含金属微量元素添加剂残留鸡粪对荔枝果品质量的影响

Effect of application of chicken manure bearing metal microelement additive residue on litchi fruit quality

养殖场禽畜粪的高金属残留可能带来的农产品金属污染广受社会关注,也是一个值得深入探讨的科学问题。研究在荔枝上施用含有较高金属微量元素添加剂残留的粪肥对荔枝果实品质及质量安全的影响,有助于科学回答高金属残留的养殖场粪肥是否可施用于荔枝的疑问。在饲料中以3种用量(1、2和4 kg/t)添加金属微量元素添加剂(含Fe、Mn、Cu和Zn 4种金属硫酸盐),并进行鸡养殖试验,分别收集3种鸡粪,在2015~2018年进行2个荔枝施用鸡粪的田间试验。其一是以等用量(株施40 kg)施用3种鸡粪,其二是以不同用量(株施0、20、40和80 kg)施用同种鸡粪(饲料中添加2 kg/t添加剂),研究连续3年施用鸡粪对荔枝果实品质影响的添加剂剂量及鸡粪用量效应。结果显示,以相同用量连续施用金属含量不同的3种鸡粪,每年除果实固形物含量随鸡粪金属含量提高而降低外,果实可溶糖、糖酸比、风味氨基酸和总游离氨基酸含量差别不大,但不同年份果实品质差异显著(P<0.05);同时,除果肉Mn和Zn含量随鸡粪施用年限增加而显著提高外(P<0.01),果实(果肉、果皮和果核)其他金属含量未随鸡粪金属含量或施用年限的增加而提高。以不同用量施用同种鸡粪,荔枝果实除可溶糖含量有随粪肥用量和施用年限增加而降低的趋势外,处理间其他品质的差异不明显,果实4种金属含量与鸡粪用量关系不大,也未随施用年限的增加而提高。连续3年在荔枝上施用含较高金属残留的鸡粪,整体上对荔枝果实品质并未造成明显不良影响,对果实金属含量影响也未具有饲料添加剂剂量及鸡粪用量效应。由于我国现行食品卫生标准没有限定这4种金属含量,在常规用量下(每年每株通常不超过40 kg),即使连续施用高金属残留的粪肥,也难以产生荔枝果实4种金属污染问题。

Potential metal contamination risk by application of animal manure containing high levels of metal residue is widely concerned,and is also a scientific issue worthy of in-depth discussion. In this work,the influence of fruit quality and safety for litchi plants applied with chicken manures bearing high contents of metal residue was investigated in order to answer the question that whether animal manure from intensive animal farms can be safely used in litchi production. Various dosages of metal micronutrient additives(1,2 and 4 kg/t) bearing the sulfate of Fe,Mn,Cu and Zn were added into chicken diets. Chicken feeding experiment with the given diets were conducted and the chicken manures were collected separately and applied annually to litchi trees in two field trials during 2015 ~ 2018. The experiment 1 consisted of three manures at 40 kg per plant and the experiment 2 included four rates(0,20,40 and 80 kg) of manure from chickens fed with 2 kg microelement additive per ton,the effect of additive dosage and chicken manure dosage on litchi fruit quality after applying chichen manure for 3 consecutive years. Experiment 1 showed that,fruit quality including soluble sugar,the ratio of sugar over titratable acid,flavor amino acid and total free amino acid,was generally not affected by metal concentrations in the manures except soluble solid that was reduced with the increase of metal content. However,significant difference in fruit quality as affected by three manures was observed among years(P<0.05). Fe,Mn,Cu and Zn contents in litchi fruit including pulp,peel and seed,were not closely related with the four metal concentrations in the manure and application years except increased Mn and Zn in pulp responded to an increase in application years(P<0.01). Experiment 2 indicated that generally,fruit soluble sugar content decreased with increasing manure dosage and application year,however,all the other quality indices of litchi fruit were not influenced by manure dosages. Fruit(including pulp,peel and seed)metal contents were not closely related to manure dosage,and it does not increase with the increase of application years except pulp Mn and Zn contents that significently increased with time. Litchi fruit quality was not markedly impacted by high dosage of chicken manure bearing high levels of Fe,Mn,Cu and Zn for three years. Application rate of chicken manure bearing high level of metals had little impact on fruit metal contents as well. Since there are no limits for Fe,Mn,Cu and Zn in food issued yet in the Chinese food hygiene standard,even if the continuous application of high metal residue manure under the conventional dosage(usually no more than 40 kg per plant per year). it is difficult to cause the four metal pollution problems of litchi fruits.