,1,*Effects of Reduced Nitrogen on Soil Ammonification, Nitrification, and Nitrogen Fixation in Maize-soybean Relay Intercropping Systems
YONG Tai-Wen1, CHEN Ping1,**, LIU Xiao-Ming1,2, ZHOU Li1,3, SONG Chun4, WANG Xiao-Chun1, YANG Feng1, LIU Wei-Guo1, YANG Wen-Yu,1,*通讯作者:
第一联系人:
收稿日期:2017-12-15接受日期:2018-07-20网络出版日期:2018-07-30
| 基金资助: |
Received:2017-12-15Accepted:2018-07-20Online:2018-07-30
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雍太文, 陈平, 刘小明, 周丽, 宋春, 王小春, 杨峰, 刘卫国, 杨文钰. 减量施氮对玉米-大豆套作系统土壤氮素氨化、硝化及固氮作用的影响[J]. 作物学报, 2018, 44(10): 1485-1495. doi:10.3724/SP.J.1006.2018.01485
YONG Tai-Wen, CHEN Ping, LIU Xiao-Ming, ZHOU Li, SONG Chun, WANG Xiao-Chun, YANG Feng, LIU Wei-Guo, YANG Wen-Yu.
大量的肥料投入增加了生产的环境代价, 威胁到农业的可持续发展[1]。豆科与禾本科间套作是实现粮食安全、农业可持续发展的一条有效途径[2], 其间套作系统既可改善土壤微生物群落结构, 促进氮素循环利用[3], 降低氮素淋失量及氮排放量[4,5], 又可通过种间互惠及养分吸收生态位的分离, 平衡种间养分竞争利用, 提高氮素利用效率、减少氮素投入[2,6]; 此外, 包含豆科的种植系统可通过根瘤固氮增加土壤氮素供应, 减少氮肥施用量[7], 例如, 大豆年均固氮量为118 kg N hm-2, 苜蓿年均固氮量为218 kg N hm-2 [7]。土壤可通过氨化、硝化及反硝化作用将氮素从有机态转化为无机态供植物吸收[8], 而硝化和反硝化过程中部分氮素将以氨和N2O的形态进入大气造成氮素损失[8]。减少氮肥投入量可降低土壤氮素淋失量及排放量[4,9], 优化氨氧化细菌和反硝化细菌群落结构, 提高土壤氮素含量及植物氮素吸收量, 实现增产节肥[3]。此外, 长期套作下无氮和大量施氮均不利于系统增产及可持续[10], 种间行施肥较种内行施肥更有利于养分利用及系统增产[11,12]。
玉米-大豆套作是我西南地区一种主要的绿色高效旱地种植模式, 前人关于玉米-大豆带状套作模式的群体配置技术[13]、化学调控技术[14]、品种与播期调控技术[15]、耐荫抗旱研究[14,16]等方面进行了深入细致的研究, 并提出了玉米-大豆套作减量一体化施肥技术, 该技术不仅使套作系统产量显著增加[17], 还能够促进作物氮素吸收[18], 增加大豆根瘤固氮能力[19], 但是, 该套作模式通过施氮技术优化对土壤氮素转化过程及氮排放的影响尚不清楚, 其节肥的土壤生态机理还有待进一步研究。因此, 本试验在前期研究基础上, 通过大田定位试验与池栽试验相结合, 拟从土壤氮素氨化、硝化、固氮等转化过程及土壤氮排放、NO3--N累积角度来探究减量一体化施肥下玉米-大豆套作的土壤氮素循环规律, 进一步完善玉米-大豆套作系统氮素高效利用机理, 为玉米-大豆套作模式均衡增产和施肥技术优化提供理论和实践依据。
1 材料与方法
1.1 试验时间、地点
2012年3月至2013年10月在四川省现代粮食产业(仁寿)示范基地进行大田试验。2012年大田试验土壤: pH 6.8, 有机质17.26 g kg-1, 全氮0.90 g kg-1, 全磷0.50 g kg-1, 全钾14.28 g kg-1, 碱解氮77.35 mg kg-1, 速效磷22.83 mg kg-1, 速效钾196.63 mg kg-1。2013年3月至2014年10月在四川省雅安市四川农业大学教学农场干旱棚试验池进行池栽试验。2013年池栽试验土壤: pH 6.6, 有机质29.8 g kg-1, 全氮 1.6 g kg-1, 全磷 1.28 g kg-1, 全钾 16.3 g kg-1, 速效氮317 mg kg-1, 速效磷42.2 mg kg-1, 速效钾382 mg kg-1。1.2 试验材料
玉米品种为“登海605”, 由山东登海种业股份有限公司提供; 大豆品种为“南豆12”, 由四川省南充市农业科学研究院大豆研究所提供。1.3 试验方法
1.3.1 大田定位试验 采用二因素裂区设计, 主因素为种植模式, 即玉米单作(MM)、大豆单作(MS)、玉米-大豆套作(IMS); 副因素为玉米大豆施氮总量, 设不施氮(NN)、减量施氮(RN: 180 kg N hm-2, 根据当地玉米施氮量确定)、常量施氮(CN: 240 kg N hm-2, 根据当地玉米与大豆的总施氮量确定), 且玉米与大豆施氮比为3∶1, 共9个处理, 重复3次。每个处理连续种3带, 带长6 m、带宽2 m, 单个小区面积36 m2。单作采用等行距种植, 玉米、大豆行距分别为100 cm和50 cm, 穴距均为17 cm, 出苗后均穴留1株, 玉米和大豆密度分别为5.85万株 hm-2和11.7万株 hm-2。玉米-大豆套作采用宽窄行种植, 玉米宽行160 cm, 窄行40 cm, 玉米宽行内种2行大豆, 大豆行距40 cm, 玉米与大豆间距60 cm, 穴距17 cm; 玉米、大豆单作与套作的密度相同, 玉米穴留1株, 大豆穴留2株(图1)。