关中灌区有机肥替代化肥的玉米种植效果研究
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摘要
【目的】研究有机肥与化肥配施对玉米生长和土壤无机氮含量的影响,筛选适合玉米生长的施肥处理,为玉米农田生产力提升和氮肥过量的污染控制提供参考。【方法】试验共设置A、B、C、D、E、F、G、H 8个处理,分别为不施肥(对照)、施用100%化肥(N 0.20 g/kg,P_2O_5 0.10 g/kg,K_2O 0.10 g/kg)、施用80%化肥、施用50%化肥、施用50%化肥+50%猪粪、施用50%化肥+50%蚯蚓粪、施用扩蓄增容肥(N 0.20 g/kg,P_2O_5 0.13 g/kg,K_2O 0.10 g/kg)、施用玉米专用肥(N 0.20 g/kg,P_2O_5 0.04 g/kg,K_2O 0.03 g/kg),其中B、C、D处理为减氮处理,B、E、F、G、H处理为等氮(施氮量均为0.20 g/kg)处理,采用盆栽试验,于拔节期和大喇叭口期采集玉米地上部、根部样品及土样,测定并分析玉米生长性状及土壤无机氮含量,探究减氮及等氮条件下不同施肥处理对玉米生长及土壤养分的影响。【结果】盆栽条件下,施氮量为0.20 g/kg时,减氮50%～80%不会显著影响拔节期和大喇叭口期玉米的生长。在玉米拔节期和大喇叭口期,等氮条件下猪粪、蚯蚓粪与化肥配合施用处理的玉米株高、叶片SPAD值、地上部干质量、根系干质量、根系表面积、根系体积、根系活力、根系长度均较高;而土壤硝态氮和铵态氮含量整体呈波动下降趋势。【结论】盆栽条件下,各减氮处理均未显著影响玉米大部分生长性状及土壤无机氮含量,揭示减氮对玉米生产是可行的,且以猪粪、蚯蚓粪与化肥配施效果较好。
【Objective】 The effect of organic and chemical fertilizer applications on growth of maize and inorganic nitrogen content was studied and fertilizer treatments suitable for maize growth were screened to provide reference for improvement of maize farmland productivity and nitrogen pollution control.【Method】 Eight treatments were set up:A no fertilization(control),B application of 100% chemical fertilizer(N 0.20 g/kg,P_2O_5 0.10 g/kg,and K_2 O 0.10 g/kg),C application of 80% chemical fertilizer,D application of 50% chemical fertilizer,E application of 50% chemical fertilizer +50% pig manure,F application of 50% chemical fertilizer +50% wormcast,G application of soil amendment fertilizer(N 0.20 g/kg,P_2O_5 0.13 g/kg,and K_2O 0.10 g/kg) and H application of maize specific fertilizer(N 0.20 g/kg,P_2O_5 0.04 g/kg,and K_2O 0.03 g/kg).B,C and D were nitrogen reduction treatments,while B,E,F,G and H were equal nitrogen treatments,and the nitrogen application was 0.20 g/kg.The shoot and root growth characters of maize in pot experiment and soil inorganic nitrogen contents were collected at jointing stage and big trumpet stage.Then,the effects of reduced nitrogen and equal nitrogen treatments on maize growth and soil inorganic nitrogen content were analyzed.【Result】 With the nitrogen application of 0.20 g/kg,nitrogen reduction of 50%-80% did not significantly affect the growth of maize at the jointing stage and the big trumpet stage.Under equal nitrogen conditions,pig manure and wormcast with chemical fertilizer treatments in the jointing stage and the big trumpet stage,the plant height,leaf SPAD value,shoot dry weight,root dry weight,root surface area,root volume,root activity and root length were all high.Nitrate nitrogen and ammonium nitrogen contents in the jointing stage and the big trumpet stage showed a fluctuating downward trend. 【Conclusion】 Under pot experiment,nitrogen reduction treatments had no significant effect on the growth characters of maize and soil inorganic nitrogen content,indicated that reducing nitrogen was feasible for maize production.Application of pig manure and wormcast with chemical fertilizers had better effects.
