| Mechanical rice transplanting is an inevitable choice in the course when the rice production technology enters into the period of transformation and upgrading. Raising rice seedlings is the key to mechanical transplanting. Recently, farmers usually used nutritional soil to raise rice seedlings, which had obvious deficiencies in our country. This study aimed to select rice seedling substrate for mechanical transplanting from seven different combinations, which used inorganic and organic substrates, agricultural wastes and soil as materials. Then we optimized the substrate. In order to explore the fertilizing levels, the effects of fertilizers application on the quality of rice seedlings were studied in this research. The results provided a theoretical basis for developing a newly rice substrate. The main results were as follows:1. The selected experiment of rice seedling substrates showed that the combination of perlite, soil and peat was suitable for raising rice seedlings. The comprehensive evaluation index of rice seedlings was higher than other treatments. Rice seedlings had the better index of agronomic performance and gained the higher biomass and nutrient accumulation.2. The result of the optimized experiment indicated that the physical and chemical properties of substrate(soil: perlite: peat =2:3:5) were appropriate. The emergence rate, plant height, stem diameter and leaf length of seedlings were better than other treatments; the seedling root also grew better than other treatments, such as the total root length, root surface area, root volume and root tips. The dry matter accumulation of the seedlings was also significantly higher than other treatments. Synthesized the whole factors, it indicated that the substrate of formula 4 was suitable for raising rice seedlings instead of nutritional soil.3. Effect of five nitrogen fertilizing levels(N 0 g/tray, 0.4 g/tray, 1.2 g/tray, 2.0 g/tray,2.8 g/tray) on rice seedlings quality and nutrient absorption were studied by the experiments. The results showed that with the improvement of nitrogen fertilizing level, the available N of substrate exhibited an exponent curve. The shoot fresh and dry matter and the root dry matter accumulation of rice seedlings increased in the low nitrogen levels, but inhibited growth in the high nitrogen fertilizing condition. The rate of seedlings and root activity decreased and the hydroponic root ability increased with the increased of nitrogen fertilizing levels. When the nitrogen was more than 2.0 g per tray, the emergence rate of rice dropped and the growth of root inhibited. N absorption characteristics under different nitrogen fertilizing levels showed that the content of N, N accumulation amount and N total absorption amount of each tray of the seedlings increased with the increased nitrogen fertilizer levels. The research also indicated that when nitrogen fertilizing was in a certain level, it can improve seedlings to uptake phosphorus, potassium, but under the high nitrogen fertilizing level, it suppressed the seedlings to uptake P and K.With increased of phosphate fertilizing levels, the aviliable P of substrate increased linearly. It promoted shoot growth and increased the shoot fresh and dry matter accumulation of rice seedlings. When the phosphate was more than 1.2 g per tray, the root ability descreased and the quality of seedlings was declined. P absorption characteristics of seedlings in this experiment showed that the content of P, P accumulation amount and P absorption amount of each tray increased with the increased phosphorus fertilizing levels. It had not significantly influence on N and K absorption.Under the different potassium fertilizing levels, the aviliable K of substrate increased linearly. Applying K fertilizer could promote the shoot growth of seedlings and dry matter accumulation, improve the emergence rate and root activity of seedlings. When the potassium was more than 1.6 g per tray, the quality of seedlings declined. In terms of potassium absorption, the content of K of seedlings increased, K accumulation amount and the K absorption amount of each tray increased in the low potassium fertilizing, and then not to increase.4. The effect of different Fe, Zn fertilizer levels on rice seedlings quality was studied in this experiment. It showed that applied Fe fertilizer could improve seedling quality, especially improved the shoot and root dry matter and soluble sugar content, enhanced the rooting ability of rice seedlings. The rice seedlings quickly turned green after transplanting. Applied Zinc fertilizer also could improve seedling quality, such as increased the seedlings dry matter and soluble sugar content, improved seedlings root ability and root activity. It also could improve the root growth of seedlings.In summary, the best substrate was made up of the pearlite, soil and peat(2:3:5) and applied 1.2 g N, 1.2 g P2O5, 0.8 g K2 O per tray, which provided the suitable environment for seedlings growth and achieved the goal for raising vigorous rice seedlings. |
