不同农艺措施对双季稻植株地上部镉积累的影响

doi:10.15933/j.cnki.1004-3268.2020.01.005

摘要/Abstract

摘要： 设置施用1 000 kg/hm²生物炭（生物炭1处理）、施用2 000 kg/hm²生物炭（生物炭2处理）、喷施叶面肥、控水4种农艺措施，以常规栽培为对照，研究各农艺措施对双季稻植株地上部镉积累的影响，明确双季稻在各农艺措施下的镉积累规律，以期为湖南省镉污染稻田双季稻降镉农艺措施的选择提供参考。结果表明，与对照相比，4种农艺措施总体上均增加了早稻的穗数、穗粒数，进而提高产量，其中，陆两优996产量达到显著水平，增幅为11.59%～14.36%，但对晚稻产量无显著影响；与对照相比，喷施叶面肥处理显著增加了晚稻丰源优299成熟期茎的镉含量，增幅为15.54%，显著降低了其成熟期叶的镉含量，降幅为53.00%；施用生物炭1、生物炭2处理显著降低了晚稻丰源优299成熟期茎、叶、谷壳、糙米的镉含量及地上部镉积累总量，分别使糙米的镉含量降低了39.76%、26.40%，分别使地上部镉积累总量降低了24.45%、22.83%；与叶面肥处理相比，生物炭1、生物炭2处理显著降低早稻陆两优996成熟期茎、叶、糙米的镉含量，分别使糙米的镉含量降低了37.71%、35.17%；与对照相比，控水处理显著降低晚稻湘晚籼13号和丰源优299成熟期谷壳的镉含量，降幅分别为38.25%和10.37%，但对其他指标无明显影响。综上，施加生物炭能有效降低水稻植株和糙米的镉含量。

关键词: 农艺措施, 双季稻, 产量, 植株地上部, 糙米, 镉含量

Abstract: The effects of four kinds of agronomic measures[applying 1 000 kg/ ha biochar(biochar 1 treatment),applying 2 000 kg/ha biochar(biochar 2 treatment),spraying foliar fertilizer,water control]on cadmium accumulation in aboveground parts of double-cropping rice were studied with conventional cultivation as control, so as to found out the cadmium accumulation law under different agronomic measures and provide reference for the choice of agronomic measures in double-cropping rice paddy polluted by cadmium in Hunan Province.The results showed that four kinds of agronomic measures increased the spike number and grain number per ear of early rice compared with the control,and then increased the yield,among them,the yield of Luliangyou 996 reached a significant level,with the increase rate of 11.59%—14.36%,but each treatment had no significant effect on the yield of late rice compared with control. Compared with the control,the cadmium content of spraying foliar fertilizer treatment in the stem of late rice Fengyuanyou 299 increased by 15.54%,and decreased by 53.00% in the leaves during the mature period.The biochar 1 and biochar 2 treatments significantly reduced the cadmium content in husk,stem,leaf,brown rice and the cadmium accumulation in overground part of late rice Fengyuanyou 299 during the mature period, the cadmium accumulation in brown rice reduced by 39.76% and 24.60%,and the cadmium accumulation in overground part of plant reduced by 24.45% and 22.83% respectively. Compared with spraying foliar fertilizer treatment,the biochar 1 and biochar 2 treatments significantly reduced the content of cadmium in stem,leaf and brown rice of early rice Luliangyou 996 during the mature period,and reduced the content of cadmium in brown rice by 37.71% and 35.17% respectively.Compared with the control,the content of cadmium in rice husk of late rice Xiangwanxian No.13 and Fengyuanyou 299 during the mature period decreased by 38.25% and 10.37% respectively,but there was no obvious effect on other indicators.The above results showed that the application of biochar could effectively reduce the cadmium accumulation in rice plants and brown rice.

Key words: Agronomic measure, Double-season rice, Yield, Overground part of plant, Brown rice;Cadmium content

祝志娟, 傅志强. 不同农艺措施对双季稻植株地上部镉积累的影响[J]. 河南农业科学, 2020, 49(1): 31-43.

ZHU Zhijuan, FU Zhiqiang. Effects of Different Agronomic Measures on Cadmium Accumulation in Overground Part of Double-Cropping Rice[J]. Journal of Henan Agricultural Sciences, 2020, 49(1): 31-43.

参考文献

［1］孙亚莉,徐庆国,贾巍.镉胁迫对水稻的影响及其调控技术研究进展［J］.中国农学通报,2017,33(10):1-6.