玉米氮肥分为底肥和大喇叭口期追肥2次施用, 大豆氮肥按底肥施用; 玉米单作和大豆单作按传统株间穴施方式施肥; 玉米-大豆套作按玉米、大豆一体化施肥方式, 即玉米底肥统一按72 kg N hm-2株间穴施; 玉米大喇叭口期追肥则与大豆磷钾肥一起混合施用, 在玉米、大豆之间, 距玉米25 cm处开沟施肥。各作物氮肥施用方式及施用量见表1, 单、套作玉米及单作大豆的磷钾肥随底肥施用, 玉米施用量为P2O5 105 kg hm-2、K2O 112.5 kg hm-2, 大豆施用量为P2O5 63 kg hm-2、K2O 52.5 kg hm-2。2012年, 玉米4月1日播种, 7月29日收获; 大豆6月10日播种, 10月31日收获; 2013年, 玉米4月3日播种, 8月1日收获; 大豆6月11日播种, 10月29日收获。Table 1
表1
表1不同种植方式下的氮肥施用量
Table 1
| 种植模式 Planting patterns | 施氮处理 N application | 施氮总量 Total N application rate | 底肥 Base fertilizer | 追肥 Top fertilizer |
|---|---|---|---|---|
| 玉米单作 MM | 减量施氮RN | 135 | 72 | 63 |
| 常量施氮CN | 180 | 72 | 108 | |
| 大豆单作 MS | 减量施氮RN | 45 | 45 | 0 |
| 常量施氮CN | 60 | 60 | 0 | |
| 玉米-大豆套作 IMS | 减量施氮RN | 180 | 72 | 108 |
| 常量施氮CN | 240 | 72 | 168 |
新窗口打开|下载CSV
图1
新窗口打开|下载原图ZIP|生成PPT图1作物种植模式及土壤取样布局示意图
A为玉米-大豆套作; B为玉米单作; C为大豆单作。
Fig. 1Schematic diagram of planting patterns and soil sample points
A: maize/soybean relay intercropping; B: maize monoculture; C: soybean monoculture.
1.3.2 池栽试验 采用二因素随机区组设计, 因素一为种植模式, 即玉米单作(MM)、大豆单作(MS)、玉米-大豆套作(IMS); 因素二为玉米大豆施氮总量, 分别为不施氮(NN), 减量施氮(RN: 180 N kg hm-2), 3次重复, 共6个处理。每个小区面积2.0 m×2.5 m = 5.0 m2。作物种植模式, 施肥方式及田间管理同大田试验。2013年, 4月8日播种玉米, 8月5日收获; 6月15日播种大豆, 11月5日收获; 2014年, 4月10日播种玉米, 8月6日收获; 6月14日播种大豆, 11月6日收获。
1.4 大田土壤样品的采集与测定
于玉米拔节期(V6)、大喇叭口期(12)、抽雄吐丝期(VT)、成熟期(R6)、大豆五节期(V5)、盛花期(R2)、结荚期(R4)、鼓粒期(R6)、成熟期(R8)[20]用土钻分带分作物采集土壤样品(0~20 cm)。参照刘小明等[21]土样采集方法, 单作玉米在距玉米行0 cm和25 cm处取样, 单作大豆样在距大豆行0 cm和25 cm处取样, 玉米-大豆套作下玉米带(或大豆带)分别在垂直玉米行(或大豆行)距窄行0 cm、20 cm, 距宽行20 cm、40 cm处取样, 去除样品中可见细根后按四分法制样(图1)。1.4.1 土壤固氮作用强度测定 大田土壤固氮作用强度测定参照赵伟等[22]的方法。采用恒温培养测全氮法, 称取已过2 mm筛的新鲜土样50 g, 装入已灭菌的100 mL烧杯, 添加1 g葡萄糖并拌匀, 再添加蒸馏水至田间持水量的60%, 最后放入25℃恒温室内培养30 d, 培养期间及时补足损失的水分。将培养完成后的土壤, 立即烘干并过0.149 mm筛, 用凯氏定氮仪测定其全氮含量, 同时测定未经培养的土壤全氮含量作为对照。
1.4.2 土壤硝化作用强度测定 大田土壤硝化作用强度测定参照Chu等[23]采用土壤悬液法。首先, 采用烘干法测定各土样含水率, 用以矫正硫酸铵和蒸馏水添加体积。然后, 取10 g新鲜土样装入已灭菌的100 mL烧杯, 加入硫酸铵和蒸馏水的总体为2 mL, 对照处理添加蒸馏水2 mL, 然后密封放在黑暗中以28℃孵化48 h后, 添加40 mL 2 mol L-1的KCl浸提1 h后, 过滤并测定NO3--N含量。
1.4.3 土壤氨化作用强度测定 大田土壤氨化作用强度测定参照蔡艳等[24]的方法。采用土壤培养法, 称取已过2 mm筛的土样10 g放入已灭菌的100 mL三角瓶, 添加20 g L-1蛋白胨溶液1 mL, 用已灭菌的蒸馏水将土壤含水量调至添加最大持水量的60%, 密封后将土样置于25℃恒温室培养7 d。培养结束后按照水土比5∶1添加1 mol L-1 KCl溶液并振荡1 h, 过滤并测定土壤NH4+-N含量, 同时测定对照组含量, 将处理组与对照组差值换算为单位干土中NH4+-N的毫克数, 即为土壤氨化作用强度[21]。
1.4.4 土壤氨挥发量测定 大田土壤氨挥发量测定参照王朝辉等[25]方法, 在作物施肥或追肥次日采用密闭箱法并稍有改进测定土壤氨挥发量, 用铁丝支架将盛有20 mL 2% 的硼酸的培养皿固定于距土壤8 cm高处, 将20 cm×20 cm×20 cm的聚氯乙烯密闭箱盖上, 在上午8:00—10:00连续收集后测定氨挥发量, 开始1周每天取样一次, 随后2~3 d取样一次, 直至处理组和对照组数据相近, 汇总计算总挥发量[21]。
