Chengchun YANG，Hongxin LlN，Zhanqi YUAN，Yunping XlAO，Rengen LlUSoil and Fertilizer&Resources and Environment Institute，Jiangxi Academy of Agricultural Sciences/Key Laboratory of Crop Ecophysiology and Farming System for the Middle and Lower Reaches of the Yangtze River，Ministry of Agriculture，P.R.China/ National Engineering and Technology Research Center for Red Soil Improvement，Nanchang 330200，China

Effects of Ratio of Row Spacing to lntrarow Spacing on Yield and Nitrogen Accumulation and Utilization of Early and Late Rice

Chengchun YANG，Hongxin LlN*，Zhanqi YUAN，Yunping XlAO，Rengen LlU
Soil and Fertilizer&Resources and Environment Institute，Jiangxi Academy of Agricultural Sciences/Key Laboratory of Crop Ecophysiology and Farming System for the Middle and Lower Reaches of the Yangtze River，Ministry of Agriculture，P.R.China/ National Engineering and Technology Research Center for Red Soil Improvement，Nanchang 330200，China

［Objective］The aim was to provide a theoretical basis for the rational configuration of ratio of row spacing to intrarow spacing（RS/IS）of double-cropping rice.［Methods］With early rice ‘Ganxin 203’and‘Zhongjiazao 17’and late rice‘Ganxin 688’and‘WufengyouT025’as materials，the effects of RS/IS on yield，nitrogen accumulation and utilization were studied in the same planting density of 31.20×104hills/hm2. ［Results］The results showed that yield of early rice was higher in RS/IS2.8（30.0 cm ×10.7 cm）and RS/IS2.0（25.0 cm ×12.8 cm）treatment，and lower in RS/IS5.0（40.0 cm ×8.0 cm）and RS/IS1.3（20.0 cm ×16.0 cm）treatment，while late rice were higher in RS/IS5.0 and RS/IS2.0treatment，and lower in RS/IS2.8and RS/IS1.3treatment.Total nitrogen accumulation and apparent utilization ratio of nitrogen of early rice were higher in RS/IS2.0treatment and lower in RS/IS5.0treatment，while，for late rice were higher in RS/IS2.8treatment and lower in RS/IS5.0treatment. Nitrogen requirement for 100 kg grain production of early rice was higher in RS/IS1.3treatment and lower in RS/IS2.0treatment，while，for late rice were higher in RS/IS2.8treatment，lower in RS/IS5.0treatment. ［Conclusion］In sum，4 varieties of early and late rice obtained higher yield in 25.0 cm ×12.8 cm and lower yield in 20.0 cm × 16.0 cm，and total nitrogen accumulation，nitrogen requirement for 100 kg grain production and apparent utilization ratio of nitrogen were all lower in 40.0 cm×8.0 cm.