SU Y L,XU Q G,JIA W.Advance in cadmium stress on rice and its regulation and control technology［J］.Chinese Agricultural Science Bulletin,2017,33(10):1-6.

［2］刘利成,刘三雄,黎用朝,等.水稻镉积累与调控研究进展［J］.中国农学通报,2016,32(24):1-5.

LIU L C,LIU S X,LI Y C,et al.Research progress of cadmium accumulation and regulation in rice［J］.Chinese Agricultural Science Bulletin,2016,32(24):1-5.

［3］孙聪,陈世宝,宋文恩,等.不同品种水稻对土壤中镉的富集特征及敏感性分布［J］.中国农业科学,2014,47(12):2384-2394.

〖JP2〗SU C,CHEN S B,SONG W E,et al.Accumulation characteristics of cadmium by rice cultivars in soils and its species sensitivity distribution［J］.Scientia Agricultura Sinica,2014,47(12):2384-2394.

［4］李坤权,刘建国,陆小龙,等.水稻不同品种对镉吸收及分配的差异［J］.农业环境科学学报,2003,22(5):529-532.

LI K Q,LIU J G,LU X L,et al.Uptake and distribution of cadmium in different rice cultivars［J］.Journal of AgroEnvironment Science,2003,22(5):529-532.

［5］高敏,周俊,刘海龙,等.叶面喷施硅硒联合水分管理对水稻镉吸收转运特征的影响［J］.农业环境科学学报,2018,37(2):215-222.

GAO M,ZHOU J,LIU H L,et al.Effect of silica and selenite foliar sprays on the uptake and transport of cadmium by rice under water management［J］.Journal of AgroEnvironment Science,2018,37(2):215-222.

［6］黄太庆,江泽普,黄雁飞,等.不同配方含硒叶面肥对水稻富硒降镉的影响［J］.南方农业学报,2017,48(7):1185-1189.

HUANG T Q,JIANG Z P,HUANG Y F,et al.Effects of different foliar fertilizers containing Se on Seenrichment and Cdreduction in rice［J］.Journal of Southern Agriculture,2017,48(7):1185-1189.

［7］王凯,徐世龙,杨远柱.水稻镉吸收与转运机理研究进展［J］.作物研究，2014，28（8）：926-930.

WANG K,XU S L,YANG Y Z.Advances in research on mechanism of cadmium uptake and transport in rice ［J］.Crop Research,2014,28(8):926-930.

［8］史磊,郭朝晖,梁芳,等.水分管理和施用石灰对水稻镉吸收与运移的影响［J］.农业工程学报,2017,33(24):111-117.

SHI L,GUO Z H,LIANG F,et al.Effects of lime and water management on uptake and translocation of cadmium in rice［J］.Transactions of the Chinese Society of Agricultural Engineering,2017,33(24):111-117.

［9］王建乐,谢仕斌,林丹虹,等.5种钝化剂对镉砷污染稻田的田间修复效果对比［J］.环境工程学报,2019,13(11):2691-2700.

WANG J L,XIE S B,LIN D H,et al.Comparative of the field remediation effect of cadmium and arsenic contaminated paddy by five passivalors ［J］.Chinese Journal of Environmental Engineering,2019,13(11):2691-2700.

［10］李义纯,王艳红,唐明灯,等.改良剂对根际土壤-水稻系统中镉运移的影响［J］.环境科学,2019,40(7):1341-1346.

LI Y C,WANG Y H,TANG M D,et al.Effects of an amendment on cadmium transportation in the rhizosphere soilrice system［J］.Environmental Science,2019,40(7):1341-1346.

［11］张丽娜.不同调控措施对土壤-水稻系统中镉行为的影响［D］.南京：南京农业大学,2007.

ZHANG L N.Effects of different control measures on cadmium behavior in soilrice system［D］.Nanjing:Nanjing Agricultural University,2017.

［12］邓晓霞,黎其万,李茂萱,等.土壤调控剂与硅肥配施对镉污染土壤的改良效果及水稻吸收镉的影响［J］.西南农业学报,2018,31(6):1221-1226.

DENG X X,LI Q W,LI M X,et al.Remediation effects of regulating agents and silicon application on Cd contaminated soil and Cd uptake of rice［J］.Southwest China Journal of Agricultural Sciences,2018,31(6):1221-1226.

