Effects of Different Seedling Raising Substrates on Quality of Rice Seedlings

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1. Tongcheng Rice Research Institute, Tongcheng 231400, China; 2. Anqing Planting Industry Administration, Anqing 246003, China

Abstract Five different seedling raising substrates were used to take the place of the nutrient soil to cultivate rice seedling mechanical transplanting in Anqing, Anhui Province. The emergence rate, survival rate, quality of aboveground parts of seedlings, root system and dry weight and fresh weight were surveyed and analyzed. The results showed that the rice seedling raising substrates could significantly improve the seedling quality and survival rate of mechanically transplanted seedlings, especially the seedling raising substrates produced by Anhui Province Lufu Agriculture Science and Technology Stock Co., Ltd. and Anhui Anqing Yike Seedling Material Co., Ltd. Finally, it is recommended to promote the seedling raising substrate in large area, to lay a solid foundation for realizing high yield, high quality, and high efficiency of rice.

Key words Rice, Seedling raising substrate, Seedling quality, Survival rate

1 Introduction

In recent years, the area of mechanical rice transplanting in Anqing City of Anhui Province has been expanding continuously. The preparation of nutrient soil and fertilization has become a bottleneck restricting the further expansion of large area of mechanical rice transplanting. The operation of replacing the nutrient soil with rice seedling raising substrate is simple. Simply through sowing the seeds and watering properly, users can raise the seedlings with developed roots, robust seedling plants, and thus realize dummy operation of mechanical transplanting of rice seedlings[1-4]. At present, there are many varieties of rice seedlings in Tongcheng City of Anhui Province. These varieties have played a positive role in reducing the labor intensity of rice mechanization, nutrient soil fertility, and accelerating the pace of industrialization. In order to explore the effects of these seedling raising substrates on the quality of seedlings, and grasp the seedling strengthening technology suitable for mechanical transplanting, we carried out a comparative study on the effects of different seedling raising substrates on the quality of mechanically transplanted seedlings in 2017.

2 Materials and methods

2.1ExperimentalvarietiesandsubstratesThe experimental variety was Y Liangyou 900, and the experimental substrates were substrates produced by Jiangsu Huai’an Chaimihe Substrate Fertilizer Co., Ltd., Anhui Anqing Yike Seedling Material Co., Ltd., Shandong Shangdao Biotechnology Co., Ltd., Anhui Province Lufu Agriculture Science and Technology Stock Co., Ltd., and Jinan Luqing Seed and Seedling Co., Ltd. and materials were fertility improved nutrient soil.

2.2ExperimentdesignThe experiment was designed with five treatments: J1 was substrate produced by Jiangsu Huai’an Chaimihe Substrate Fertilizer Co., Ltd., J2 was substrate produced by Anhui Anqing Yike Seedling Material Co., Ltd., J3 was substrate produced by Shandong Shangdao Biotechnology Co., Ltd., J4 was substrate produced by Anhui Province Lufu Agriculture Science and Technology Stock Co., Ltd., and J5 was substrate produced by Jinan Luqing Seed and Seedling Co., Ltd. and the fertility improved nutrient soil was taken as the control (CK). These six treatments were arranged randomly, no repetition was set.

2.3Seedlingraisingandseedlingbedstagemanagement

2.3.1 Seed treatment before sowing of the experimental varieties. The experimental varieties were sun-dried before sowing. Three days later, the seeds were soaked with prochloraz, and after germination, the seeds were dried for sowing.

2.3.2 Preparation of seedling bed. The area of the seedling bed was about 10 m2, and no water was poured during seedling raising, the seedling bed was high and the bed surface was flat.

2.3.3 Sowing. The sowing was carried out on May 15, 2017. Each plate was sown with 80 g dry rice seeds (or 100 g wet germinated rice). When sowing, the bottom substrate thickness was 2.0-2.5 cm, and the seed substrate thickness was about 0.5 cm. The principle was no leakage of seeds. Too thick substrate may lead to caking. The substrate seedling raising adopted the same variety of substrate to cover seeds, and the control adopted common nutrient soil to cover seeds.

2.3.4 Seedling bed management. The seedling raising plate adopted plastic hard plate with length of 60 cm and width of 25 cm. The plates were stacked within seedling raising greenhouse for 3 d, then placed in seedling bed for raising. Before emergence, the seedlings were covered with agricultural non-woven fabrics. Wet seedling raising method was used in seedling management, and other measures for water, fertilizer, pests and diseases were the same as conventional management, and the seedling age was 26 d.