1.4.5 土壤N2O排放量测定 土壤N2O排放量测定参照Luo等[26]采用静态箱-气相色谱法并稍有改进测定N2O排放, 即在玉米大喇叭口期(V12)、玉米大豆共生期(玉米抽雄吐丝期VT、大豆五节期V5)和大豆鼓粒期R5, 随机放置PVC静态箱(直径20 cm, 高20 cm)收集24 h, 然后抽取50 mL气样运用Agilent 6850气相色谱仪分析, 汇总计算总排放量。
1.4.6 NO3--N含量测定 NO3--N含量测定参照赵伟等测定采用KCl浸提法[22], 浸提及测定步骤与土壤硝化作用中NO3--N含量测定步骤相同[23]。池栽各作物单作与套作下的土壤样品取样制备方法同大田试验, 于玉米、大豆成熟期用土钻分带分作物采集土壤样品, 取样区间为20 cm一层, 共取5层。
土壤固氮作用强度(mg g-1) = 培养后土样全氮含量(mg g-1) - 未培养土样全氮含量(mg g-1)
土壤硝化作用强度(mg g-1 d-1) = 培养后土样NO3--N含量(mg g-1 d-1) - 空白土样NO3--N含量(mg g-1 d-1)
土壤氨化作用强度(mg g-1) = 培养后土样NH4+-N含量(mg g-1) - 空白土样NH4+-N含量(mg g-1)
土壤氨挥发量(kg hm-2) = 单位面积氨吸收量(g m-2)×10
土壤N2O排放量(kg hm-2) = 单位面积N2O排放量(g m-2)×10
NO3--N累积量(kg hm-2) = 土层厚度(cm)×土壤容重(g cm-3)×NO3--N含量(mg kg-1干土)/10
1.5 数据处理
采用Microsoft Excel 2003 整理数据, SigmaPlot v.12.5作图, DPS v.7.05软件进行方差分析和LSD显著性测验(P<0.05)。2 结果与分析
2.1 土壤氮素转化强度
2.1.1 种植模式及施氮水平对土壤硝化作用强度的影响 与相应单作相比, 套作下玉米、大豆的土壤硝化作用强度提高, 全生育期下玉米平均提高7.2%, 大豆平均提高14.3% (图2)。不同种植模式下, 施氮较不施氮提高了作物土壤硝化作用强度, 但RN与CN间差异不显著; IMS内大豆的土壤硝化作用强度, RN比CN高12.2%。图2
新窗口打开|下载原图ZIP|生成PPT图2不同种植与施氮方式下土壤硝化作用强度(仁寿大田, 2013)
A: 玉米土壤。MMNN: 单作玉米不施氮; MMRN: 单作玉米减量施氮; MMCN: 单作玉米常规施氮; IMNN: 套作玉米不施氮; IMRN: 套作玉米减量施氮; IMCN: 套作玉米常规施氮。B: 大豆土壤。MSNN: 单作大豆不施氮; MSRN: 单作大豆减量施氮; MSCN: 单作大豆常规施氮; ISNN: 套作大豆不施氮; ISRN: 套作大豆减量施氮; ISCN: 套作大豆常规施氮。 横坐标轴为生育时期, 玉米生育时期分别为拔节期(V6)、大喇叭口期(V12)、抽雄吐丝期(VT)和成熟期(R6), 大豆生育时期分别为五节期(V5)、盛花期(R2)、结荚期(R4)、鼓粒期(R6)和成熟期(R8)。同一生育时期下, 相同种植模式不同氮水平间字母不同表明差异显著(LSD, P < 0.05)。
Fig. 2Nitrifying capacities of soil under different N rates and planting patterns (field trial in Renshou, 2013)
A: soil of maize strips. MMNN: monoculture maize with no N; MMRN: monoculture maize with reduced N; MMCN: monoculture maize with conventional N; IMNN: intercropped maize with no N; IMRN: monoculture maize with reduced N; IMCN: intercropped maize with conventional N. B: soil of soybean strips. MSNN: monoculture maize with no N, MSRN: monoculture maize with reduced N; MSCN: monoculture maize with conventional N; ISNN: intercropped maize with no N; ISRN: monoculture maize with reduced N; ISCN: intercropped maize with conventional N. The abscissa is for the growth stages, the growth stages of maize include jointing stage (V6), 12th leaf (bell stage, V12), tasseling stage (VT), full maturity (R6), and the growth stages of soybean include the fifth trifoliolate stage (V5), full bloom stage (R2), full pod stage (R4), full seed stage (R6), full maturity stage (R8). At the same growth stage, bars represented by different letters between N levels are significantly different under the same planting pattern (LSD, P < 0.05).
