Study On Influence Of Cover Crop In Vineyard On Vine And Wine

Cover crop in the vineyard as an excellent soil management method,it is of greatsignificance to protection of environment and sustainable development of agriculture.Itbecomes a focal point to study about influence of vineyard cover crop on soil fertility andquality of grape and wine.Soil microbiological characteristic can reflect the soil qualitychanges sensitively,also is it very important to soil structure and plant nutrition cycling.Hence,it becomes an important index to be used as one of soil fertility assessment.Polyphenols,anthocyanin and volatile compounds,along with their interactions,areresponsible for color and aroma,respectively,and affecting wine quality and style.Today agrowing number of consumers are showing interest in wines that are more aroma andcomplex and wines with numerous attributes are considered to be of higher quality.Wine grape cultivar Cabernet Sauvignon as experimental materials,permanent covercrop in vineyard inter-row with white clover(Trifolium repens),alfalfa(Medicago sativa)andtall fescue(Festuca arundincea Schreb.)in Yangling,Shaanxi,with comparison of cleantillage.The effect of cover crop in vineyard on soil microorganism,soil enzyme activity andsoil nutrient were investigated,the relationgships between soil nutrient contents and soilmicrobiological factors of four treatments were studied through correlation analysis and pathanalysis.Localized measure of soil moisture content with TRIME-TDR during vine growthseason,and monomeric phenol,anthocyanin and volatile compounds were determined andanalysed by HPLC and SPME-GC/MS.The effect of cover crop in vineyard on vine and winewere illustrated.The outcome of this study will provide the foundation for a continuing studyand extend.The results were as bellows:(1)soil microorganism quantity,soil enzyme activity and soil nutrient content decreasedwith deeper of soil layer and they were all higher in topsoil.Bacteria was 90% of totalmicroorganism amount,followed by actinomyces and azotobacter,soil microorganismquantity,soil enzyme activity and soil nutrient content take on some regularity with seasonalchange,thereinto,the number of bacteria,actinomyces,azotobacter andcellulose-decomposing microorganisms,the activity of urease,sucraseamylase,phosphataseand catalase were apparently larger in July and September than that in April and December, especialy largest in July.The number of fungi was higher in April and December and lower inJuly and September,but the peak value of soil cellulase activitywas in September and Julyunder the treatments of vineyard cover crop and clean tillage(CK),respectively.The contentof soil hydrolyzable N,available K,total N,total P and organic matter increased in the order:December,Apil and September.(2)With comparison to clean tillage,as a whole,the number of soil bacteria,fungi,azotobacter,cellulose-decomposing microorganisms and the activity of phosphatase,amylase,cellulase and catalase were increased under cover crop treatments,with the exception of tallfescue treatment decreased soil actinomyces quantity and activity of urease and sucrase.Thesoil organic matter were increased remarkably and available P,total P reduced by cover croptreatments,white clover and alfalfa treatments increased the contents of soil hydrolyzable N,total N,available K evidently,while tall fescue treatment decreased them.Therefore,whenviewed as a whole,compared with those of clean tillage,improvement of the soilmicroorganism quantity,soil enzyme activity and soil nutrients in white clover and alfalfatreatments more effectively than that in tall fescue.But it was propitious to enhance activitionof the available P and amylase activity with tall fescue treatment.(3)There are correlativity between soil microorganism quantity,soil enzyme activity andsoil nutrient.The contents of soil organic matter,total N,hydrolyzable N,total P and availableK showed significant or very significant position correlations with soil biological factors,except that soil catalase was negatively correlated with all kinds of soil nutrient contents.Thesoil microorganism quantity also were very significant position correlations with soil enzymeactivity.Correlation analysis and path analysis indicated that in the vineyard intercroppingsystem,soil phosphatase,urease,amylase,actinomyces,bacteria was the most importantfactor affecting the soil fertility,these soil microorganism and soil enzyme were goodassessment indicators of soil fertility,in which,soil bacteria had indirect effect on soilfertility.(4)The localized observation of soil moisture content was carried out in vineyard,theresult showed that cover cropping brought out competition for soil water in the differentrainfall year,the soil moisture content of cover crop treatments was reduced obviously,especially,the water competition was more severe in the year that short soil water storage inwinter and atmospheric drought in spring.Whereas,cover cropping could regulate soil waterand improve utilization ratio of soil water.At the same time,after planting grasses in vineyard,soil physical characteristics were improved,such as soil bulk density decreased by 8.5%～9.8% and soil porosity increased by 11.5%～13.9% in the depth of 0～60 cm comparisedwith bare soil treatment. (5)There are ten monomeric phenols and nine anthocyanins were detected in grape berryand wine of Cabernet Sauvignon with HPLC.Catechin and Mv-3-O-Glu was the mostabundant compound of polyphenol compound and anthocyanin in gape and wine,respectively.The percentage of hydroxybenzoic acids in the total polyphenol content was more higher thanthat of hydroxycinnamic acids.Cover crop system had high monomeric phenol content andtotal phenolic compounds content,the tall fescue treatment had the most obvious effect,secondly,white clover and alfalfa treatments were higher compared to the soil tillage.Inaddtion,Cover crop system increased the total anthocyanin content in order of the fourtreatments:alfalfa,tall fescue,white clover and soil tillage.(6)Aroma compounds of wine were analysed by solid-phase microextraction gaschromatography-mass spectrometry(SPME-GC/MS).47 volatile compounds of wine wereidentified and semi-quantified,especially abundant in esters and higher alcohols,the majorones being Isoamyl alcohol,Isobutyl alcohol,phenylethyl alcohol,hexanol,ethyl acetate,ethyl octanoate,isoamyl acetate and ethyl decanoate.The permanent cover crops increasedtotal content of wine aroma compounds compared to the bare soil.Alfalfa sward was highestfollowed by the tall fescue treatment.Wines made from grapes with different cover cropswere better in aroma compounds,so it can improve the wine quality.(7)Compared to soil tillage,the three cover crop treatments showed a lower total N ofgrape berry and juice,while a higher total N of wine,total content of free amino acid in grapeberry and wine,except total content of amino acid in grape berry was lower in white clovertreatment.Proline was the most abundant amino acid in grape and wine wtih the fourtreatments,it account for 45.94%～56.85 % and 90.11%～92.45% of the total amino acidin grape and wine respectively,in the following,it were lysine,arginine and serine,asparagicacid.Although the total N of grape berry was decreased under cover crop treatments,therewere no differences in duration of alcohol fermentation between treatments because ofincreasing of aminio acid.The color density and tastes of wine were improved significantlyunder green covering.Compared with those of clean tillage,significant difference in grapeand wine configuration,color and aroma occurred.It can be concluded that green coverimproved the quality of grape berry and wine evidently.