【Objective】 The effect of organic and chemical fertilizer applications on growth of maize and inorganic nitrogen content was studied and fertilizer treatments suitable for maize growth were screened to provide reference for improvement of maize farmland productivity and nitrogen pollution control.【Method】 Eight treatments were set up:A no fertilization(control),B application of 100% chemical fertilizer(N 0.20 g/kg,P_2O_5 0.10 g/kg,and K_2 O 0.10 g/kg),C application of 80% chemical fertilizer,D application of 50% chemical fertilizer,E application of 50% chemical fertilizer +50% pig manure,F application of 50% chemical fertilizer +50% wormcast,G application of soil amendment fertilizer(N 0.20 g/kg,P_2O_5 0.13 g/kg,and K_2O 0.10 g/kg) and H application of maize specific fertilizer(N 0.20 g/kg,P_2O_5 0.04 g/kg,and K_2O 0.03 g/kg).B,C and D were nitrogen reduction treatments,while B,E,F,G and H were equal nitrogen treatments,and the nitrogen application was 0.20 g/kg.The shoot and root growth characters of maize in pot experiment and soil inorganic nitrogen contents were collected at jointing stage and big trumpet stage.Then,the effects of reduced nitrogen and equal nitrogen treatments on maize growth and soil inorganic nitrogen content were analyzed.【Result】 With the nitrogen application of 0.20 g/kg,nitrogen reduction of 50%-80% did not significantly affect the growth of maize at the jointing stage and the big trumpet stage.Under equal nitrogen conditions,pig manure and wormcast with chemical fertilizer treatments in the jointing stage and the big trumpet stage,the plant height,leaf SPAD value,shoot dry weight,root dry weight,root surface area,root volume,root activity and root length were all high.Nitrate nitrogen and ammonium nitrogen contents in the jointing stage and the big trumpet stage showed a fluctuating downward trend. 【Conclusion】 Under pot experiment,nitrogen reduction treatments had no significant effect on the growth characters of maize and soil inorganic nitrogen content,indicated that reducing nitrogen was feasible for maize production.Application of pig manure and wormcast with chemical fertilizers had better effects.
引文
[1] 张伟锋,刘新娇,李秋枫,等.世界玉米生产与贸易概况分析 [J].世界农业,2014(3):111-114. Zhang W F,Liu X J,Li Q F,et al.World corn production and Trade overview analysis [J].World Agriculture,2014(3):111-114.
[2] 于振文.作物栽培学各论 [M].北京:中国农业出版社,2013. Yu Z W.Crop cultivation theory [M].Beijing:China Agriculture Press,2013.
[3] 张师,冯乃杰.不同种类氮肥对玉米生长及经济性状的影响 [J].广东农业科学,2014,41(2):75-78. Zhang S,Feng N J.Effect of different types of nitrogen fertilizer on growth and economic traits of Zea mays [J].Guangdong Agricultural Sciences,2014,41(2):75-78.
[4] 吴建新,左强,王甲辰,等.不同施肥措施对球茎茴香产量、品质及氮平衡的影响 [J].北方园艺,2010(10):15-18. Wu J X,Zuo Q,Wang J C,et al.Effect of different fertilizer application on yield , quality of florence fennel and nitrogen balance [J].Northern Horticulture,2010(10):15-18.
[5] Zhu Z L,Chen D L.Nitrogen fertilizer use in China:contributions to food production,impacts on the environment and best management strategies [J].Nutrient Cycling in Agroecosystems,2002,63(2):117-127.
[6] Guo J H,Liu X J,Zhang Y,et al.Significant acidification in major Chinese croplands [J].Science,2010,327(5968):1008-1010.
[7] Nosengo N.Fertilized to death [J].Nature,2003,425(6961):894-895.
[8] 郑伟,何萍,沙之敏,等.施氮对不同土壤肥力下玉米氮素吸收和利用的影响 [J].植物营养与肥料学报,2011,17(2):301-309. Zheng W,He P,Sha Z M,et al.Effect of N application on nitrogen absorption and uilization of spring maize under different soil fertilities [J].Plant Natrition and Fertilizer Science,2011,17(2):301-309.
[9] 何萍,徐新朋,仇少君,等.我国北方玉米施肥产量效应和经济效益分析 [J].植物营养与肥料学报,2014,20(6):1387-1394. He P,Xu X P,Qiu S J,et al.Yield response and economic analysis of fertilizer application in maize grown in North China [J].Journal of Plant Nutrition and Fertilizer,2014,20(6):1387-1394.