2.1.2 种植模式及施氮水平对氨化作用强度的影响
与相应的单作相比, 套作玉米(IM: maize intercropped)和套作大豆(IS: soybean intercropped)的土壤氨化作用强度提高, 全生育期下IM较MM平均提高19.1%, IS较MS平均提高21.9% (图3)。单套作模式下玉米、大豆土壤的氨化作用强度均随施氮量的增加而增加, 其中, IM下土壤氨化强度RN比CN低23.7%, IS下土壤氨化强度RN比CN低8.7%。
图3
新窗口打开|下载原图ZIP|生成PPT图3不同种植与施氮方式下土壤氨化作用强度(仁寿大田, 2013)
A: 玉米土壤; B: 大豆土壤。缩写同
Fig. 3Ammonifying capacities of soil under different N rates and planting patterns (field trial in Renshou, 2013)
A: soil of maize strips; B: soil of soybean strips. Abbreviations are the same as those as in
2.1.3 种植模式及施氮水平对固氮作用强度的影响
全生育期下IM与MM在土壤固氮作用强度无显著差异, 而IS的土壤固氮作用强度在V5期较MS显著降低32.3%, R2期后差异不显著(图4)。单套作模式下玉米、大豆的土壤固氮作用强度均随施氮量的增加而降低, 而全生育时期下IM土壤固氮作用强度RN比CN高29.7%, IS下土壤固氮作用强度RN比CN高32.0%。
图4
新窗口打开|下载原图ZIP|生成PPT图4不同种植与施氮方式下土壤固氮作用强度(仁寿大田, 2013)
A: 玉米土壤; B: 大豆土壤。缩写同
Fig. 4Nitrogen-fixing capacities of soil under different N rates and planting patterns (field trial in Renshou, 2013)
A: soil of maize strips; B: soil of soybean strips. Abbreviations are the same as those as in
2.2 种植模式及施氮水平对土壤氨挥发强度的影响
与IMS系统的氨挥发累积量相比, MM与其无显著差异, MS则显著降低(图5)。不同种植模式下, 氨挥发累积量均随施氮量的增加而增加。不同氮水平下, 与CN相比, 全生育时期下RN的MM、MS、IMS的氨挥发累积量两年平均降低37.5%、26.3%和37.2%。进一步分析氨挥发损失率(图6), 各施氮处理下均以MM的氨挥发损失率最高。与CN相比, 全生育时期下RN的MM、MS、IMS的氨挥发损失率分别降低34.3%、16.9%和32.6%; 而RN下的IMS的氨挥发损失率比MM低20.3%。图5
新窗口打开|下载原图ZIP|生成PPT图5不同种植模式下不同施氮量的氨挥发累积量(仁寿大田, 2013)
MM: 玉米单作; MS: 大豆单作; IMS: 玉米-大豆套作。NN: 不施氮; RN: 减量施氮; CN: 常规施氮。同一种植模式下不同字母标记表明不同氮水平处理间差异显著(LSD, P < 0.05)。
Fig. 5Cumulated amount of ammonia volatilization of different N application rates under different planting pattern (field trial in Renshou, 2013)
MM: monoculture maize; MS: monoculture soybean; IMS: maize-soybean relay intercropping. NN: no N; RN: reduced N; CN: conventional N. Bars represented by different letter are significantly different between N levels under the same planting pattern (LSD, P < 0.05).
图6
新窗口打开|下载原图ZIP|生成PPT图6不同种植模式下不同施氮量的氨挥发损失率(仁寿大田, 2013)
MM: 玉米单作; MS: 大豆单作; IMS: 玉米-大豆套作。RN: 减量施氮; CN: 常规施氮。同一种植模式下不同字母标记表明不同氮水平处理间差异显著(LSD, P < 0.05)。
Fig. 6Loss rate of ammonia volatilization of different N application rates under different planting pattern (field trial in Renshou)
MM: monoculture maize; MS: monoculture soybean; IMS: maize-soybean relay intercropping. RN: reduced N; CN: conventional N. Bars represented by different letter are significantly different between N levels under the same planting pattern (LSD, P < 0.05).
2.3 种植模式及施氮水平对土壤N2O排放的影响
不同种植模式间全生育时期总N2O排放量无显著差异, 各种植模式下的总N2O损失量均随施氮量的增加而增加(图7-A)。不同氮水平下, 与CN相比, 全生育时期下RN的MM、MS、IMS的N2O损失量显著降低38.8%、40.1%和41.0%。进一步分析N2O损失率, 全生育时期下不同施氮处理均表现为MS>MM>IMS (图7-B)。不同氮水平下, 与CN相比, RN下的MM、MS、IMS的N2O损失率分别降低32.9%、35.4%和35.0%; 在RN下, IMS的N2O损失率比MM、MS的分别低31.0%和75.6%。图7
新窗口打开|下载原图ZIP|生成PPT图7不同种植模式和施氮量下土壤N2O排放特征(仁寿大田, 2013)
A: N2O排放量; B: N2O损失率。MM: 玉米单作; MS: 大豆单作; IMS: 玉米-大豆套作。NN: 不施氮; RN: 减量施氮; CN: 常规施氮。同一种植模式下不同字母标记表明不同氮水平处理间差异显著(LSD, P < 0.05)。
Fig. 7Characteristics of N2O emission under different planting pattern and N application rates (field trial in Renshou, 2013)
A: N2O emissions; B: the loss rate of N2O. MM: monoculture maize; MS: monoculture soybean; IMS: maize-soybean relay intercropping. NN: no N; RN: reduced N; CN: conventional N. Bars represented by different letter are significantly different between N levels under the same planting pattern (LSD, P < 0.05).
2.4 种植模式及施氮水平对土壤NO3--N累积量的影响
不同种植模式下, 随土壤层次的增加, 玉米、大豆的土壤NO3--N累积量均降低(图8和图9)。在NN下MM与IM的土壤NO3--N累积量无显著差异; 而RN下IM的土壤NO3--N累积量较MM显著提高, 且0~100 cm土层的NO3--N总积累量IM较MM提高了7.1%。IS的土壤NO3--N累积量低于MS, 且RN处理下, 0~100 cm土层的NO3--N积累量IS较MS降低了12.9%。不同氮水平下, 施氮较不施氮显著提高了玉米、大豆的土壤NO3--N累积量; IM和IS处理下0~100 cm土层的NO3--N积累量在施氮后较不施氮分别提高了49.4%和14.7%。图8
新窗口打开|下载原图ZIP|生成PPT图8不同种植方式下的玉米土壤NO3--N累积量(雅安池栽)
MMNN: 单作玉米不施氮; MMRN: 单作玉米减量施氮; IMNN: 套作玉米不施氮; IMRN: 套作玉米减量施氮。同一取样区间下, 相同种植模式不同氮水平间字母不同表明差异显著(LSD, P < 0.05)。
Fig. 8NO3--N accumulation amount of maize under different planting patterns (plot trial in Ya’an)
MMNN: monoculture maize with no N; MMRN: monoculture maize with reduced N; IMNN: intercropped maize with no N; IMRN: monoculture maize with reduced N. At the same sampling interval, bars represented by different letter are significantly different between N levels under the same planting pattern (LSD, P < 0.05).
