Effect Of Slow-release Fertilizer On Yield And Starch Quality Of Lotus

Lotus(Nelumbo nucifera Gaertn.)is a perennial aquatic herb in the Nelumbonaceae.Lotus rhizome is the largest aquatic vegetable cultivated in China.It is mainly planted in the middle and lower reaches of the Yangtze River and Yellow River,in the Pearl River Basin,with Jiangsu,Hubei and Anhui provinces as the main production areas.Lotus rhizome is rich in starch,soluble sugar and vitamins and has good edible and medicinal value.Processed products such as frozen lotus rhizome,fresh lotus rhizome and salted lotus rhizome sell well at home and abroad,and are deeply loved by people.Starch is the main storage substance in lotus rhizomes,accounting for more than 70%of dry matter,and starch content and quality were closely related to lotus processing quality.In the process of crop cultivation,rational fertilization can effectively promote the growth and yield of crops,but also improve the starch content and quality characteristics of crops.At present,the phenomenon of excessive fertilization in lotus production is still common in China,which leads to the problem ofwater pollution.At the same time,difficult fertilization and high labor costs in the process of lotus growth also restrict the development of the lotus industry.Slow release fertilizer(SRF),as a new type of environmental fertilizer,can be released slowly after one-time fertilization to meet fertilizer demand throughout the crop growth period.However,the application of SRF in lotus production and its effect on the growth and development of lotus are rarely reported.Therefore,the effects of SRF on the yield and starch quality of lotus can provide theoretical basis and technical guidance for light,simplified and precise fertilization of lotus.This paper studied the effects of the application amount and time of SRF on the yield and starch quality of lotus.The main results are as follows:1.Effects of SRF on lotus growth,photosynthetic characteristics and yield.SRF treatment can increase the number and area of erect leaf,delay the senescence of erect leaf,improve SPAD,net photosynthetic rate(Pn)and stomatal conductance(Gs)of erect leaf,and thus increase yield of lotus rhizome.When the application rate of SRF was 69.00 kg·667 m-2,the number and area of lotus erect leaf reached the maximum on 45 and 60 days after fertilization,respectively.SPAD,Pn and Gs of lotus erect leaf peaked at 40 days after fertilization.The rhizome yield of lotus reached the maximum 2014.52 kg·667 m-2,which increased by 19.16%compared with CK treatment.One-time SRF application at the first erect leaf stage,the number and area of lotus erect leaf reached the maximum on 45 and 60 days after fertilization,respectively.SPAD,Pn and Gs of lotus erect leaf peaked at 40 days after fertilization,which were 48,2.73 μmol·m-2·s-1 and 0.35 mmol·m-2·s-1,respectively.The rhizome yield of lotus reached the maximum 2684.34 kg·667 m-2,which increased by 16.96%compared with CK treatment.2.Effects of SRF on starch content,granule morphology,number and pasting properties of lotus rhizome.When the application rate of SRF was 69.00 kg·667 m-2,the total starch content and amylose content of lotus rhizome reached the maximum(17.07%and 5.32%),respectively,which were significantly higher than other treatments,and increased by 8.86%and 9.27%compared with CK treatment.The number of long oval starch and nearly circular starch granules reached the maximum value,increasing by 39.43%and 17.94%compared with CK treatment;the peak viscosity of lotus rhizome starch decreased significantly,and the setback value and pasting temperature increased significantly to the maximum value.One-time SRF application at the first erect leaf stage,the starch content and the number of starch granules in the rhizome of lotus significantly increased,and the contents of total starch,amylose and amylopectin reached the maximum,which were 16.58%,5.68%and 10.90%,respectively.Compared to CK treatment,they increased by 7.31%,11.37%and 5.31%,respectively.The number of long oval starch granules and nearly circular starch granules reached the maximum value(36 and 67,respectively),and the peak viscosity of starch in the rhizome of lotus significantly decreased to the lowest value(6545 cP),and the setback viscosity and pasting temperature significantly increased to the maximum value(628 cP and 74.65℃).3.Effects of SRF on key enzymes and related starch synthesis genes in lotus rhizome.SRF treatment increased the expression of starch synthesis key enzyme genes,led to the enhancement of starch synthesis key enzyme activities,and finally promoted starch synthesis.The application rate of SRF was 69.00 kg·667 m-2,the relative expression of NnGBSS,NnSBEⅠ,NnSBEⅡ and NnSSSⅣ increased significantly to the maximum value at the middle swelling stage of the lotus rhizome.GBSS,SBE,and SBSS activities reached the maximum values(86.54 Ug-1 FW,64.20 Ug-1 FW,and 76.54 Ug-1 FW,respectively)at the middle swelling stage of lotus rhizome.One-time SRF application at the first erect leaf stage,the relative expression levels of NnGBSS and NnSSSⅣ in the rhizome of lotus were significantly increased at the middle swelling stages,and reached the maximum at the middle swelling stages,which were increased by 121.89%and 76.88%compared with CK treatment.led to the enhanced activities of GBSS and SSS,the maximum values of 89.87 U·g-1 FW and 69.87 U·g-1 FW were increased by 177.97%and 203.25%compared with CK treatment.