Effects of uniconazole rate on agronomic traits and physiological indexes of rapeseed blanket seedling

Mechanized transplanting of rapeseed(Brassica napus L.)blanket seedling is an innovative cultivation technology.Cultivating high quality blanket seedling to ensure high survival rate of seedling after transplanting is the key of the technology.The effects of different uniconazole rates of 0,0.5,1.0,1.5 and 2.0 mg/tray,spraying at one leaf and one heart stage,on selected agronomic traits,physiological indexes and survival rate of two rapeseed cultivars(‘Qinyou 100 and’Yangyou 90)were investigated in 2018 and 2019.Our results showed that the plant height decreased significantly with the increase of uniconazole rate.However,the collar diameter increased significantly with the increase of uniconazole rate up to 1.5 mg/tray,and the leaf area,dry weights of root and shoot increased with increased uniconazole rate up to 1.0 mg/tray.The root to shoot ratios,N concentrations of root and shoot with the uniconazole rates of 1.0 and 1.5 mg/tray were higher than those with other treatments.As uniconazole rate increasing,gibberellin(GA)and auxin(IAA)concentrations of root and shoot decreased,while abscisic acid(ABA)concentrations increased,and cytokinin(CTK)concentrations topped at uniconazole rate of 1.0 mg/tray and decreased thereafter.The seedling survival rates with 1.0 and 1.5 mg/tray were greatly higher than those in other treatments.Regression analysis suggested plant survival rate was positively related to CTK concentrations and negatively to GA concentrations of root and shoot.To achieve high survival rate after mechanized transplanting,our study revealed that the uniconazole applied at a rate of 1.0 mg/tray was recommended as the best,followed by 1.5 mg/tray.The findings would help to enhance qualities of rapeseed blanket seedling and to promote popularization of mechanized transplanting of rapeseed production.

Critical equation of seedling block falling off in transplanting process and the optimization experiment of rape blanket seedling transplanter

Considering both high efficiency and high seedling standing quality is a significant objective for crop mechanized transplanting.Rape blanket seedling transplanting is an innovative and efficient transplanting technique.However,falling off phenomenon has become a common problem facing rape blanket seedling transplanting fields that causes seedling standing quality decrease and restricts crop growth.In this study,the rape blanket seedling of Ningza-1838 varieties and 35 d of seedling age was taken as the research object.The critical falling off equations of seedling was established by dynamic analysis.Main factors affecting seedling falling off were obtained.The critical value of each factor was calculated which were as follows:the rotation speed of the planting mechanism was 24.6 rad/s,the substrate moisture content was 50.4%and the longitudinal picking seedling quantity was 14.7 mm.Taking the seedling falling off rate as evaluation index,the measured critical value of seedling falling off was determined by high speed photography experiment.Under the condition that substrate moisture content was 55%and the longitudinal seedling quantity was 15 mm,the seedling falling off rate sharply increased when the transplanting mechanism rotation speed was increased from 24 rad/s to 26 rad/s.Under the condition that the rotation speed was 22 rad/s and the longitudinal picking seedling quantity was 15 mm,the seedling falling off rate rapidly decreased when the moisture content was increased from 47%to 53%.When moisture content exceeded 53%,this exhibited no obvious change.Under the condition that the moisture content was 50%and the rotation speed was 22 rad/s,the seedling falling off rate swiftly raised when the longitudinal picking seedling quantity was increased from 14 mm to 17 mm.The experimental results showed that the seedling falling off rate increased significantly near the critical value.The experimental results showed that the seedling falling off rate changed significantly near the critical value.It proved that the model was correct.Response surface experiments with the Box-Behnken design were conducted to determine the optimal combination parameters,which were as follows:substrate moisture content was 56.24%,planting mechanism rotation speed was 22.04 rad/s,and longitudinal picking seedling quantity was 14.91 mm.At this time,the seedling falling off rate was 1.36%,which ensured that seedlings could be transplanted stably under the carrier of seedling needle.The verification test was conducted,and the working parameters were adjusted according to the optimization results in experiment.The results of verification test were highly consistent with the optimization solution.The present study may provide a theoretical method for improving seedling standing quality of rape blanket seedling,and laid a foundation for the popularization and development of rape carpet seedling transplanting.

Effects of Seed Rate on Root Twining Power and Seedling Quality of Machine-transplanted Super Rice

In order to investigate the effects of seed rate on root twining power and seedling quality of machine-transplanted super rice cultivars, Yongyou 12 and Zhongzheyou No.l, total 6 seed rates were arranged, and the growth characteris- tics, quality and root twining power of machine-transplanted rice seedlings were studied. The results showed that seed rate had great effects on root twining power and qualityof rice seedlings; with the increase of seed rate, the root twining power of rice seedlings was increased, but the quality of rice seedlings was significantly reduced; under the condition of high seed rate, rice seedlings were weak with less accumulate dry matter and nonuniform growth, and the proportion of weak seedlings was higher. When the seed rate of both rice cultivars was reduced by 10 g/tray, the average seedling height was increased by 0.5 cm, leaf age was increased by 0.1, stem base diameter was increased by 0.1 cm, and root number per plant was increased by 0.3. When the seed rate was increased by 10 g/tray, the accumulated dry matter per plant was reduced by 5.1 mg. With the increase of seed rate, the seedling quality of Zhongzheyou No.1 was decreased rapidly, and the proportion of weak seedlings was increased rapidly. However, Yongyou 12 has a larger elasticity in seed rate. When the seed rate reached to 50 g/tray, blanket seedlings of Yongy- ou 12 were nursed with uniform growth and higher quality, but the shoots were sparse with lower leaf area index. However, when the seed rate was up to 50 g/tray, blanket seedlings of Zhongzheyou No.1 were nursed with uniform growth and higher quality, as well as higher-density shoots. From a comprehensive point of view, the optimum seed rates of Yongyou 12 and Zhongzheyou No.1 were 65 and 50 g/tray, respectively.