[10] Cui Z,Zhang F,Chen X,et al.On-farm evaluation of an in-season nitrogen management strategy based on soil Nmin test [J].Field Crops Research,2008,105(1/2):48-55.
[11] 张福锁,王激清,张卫峰,等.中国主要粮食作物肥料利用率现状与提高途径 [J].土壤学报,2008,45(5):915-924. Zhang F S,Wang J Q,Zhang W F,et al.Nutrient use efficiencies of major cereal crops in China and measures for improvement [J].Acta Pedologica Sinica,2008,45(5):915-924.
[12] Yaduvanshi N P S.Substitution of inorganic fertilizers by organic manures and the effect on soil fertility in a rice-wheat rotation on reclaimed sodic soil in India [J].Journal of Agricultural Science,2003,140(2):161-168.
[13] 宋日,吴春胜,马丽艳,等.有机无机肥料配合施用对玉米根系的影响 [J].作物学报,2002,28(3):393-396. Song R,Wu C S,Ma L Y,et al.Effect of application of combined fertilizers on the root system of maize [J].Acta Agronomica Sinica,2002,28(3):393-396.
[14] 谢军,赵亚南,陈轩敬,等.有机肥氮替代化肥氮提高玉米产量和氮素吸收利用效率 [J].中国农业科学,2016,49(20):3934-3943. Xie J,Zhao Y N,Chen X J,et al.Nitrogen of organic manure replacing chemical nitrogenous fertilizer improve maize yield and nitrogen uptake and utilization efficiency [J].Scientia Agricultura Sinica,2016,49(20):3934-3943.
[15] 商跃凤.有机无机复混肥对水稻氮素利用率的影响 [J].西南大学学报(自然科学版),2001,23(3):264-266. Shang Y F.Influence of orgsnic-inorgsnic compound fertilizers on nitrogen recovery in paddy rice [J].Journal of Southwest Agricultural University(Natural Science Edition),2001,23(3):264-266.
[16] Tomati U,Galli E,Grappelli A,et al.Effect of earthworm casts on protein synthesis in radish (Raphanus sativum) and lettuce (Lactuga sativa) seedlings [J].Biology and Fertility of Soils,1990,9(4):288-289.
[17] 潘婷.扩蓄增容肥对作物产量效应及土壤肥力影响研究 [D].陕西杨凌:西北农林科技大学,2014. Pan T.Effects of soil amendment fertilizer on crop yield and soil fertility [D].Yangling,Shaanxi:Northwest A&F University,2014.
[18] 陈新红.作物栽培学实验 [M].南京:南京大学出版社,2014. Chen X H.Crop cultivation experiment [M].Nanjing:Nanjing University Press,2014.
[19] 白宝璋,金锦子,白崧,等.玉米根系活力TTC测定法的改良 [J].玉米科学,1994,2(4):44-47. Bai B Z,Jin J Z,Bai S,et al.Improvement of TTC method determining root activity in corn [J].Maize Science,1994,2(4):44-47.
[20] 鲍士旦.土壤农化分析 [M].3版.中国农业出版社,2000. Bao S D.Agricultural chemistry analysis for soil. [M].3rd ed.Beijing:China Agriculture Press,2000.
[21] 林云,张荣飞,王岳能.现代统计分析方法 [M].杭州:浙江大学出版社,1991. Lin Y,Zhang R F,Wang Y N.Modern statistical analysis method [M].Hangzhou:Zhejiang University Press,1991.
[22] 史振声,李海燕,李凤海,等.玉米株高的年际间变化及其与产量的关系研究 [J].玉米科学,2013(5):24-29. Shi Z S,Li H Y,Li F H,et al.Relationship between the interannual change of maize height and yield [J].Maize Science,2013(5):24-29.
[23] 殷立娟,石德成.东北碱化草地的主要盐分Na2CO3对羊草危害因素分析 [J].草业学报,1993(1):1-5. Yin L J,Shi D C.An analysis of a main salt of alkalizing meadow steppe Na2CO3:harming factors to Leymus chinensis [J].Acta Prataculturae Sinica,1993(1):1-5.
[24] 霍可以.玉米品种的筛选及耐瘠性状研究 [D].贵阳:贵州大学,2007. Huo K Y.Screening of barren-tolerant maize varieties [D].Guiyang:Guizhou University,2007.