图9
新窗口打开|下载原图ZIP|生成PPT图9不同种植方式下的大豆土壤NO3--N累积量(雅安池栽)
MSNN: 单作大豆不施氮; MSRN: 单作大豆减量施氮; ISNN: 套作大豆不施氮; ISRN: 套作大豆减量施氮。同一取样区间下, 相同种植模式不同氮水平间字母不同表明差异显著(LSD, P < 0.05)。
Fig. 9Soil NO3--N accumulation amount of soybean strips under different planting patterns (plot trial in Ya’an)
MSNN: monoculture soybean with no N; MSRN: monoculture soybean with reduced N; ISNN: intercropped soybean with no N; ISRN: monoculture soybean with reduced N. At the same sampling interval, bars represented by different letter are significantly different between N levels under the same planting pattern (LSD, P < 0.05).
3 讨论
3.1 减量施氮下玉米-大豆套作系统土壤N转化的特征
禾本科-豆科间套作是一种氮高效的种植模式, 在满足禾本科生长发育的氮素需求同时, 充分发挥豆科作物的固氮作用减少了化学氮肥的投入量[4]。合理的养分管理策略是间套作系统高产的基础, 长期间套作下无氮肥或大量氮肥投入, 均不利于系统增产及可持续发展[10]。有机态氮肥施用后, 在土壤微生物的作用下转化为无机氮才能被作物吸收利用[22]。因此, 施氮增强了土壤的氨化作用强度、硝化作用强度, 提高了土壤NO3--N和NH4+-N含量[27,28,29,30,31,32,33,34,35,36,37,38,39]。但是, 氮肥投入增强了土壤硝化-反硝化作用, 提高了N2O排放量[30], 减弱了土壤的固氮作用[28], 增加农业生产的环境成本。本研究中, 套作提高了作物的土壤硝化作用强度及氨化作用强度。这是因为套作提高了根际土壤细菌数量, 根际土壤中amoA和nirS基因丰度及多样性指数较相应单作显著提高, 而nirS基因丰度及多样性指数较相应单作显著降低[3], 增强土壤自生固氮作用。但是, 套作大豆土壤NO3--N含量显著低于单作。这与前人研究结果一致, 即间作蚕豆土壤中的NO3--N含量及积累量低于单作[31]。这是由于玉米的氮素竞争能力强于大豆, 通过氮素的竞争利用降低了土壤NO3--N含量[32]。在套作系统内, 与常规施氮相比, 减氮并未显著降低玉米的氨化作用强度; 而提高了大豆土壤的硝化作用强度, 降低了氨化作用强度。这是因为一方面, 高氮投入抑制了土壤硝化细菌的生长增殖, 减氮在减轻其抑制作用的同时降低了土壤的NO3--N和NH4+-N含量[29]; 另一方面, 玉米对土壤氮素的竞争吸收使得土壤无机氮向玉米侧集中, 大豆侧土壤中氮素的含量降低, 在一定程度上缓解高氮对土壤硝化细菌的抑制作用; 同时, 氨化作用强度的降低可避免土壤中NH4+-N离子浓度过高而发生挥发损失[29,32]。本试验中, 套作系统内的减氮处理下, 玉米、大豆土壤固氮作用强度显著高于常规施氮。前人研究指出套作较单作显著提高了土壤自身固氮菌数量[33], 土壤固氮作用与土壤各养分含量呈负相关。这暗示着套作减氮有利于土壤自生固氮菌群落结构的改善, 提高其对氮素固定量。因此, 玉米-大豆套作体系下的氮肥减量有利于氮素的转化及作物间和谐共生, 而除施肥以外大豆的自生固氮可增加土壤氮素含量, 大豆根瘤固氮的衰老周期变化调节着共生固氮量, 从而一定程度影响着土壤氮肥的投入, 而尚未有人研究玉米-大豆套作体系下大豆共生固氮衰老周期的变化特征, 因此该领域还需进一步研究。3.2 减量施氮下玉米-大豆套作系统的氮排放特征
氮肥被作物吸收利用的同时, 一部分通过氮肥损失途径损失掉, 剩下的则残留在土壤中。氮肥的损失途径主要为氨挥发及N2O排放, 氨挥发主要受土壤氨浓度影响, N2O主要产生于硝化-反硝化作用[8,30]。施氮通过增强土壤的硝化-反硝化作用, 增加了N2O排放[30], 同时, 土壤氨浓度的增加促进了氨挥发[21]。本研究中, 套作系统的氨挥发损失率和N2O损失率显著低于玉米单作。前人研究表明, 间套作可通过根际微生物群落结构的优化, 提高土壤的氨化作用强度、硝化作用强度, 降低反硝化作用强度, 从而降低N2O排放[3,8]。套作系统内减氮较常规施氮, 显著降低氨挥发损失量及其损失率和N2O排放量及其损失率。前人研究表明, 不同施氮水平下大豆/甘蔗间作系统的氮素淋失无显著差异, 但是高氮肥投入增加了氨挥发量和N2O排放量[34]。这可能是因为高氮肥投入增强了土壤反硝化作用, 使氮素更多地转化为N2O[35]; 同时长期施用无机氮肥导致土壤酸化, 进一步增加土壤的N2O排放[4]。然而, 包含豆科的间套作则可通过豆科的生物固氮减少化学氮肥的投入, 进而减少N2O的排放, 降低环境污染风险[36]。周丽等[3]研究表明, 玉米-大豆套作减氮可提高作物根际土的amoA基因丰度及多样性指数, 降低作物根际土的nirS基因丰度及多样性指数。因此, 间套作中减氮进一步提高土壤的氨化和硝化作用强度, 降低土壤的反硝化作用强度, 实现氮排放降低[3-4,8,21]。此外, 与相应单作相比, 玉米-大豆套作系统中玉米土壤的NO3--N累积量增加, 大豆NO3--N累积量降低。叶优良等[31]研究表明, 蚕豆玉米间作导致蚕豆土壤硝态氮积累降低; 这是因为间套作系统内存在氮素的竞争吸收, 导致氮素竞争能力相对较弱的豆科土壤中氮素积累降低[31,32,33]。综上所述, 玉米-大豆套作减氮处理可维持土壤肥力, 同时降低潜在的农业环境污染风险。但是, 玉米-大豆系统的氮素损失途径除N2O和氨排放之外还有氮素淋失, 夏季丰富的降雨对该套作系统下土壤氮素淋失影响尚不明确,有待进一步研究。4 结论
在共生期内, 与相应单作相比, 套作提高了玉米和大豆的土壤硝化作用、氨化作用强度, 但土壤固氮作用无显著变化, 提高了表层土中硝态氮残留量, 降低了氨挥发率、损失率及N2O损失率。与常规施氮相比, 减氮降低了玉米土壤硝化作用、氨化作用及大豆土壤氨化作用, 增强了玉米土壤固氮作用强度、大豆硝化作用和固氮作用, 降低了氮排放。减量施氮的玉米-大豆套作系统可增强耕层土壤NO3--N积累, 为作物氮素吸收提供充足氮源。参考文献 原文顺序
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被引期刊影响因子
DOI:10.1016/j.envpol.2016.08.078URLPMID:27613318 [本文引用: 1]
China's Central government has released an ambitious plan to tackle the nation's water pollution crisis. However, this is inhibited by a lack of data, particularly for groundwater. We compiled and analyzed water quality classification data from publicly available government sources, further revealing the scale and extent of the crisis. We also compiled nitrate data in shallow and deep groundwater from a range of literature sources, covering 52 of China's groundwater systems; the most comprehensive national-scale assessment yet. Nitrate pollution at levels exceeding the US EPA's maximum contaminant level (10mg/L NO 3 N) occurs at the 90th percentile in 25 of 36 shallow aquifers and 10 out of 37 deep or karst aquifers. Isotopic compositions of groundwater nitrate (δ 15 N and δ 18 O NO3 values ranging from6114.9‰ to 35.5‰ and618.1‰ to 51.0‰, respectively) indicate many nitrate sources including soil nitrogen, agricultural