Effects of Different Planting Densities on the Yield of Rice Developed from Seedlings Dry Raised in Plug Trays

Shurong XIN Xiuying YU Wenfan BIAN Qinglei ZHAO Li YAO1, Bing GUO Xibo WU Hongtao SHAN Ye TIAN1, Baogang ZHU Zhengtao YANG

Abstract ［Objectives］ This study was conducted to investigate the effects of different planting densities on rice tillering dynamics and yield.

［Methods］ The effects of different planting densities on rice yield were studied based on seedlings dry raised in plug trays.

［Results］ Planting density had obvious effects on tillering dynamics, number of panicles per unit area, number of grains per panicle and rice yield under the condition of seedlings dry raised in plug trays. Comprehensive analysis showed that the row spacing×hill spacing=25 cm×14 cm, that is, the planting density of 2.85×105 hills/hm2, achieved the highest yield, at 9 960 kg/hm2.

［Conclusions］ This study provides a scientific basis for optimizing rice cultivation techniques and achieving high yield and high efficiency in rice production.

Key words Seedlings dry raised in plug trays; Rice; Planting density; Yield

Received: March 9, 2020Accepted: May 9, 2020

Supported by Major Applied Agricultural Technology Innovation Project of Shandong Province (SD2019ZZ020); Key R&D Program of Shandong Province (2019GSF109078); Rice Innovation Team Construction Project of Shandong Modern Agricultural Industry Technology System (SDAIT-17-09); Innovation Project of Shandong Academy of Agricultural Sciences (CXGC2018E03); Youth Fund Project of Shandong Academy of Agricultural Sciences (2015YQN25).

Shurong XIN (1966-), female, P. R. China, researcher, devoted to research about rice cultivation and resource environment.

*Corresponding author. E-mail: 804212947@qq.com.

Rice planting density is an important factor affecting yield［1-2］. Within a certain range of planting density, the yield increases with the increase of planting density, but excessive planting density will lead to a decline in the population quality and a decrease in rice production. Previous studies have shown that a reasonable planting density can make the rice population in the paddy field fully and effectively use light energy and fertility, thereby ensuring the normal development of individuals and the coordinated development of the population, harmonizing the number of panicles per unit area and the number of grains per panicle, and ultimately increasing rice yield［3-4］. Therefore, proper transplanting density is one of the key factors to ensure high yield of rice. Existing related researches are mostly concentrated in the paddy field for machine transplanting of strong seedlings. For the suitable transplanting density of rice under the conditions of seedling dry raised in plug trays, no systematic research has been carried out in the Shandong rice area. In order to explore the effects of different planting densities on the tillering dynamics and yield of rice, a planting density experiment was conducted to provide a scientific basis for optimizing rice cultivation techniques and achieving high yield and high efficiency in rice production.

Materials and Methods

Experimental site and materials

The experiment was conducted in Hedong District, Linyi City, Shandong Province from May to October 2019. The area belongs to the Yishu River alluvial plain, and has a temperate continental monsoon climate, with an average annual rainfall of 800 mm , an average annual temperature of 13 ℃, and an average frost-free period of 200 d. The experiment used bowl trays to raise seedlings, and the tested variety was Lindao 16. The soil in the field to be tested was loam, and the basic fertility was total nitrogen 2.01 g/kg, alkali-hydrolyzable nitrogen 103.41 mg/kg, rapidly available phosphorus 43.7 mg/kg, and rapidly available potassium 102.6 mg/kg.

Experimental design

The experiment included two factors: row spacing and hill spacing. The row spacing was set at three levels of 20, 25, and 30 cm , which were designated A1, A2, and A3, respectively, and the hill spacing was set at three levels of 12, 14 and 16 cm, which were designated B1, B2 and B3, respectively. Nine treatments were formed, namely A1B1, A1B2, A1B3, A2B1, A2B2, A2B3, A3B1, A3B2 and A3B3. The experiment adopted random block design, with 3 replicates for each treatment, and the plot area was 50 m2 (5 m×10 m). Sowing was carried out on May 20 at a seeding rate of 5 seeds/hole, and the seedlings were transplanted on June 19. The specific experimental design is shown in Table 1.

