢(shì)，其中以33.3萬(wàn)穴/hm2的產(chǎn)量最高，為9.66 t/hm2，較25.0萬(wàn)穴/hm2、17.5萬(wàn)穴/hm2分別增加了12.2%、22.4%。在高機(jī)插密度下，陵兩優(yōu)104有效穗多，葉面積指數(shù)較大，冠層光輻射截獲率高，葉片光合能力強(qiáng)，有利于增加群體干物質(zhì)生產(chǎn)量而獲得高產(chǎn)。

機(jī)插秧；密度；產(chǎn)量

科技部農(nóng)業(yè)科技成果轉(zhuǎn)化基金項(xiàng)目。

楊 廣（1968-），男，湖南長(zhǎng)沙市人，高級(jí)農(nóng)藝師，研究方向?yàn)檗r(nóng)業(yè)技術(shù)推廣。陳佳娜（1990-），女，湖南婁底市人，碩士研究生，研究方向?yàn)樽魑镌耘嗯c耕作學(xué)。*同等貢獻(xiàn)作者。**通訊作者，E-mail：ybzou123@126. com；yzhuyah@163.com。

2015-01-04

2015-02-15

Supported by Agriculture Science Technology Achievement Transformation Fund of Ministry of Science and Technology.

.E-mail:ybzou123@126.com；yzhuyah@163.com

January 4，2015Accepted:February 15，2015