fertilizers, untreated wastewater and/or manure, and locally show evidence of de-nitrification. From these data, it is clear that contaminated groundwater is ubiquitous in deep aquifers as well as shallow groundwater (and surface water). Deep aquifers contain water recharged tens of thousands of years before present, long before widespread anthropogenic nitrate contamination. This groundwater has therefore likely been contaminated due to rapid bypass flow along wells or other conduits. Addressing the issue of well condition is urgently needed to stop further pollution of China's deep aquifers, which are some of China's most important drinking water sources. China's new 10-point Water Pollution Plan addresses previous shortcomings, however, control and remediation of deep groundwater pollution will take decades of sustained effort.
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Annual biological N 2 fixation by legumes and by free-living non-symbiotic organisms was estimated for all Canadian farmland from 1981 to 2006 using the Canadian Agricultural Nitrogen Budget (CANB v3.0) model. Published average N 2 fixation rates were adjusted using variations in crop yield, and the total amount of N 2 fixed was estimated at the Soil Landscape of Canada polygon level (1:1,000,000) and then scaled up to provincial and national levels. The adjusted N 2 fixation rates ranged from 54 to 15002kg02N02ha 611 (average 9502kg02N02ha 611 ) for pulse crops, 57 to 20102kg02N02ha 611 (average 11802kg02N02ha 611 ) for soybean ( Glycine max (L.) Merr.), 27 to 14102kg02N02ha 611 (average 7902kg02N02ha 611 ) for hay [i.e., a mixture of alfalfa ( Medicago sativa L.), clover ( Trifolium ), timothy ( Phleum pratense ) and brome ( Bromus ) grasses, etc.] and 141 to 30002kg02N02ha 611 (average 21802kg02N02ha 611 ) for alfalfa. Total estimated N 2 fixation for all Canadian farmland increased from 0.99602Tg in 1981 to 1.76702Tg in 2006, primarily due to an increased legume hectare over time (from 9 to 1502Mha). These four legume crops accounted for 82–89% of total N 2 fixation in Canada. Provincial averages of N 2 fixation by total farmland area varied from 6 to 1902kg02N02ha 611 in Saskatchewan, 16 to 2702kg02N02ha 611 in Alberta and Manitoba, 44 to 7902kg02N02ha 611 in Ontario and Quebec and 27 to 4702kg02N02ha 611 in Atlantic provinces. Because the Prairies provinces contain 75% of total farmland, the national averages of N 2 fixation by total farmland was heavily weighted by the estimates for the Prairies and ranged from 16 to 2902kg02N02ha 611 .
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Abstract: Field experiments were conducted to determine the optimal field combination that benefited soybean carbon-nitrogen metabolism and yield in aize/ soybean relay-cropping system. Split plot design was adopted, with different plant-types of maize as main plots, planting width as sub-plots. The results showed that under large width and relay cropping with erect maize, shade damage to soybean was reduced. The trend of soybean carbon-nitrogen metabolism was beneficial to high yield. The content of carbon and nitrogen and the activity of SPS and GS kept at a high level at every growing stage. After R4, the starch in leaf degraded into sugar quickly and transferred to grain, and the decreasing rate of nitrogen slowed down. Basis on our previous research work, the result suggested that R2 was the crucial stage for soybean to experience light change (maize harvest time was around R2), so the carbon-nitrogen metabolism ability of soybean at R2 had a strong impact for yield. And the carbon-nitrogen metabolism levels of soybean at R6 could partly reflect yield. In conclusion, relay-cropping soybean with erect maize in planting width 1.17m / 0.83m (soybean/maize) was the best field combination that could ensure high yield and efficiency all year round.