Investigation items

On the day of transplanting, the number of tillers of the basic seedlings was recorded, and the tillering dynamics of each treatment was recorded on 10, 20, 30 and 40 d after transplanting. The number of panicles per unit area and the number of grains per panicle in each treatment were recorded in the maturation stage, and the yield per unit area was calculated.

Yield (kg/hm2) =Number of panicles (104 panicles/hm2)×Number of grains per panicle (grains per panicle) ×1 000-grain weight (g) ×10 000×0.85/1 000

Data statistics and analysis

Microsoft Excel 2007 software was used for data processing and analysis.

Results and Analysis

Effects of different planting densities on the tillering dynamics of rice plants developed from seedlings dry raised in plug seedlings

It can be seen from Table 2 that under the experimental conditions, the growth periods of various treatments with different transplanting densities were basically the same. Each treatment reached the maximum tillering period around 30 d after transplanting. Among them, the number of tillers was highest in treatment A3B3, reaching 212/10 hills, and the lowest in treatment A1B1, only 147/10 hills. However, after reaching the maximum tillering period, the number of tillers decreased in each treatment as more ineffective tillers appeared. At the heading stage, the number of tillers was still the highest in treatment A3B3, at 149/10 hills, and still the lowest in treatment A1B1, only 96/10 hills. It indicated that rice had the ability of self-regulating population, and the number of tillers of rice increased with the decrease of planting density.

Effects of different planting densities on the yield of rice plants developed from seedlings dry raised in plug seedlings

It can be seen from Table 3 that under different planting density conditions, the 1 000-grain weights of various treatments were completely the same, indicating that the 1 000-grain weight was not greatly affected by the planting density. Under the condition of the same row spacing, the number of panicles in each treatment decreased with the increase of hill spacing, while the number of grains per panicle increased with the increase of hill distance. However, under the condition of the same hill spacing, the number of panicles in each treatment tended to increase first and then decrease with the row spacing increasing, while the number of grains per panicle increased with the increase of row spacing. In general, the number of panicle was the largest in treatment A2B1 (row spacing×hill spacing=25 cm×12 cm, planting density:

3.33×105 hills/hm2), at 4.09 ×106 panicles, and the smallest in treatment A3B3 (row spacing×hill spacing=30 cm×16 cm, planting density: 2.09×105 hills/hm2), at 3.11 ×106 panicles. The number of grains per panicle was the largest in treatment A3B3 (row spacing×hill spacing=30 cm×16 cm, planting density: 2.09 ×105 hills/hm2), at 122.7 grains/panicle, and the smallest in treatment A1B1 (row spacing×hill spacing=20 cm×12 cm, planting density: 4.17×105 hills/hm2), at 96.7 grains/panicle. In terms of final yield, the yield was the highest in treatment A2B2 (row spacing×hill spacing=25 cm×14 cm, planting density: 2.85×105 hills/hm2), at 9 960 kg/hm2, and the least in treatment A3B3 (row spacing×hill spacing=30 cm×16 cm, planting density: 2.09×105 hills/hm2), at 8 644.5 kg/hm2. The above analysis showed that the number of panicles and the number of grains per panicle are two important factors that constitute rice yield. The highest rice yield was not achieved under the condition of the highest number of panicles or the largest number of grains per panicle, and only by properly matching the two factors could an ideal result be achieved.

Conclusions

The planting density of seedlings dry raised in plug trays had no effects on the growth period and 1 000-grain weight of rice. The planting density mainly affected the tillering dynamics of rice, which in turn affected the number of panicles per unit area and the number of grains per panicle, and ultimately affected the yield of rice. The optimal planting density of Lindao 16, the main planted variety in Linyi, was row spacing×hill spacing=25 cm×14 cm, that is, the planting density of 2.85×105 hills/hm2.

Shurong XIN et al. Effects of Different Planting Densities on the Yield of Rice Developed from Seedlings Dry Raised in Plug Trays

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Editor: Yingzhi GUANGProofreader: Xinxiu ZHU