Effect Of High Nitrogen Compound Fertilizer On Carbon Metabolism And Mineral Nutrient Content Of Litchi Leaves

Litchi orchards in our country have problems such as unreasonable fertilization structure,single fertilizer types,outdated fertilization methods,and unscientific fertilization.Therefore,in order to explore the law of fertilizer requirement of litchi,this study adopted fertilization on litchi during the vegetative growth period（fertilization rate CK:0 g/plant,T1:5 g/plant,T2:10 g/plant,T3:15 g/plant,T4:20 g/plant,T5:25 g/plant）,analyzed the dynamic changes of leaf nutrient element content and leaf physiological changes,the main results are as follows:（1）Under the optimum fertilization amount（20 g/plant）,the leaf N element content was significantly increased after 4 days of fertilization,and the fertilizer efficiency could last for more than 58 days;the leaf P element nutrition level was significantly improved after 6 days of fertilization,and the fertilizer efficiency Sustainable for more than 50 days;leaf K element nutrition level increased significantly after 2 days of fertilization,and the fertilizer effect could last for more than 52 days;leaf Mg element nutrition level increased significantly after 4 days of fertilizer application,and the fertilizer effect could last for more than 44 days;leaf Zn element nutrition The level increased significantly after 2 days of fertilization,and the fertilizer effect could last for more than 24 days;the nutrient level of leaf Fe significantly increased after 2 days of fertilization,and the fertilizer effect could last for more than 66 days;the nutrient level of leaf B element significantly increased after4 days,and the fertilizer effect It can last more than 44 days.（2）The maximum levels of chlorophyll a content,chlorophyll b content,sucrose phosphate synthase activity,pyruvate kinase enzyme activity,nitrate reductase activity,soluble sugar content,and soluble protein content between the treatment groups The performance was T5>T4>T3>T2>T1,but the T5 treatment group showed yellowing of a few leaf tips after fertilization,and the phenomenon of macular degreening along the leaf edge direction,it is speculated that fertilization 25 g/plant is close to B Elemental poisoning interval.（3）The content of chlorophyll a in fertilization treatment is as follows:after 4 days of fertilization,the content of chlorophyll a in the litchi leaves begins to increase significantly,and there is not much difference between the T4 and T5 treatment groups.The content of chlorophyll a reaches the high level around 10 days,14-16 d is the highest content.After44 days,the chlorophyll a content attenuated to the same as CK.The content of chlorophyll b was as follows:after 2 days of fertilization,the content of chlorophyll b in litchi leaves began to increase significantly,and there was no significant difference between the T4 and T5 treatment groups.The content of chlorophyll b reached a high level around 8 days,and the highest value was 12-14 days,26-28 d,the chlorophyll b content attenuated to the same as CK.（4）The effect of fertilization treatment on sugar and protein content is as follows:soluble sugar content began to increase significantly after 4 days of fertilization,and reached the maximum value on 16-18 days,then slowly decayed,There was no significant difference between T4 and T5,but it was significantly higher than that of other treatment groups during the same period.The soluble protein content showed strong fluctuations.After 8 days of fertilization,the soluble protein content in the leaves began to increase significantly;the differences between the three treatment groups T3,T4,and T5 were not significant,but were significantly higher than those of other treatment groups and CK.It reached the maximum on the 16th day,and then began to decay volatility,and then decayed to the same level as CK after 70 days.（5）The effect of fertilization treatment on the activity of sucrose phosphate synthetase was as follows:on the 6th day after fertilization,the activity of sucrose phosphate synthetase began to increase significantly,the activity reached the maximum value at16-18 days,and the maximum T4 value was 57.94 mg h^-1﹒g^-1FW,T5 max 58.68 mg﹒h^-1﹒g^-1FW,the activity decayed to CK level at the longest 74 days.Through correlation analysis,it was found that the activity of sucrose phosphate synthase in litchi leaves was significantly positively correlated with the Zn content in the leaves,and extremely significantly positively correlated with the contents of N,P,K,Mg,Fe,and B.