DOI:10.7505/j.issn.1007-9084.2014.02.010URL [本文引用: 1]
Abstract: Field experiments were conducted to determine the optimal field combination that benefited soybean carbon-nitrogen metabolism and yield in aize/ soybean relay-cropping system. Split plot design was adopted, with different plant-types of maize as main plots, planting width as sub-plots. The results showed that under large width and relay cropping with erect maize, shade damage to soybean was reduced. The trend of soybean carbon-nitrogen metabolism was beneficial to high yield. The content of carbon and nitrogen and the activity of SPS and GS kept at a high level at every growing stage. After R4, the starch in leaf degraded into sugar quickly and transferred to grain, and the decreasing rate of nitrogen slowed down. Basis on our previous research work, the result suggested that R2 was the crucial stage for soybean to experience light change (maize harvest time was around R2), so the carbon-nitrogen metabolism ability of soybean at R2 had a strong impact for yield. And the carbon-nitrogen metabolism levels of soybean at R6 could partly reflect yield. In conclusion, relay-cropping soybean with erect maize in planting width 1.17m / 0.83m (soybean/maize) was the best field combination that could ensure high yield and efficiency all year round.
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). The results demonstrated that, the ), transpiration rate (), stomatal conductance (), photosynthetic capacity (), dry matter accumulation of soybean increased initially and then decreased in the later stage. Compared with soybean monocropping, the , , and of intercropped soybean decreased significantly in the intergrowth stage (V5), but had no significant differences at R2, R4, and R6 stages. Although the below-ground, above-ground and total dry matter accumulation of soybean significantly decreased during the whole growth period, the crop growth rate from R4 to R6 stages and economic coefficient significantly increased. In the maize-soybean relay strip intercropping system, N application significantly enhanced the , , , dry matter accumulation, pod number per plant, and grain yield of soybean. Compared with the conventional N application ), of soybean under the reduced amount of N application (180 N kg ha) increased by 3.57% and 11.82% at R4 and R6 stages, respectively. Furthermore, the total dry matter accumulation increased by 5.06% and 10.21% at R6 and R8 stages, and pod number per plant and grain yield increased by 8.30% and 10.15%, respectively. Finally, the maize-soybean relay strip intercropping system possessed the highest yield under the N application rate of 180 N kg ha, with the economic coefficient and land equivalent ratio (LER) of 0.49 and 2.17, respectively. Taken together, the reduced N application in maize-soybean relay strip intercropping system can increase the yield of soybean and whole the system through improving soybean photosynthetic characteristics and enhancing dry matter accumulation.
DOI:10.3724/SP.J.1006.2014.01629URL [本文引用: 1]
). The results demonstrated that, the ), transpiration rate (), stomatal conductance (), photosynthetic capacity (), dry matter accumulation of soybean increased initially and then decreased in the later stage. Compared with soybean monocropping, the , , and of intercropped soybean decreased significantly in the intergrowth stage (V5), but had no significant differences at R2, R4, and R6 stages. Although the below-ground, above-ground and total dry matter accumulation of soybean significantly decreased during the whole growth period, the crop growth rate from R4 to R6 stages and economic coefficient significantly increased. In the maize-soybean relay strip intercropping system, N application significantly enhanced the , , , dry matter accumulation, pod number per plant, and grain yield of soybean. Compared with the conventional N application ), of soybean under the reduced amount of N application (180 N kg ha) increased by 3.57% and 11.82% at R4 and R6 stages, respectively. Furthermore, the total dry matter accumulation increased by 5.06% and 10.21% at R6 and R8 stages, and pod number per plant and grain yield increased by 8.30% and 10.15%, respectively. Finally, the maize-soybean relay strip intercropping system possessed the highest yield under the N application rate of 180 N kg ha, with the economic coefficient and land equivalent ratio (LER) of 0.49 and 2.17, respectively. Taken together, the reduced N application in maize-soybean relay strip intercropping system can increase the yield of soybean and whole the system through improving soybean photosynthetic characteristics and enhancing dry matter accumulation.
