Effects Of Seedling Ages On Growth And Yield In Mechanical Transplanting Rice

This study was conducted with rice varieties Hyou518,Shengtaiyou9712 and Zhunliangyou608 as materials and the field experiment about the elasticity of seedling age of mechanized transplanting rice was conducted in Yanxi Town, Liuyang City, Hunan province in 2004.The study was aimed at determining the appropriate seedling age and provide evidence for realizing the high yield and high efficiency of mechanized planting rice through researching and comparing the seedling quality, mechanized transplanting quality, growth and development and yield formation of mechanized transplanting rice under different seedling age. The key outcomes are as follows.(1) With the extension of seedling age, the leafage, seedling height, base stem width, green leaf number per plant of mechanized planting rice all increased significantly. For example, the leafage of the 37-day-old seedling was one leaf more and the plant height was five to fifteen centimeters higher than that of the 25-day-old one. The overlength of seedling age led to bad seedling quality, higher plant height, more yellow leaf, less root number, which went against the growth and development of mechanized transplanting rice.(2) The seedling age had obvious effects on the transplanting quality of mechanized transplanting rice. With the extension of seedling age, the percentage of seedlings, omission, floating, lodging and bending increased significantly. For example, the 25-day-old seedlings were 1% to 2%,0%,10% and 7% respectively, but the 37-day-old seedlings were 8%,4%, 20% and 15% respectively.(3) Different seedling age had certain effects on the population dynamic growth and population qualities of mechanized transplanting rice. With the extension of seedling age, leaf age number increased correspondingly, tiller number showed a gradual decrease and the difference between the maximum tiller phase and the valid tiller phase gradually decreased. There was a significant difference among different seedling age treatment. With the extension of seedling age, LAI decreased and the LAI of the 25-day-old seedling was significantly bigger than that of the 37-day-old seedling. With the extension of seedling age, dry matter accumulation gradually decreased, which indicated that short seedling age treatment had a higher dry matter accumulation than long seedling age treatment and it was easier for short seedling age to achieve high yield.(4) For mechanized transplanting rice of different seedling age, the net photosynthetic rate of flag leaf showed, as a whole, a decrease with the extension of seedling age. In booting stage, full heading stage and the 15 days after full heading stage, the net photosynthetic rate of the 25-day-old seedling all higher than that of the 37-day-old seedling. With the extension of seedling age, the light transmittance ratio of the canopy of mechanized transplanting rice decreased significantly. Long seedling age resulted in lower light transmittance ratio of the canopy and poor ventilation and light, therefore there could not be a better population structure, which affected the increase of the yield.(5) All the seedling age treatments had different sowing phases, but had a same transplanting phase. With the extension of seedling age, the older seedling had a longer returning green stage and the initiation stage, full heading stage and mature stage put off respondingly. The number of days of growth period showed the same trend:25-day-old< 28-day-old< 31-day-old< 34-day-old< 37-day-old.The seedling age of mechanized transplanting rice all had significant effects on the yield, panicle per square meter, spikelet number per panicle, seed-setting rate and 1000-grain weight and all of them decreased significantly with the extension of seedling age:25-day-old>28-day-old>31-day-old> 34-day-old>37-day-old.The results indicated that seedling age had a very significant effect on mechanized transplanting rice:the shorter the seedling age, the higher the yield, and vice versa.