［13］金华,魏祥东,邹慧玲,等.土壤改良剂对镉向水稻中迁移转运的影响［J］.安徽农业科学,2018,46(31):59-61,82.

JIN H,WEI X D,ZOU H L,et al.Effects of soil conditioner on migration and transport of Cd into rice［J］.Journal of Anhui Agricultural Sciences,2018,46(31):59-61,82.

［14］王凯荣,张玉烛,胡荣桂,等.不同土壤改良剂对降低重金属污染土壤上水稻糙米铅镉含量的作用［J］.农业环境科学学报,2007,26(2):476481.

WANG K R,ZHANG Y Z,HU R G,et al.Effects of different types of soil amelioration materials on reducing concentrations of Pb and Cd in brown rice in heavy metal polluted paddy soils［J］.Journal of AgroEnvironment Science,2007,26(2):476-481.

［15］史磊,郭朝晖,彭驰,等.石灰组配土壤改良剂抑制污染农田水稻镉吸收［J］.农业工程学报,2018,34(11):209-216.

〖JP2〗SHI L,GUO Z H,PEN C,et al.Lime based amendments inhibiting uptake of cadmium in rice planted in contaminated soils［J］.Transactions of the Chinese Society of Agricultural Engineering,2018,34(11):209-216.

［16］胡雪芳,田志清,梁亮,等.不同改良剂对铅镉污染农田水稻重金属积累和产量影响的比较分析［J］.环境科学,2018,39(7):3409-3417.

HU X F,TIAN Z Q,LIANG L,et al.Comparative analysis of different soil amendment treatments on rice heavy metal accumulation and yield effect in Pb and Cd contaminated farmland［J］.Environmental Science,2018,39(7):3409-3417.

［17］黄道友,陈惠萍,龚高堂,等.湖南省主要类型水稻土镉污染改良利用研究［J］.农业现代化研究,2000,21(6):365-370.
HUANG D Y,CHEN H P,GONG G T,et al.Research report on improvement and utilization of main type paddy soil polluted by cadmium in Hunan Province［J］.Research of Agricultural Modernization,2000,21(6):365-370.

［18］朱维,周航,吴玉俊,等.组配改良剂对稻田土壤中镉铅形态及糙米中镉铅累积的影响［J］.环境科学学报,2015,35(11):3688-3694.

ZHU W,ZHOU H,WU Y J,et al.Effects of combined amendmenton forms of cadmium/lead in paddy soil and accumulation of cadmium/lead in brown rice［J］.Acta Scientiae Circumstantiae,2015,35(11):3688-3694.

［19］余洪章.修复性土壤调理剂对降低土壤和稻米中镉砷效果的研究［J］.湖南农业科学，2019(6):41-43.

YU H Z.Effects of compound soil conditioner on cadmium and arsenic reduction in midseason hybrid rice and paddy soil［J］.Hunan Agricultural Sciences,2019(6):41-43.

［20］李智鸣,郭雄飞.不同叶面肥对水稻产量及镉含量的影响［J］.现代农业科技,2019(19):9，12.

LI Z M,GUO X F.Effects of different foliar fertilizers on rice yield and cadmium content ［J］.Modern Agricultural Sciences and Technology,2019(19):9,12.

［21］黄太庆,江泽普,廖青,等.含硒叶面肥的施用方法对水稻精米硒、镉富集的影响［J］.西南农业学报,2017,30(6):1376-1381.

HUANG T Q,JIANG Z P,LIAO Q,et al.Effect of different selenium foliar fertilizers application methods on selenium and cadmium enrichment in polished rice［J］.Southwest China Journal of Agricultural Sciences,2017,30(6):1376-1381.

［22］蔡亮亮,赵龙,孙在金,等.中低镉胁迫下叶面肥对水稻生长状况及镉积累调控效果的影响［J］.中国农学通报,2018,34(17):1-7.

CAI L L,ZHAO L,SUN Z J,et al.Low and medium Cd stress and foliage fertilizer:Effects on growth and cadmium accumulation regulation of rice［J］.Chinese Agricultural Science Bulletin,2018,34(17):1-7.

［23］郭天宇,徐宁彤,曲琪环.叶面喷施不同硒肥对水稻含硒量及产量的影响［J］.江苏农业科学,2017,45(7):59-61.