3 Results and analysis

3.1EffectsofdifferentsubstratesonemergencerateandsurvivalrateofseedlingsIn 15 d after transplanting the seedlings, the emergence rate and survival rate of seedling raising substrate were surveyed. Each variety substrate selected two seedling plates, and each seedling plate selected 0.09 m2for survey and calculating the average value. From the survey results (Table 1), the emergence rate of the five treatments was higher than that of the nutrient soil, and the emergence rates of J4 and J2 were 7.7 and 7.2 percentage points higher than that of CK, respectively; the emergence rates of J5 and J1 were 4.2 and 4.9 percentage points higher than that of CK, respectively. From the perspective of the survival rate, the treatment was in the range of 81.6%-87.8%, and the survival rate of J4 and J2 treatments was 5.7 and 4.4 percentage points higher than that of CK, respectively. The survival rate of J3 and J5 was 0.2 and 0.5 percentage points lower than that of CK, respectively. Thus, it could be proved that the rice seedling raising substrate could increase the emergence rate and survival rate, especially J4 and J2 treatments had more obvious advantages.

Table1Effectsofdifferentsubstratesonemergencerateandsurvivalrateofseedlings

TreatmentEmergence rateEmergencerate∥%Growthrate∥%Rank Survival rateSurvivalrate∥%Growthrate∥%RankJ190.54.9483.31.23J292.87.2286.54.42J391.15.5381.6-0.55J493.37.7187.85.71J589.84.2581.9-0.24CK85.6-682.1--

Table2Effectsofdifferentsubstratesonthequalityofabovegroundpartsofriceseedlings

TreatmentLeaf ageLeafage∥leafGrowthrate∥%Seedling heightSeedlingheight∥cmGrowthrate∥%Leaf areaLeafarea∥cm2/plantGrowthrate∥%Basal stem widthStemdiameter∥cmGrowthrate∥%J14.00.429.20.55.50.90.370.05J24.00.425.3-3.45.91.30.390.07J33.4-0.225.4-3.34.3-0.30.340.02J43.80.225.7-3.05.81.20.410.09J53.90.324.9-3.85.30.70.350.03CK3.6-28.7-4.6-0.32-

Table3Effectsofdifferentsubstratesonthedryandfreshweightofriceseedlings

3.2EffectsofdifferentsubstratesonthequalityofabovegroundpartsofriceseedlingsFrom Table 2, it can be seen that the number of leaves, leaf area and basal stem width of the seedlings treated by substrates were greater than that of CK, but the increasing degree in different treatments was different. In terms of the number of leaves, the leaf age of J3 treatment was slightly smaller than that of CK (less than 0.2 leaves), while other treatments had more leaves than that of CK. Among them, the number of leaves treated by J1 and J2 substrates was 4.0 pieces, 0.4 pieces (11.11%) more than that of CK; in terms of the leaf area, the largest increase of leaf area was J2 and J4, respectively, 5.9 and 5.8 cm2/plant. The leaf area per plant increased by 1.3 and 1.2 cm2, respectively; the leaf area (4.3 cm2) treated with J3 substrate was 0.3 cm2less than that of CK. In terms of the basal stem width, the basal stem width of the seedlings treated by substrate raising was 0.02-0.09 cm thicker than the nutrient soil treated seedlings, especially J4 and J2 substrate treated seedlings, the basal stem width of J4 and J2 was 0.41 and 0.39 cm, respectively, 0.09 and 0.07 cm greater than that of CK. The thicker the basal stem width, the stronger tillering ability it has, and the more favorable for growth after transplanting. As regards the seedling height, except for the height of the seedlings treated by J1 was 0.5 cm higher than that of CK, the seedling height of the other four treatments were more than 3.0 cm lower than that of CK, and the seedlings with greater decrease of the height were treated by J5 and J2, respectively, up to 3.8 and 3.4 cm, respectively. The decrease of seedling height is favorable for preventing the seedlings from being injured during the mechanical transplanting and for extending the seedling hardening stage, but not favorable for rapid restoration and tillering of seedlings. According to the survey data of aboveground parts seedlings, the overall quality of seedlings treated by substrates was better than the nutrient soil treated seedlings. In other words, the substrate seedling raising is favorable for leaf growth, leaf area and basal stem width.

3.3EffectsofdifferentsubstratesonthedryandfreshweightofriceseedlingsAccording to Table 3, the fresh weight and dry weight of seedlings treated through substrate raising were greater than that of the nutrient soil treated seedlings. The increase of fresh weight of 100 seedlings was in the range of 3.97-41.81 g; the fresh weight of 100 seedlings of J4 and J2 treatments was 188.87 and 188.02 g, respectively, increasing by 41.81 and 40.95 g compared with that of CK (147.06 g), the growth rate was 28.42% and 27.85%, respectively; J5 treatment had the lowest growth rate, the fresh weight of 100 seedlings of J5 was 151.02 g, increasing by 3.97 g compared with that of CK, and the growth rate was 2.7%. In terms of the dry weight, the dry weight of J4 and J2 treatments was 27.81 and 27.51 g, respectively, increasing by 20.18% and 19.14% compared with that of CK; the growth rate of dry weight of J5 and J3 was small, increasing by 5.27% and 8.56% compared with that of CK. As to the fresh and dry weight, the ratio of fresh weight to dry weight of J1-J5 treatments and CK treated seedlings was 6.47∶1, 6.82∶1, 6.97∶1, 6.79∶1 and 6.20∶1, respectively. These data indicate that the moisture of seedlings treated by J3 substrate was slightly higher and the seedlings were more green, while the ratio of fresh weight to dry weight of CK was the smallest.

