Effects of Cultivation Methods on Yield Formation and Photosynthetic Characteristics of Zhuliangyou 4024 and H You 159 as Doublecropping Rice

Licheng LIU , Liheng JING Rong LI, Chuan HE Shan HONG Huabing DENG*

1. Rice Research Institute of Hunan Agricultural University, Changsha 410128, China;

2. Hunan Rice Research Institute, Changsha 410125, China;

3. Leiyang Agricultural Bureau, Hengyang 421800, China

Transplanting is a tradition as apart of rice planting in China,with a history of 2 000 years[1].However,it is a complicated work requiring more labors with a low efficiency.Currently,lots of labor forces in rural areas are moving to urban areas,and the number of leftover labors drops dramatically,leading to shortage of labor in cultivating rice. Hence, it becomes necessary to research and develop simple cultivation technology to adapt to the situation of rural to urban migration, and formulate standard cultivation technology procedures at large scales. The seedling broadcasting technology was researched by Japan since the 1970s[2], and introduced to China in the 1980s[3]. For years of efforts, the seedling broadcasting technology develops maturely and a complete seedling broadcasting technology system has been formulated characterized by labor and timesaving and high efficiency and yield,on basis of research and extension. It is notable that the research and extension of seedling broadcasting technology is a kind of reform in rice culti vation history in China[4-5].The research took Zhuliangyou 4024, a hybrid early rice,and H you 159, a hybrid late rice,which was nationally approved,as test materials. Photosynthetic traits and yield and yield components of tested materials were compared under two cultivation methods, i.e., seedling broadcasting and transplanting in order to select optimal cultivation model of the two rice varieties and provide references for high-yielding cultivation of double-cropping rice in Hunan Province.

Test Materials and Methods

est materials

The test materials included Zhuliangyou 4024,a hybrid early rice, and H you 159, a hybrid late rice. The treatment with Jinyou 402 was a control variety of early rice and the treatment with Jinyou 207 was the controlvariety of late rice.

Test design

The test was conducted in an experimental field in Rice Research Institute of Hunan Agricultural University.Specifically, both of early and late rice were arranged as per seedling broadcasting and transplanting, with three repetitions according to split-plot design. It is notable that the cultivation method was dominant and the species was sub-dominant.Every test plot was 13.2 m2, where the planting density kept 300 000 plant/ha.Early rice was sown on March 26, followed by seedling broadcasting or transplanting on April 26. In contrast, late rice was sown on June 22,followed by seedling broadcasting or transplanting on July 22. In the research, early rice and late rice were grown on the same field,and other management was the same as double-cropping rice in local regions.

Measurement items and methods

Measurement of chlorophyll content of flag leaves(SPAD) After rice heading, chlorophyll content was measured with a chlorophyll meter(SPAD502);10 rice plants were signed in every test plot;SPAD values of upper, middle and down parts of flag leaves of main stems were measured to get means. It is notable that measurement proceeded once every 4 days.

Measurement of photosynthetic rate of flag leaves One flag leaf of main stem of three normal -growing plants were signed with a plate in every test plot in full-heading stage, 13 d after full-heading and mature stage to measure photosynthetic rate with a Li-6200 photosynthetic meter.

Yield and yield structure In mature stage,20 rice plants were transplanted from every test plot and the treatment of seedling broadcasting involved the rice at 0.48 m2to compute the number of productive tillers per unit area. For transplanting, 5 rice plants with the productive tillers number similar to average were collected and the rice in an area of 0.24 m2underwent seedling broadcasting in order to explore total grain number per panicle, the number of practical grain,and 1 000-grain weight. Subsequently, rice plants with an area of 10 m2were threshed of every test plot and water was measured after drying to convert into rice weight containing 14% moisture content in order to compute practical yield.

Statistical and analysis methods

Original data and maps were cleared with MS Excel 2003 and analysis of variance proceeded based on DPS data processing system.

Results and Analysis

Effects of cultivation methods on SPAD values of flag leaves of double-cropping rice

As shown in Fig.1,the changes of SPAD of flag leaves kept similar trend(increasing to decreasing) for the treatments with Zhuliangyou 4024, H you 159, as well as Jinyou 402 and Jinyou 207 in control groups.

Specifically,full-heading date was on June 20 in the treatment with Zhuliangyou 4024 as per transplanting and June 18 in the treatment as per seedling broadcasting.After full-heading, SPAD values of flag leaves kept slow growing and achieved the highest on June 28 for the two treatments.However, 20 d after full heading date,SPAD value declined remarkably of flag leaves. SPAD values of Zhuliangyou 4024 and Jinyou 402 of the treatment with seedling broadcasting were higher than that of the treatment with transplanting.In general,for either seedling broadcasting or transplanting,SPAD values of flag leaves of Zhuliangyou 4024 kept higher compared with Jinyou 402 since July 2.