GUO T Y,XU N T,QU Q H.Effects of spraying different selenium fertilizers on leaves on selenium content and yield of rice ［J］.Jiangsu Agricultural Sciences,2017,45(7):59-61.

［24］李嘉琳,梁金明,陈波华,等.叶面肥与不同类型钝化材料组合施用对水稻累积镉效应研究［J］.农业环境科学学报,2019,38(10):89-96.LI J L,LIANG J M,CHEN B H,et al.Effect of integrative remediation measures,based on foliar fertilizer and several passivation materials,on Cd accumulation in rice［J］.Journal of AgroEnvironment Science,2019,38(10):89-96.

［25］徐琴,王孟,谢义梅,等.施硒对水稻外观品质及籽粒硒、镉和砷含量的影响［J］.中国农业科技导报,2019,21(5):141-146.

XU Q,WANG M,XIE Y M,et al.Effect of selenium application on appearance quality,grain selenium,cadmium and arsenic content in rice［J］.Journal of Agricultural Science and Technology,2019,21(5):141-146.

［26］王蜜安,尹丽辉,彭建祥,等.综合降镉（VIP）技术对降低糙米镉含量的影响研究［J］.中国稻米,2016,22(1):43-47.

WANG M A,YIN L H,PEN J X,et al.Effects of VIP technology on reducing cadmium content in rice［J］.China Rice,2016,22(1):43-47.

［27］张文.VIP降镉技术在不同土壤环境下对水稻的降镉效果及机理研究［D］.长沙：湖南农业大学,2017.

ZHANG W.Study on effect of cadmium reduction and mechanism of VIP technology in different soil environment in rice［D］.Changsha:Hunan Agricultural University,2017.

［28］杨小粉,刘钦云,袁向红,等.综合降镉技术在不同污染程度稻田土壤下的应用效果研究［J］.中国稻米,2018,24(2):37-41.

YANG X F,LIU Q Y,YUAN X H,et al.Effects of VIP technology on reducing cadmium under different cadmium pollution degree paddy soil［J］.China Rice,2018,24(2):37-41.

［29］谢敏,黎良平,戴典.VIP+n技术对重金属污染土壤和稻谷降镉效果研究［J］.吉林农业,2017(8):75-77.

XIE M,LI L P,DAI D.Study on the effect of VIP+n technology on heavy metal contaminated soil and rice cadmium reduction［J］.Jilin Agriculture,2017(8):75-77.

［30］廖雄辉,龙琴,王惠群,等.南荻炭与镉钝化剂互作对水稻镉含量和产量的影响［J］.农业环境科学学报,2018,37(9):1818-1826.

LIAO X H,LONG Q,WANG H Q,et al.Interaction effects of Miscanthus lutarioripariusderived biochar and cadmium passivators on rice cadmium content and yield［J］.Journal of AgroEnvironment Science,2018,37(9):1818-1826.

［31］唐金花.VIP+n 技术对重金属污染农田中稻谷降镉效果的影响［J］.湖南农业科学，2018(9):48-50.

TANG J H.Effect of VIP+n technology on cadmium reduction in paddy fields polluted by heavy metals［J］.Hunan Agricultural Sciences,2018(9):48-50.

［32］陈京都,何理,许珂,等.镉胁迫对不同基因型水稻生长及矿质营养元素吸收的影响［J］.生态学杂志,2013,32(12):3219-3225.

CHEN J D,HE L,XU K,et al.Growth and nutritional element absorption of different rice genotypes under cadmium stress［J］.Chinese Journal of Ecology,2013,32(12):3219-3225.

［33］仲晓春,陈京都,郝心宁.水稻作物对重金属Cd的积累、耐性机理以及栽培调控措施进展［J］.中国农学通报,2015,31(36):1-5.

ZHONG X C,CHEN J D,HAO X N.Research process of accumulation,tolerance mechanism and cultivation control measures of heavy metal cadmium in rice crops［J］.Chinese Agricultural Science Bulletin,2015,31(36):1-5.

［34］史静,李正文,龚伟群,等.两种常规水稻Cd、Zn吸收与器官分配的生育期变化：品种、土壤和Cd处理的影响［J］.生态毒理学报,2007,2(1):32-40.

SHI J,LI Z W,GONG W Q,et al.Uptake and partitioning of Cd and Zn by two nonhybrid rice cultivars in different growth stages:Effect of cultivars,soil type and Cd spike［J］.Asian Journal of Ecotoxicology,2007,2(1):32-40.