[25] 林希昊,陈秀龙,杨礼富,等.假臭草浸提液对玉米根系活力的影响 [J].热带作物学报,2010,31(5):867-871. Lin X H,Chen X L,Yang L F,et al.Allelopathic study on aqueous extract of praxelis clematidea on root activity in maize [J].Chinese Journal of Tropical Crops,2010,31(5):867-871.
[26] 王爽,孙磊,陈雪丽,等.不同施氮水平对玉米产量、氮素利用效率及土壤无机氮含量的影响 [J].生态环境学报,2013(3):387-391. Wang S,Sun L,Chen X L,et al.Effects of different nitrogen fertilization levels on maize yield,nitrogen utilization and inorganic nitrogen content in soil [J].Ecology and Environmental Sciences,2013(3):387-391.
[27] 郎晓峰,徐阳春,沈其荣.不同有机无机复混肥对土壤供氮和玉米生长的影响 [J].生态与农村环境学报,2008,24(3):33-38. Lang X F,Xu Y C,Shen Q R.Effect of formation of organic-inorganic mixed fertilizers on soil N supply and growth of maize [J].Journal of Ecology and Rural Environment,2008,24(3):33-38.
[28] 韩晓增,王凤仙,王凤菊,等.长期施用有机肥对黑土肥力及作物产量的影响 [J].干旱地区农业研究,2010,28(1):66-71. Han X Z,Wang F X,Wang F J,et al.Effects of long-term organic manure application on crop yield and fertility of black soil [J].Agricultural Research in the Arid Areas,2010,28(1):66-71.
[29] 邢英英,张富仓,王秀康.不同生育期水分亏缺灌溉和氮营养对玉米生长的影响 [J].干旱地区农业研究,2010,28(6):1-11. Xing Y Y,Zhang F C,Wang X K,et al.Study on regulated deficit irrigation technology for potato covered by straw without tillage [J].Agricultural Research in the Arid Areas,2010,28(6):1-11.
[30] 张玉平,荣湘民,刘强,等.猪粪与化肥配施对春玉米碳氮代谢及产量与品质的影响 [J].湖南农业大学学报(自然科学版),2012,38(3):319-324. Zhang Y P,Rong X M,Liu Q,et al.Effects of combination of organic manure and inorganic fertilizer on yield,quality and metabolism of carbon and nitrogen of spring maize [J].Journal of Hunan AgriculturalUniversity (Natural Sciences Edition),2012,38(3):319-324.
[31] 李欢,向丹,李晓林,等.蚯蚓粪和生物有机肥对土壤养分及夏玉米产量的调控作用 [J].土壤通报,2011(5):1179-1183. Li H,Xiang D,Li X L,et al.The regulation of verticompost and microbial organic fertilizer on soil nutrients and summer maize yield [J].Chinese Journal of Soil Science,2011(5):1179-1183.
[32] Cookson W R,Abaye D A,Marschner P,et al.The contribution of soil organic matter fractions to carbon and nitrogen mineralization and microbial community size and structure [J].Soil Biology and Biochemistry,2005,37(9):1726-1737.
[33] Weier K L,Macrae I C,Myers R J K.Denitrification in a clay soil under pasture and annual crop:estimation of potential losses using intact soil cores [J].Soil Biology & Biochemistry,1993,25(8):991-997.
[2] 于振文.作物栽培学各论 [M].北京:中国农业出版社,2013. Yu Z W.Crop cultivation theory [M].Beijing:China Agriculture Press,2013.
[3] 张师,冯乃杰.不同种类氮肥对玉米生长及经济性状的影响 [J].广东农业科学,2014,41(2):75-78. Zhang S,Feng N J.Effect of different types of nitrogen fertilizer on growth and economic traits of Zea mays [J].Guangdong Agricultural Sciences,2014,41(2):75-78.
[4] 吴建新,左强,王甲辰,等.不同施肥措施对球茎茴香产量、品质及氮平衡的影响 [J].北方园艺,2010(10):15-18. Wu J X,Zuo Q,Wang J C,et al.Effect of different fertilizer application on yield , quality of florence fennel and nitrogen balance [J].Northern Horticulture,2010(10):15-18.
[5] Zhu Z L,Chen D L.Nitrogen fertilizer use in China:contributions to food production,impacts on the environment and best management strategies [J].Nutrient Cycling in Agroecosystems,2002,63(2):117-127.