As for late rice H you 159, fullheading date of the transplanting treatment was on September 8 , while the seedling broadcasting treatment was on September 6. SPAD value of flag leaves declined significantly 4 d after full-heading. Furthermore, the decrease continued increasing 16 d after full heading. Comparatively speaking,the SPAD value of the seedling broadcasting treatment was always higher than that of the transplanting treatment, and SPAD values of the former dropped slowly, which indicated that seedling broadcasting is conductive to maintaining high content of chlorophyll of flag leaves and delaying senescence, guaranteeing abundant nutrients transporting to grains and improving rice yield.

Effects of cultivation methods on photosynthetic rate of flag leaves

As shown in Table 1, photosynthetic rate of flag leaves of Zhuliangyou 4024 and Jinyou 402 maintained higher under the seedling broadcasting treatment 13 d after full-heading and in mature stage . Compared with Jinyou402, photosynthetic rate declined slowly of Zhuliangyou 4024 and kept higher in mature stage.

The photosynthetic rates of H you159 and Jinyou 207 both dropped after full-heading and the decrease maintained higher from the 13 d after fullheading to mature stage. Besides, the photosynthetic rates of the seedling broadcasting treatment kept higher compared with the transplanting treatment. Additionally, photosynthetic rate of H you 159 was extremely higher than that of Jinyou 207 on 13 d after full-heading date.

In general,the photosynthetic rate of flag leaves kept decreasing from full-heading stage, but the photosynthetic rate of the seedling broadcasting treatment was higher compared with the transplanting treatment,which incorporated that seedling broadcasting treatment would delay senescence of flag leaves,enhance photosynthetic rate and increase accumulation of photosynthate in grain-filling stage.

Table 1 The photosynthetic rate in flag leaf of Zhuliangyou 4024 and H you 159 under different cultivation methods μmol CO2/m2·s

Table 2 Yield and its components of Zhuliangyou 4024 and H you 159 under different cultivation methods

Effects of cultivation methods on yield and yield components of double-cropping rice

As shown in Table 2, the yield of Zhuliangyou 4024 reached 8.26 t/hm2under the seedling broadcasting treatment,which grew by 2.86%compared with the transplanting treatment,showing little differences. The yield of Jinyou 402 was 8.04 t/hm2under seedling broadcasting treatment,which was significantly higher than that of the transplanting treatment .Besides, the average yield of the treatments with Zhuliangyou 4024 was 5.85% higher compared with the control variety with Jinyou 402. According to further analysis on yield components, it can be concluded that the grains per panicle of Zhuliangyou 4024 and Jinyou 402 under seedling broadcasting treatment were both higher than that under transplanting treatments,but the effective panicles,setting percentage and 1 000-grain weight between seedling broadcasting treatments and transplanting treatments tended to change little. In addition, the effective panicles and 1 000-grain weight of Zhuliangyou 4024 were significant higher than that of the control variety Jinyou 402.

The yields of H you 159 and Jinyou 207 were 8.17 and 7.77 t/hm2respectively under seedling broadcasting treatment, which increased by 8.79% and 6.15% compared with the transplanting treatment , showing significant differences. What’s more, the cultivation methods have effects on the number of effective panicles and grains per panicle.For example,compared with the transplanting treatment,the number of effective panicles grewand panicle size decreased in the seedling broadcasting treatment.Compared with Jinyou 207, although the panicle size and the number of grain per panicle of H you 159 maintained smaller,the number of effective panicles and 1000-grain weight both increased, with yield increased by 3.98%.

In generally transplanting, the yield of the 4 rice varieties under seedling broadcasting treatment was higher than that under the transplanting treatment, which possibly caused by smaller damages in root,and faster resuming growth under seedling broadcasting treatment.

Conclusions and Discussions

The research showed that Zhuliangyou 4024, H you 159, Jinyou 402 and Jinyou 207 performed similarly in terms of SPAD values and photosynthetic rates . SPAD values and photosynthetic rates under seedling broadcasting treatment kept higher compared with the transplanting treatment after full-heading. In generally, photosynthesis of flag leaf under the seedling broadcasting treatment took advantage in compared with the transplanting treatment. On one hand, the content of chlorophyll in the seedling broadcasting treatment maintained higher after full-heading stage, which improves photosynthetic rate,increases accumulation of photosynthetic products[6]and guarantees the supply of nutrients for rice in grain-filling stage.On the other hand,for rice cultivated under seedling broadcasting,the content of chlorophyll declined slowly after full-heading stage, which is conductive to delaying senescence and keeping function of leaves and roots.

The research showed that the yields of Zhuliangyou 4024and Hyou 159 under seedling broadcasting treatment were higher than that of the transplanting treatment with 2.86%and 8.79% respectively. The seedling broadcasting treatment is conductive to the formation of effective panicles and obtaining high yield,that consistent with the results of Peng[7],Zhang[8]and Cai[9].

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