Rice；Ratio of row spacing to intrarow spacing；Yield；Nitrogen accumulation

P lanting density and nitrogenous fertilizer are two important factors regulating，controlling and affecting the growth and development，spatial distribution，canopy structure and yield formation of rice（Oryza sativa）populations.Previous study has indicated that planting density has more influence on crop canopy structure and function than other cultivation measures［1］.In different densities［2］，wide space between rows （large RS/IS）is beneficial to improving group ecological environment of multi-tiller-curved panicle rice variety，while narrow space between rows （small RS/IS） helps improve space utilization of few tillers-erect panicle variety.Summer maize［3］，for its different varieties and densities，the suitable values for constructing ideal canopy and achieving high photosynthetic efficiency are different.Nitrogen application［4］can improve the indexes of each leaf area，leaf angle and layered leaf area of different wheat varieties，moreover，its regulating effect on middle-leaf varieties is higher than compact varieties，because the yield-increasing potential of compact varieties［5］depends on larger leaf area index，blade photosynthetic efficiency，solar altitude and solar radiation intensity，etc.For different nitrogen fertilizer levels and planting densities，the optimum values of ratio of row spacing to intrarow spacing（RS/IS）of different rice cultivars are also different，for example，in the planting density and nitrogen fertilizer of 30.0×104hills/hm2and 225 kg/hm2，respectively，yield of double-cropping early rice‘Luliangyou 996’and‘Ganxin 203’were higher in RS/IS2.8［6］and RS/IS2.0treatment，respectively；while in the planting density and nitrogen fertilizer of 25.0×104hills/hm2and 240 kg/hm2，respectively，while yield of double-cropping late rice ‘Tianyouhuazhan’and‘Ganxin 688’were higher in RS/IS4.0［6］and RS/IS1.0 treatment，respectively.In the planting density and nitrogen fertilizer of 37.5× 104hills/hm2and 280.5 kg/hm2，yield of middle-season rice ‘Zaofeng No.9’was higher in RS/IS2.0［7］treatment.In the nitrogen fertilizer of 280.5 kg/hm2，yield of middle-season rice‘Honglianyou No.6’were higher in RS/IS2.3，RS/ IS1.6and RS/IS1.3treatment in the planting density of 19.5×104，27.0×104and 34.5×104hills/hm2，respectively. In the planting density and nitrogen fertilizer of 25.0×104hills/hm2and 280.5 kg/hm2，yield of middle-season rice ‘Fengyouxiangzhan’and‘Wuyungeng No.7’were both higher in RS/IS2.3treatment［9］.In the planting density，the ratio of RS/IS determines the horizontal distribution and coordinate of rice planting，regulates and controls the top three leaves gesture and photosynthetic gesture after heading，thereby playing an important role in yield formation.There have been many researches on the effects of ra-tio of RS/IS on rice yield formation，but the reports on the relationship between RS/IS and nitrogen accumulation and utilization of different rice varieties are few.Therefore，we illustrated the effects of ratio of RS/IS on yield，nitrogen accumulation and utilization of early and late rice in this study，to provide theoretical basis for the rational allocation of RS/IS.

Materials and Methods

Experimental materials

The experiments were done in Red Soil Institute of Zhanggong Town，Jinxian County，Jiangxi Province in 2011 and 2012.The experimental soil properties from early rice field were: pH 5.90，27.30 g/kg organic matter（OM），94.40 mg/kg available nitrogen（N），33.70 mg/kg available phosphorus（P）and 61.00 mg/kg rapidly available potassium （K）；and the soil properties from late rice field were:pH 4.92，25.60 g/kg OM，219.00 mg/kg available N，47.60 mg/kg available P and 34.00 mg/kg rapidly available K.The seedling raising pattern of early rice was dry seedbed，the sowing and transplanting dates were March 23 and April 23，respectively，basic seedlings were 3 seedlings/hill（did not contain seedling tillers）；while wet seedbed method was used for late rice，the sowing and transplanting dates were June 25 and July 26，respectively，basic seedlings were 2 seedlings/hill（did not contain seedling tillers）.

Experimental design

The split-split plot design was adopted for the experiment，the main plot was rice varieties and the split plots were divided into CK treatment and N fertilization treatment，the splitsplit plot with the area of 15 m2was ratio of RS/IS，repeated three times.Early rice varieties were ‘Ganxin 203’and‘Zhongjiazao 17’，and late rice varieties were‘Ganxin 688’and‘Wufengyou T025’.N application of CK group，early rice group and late rice group were 0，180 and 210 kg/hm2，respectively.For both early rice group and late rice group，P2O5and K2O application were 75 and 165 kg/hm2，respectively，and the transplant density was 31.20×104hills/hm2，4 kinds of ratio of RS/IS were designed as follows: 40.0 cm×8.0 cm （RS/IS5.0），30.0 cm× 10.7 cm （RS/IS2.8），25.0 cm×12.8 cm（RS/IS2.0）and 20.0 cm×16.0 cm（RS/IS1.3）.N and K fertilizers were used based on base fertilizer∶fertilizer for tillering∶fertilizer for head sprouting=5∶2∶3 and 4∶2∶4，respectively，P fertilizer was used as base fertilizer. Urea，calcium magnesium phosphate and potassium chloride （KCl）were used as N，P and K fertilizers.Other conditions were the same as high-yield cultivation technique.

Measured indexes

（1）N contents 5 hills stem tillers during the mature period were sampled for each plot，then the roots were cut off，and three parts of blade，stemsheath and spike of rice were wrapped to dry in the oven at 105℃for 15 min，after that maintained at 80℃until drying，finally weighed.The weighed samples were used to determine N contents in stem-sheath，blade and spike of rice.

（2）Yield and component 30 hills each plot were sampled to study effective panicles，based on this，grain number per spike，unfilled grain and 1 000-kernel weight were investigated. In each plot，200 hills rice were cut to dry in the sun and weigh.

