| The banana grows in the tropic and subtropic regions and suffers high temperature and heavy rainfall which causes nutrients leaching and runoff during the plant growth.The banana plantation is small or the banana mainly cultivated by individual farmers who are lack of technology,especially knowledge of balanced fertilization.Therefore,phenomenon of banana malnutrition has been easily observed in banana orchards.Shortage of nutrients has been limiting factor for banana healthy growth.However,there are few reports on nutrition properties especially nitrogen(N),phosphorus(P),potassium(K),calcium(Ca),magnesium(Mg),sulfur(S)concentration,their accumulation,allocation and remobilization among the organs under shortage one of the six nutrients during the banana growth.Meanwhile,there is no detailed nutrient deficiency symptom of different nutrient at the same growth stage or the symptom of one element deficiency at different stages.In other word,the farmers expect typical picture and detail illustration of banana nutrients deficiency to carry out nutrition diagnosis.In order to carry out balanced fertilization during banana production,the influences of nutrient deficiency on nutrition status have been studied throughly and pictures of typical symptoms of different organs about nutrient deficiency been taken at different stage during banana growth by use of quartz sand culture.The main results are as followings.1.The nutrient deficiency leaded to obvious symptoms on the banana leaf firstly.The response time of bananas for different nutrient deficiency is in order of nitrogen deficiency > potassium deficiency and magnesium deficiency > sulfur deficiency >phosphorus deficiency and calcium deficiency.And the leave presents typical symptoms of nutrient deficiency earliest.2.Chlorosis was the common symptoms noticed on leaves of banana treated with N,Mg or S deficiency.However,the new leaves of banana plant appeared inter-veinalchlorosis under Mg deficiency stress.Homogeneous etiolation and yellow-white leaves were observed in S deficiency banana.N deficiency resulted in chlorosis of young leaves and yellow color and necrosis on older leaves started from top of the leaves to the end of it and turned dry with light-brown color.K deficiency leaded the middle leaves of banana turning into yellow from the tip to the whole leaf even turn into nigger-brown withered.The banana blade appeared necrosis with either P or Ca deficiency.When the banana suffered P shortage,the necrosis appeared on the tip of old leaves and then turned into jagged.Ca deficiency made white spots from the edge of the banana new leaves,and then became necrosis.More serious Ca deficiency caused the new leaves appearing notches and even only the vein left.Except for Ca deficiency,the average growth rate of banana plant decreased from about 2.0 cm per week to 0,0.7,0.3,0.6 and 0.6 cm per week after 28,70,49,56 and 56 days of N,P,K,Mg and S deficiency respectively.3.N deficiency would increase the allocation proportion of nutrient in the banana roots.But the nutrient allocation in the leaves was declining under N deficiency.Lack of N made the proportion of N in the roots of banana increase from 9.5%~12.1% to 18.5%~22.2%.P deficiency increased the allocation proportion of P and K in banana roots and leaves,and the proportion of P increased from 34.1%~38.2% to 41.5%~45.1% in the banana leaves.The allocation ratio of K in the banana root and leaf was increased by K deficiency.Meanwhile,lack of K enhanced the proportion of Ca and Mg in the leaves.On the early stage of K deficiency,the distribution proportion of K in banana roots increased from12.5% to 19.6%.On the early stage of Ca deficiency,Ca deficiency did not influence the distribution of N,P and K among root,stem and leaf of banana.With more advanced lack of Ca,Ca deficiency inhabited the transport of N,P and K to the banana leaves.Mg deficiency increased the proportion of Ca and P in the banana leaves.On the middle and late stages of S deficiency,the proportion of Ca,Mg,and S was increased in the banana leaf,but also the percentage of N,P and K was declining.4.Restoration of the nutrient at the early stage of nutrient deficiency,the banana growth status improved significantly.The leaf colour recovered firstly,after re-supplying nutrient to banana.And then the plant height and leaf area were improved with re-supplying nutrient.Re-supplying nutrient treatment could not fully recover the nutrient concentrationsin banana leaves and roots,except for the S.In the restoration of N treatment,the concentrations of P(5.8 g/kg),Ca(9.3 g/kg),Mg(4.3 g/kg)and S(2.8 g/kg)of banana roots were significantly lower than normal concentrations(e.g.7.2 g/kg,10.8 g/kg,4.8 g/kg,4.0 g/kg,respectively).In the treatment of P re-supply,the concentrations of N(21.2 g/kg),P(5.2 g/kg),K(52.2 g/kg)and Mg(3.3 g/kg)in the banana roots and the concentrations of K(53.5 g/kg),S(2.1 g/kg)in the banana leaves were significantly lower than normal concentrations(e.g.23.6 g/kg,6.7 g/kg,61.8 g/kg,4.3 g/kg,59.0 g/kg,2.8 g/kg,respectively).The concentrations of S(1.6 g/kg)in banana roots and K(50.9 g/kg)in leaves in the K re-supply treatment were significantly lower than normal concentrations(e.g.2.1 g/kg,52.6 g/kg,respectively).The concentrations of N(22.9 g/kg),K(47.2 g/kg),Ca(9.0 g/kg)and Mg(2.8 g/kg)in the banana roots and K(49.7 g/kg)and Ca(13.3 g/kg)in banana leaves after K re-supply were significantly less than the normal concentrations(e.g.23.6 g/kg,61.8 g/kg,10.4 g/kg,4.3 g/kg,59.0 g/kg,16.9 g/kg respectively).The concentration of Mg(2.3 g/kg)in banana leaves in Mg re-supply treatment was not restored to normal level(2.5 g/kg).5 Nutrient deficiency affected the banana nutrient homeostasis and leaded to malnutrition.Measures to restore the lacked nutrients should avoid resulting in the other nutrients’ malnutrition or overnutrition.1)At the early stage of N deficiency,the concentrations of N,Ca,Mg in the banana plant were relatively deficient,while the concentrations of K,P,S showed relative surplus.Therefore,N,Ca,Mg fertilizer should be restored at first with adequate amount,and properly to reduce the K,P,S supply.2)Similarly,under the P deficiency,phosphate fertilizer should be applied immediately,while K,P,S,Ca fertilizer supplement should be reduced based on the original fertilization dosage.3)K deficiency caused serious shortage of potassium in the banana plant.At this time,K fertilizer should be provided to plant,meanwhile the application rates of S,N,Ca,and P fertilizer should be properly reduced the S,N,Ca,and P fertilization dosage.4)Under the Ca deficiency,Ca fertilizer should be added immediately,while the amount of Mg,P,S,K and N fertilizer should be appropriately reduced.5)On Mg deficiency,Mg fertilizer should be appropriately increased,while P,K,Ca,N,S fertilizer dosage should be appropriately reduced on the base of the original supplement.6)On the early stage of Sdeficiency,the dosage of nutrient needed by banana was in order of P> S> Ca> N> Mg> K.Therefore,P,S fertilizer should be increased in a high amount,and K,Mg,N fertilizer at a lower rate.Normal management of fertilization characterized by high amount of NPK and Ca,Mg and S should be carried out when the banana growth restored to the normal status completely. |
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