Table4Effectsofdifferentsubstratesontraitsoftherootsystem

TreatmentTotal number of roots per plantNumber of roots∥pcsGrowth rate∥%Length of the longest rootRoot length∥cmGrowth rate∥%Number of white roots per plantNumber of white roots∥pcsGrowth rate∥%J112.5-0.7910.6010.325.61J215.724.6012.517.9213.260.97J312.2-3.1710.2-3.779.617.07J415.422.2212.316.0413.665.85J513.35.5611.710.388.42.44CK12.6-10.6-8.2-

3.4EffectsofdifferentsubstratesontherootsystemandofriceseedlingsAccording to the data of Table 4, the total number of roots and number of white roots of seedlings treated by different substrates were larger than that of CK, but the degree of influence of different substrates was different. The total number of roots per plant of J3 and J1 treatments was smaller than that of CK, 0.4 and 0.1 pieces less than that of CK, the degree of decrease was 3.17% and 0.79%, respectively. The total number of roots of J2 and J4 treatments increased 3.1 and 2.8 pieces compared with that of CK, the growth rate was 24.60% and 22.22%, respectively. Compared with CK, the root length was basically the same as that of one treatment, and one treatment decreased (treatment J3 decreased by 0.4 cm, the rate of decrease was 3.77%), and three treatments increased. In J2 treatment, the longest root system (12.5 cm), 1.9 cm longer than that of CK, the growth rate was 17.92%; in J4 treatment, the longest root system (12.3 cm), 1.7 cm longer than that of CK, the growth rate was 16.04%; in J5 treatment, the longest root system (11.7 cm), 1.1 cm longer than that of CK, the growth rate was 10.38%. According to the number of white roots per plant, all substrate treated seedlings were larger than that of CK. From J1 to J5, the number of white roots increased by 2.1, 5.0, 1.4, 5.4 and 0.2 pieces, respectively, with an increase of 25.61%, 60.97%, 17.07%, 65.85% and 2.44%, respectively. Among them, the growth rate of J2 and J4 treatments exceeded 50%. The increase in the number of white roots indicates that the quality of the seedlings is good. After transplanting, the seedlings will rapidly develop and generate many branches, thus favorable for realizing high yield. This is an important indicator of the quality of the seedlings. Therefore, substrate can provide better environment for the growth of root system, and benefit the generation of many more root, and better roots, and accordingly hardening the seedlings.

4 Conclusions

In terms of the emergence rate and the survival rate of seedlings, the effects of J2 and J4 treatment were good, the emergence rate was 8.41% and 9.00% higher than that of CK, and the survival rate was 5.36% and 6.94% higher than that of CK. In terms of the quality of the seedlings, J1 and J2 treatments can effectively increase leaf growth speed, J2 and J3 treatments reduce seedling height, promote dwarfing and hardening of seedlings, and J2 and J4 treatments can increase leaf area per plant and increase the basal stem width, favorable for photosynthesis, promote the tillering and nutrient accumulation. As regards the effects of the seedling raising substrate on the fresh and dry weight of the seedlings, the fresh and dry weight of the seedlings was larger than that of the nutrient soil treated seedlings, especially J4 and J2 treatments, the fresh weight increased by 28.43% and 27.85%, respectively, increasing by 20.18% and 19.14% respectively. From the perspective of the effects of different substrates on the quality and number of the root system, the total number of roots per plant, the number of white roots, and the root length were larger in J4 and J2 treatments. Specifically, the growth rate of total number of roots per plant was 22.22% and 24.60%, the growth rate of number of white roots was 65.85% and 60.97%, and the largest growth rate of root length was 16.04% and 17.92%, respectively. The experimental results indicate that the substrate raising has a great effect on promoting the emergence of rice seeds, increasing the survival area and improving the quality of seedlings, so it is worth promoting this method. According to the existing experimental data, the rice seedling raising substrates could significantly improve the seedling quality and survival rate of mechanically transplanted seedlings, and the seedling raising substrates produced by Anhui Province Lufu Agriculture Science and Technology Stock Co., Ltd. and Anhui Anqing Yike Seedling Material Co., Ltd. have obvious advantages.