［35］彭欧,铁柏清,叶长城,等.稻米镉关键积累时期研究［J］.农业资源与环境学报,2017,34(3):272-279.

PEN O,TIE B Q,YE C C,et al.The key period of cadmium accumulation in rice［J］.Journal of Agricultural Resources and Environment,2017,34(3):272-279.

［36］王德胜,胡芸莎,曹琦,等.棉秆生物炭对南疆地区水稻产量和氮素利用效率的影响［J］.江苏农业科学,2018,46(20):52-55.

WANG D S,HU Y S,CAO Q,et al.Effects of cotton stalk biochar on rice yield and nitrogen use efficiency in southern Xinjiang［J］.Jiangsu Agricultural Sciences,2018,46(20):52-55.

［37］刘晓霞,吴东涛,朱伟锋,等.外源添加生物炭对水稻产量和土壤性质的影响［J］.浙江农业科学,2016,57(11):1776-1779.

LIU X X,WU D T,ZHU W F,et al.Effects of exogenous biochar addition on rice yield and soil properties ［J］.Journal of Zhejiang Agricultural Sciences,2016,57(11):1776-1779.

［38］赫天一.生物炭对土壤镉赋存形态和水稻镉积累的影响［D］.沈阳：沈阳农业大学，2017.

HE T Y.Effects of biochar on soil Cd fractions and Cd accumulation in rice［D］.Shenyang:Shenyang Agricultural University,2017.

［39］史国志,马庆辉,鲁欣,等.生物炭对白浆土水分渗透性及水稻产量的影响［J］.现代化农业,2018(9):24-27.

SHI G Z,MA Q H,LU X,et al.Effect of biochar on water permeability and rice yield of albic soil［J］.Modernizing Agriculture,2018(9):24-27.

［40］张丽娜,宗良纲,付世景,等.水分管理方式对水稻在Cd污染土壤上生长及其吸收Cd的影响［J］.安全与环境学报,2006,6(5):49-52.

ZHANG L N,ZONG L G,FU S J,et al.Effects of water control on rice growth and its intake of cadmium on Cd contaminated soil［J］.Journal of Safety and Environment,2006,6(5):49-52.

［41］沈欣,朱奇宏,朱捍华,等.农艺措施对水稻镉积累的影响及其机理研究［J］.农业环境科学学报,2015,34(8):1449-1454.

SHEN X,ZHU Q H,ZHU H H,et al.Effects of agronomic measures on accumulation of Cd in rice［J］.Journal of AgroEnvironment Science,2015,34(8):1449-1454.

［42］罗德强,王绍华,姬广梅,等.水分管理对杂交籼稻产量和群体质量的影响［J］.贵州农业科学,2018,46(10):41-44.

LUO D Q,WANG S H,JI G M,et al.Effects of water management on yield and population quality of indica hybrid rice［J］.Guizhou Agricultural Sciences,2018,46(10):41-44.

［43］杨祥田,周翠,何贤彪,等.田间试验条件下不同基因型水稻对Cd和Pb的吸收分配特征［J］.农业环境科学学报,2013,32(3):438-440.

YANG X T,ZHOU C,HE X B,et al.Uptake and partition of Cd and Pb among rice genotypes in contaminated paddy soil［J］.Journal of AgroEnvironment Science,2013,32(3):438-440.

［44］陈京都,何理,林忠成,等.不同生育期类型水稻对镉积累的研究［J］.生态与农村环境学报，2013,29(3):390-393.

CHEN J D,HE L,LIN Z C,et al.Cd accumulation in japonica rice relative to growth type［J］.Journal of Ecology and Rural Environment,2013,29(3):390-393.

［45］唐非,雷鸣,唐贞,等.不同水稻品种对镉的积累及其动态分布［J］.农业环境科学学报，2013，32(6):1092-1098.

TANG F,LEI M,TANG Z,et al.Accumulation characteristic and dynamic distribution of Cd in different genotypes of rice［J］.Journal of AgroEnvironment Science,2013，32(6):1092-1098.

［46］贺慧,郑华斌,陈灿,等.不同基因型水稻镉吸收差异及镉对水稻的影响研究进展［J］.作物研究,2014,28(2):211-215.

HE H,ZHENG H B,CHEN C,et al.Research progress of cadmium absorption of different genotypes of rice and the effect of cadmium on rice［J］.Crop Research,2014,28(2):211-215.

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