（3）Data processing Based on Excel software，the average value of 2011 and 2012 data was selected to study.

Results and Analyses

Effects of ratio of RS/IS on yield and component of early and late rice

Effects of ratio of RS/IS on yield of early and late rice Yield of such four varieties as‘Ganxin 203’，‘Zhongjiazao 17’，‘Ganxin 688’and‘Wufengyou T025’of early and late rice were different in different seasons and different N fertilizer application（Fig.1）. Compared with CK group，yield of four varieties of early and late rice increased obviously after applying N fertilizer.Yield rule of CK group of four varieties of early and late rice was not obvious，while applying N fertilizer，yield rule were larger in RS/IS2.0treatment and smaller in RS/IS1.3treatment.Yield of early rice‘Ganxin 203’and‘Zhongjiazao 17’were higher in RS/IS2.8and RS/IS2.0treatment and lower in RS/IS5.0and RS/IS1.3treatment after using N fertilizer；for late rice‘Ganxin 688’and‘Wufengyou T025’，the yield were higher in RS/IS2.0treatment and lower in RS/IS5.0treatment under CK treatment，however，after using N fertilizer，the yield were higher in RS/IS5.0and RS/IS2.0treatment and lower in RS/IS2.8and RS/IS1.3treatment.

Effects of ratio of RS/IS on yield components of early and late rice

There was certain difference for early and late rice due to different variation rules of yield components in different seasons and different N fertilizer application（Table 1）.After increasing N fertilizer，effective panicles of such four varieties as‘Ganxin 203’，‘Zhongjiazao 17’，‘Ganxin 688’and‘Wufengyou T025’of early and late rice increased obviously，however，grain number per spike，unfilled grain and 1 000-kernel weight had little change. After using N fertilizer，effective panicles of early rice ‘Ganxin 203’and‘Zhongjiazao 17’were more in RS/IS2.0treatment and less in RS/IS1.3treatment；however，effective panicles of late rice ‘Ganxin688’and‘Wufengyou T025’in both N fertilizer and CK treatment were more inRS/IS1.3treatment and less in RS/IS5.0treatment.The grain number per spike of early rice in both N fertilizer and CK treatment were more in RS/IS2.8treatment and less in RS/IS1.3treatment；however，for late rice，under CK treatment，the number was more in S/IS1.3treatment and less in RS/IS2.0treatment，and under N fertilizer treatment，the number was more in RS/IS5.0and RS/IS2.8treatment and less in RS/IS2.0and RS/IS1.3treatment.From this，we drew the conclusion that the grain number per spike of early and late rice were both more in RS/IS2.8treatment.In CK treatment，the setting percentage of early rice was higher in RS/IS2.0treatment and lower in RS/IS5.0treatment，while for late rice was lower in RS/IS1.3treatment；in N fertilizer treatment，the setting percentage of early rice was higher in RS/IS2.8treatment and lower in RS/IS2.0treatment，while for late rice was higher in RS/IS1.3treatment and lower in RS/IS2.8 treatment. For 1 000-kernel weight，in CK treatment，early rice was heavier in RS/IS2.0treatment，while late rice was heavier in RS/IS2.8treatment and lighter in RS/IS2.0treatment；in N fertilizer treatment，early rice was heavier in RS/IS2.8and RS/IS1.3treatment，and lighter in RS/IS5.0and RS/IS2.0treatment，while late rice was heavier in RS/IS1.3treatment and lighter in RS/IS2.8treatment.

Table 1 Effects of ratio of RS/IS on yield components of early and late rice

Effects of ratio of RS/IS on nitrogen accumulation and utilization of early and late rice

