Effects Of Humic Acid On Physical Growth And Nutrient Solution Features Of Features Of Hydroponic Lettuce

In order to product hydroponic vegetables with low energy and high yield and good quality production,promote the development of soilless cultivation nutrient solution,explore the influence of humic acid application on physical growth,water and nutrient absorption of hydroponic vegetables and seek suitable inorganic-humic acid composite nutrient solution formula,this article carrys on research from the following aspects.All the tests used Lactuck sativa l.var.Ramosa Hort.as the test materials and composite nutrient solution were prepared adding different concentrations of humic acid into Japan yamazaki formula.First of all,we used the experiment of adding humic acid into hydroponic lettuce in the whole stages to study effects of humic acid application on growth,quality,the characteristics of nutrient and water nutrient utilization of hydroponic lettuce.Then through adding different concentrations of humic acid before harvest,we focused on comparing the different quality of lettuce regulation effects to the different humic acid.Finally,by the completely combination test,we measured the biomass and photosynthesis characteristic parameters of lettuce to study the influencing laws of humic acid on hydroponic lettuce photosynthesis.The main results were as follows:The results of the experiment of adding humic acid into hydroponic lettuce in the whole stages showed that FW and DW of hydroponic lettuce increased with the humic acid concentration rising with 0-1.41 mg/g.The nitrate and soluble sugar content of lettuce reduced obviously with the humic acid concentration raising,thus soluble protein and the VC content of lettuce increased first then decreased.At the condition of 1.41 mg/g concentration humic acid,water use efficiency(WUE)and use efficiency of mineral elements were highest.Humic acid was cushion for the nutrient solution pH value.The effect of humic acid application on nutrient absorption of lettuce was not significant.The ability to absorb inorganic nutrients was different with different humic acid concentrations treatments.By means of principal component factor(the yield,quality and nutrient absorption et.al)analysis,synthesize effect of high yield,water-saving,fertilizer production would achieve when humic acid with 1.41 mg/g concentration was added in Yamazaki formula in the whole stages.The yield of hydroponic lettuce showed a trend of decrease after the first increase with the humic acid concentration rising at 15 d before harvest.The peak value was respectively in 1.13 mg/g and 2.26 mg/g humic acid concentration The nitrate content of lettuce reduced obviously with the humic acid concentration raising,however,the soluble sugar and soluble protein increased gradually and the VC content of lettuce increased first then decreased.By means of principal component factor(the yield and quality)analysis,hydroponic lettuce would produce higher yield and improve quality when humic acid with concentration 1.13mg/g was added in Yamazaki formula.The FW,chlorophyll contents,net photosynthetic rate and chlorophyll fluorescence characteristics(F0?Fv/Fm and ?PSII)of hydroponic lettuce showed a trend of decrease with the humic acid concentration rising in the first stage.Humic acid damaged PSII optical system of seedling leaves,was not conducive to the growth of lettuce in the first stage.The FW,chlorophyll contents,net photosynthetic rate of hydroponic lettuce increasing with the humic acid concentration rising in the second stage.The chlorophyll fluorescence parameters change rule was not obvious.Adding humic acid in the second stage reduced the growth inhibition of photosynthetic electron transfer process.By means of principal component factor(the yield,chlorophyll contents,net photosynthetic rate,chlorophyll fluorescence characteristics)analysis,the first stage would not be added humic acid;completely combination test of the optimal treatment was four which the two phases concentrations of humic acid respectively were 0,1.68 mg/g.