Preparation Of The Rice Husk Hydrolysate And Its Effect Of On The Growth Of Tomato

Silicon has been widely reported to have many beneficials on improving plant tolerance to stresses from drought,salts,fungi and mites,while nano silica（n Si O₂）can be applied as a plant growth promoter and crop pesticide with a very small dose.Rice husks contain 20%-25%of silica,which can be a biogenic n Si O₂ when suspended by alkaline hydrolysis of rice husks as reported.However,little has been known about the effect of the hydrolysate of rice husks on the growth of crops.This paper has studied the preparation of the hydrolysate of rice husks and its effect on the seed germination and plant growth of tomato（Solanum lycopersicum）and cucumber（Cucumis sativus L.）.The main results are as follows:（1）Results from the hysrolysis of rice husks showed that hydrolysis rates of rice husks were 5.07%,10.50%,18.43%and 16.41%,respectively,when the hydrolysis was done in 0mol·L^-1,0.5 mol·L^-1,1 mol·L^-1and 2 mol·L^-1KOH solution,while those rates were 4.03%,7.80%,14.33%and 13.63%,respectively when the ratios of solid to water were 1∶5,1∶6,1∶7 and 1∶8 during hydrolysis.Thus,the hydrolysis conditions are established as 1mol·L^-1KOH,solid to water ratio 1∶7,95°C without pressure vessel,and 1 h of reaction time。（2）Resuilts of seed fermination tests showed that the treatment of 100 times diluent of the rice husk hydrolysate increased germination rates,germinating index,vigor index,sprout and root lengths of cucumber seeds by 19.77%、11.80%、64.23%、26.61%、58.82%,respectively,as compared with the control with germination in water,while the same treatment increased germination rates,germinating index,vigor index,sprout and root lengths of tomato seeds by 25.79%、25.66%、65.22%、24.50%、38.08%,respectively.No inhibition of germination was found in the treatment of 10 times diluent of the rice husk hydrolysate.As compared with the control with germination in water,the treatment of 10mg·L^-1n Si O₂ significaantly increased the germination rates,but the treatment of 100mg·L^-1n Si O₂showed the best effect on seed germination and sprout growth of cucumber and tomato.However,the treatment of 500 mg·L^-1n Si O₂ showed significant inhibition on sprout growth of the seeds.（3）Results from the first season soil pot experiments showed that foliar application of rice husk hydrolysates significantly enhanced tomato growth and photosynthesis as well as soil nutrient contents.In seedling stage,the treatment of spraying 300 times diluent of the rice husk hydrolysate（D3）showed best performance with significantly higher stem diameter,chlorophyll content（SPAD value）,root length,root surface area and leaf area than the treatment of spraying 200 times diluent of the rice husk hydrolysate（D2）,but D2had significantly higher plant height,the maximal quantum yield of photosynthesis system II（Fv/Fm value）and actual photochemical efficiency in photosystem II（ΦPSII value）than D3.In fruiting stage,D2 showed best performance with significantly higher above-ground dry weight and under-ground dry weight than D3,suggesting that D2promoted tomato photosynthesis and increased nutrient supply.（4）Results from the second season soil pot experiments showed that both foliar and root application of the rice husk hydrolysates improved plant growth of tomato and soil nutrient status.Foliar or root application of 200 times diluent of the rice husk hydrolysate（the treatment PD2 or the treatment GD2）had better effect on plant growth than the other treatments,while foliar or root application of 100 times diluent of the rice husk hydrolysate（the treatment PD1 or the treatment GD1）had higher soil nutrient contents,suggesting that the rice husk hydrolysate could be used as a new type fertilizer.In conclusion,the rice husk hydrolysate contains silicon and the other plant nutrients,which promote tomato growth.However,the hydrolysate as a new type of silicon fertilizer need to be further explored.