After increasing N fertilizer，total nitrogen accumulation and nitrogen requirement for 100 kg grain production of such four varieties as‘Ganxin 203’，‘Zhongjiazao 17’，‘Ganxin 688’and‘Wufengyou T025’of early and late rice increased obviously （Fig.2 and Fig.3）.Under N fertilizer treatment，total nitrogen accumulation and apparent utilization ratio of nitrogen of the four varieties of early and late rice were lower in RS/IS5.0treatment under different RS/IS ratios （Fig.4）.Under CK treatment，total nitrogen accumulation of early rice ‘Ganxin 203’and‘Zhongjiazao17’was higher in RS/IS2.0treatment and lower in RS/IS1.3treatment，while late rice‘Ganxin 688’and‘Wufengyou T025’was higher in RS/IS1.3treatment and lower in RS/IS5.0treatment，under N fertilizer treatment，early rice was higher in RS/IS2.0treatment and lower in RS/IS5.0treatment，while late rice was higher in RS/IS2.8treatment and lower in RS/IS5.0treatment.Under N fertilizer treatment，for early rice，the nitrogen requirement for 100 kg grain production and apparent utilization ratio of nitrogen were higher in RS/IS1.3and RS/IS2.0treatment，respectively，and lower in RS/IS2.0and RS/IS5.0treatment，respectively；while for late rice，the nitrogen requirement for 100 kg grain production and apparent utilization ratio of nitrogen were both higher in RS/IS2.8treatment and lower in RS/IS5.0treatment.Above all，total nitrogen accumulation，nitrogen requirement for 100 kg grain production and apparent utilization ratio of nitrogen of the four varieties of early and late rice were all lower in RS/IS5.0treatment，which indicated that ex-cessive wide RS and excessive narrow IS will affect nitrogen and its use efficiency.

Conclusion

In sum，for early rice，the yield was higher in RS/IS2.8and RS/IS2.0treatment，total nitrogen accumulation and apparent utilization ratio of nitrogen were both higher in RS/IS2.0treatment，and nitrogen requirement for 100 kg grain production was higher in RS/IS1.3treatment，while for late rice，the yield was higher in RS/IS5.0and RS/IS2.0treatment，and total nitrogen accumulation，apparent utilization ratio of nitrogen and nitrogen requirement for 100 kg grain production were all higher in RS/IS2.8treatment.In this experiment conditions，there were 4 early and late rice varieties with higher yield in 25.0 cm×12.8 cm，lower yield in 20.0 cm×16.0 cm，and lower total nitrogen accumulation，nitrogen requirement for 100 kg grain production and apparent utilization ratio of nitrogen in 40.0 cm×8.0 cm.

Discussion

In recent years，with the continuous introduction of new rice high-yielding varieties，and the improvement of agricultural production conditions，the transplant density of rice has been decreased.However，because of the short growth duration and productive tiller stage of double-cropping rice in Southern China，so ensuring effective panicles and grain number per spike per unit area is the key for high-yielding cultivation of rice.It has been proved that planting method of wide row and short space for hybrid rice is superior to wide-narrow row planting［10］. Moreover，for single late japonica hybrid rice［12］，under the same field management，yield using the method of wide row and short space is also higher than that using conventional planting methods，and under the same densities，the yield under medium row-spacing treatment［9］is significantly higher than narrow spacing treatment. Some studies suggested that suitable transplant density and the method of wide row and short space［7］are beneficial to improving rice yield and quality，moreover，the method of wide row and short space is demonstrably better than the equidistance interplanting cultivation.Other studies found that the planting method of wide row and short space is helpful not only to highyielding cultivation of rice［12］but also to high-yielding cultivation of mat grass［13］. With the popularization of doublecropping super rice varieties and the continuously improvement of machine transplanting level of rice，the transplant density of rice is reduced in actual production，thereby the plasticity of row spacing and planting distance configuration is enhanced.Hence，rational ratio of RS/IS is favourable to ensuring rice yield.Based on the research，the results showed that yield of 4 varieties of early and late rice were higher in 25.0 cm×12.8 cm （ratio of RS/IS was 2.0）and lower in 20.0 cm×16.0 cm（ratio of RS/IS was 1.3），total nitrogen accumulation，nitrogen requirement for 100 kg grain production and apparent utilization ratio of nitrogen were all lower in 40.0 cm×8.0 cm（ratio of RS/IS was 5.0）.Therefore，in this experiment condition，in the planting density of 31.20×104hills/hm2，the planting way of 25.0 cm×12.8 cm （ratio of RS/IS was 2.0）was conducive to doublecropping rice production in Jiangxi.

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Supported by the Project of"Demonstration and Integration of Agricultural Non-point Source Pollution Prevention and Control Technology in Rice Production Areas of Southern Plain of China"Belonging to National Science and Technology Program for "Twelfth Five-Year"Plan （2012BAD15B03）；Youth Innovation Funds of Jiangxi Academy of Agricultural Sciences"Effects of Row-Spacing on Yield of Different Double-Cropping Rice Varieties and Its Mechanism"（2010-CQN004）.

.E-mail:lhxtfs@163.com

December 19，2014Accepted:February 3，2015