[6] Guo J H,Liu X J,Zhang Y,et al.Significant acidification in major Chinese croplands [J].Science,2010,327(5968):1008-1010.
[7] Nosengo N.Fertilized to death [J].Nature,2003,425(6961):894-895.
[8] 郑伟,何萍,沙之敏,等.施氮对不同土壤肥力下玉米氮素吸收和利用的影响 [J].植物营养与肥料学报,2011,17(2):301-309. Zheng W,He P,Sha Z M,et al.Effect of N application on nitrogen absorption and uilization of spring maize under different soil fertilities [J].Plant Natrition and Fertilizer Science,2011,17(2):301-309.
[9] 何萍,徐新朋,仇少君,等.我国北方玉米施肥产量效应和经济效益分析 [J].植物营养与肥料学报,2014,20(6):1387-1394. He P,Xu X P,Qiu S J,et al.Yield response and economic analysis of fertilizer application in maize grown in North China [J].Journal of Plant Nutrition and Fertilizer,2014,20(6):1387-1394.
[10] Cui Z,Zhang F,Chen X,et al.On-farm evaluation of an in-season nitrogen management strategy based on soil Nmin test [J].Field Crops Research,2008,105(1/2):48-55.
[11] 张福锁,王激清,张卫峰,等.中国主要粮食作物肥料利用率现状与提高途径 [J].土壤学报,2008,45(5):915-924. Zhang F S,Wang J Q,Zhang W F,et al.Nutrient use efficiencies of major cereal crops in China and measures for improvement [J].Acta Pedologica Sinica,2008,45(5):915-924.
[12] Yaduvanshi N P S.Substitution of inorganic fertilizers by organic manures and the effect on soil fertility in a rice-wheat rotation on reclaimed sodic soil in India [J].Journal of Agricultural Science,2003,140(2):161-168.
[13] 宋日,吴春胜,马丽艳,等.有机无机肥料配合施用对玉米根系的影响 [J].作物学报,2002,28(3):393-396. Song R,Wu C S,Ma L Y,et al.Effect of application of combined fertilizers on the root system of maize [J].Acta Agronomica Sinica,2002,28(3):393-396.
[14] 谢军,赵亚南,陈轩敬,等.有机肥氮替代化肥氮提高玉米产量和氮素吸收利用效率 [J].中国农业科学,2016,49(20):3934-3943. Xie J,Zhao Y N,Chen X J,et al.Nitrogen of organic manure replacing chemical nitrogenous fertilizer improve maize yield and nitrogen uptake and utilization efficiency [J].Scientia Agricultura Sinica,2016,49(20):3934-3943.
[15] 商跃凤.有机无机复混肥对水稻氮素利用率的影响 [J].西南大学学报(自然科学版),2001,23(3):264-266. Shang Y F.Influence of orgsnic-inorgsnic compound fertilizers on nitrogen recovery in paddy rice [J].Journal of Southwest Agricultural University(Natural Science Edition),2001,23(3):264-266.
[16] Tomati U,Galli E,Grappelli A,et al.Effect of earthworm casts on protein synthesis in radish (Raphanus sativum) and lettuce (Lactuga sativa) seedlings [J].Biology and Fertility of Soils,1990,9(4):288-289.
[17] 潘婷.扩蓄增容肥对作物产量效应及土壤肥力影响研究 [D].陕西杨凌:西北农林科技大学,2014. Pan T.Effects of soil amendment fertilizer on crop yield and soil fertility [D].Yangling,Shaanxi:Northwest A&F University,2014.
[18] 陈新红.作物栽培学实验 [M].南京:南京大学出版社,2014. Chen X H.Crop cultivation experiment [M].Nanjing:Nanjing University Press,2014.
[19] 白宝璋,金锦子,白崧,等.玉米根系活力TTC测定法的改良 [J].玉米科学,1994,2(4):44-47. Bai B Z,Jin J Z,Bai S,et al.Improvement of TTC method determining root activity in corn [J].Maize Science,1994,2(4):44-47.
[20] 鲍士旦.土壤农化分析 [M].3版.中国农业出版社,2000. Bao S D.Agricultural chemistry analysis for soil. [M].3rd ed.Beijing:China Agriculture Press,2000.