（6）The effect of fertilization treatment on pyruvate kinase activity is:after the 14th day of fertilization,the activity of pyruvate kinase in the leaves of the T2,T3,T4,T5treatment groups began to increase significantly,but the T1 treatment began only on the18th day.Its activity has been in a state of ups and downs,the activity reached the maximum value from 20 to 26 days,and the T4 treatment group reached the maximum value of 3.97 mg﹒h^-1﹒g^-1FW on the 22nd day.The activity of at 14-30 days is in the middle-high level range,which is equivalent to the T3 activity in the same period.After 58days of fertilization,the activity decreased to the same level as CK.The pyruvate kinase activity in the leaves of the T5 treatment group reached the highest activity value of 4.09mg﹒h^-1﹒g^-1FW on the 22nd day,fluctuates at a high activity level from 16 to 28 days.After 28 days,the activity begins to decrease,and then fluctuates within a small range for the next 18 days.The activity decreases to the same level as CK on the 76th day.The activity of pyruvate kinase in litchi leaves was significantly and positively correlated with the content of N,P and Mg in the leaves.（7）The effect of fertilization on nitrate reductase activity is as follows:the nitrate reductase activity of the treatment group leaves has been significantly improved,and the nitrate reductase activity of the CK group has been at a low activity level,with a small fluctuation during the test period.After the 8th day of fertilization,the nitrate reductase in the leaves of all treatment combinations increased significantly,and the activity reached the maximum value after 16-20 days.T3 maximum 61.48μg NO₂^-﹒h^-1﹒g^-1FW T4maximum 61.54μg NO₂^-﹒h^-1﹒g^-1FW,T5 maximum 61.77μg NO₂^-﹒h^-1﹒g^-1FW.The three treatment groups of nitrate reductase activity were not significantly different.After reaching the maximum value,the activity began to decay,and the activity of T5 decayed to CK level on the 76th day.Correlation analysis found that the nitrate reductase activity of litchi leaves had little correlation with Zn,Fe,and B,and had a very significant positive correlation with the elements of N,P,K,Mg,Fe,and B;it showed significant activity on the 8th day after fertilization rise.Finally,according to the dynamic changes of carbon and nitrogen metabolism and nutrient content in litchi leaves during the vegetative period,the following schemes are proposed for fertilization reference:（1）For litchi trees that have not undergone leaf diagnosis or whose leaf deficiency is not obvious after leaf diagnosis,we should apply a relatively safe fertilizer dose and apply thin fertilizer.The amount of fertilization should be 10-15 g per plant（Ingredients refer to this experiment）,and the top dressing should be carried out after 24 days.（2）For the litchi tree which was found to have insufficient alkaline N content in the plant after leaf diagnosis was the main cause of deficiency,it is recommended to apply 15 g/plant fertilizer,followed by 60 days of top dressing.（3）For the litchi tree which was found to have insufficient quick-acting P content after leaf diagnosis as the main cause of deficiency,it is recommended to apply 10 g/plant fertilizer,followed by 42 days of top dressing.（4）For the litchi tree which was found to have insufficient quick-acting K content in the leaves as the main cause of lack of nutrients,it is recommended to apply 20-25 g/plant fertilizer,followed by top dressing for 50 days.（5）For the litchi tree which was found to have insufficient exchangeable Mg content in the leaves as the main cause of deficiency,it is recommended to apply 25 g/plant fertilizer and top dressing after 46 days.（6）For the litchi tree which was found to have insufficient quick-acting Zn content after leaf diagnosis as the main cause of deficiency,it is recommended to apply 20 g/plant fertilizer,and then apply fertilizer 26 days later.（7）For the litchi tree which was found to have insufficient fast-acting Fe content after leaf diagnosis as the main cause of deficiency,it is recommended to apply 25 g/plant fertilizer,followed by 60 days of top dressing.（8）For the litchi tree which is found to have insufficient quick-acting B content in the leaves as the main cause of deficiency,it is recommended to apply 20 g/plant fertilizer.If it exceeds 25g/plant,it is easy to cause boron poisoning（2 years old）.After 50 days,fertilize again.