[21] 林云,张荣飞,王岳能.现代统计分析方法 [M].杭州:浙江大学出版社,1991. Lin Y,Zhang R F,Wang Y N.Modern statistical analysis method [M].Hangzhou:Zhejiang University Press,1991.
[22] 史振声,李海燕,李凤海,等.玉米株高的年际间变化及其与产量的关系研究 [J].玉米科学,2013(5):24-29. Shi Z S,Li H Y,Li F H,et al.Relationship between the interannual change of maize height and yield [J].Maize Science,2013(5):24-29.
[23] 殷立娟,石德成.东北碱化草地的主要盐分Na2CO3对羊草危害因素分析 [J].草业学报,1993(1):1-5. Yin L J,Shi D C.An analysis of a main salt of alkalizing meadow steppe Na2CO3:harming factors to Leymus chinensis [J].Acta Prataculturae Sinica,1993(1):1-5.
[24] 霍可以.玉米品种的筛选及耐瘠性状研究 [D].贵阳:贵州大学,2007. Huo K Y.Screening of barren-tolerant maize varieties [D].Guiyang:Guizhou University,2007.
[25] 林希昊,陈秀龙,杨礼富,等.假臭草浸提液对玉米根系活力的影响 [J].热带作物学报,2010,31(5):867-871. Lin X H,Chen X L,Yang L F,et al.Allelopathic study on aqueous extract of praxelis clematidea on root activity in maize [J].Chinese Journal of Tropical Crops,2010,31(5):867-871.
[26] 王爽,孙磊,陈雪丽,等.不同施氮水平对玉米产量、氮素利用效率及土壤无机氮含量的影响 [J].生态环境学报,2013(3):387-391. Wang S,Sun L,Chen X L,et al.Effects of different nitrogen fertilization levels on maize yield,nitrogen utilization and inorganic nitrogen content in soil [J].Ecology and Environmental Sciences,2013(3):387-391.
[27] 郎晓峰,徐阳春,沈其荣.不同有机无机复混肥对土壤供氮和玉米生长的影响 [J].生态与农村环境学报,2008,24(3):33-38. Lang X F,Xu Y C,Shen Q R.Effect of formation of organic-inorganic mixed fertilizers on soil N supply and growth of maize [J].Journal of Ecology and Rural Environment,2008,24(3):33-38.
[28] 韩晓增,王凤仙,王凤菊,等.长期施用有机肥对黑土肥力及作物产量的影响 [J].干旱地区农业研究,2010,28(1):66-71. Han X Z,Wang F X,Wang F J,et al.Effects of long-term organic manure application on crop yield and fertility of black soil [J].Agricultural Research in the Arid Areas,2010,28(1):66-71.
[29] 邢英英,张富仓,王秀康.不同生育期水分亏缺灌溉和氮营养对玉米生长的影响 [J].干旱地区农业研究,2010,28(6):1-11. Xing Y Y,Zhang F C,Wang X K,et al.Study on regulated deficit irrigation technology for potato covered by straw without tillage [J].Agricultural Research in the Arid Areas,2010,28(6):1-11.
[30] 张玉平,荣湘民,刘强,等.猪粪与化肥配施对春玉米碳氮代谢及产量与品质的影响 [J].湖南农业大学学报(自然科学版),2012,38(3):319-324. Zhang Y P,Rong X M,Liu Q,et al.Effects of combination of organic manure and inorganic fertilizer on yield,quality and metabolism of carbon and nitrogen of spring maize [J].Journal of Hunan AgriculturalUniversity (Natural Sciences Edition),2012,38(3):319-324.
[31] 李欢,向丹,李晓林,等.蚯蚓粪和生物有机肥对土壤养分及夏玉米产量的调控作用 [J].土壤通报,2011(5):1179-1183. Li H,Xiang D,Li X L,et al.The regulation of verticompost and microbial organic fertilizer on soil nutrients and summer maize yield [J].Chinese Journal of Soil Science,2011(5):1179-1183.
[32] Cookson W R,Abaye D A,Marschner P,et al.The contribution of soil organic matter fractions to carbon and nitrogen mineralization and microbial community size and structure [J].Soil Biology and Biochemistry,2005,37(9):1726-1737.
[33] Weier K L,Macrae I C,Myers R J K.Denitrification in a clay soil under pasture and annual crop:estimation of potential losses using intact soil cores [J].Soil Biology & Biochemistry,1993,25(8):991-997.