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通过3年定位试验对不同培肥方式下黑土生态系统中的氮素转化作用进行了研究。结果表明,2005年和2007年培肥处理土壤的自生固氮作用强度均显著低于对照,2007年抑制强度由大到小依次为化肥高量〉农肥高量〉农肥低量〉农化等量〉化肥低量〉对照。2005年和2007年土壤氨化作用强度在生长前3个时期农肥处理一直高于化肥处理和农肥化肥配比处理,至鼓粒期各处理土壤氨化作用强度达到最高值,并且2007年大豆田的土壤氨化作用强度显著高于2005年大豆田的土壤氨化作用强度。农肥施用处理的硝化作用强度始终显著高于化肥处理和其它处理,2005年和2007年大豆田土壤的硝化作用强度均在鼓粒期（T4）达到最高。2005年和2007年各施肥处理土壤反硝化作用强度均高于对照,农肥低量处理和农肥高量处理分别比无肥处理提高了4.64%和7.14%,化肥低量处理和化肥农肥等量处理高于农肥处理,分别比无肥处理增加13.04%和10.01%,化肥高量处理最高,比无肥处理提高了16.37%,2007年大豆田反硝化作用强度显著高于2005年大豆田的反硝化作用强度,长期施用化肥增加了土壤反硝化作用强度,因此长期合理地施用有机肥对减少黑土氮素的损失有良好的作用。
URL [本文引用: 3]
通过3年定位试验对不同培肥方式下黑土生态系统中的氮素转化作用进行了研究。结果表明,2005年和2007年培肥处理土壤的自生固氮作用强度均显著低于对照,2007年抑制强度由大到小依次为化肥高量〉农肥高量〉农肥低量〉农化等量〉化肥低量〉对照。2005年和2007年土壤氨化作用强度在生长前3个时期农肥处理一直高于化肥处理和农肥化肥配比处理,至鼓粒期各处理土壤氨化作用强度达到最高值,并且2007年大豆田的土壤氨化作用强度显著高于2005年大豆田的土壤氨化作用强度。农肥施用处理的硝化作用强度始终显著高于化肥处理和其它处理,2005年和2007年大豆田土壤的硝化作用强度均在鼓粒期（T4）达到最高。2005年和2007年各施肥处理土壤反硝化作用强度均高于对照,农肥低量处理和农肥高量处理分别比无肥处理提高了4.64%和7.14%,化肥低量处理和化肥农肥等量处理高于农肥处理,分别比无肥处理增加13.04%和10.01%,化肥高量处理最高,比无肥处理提高了16.37%,2007年大豆田反硝化作用强度显著高于2005年大豆田的反硝化作用强度,长期施用化肥增加了土壤反硝化作用强度,因此长期合理地施用有机肥对减少黑土氮素的损失有良好的作用。
DOI:10.1128/AEM.01536-06URL [本文引用: 2]
DOI:10.7606/j.issn.1009-1041.2016.11.15URL [本文引用: 1]
为探讨长期施肥下黑垆土氨化作用的变化，在长期定位试验条件下，分析了长期施肥对黑垆土氨化细菌数量和氨化作用强度的影响。结果表明，在小麦连作下，各施肥处理均可不同程度提高土壤中氨化细菌数量和氨化作用强度，其中单施有机肥及有机无机肥配施的效果更明显。在不同施肥处理中，氮磷配施有机肥处理的土壤氨化细菌数量最多（7．53×108个·g^-1），是不施肥处理（CK）的189．2倍，氨化作用强度最高（1．49mg·kg^-1），较CK增加55．0%；其次为单施有机肥、氮肥配施有机肥和磷肥配施有机肥处理，其氨化细菌数量和氨化作用强度均显著高于CK。在苜蓿连作下，与CK相比，单施磷肥处理的土壤氨化细菌数量和氨化作用强度均明显降低，降幅分别为99．5％和49．7％。因此，黄土高原黑垆土区小麦连作时，长期施用有机肥及有机无机肥配施均可提高土壤有机氮的转化作用，增强其供氮能力；苜蓿连作时，长期单施磷肥可减弱土壤有机氮的转化作用。
DOI:10.7606/j.issn.1009-1041.2016.11.15URL [本文引用: 1]
为探讨长期施肥下黑垆土氨化作用的变化，在长期定位试验条件下，分析了长期施肥对黑垆土氨化细菌数量和氨化作用强度的影响。结果表明，在小麦连作下，各施肥处理均可不同程度提高土壤中氨化细菌数量和氨化作用强度，其中单施有机肥及有机无机肥配施的效果更明显。在不同施肥处理中，氮磷配施有机肥处理的土壤氨化细菌数量最多（7．53×108个·g^-1），是不施肥处理（CK）的189．2倍，氨化作用强度最高（1．49mg·kg^-1），较CK增加55．0%；其次为单施有机肥、氮肥配施有机肥和磷肥配施有机肥处理，其氨化细菌数量和氨化作用强度均显著高于CK。在苜蓿连作下，与CK相比，单施磷肥处理的土壤氨化细菌数量和氨化作用强度均明显降低，降幅分别为99．5％和49．7％。因此，黄土高原黑垆土区小麦连作时，长期施用有机肥及有机无机肥配施均可提高土壤有机氮的转化作用，增强其供氮能力；苜蓿连作时，长期单施磷肥可减弱土壤有机氮的转化作用。
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DOI:10.1080/00380768.1993.10417010URL [本文引用: 1]
It is generally recognized that the nitrification activity in acid soils is very low. Indeed, nitrification in mineral soils has been found to be negligible at pH values below 5.0 (Dancer et al. 1973; Nyborg and Hoyt 1978). However, it was reported that autotrophic nitrification occurred in some tea soils at pH levels far below 5.0 (Walker and Wickramasinghe 1979; Hayatsu and Kosuge 1993). An acidophilic ammonia-oxidizing bacterium has been recently isolated from strongly acidic tea soils in Japan (Hayatsu 1993). On the other hand, fertilization has-been considered to be an important factor influencing nitrification in agricultural soils. For example, several studies have shown that the addition of ammoniacal fertilizer to soils can lead to the increase of the populations of Nitrosomonas (McLaren 1971; Ardakani et al. 1974). Liming of acidic soils also tends to stimulate the nitrification activity (Dancer et al. 1973; Nyborg and Hoyt 1978). Although nitrification has been studied in a wide variety of agricultural soils, there is little information available on nitrification in tea soils. The effect of fertilization on nitrification in tea soils is poorly documented.
URL [本文引用: 2]
以沈阳生态站长期定位试验为研究平台,对不同施肥制度下潮棕壤氮素功能群活性进行研究。结果表明：与不施肥相比,长期施肥明显提高土壤氨化作用,硝化作用和反硝化作用强度,其中以NPK＋M处理提高幅度最大;而长期施肥均明显抑制土壤固氮作用强度,其中氮肥抑制效果远大于有机肥。相关分析结果显示：土壤氨化作用,硝化作用和反硝化作用强度均与土壤养分含量呈显著正相关;而固氮作用强度与土壤大部分养分含量呈显著负相关,表明土壤氮素功能群活性易受土壤养分状况的影响,可以灵敏地反映土壤肥力质量变化。
URL [本文引用: 2]
以沈阳生态站长期定位试验为研究平台,对不同施肥制度下潮棕壤氮素功能群活性进行研究。结果表明：与不施肥相比,长期施肥明显提高土壤氨化作用,硝化作用和反硝化作用强度,其中以NPK＋M处理提高幅度最大;而长期施肥均明显抑制土壤固氮作用强度,其中氮肥抑制效果远大于有机肥。相关分析结果显示：土壤氨化作用,硝化作用和反硝化作用强度均与土壤养分含量呈显著正相关;而固氮作用强度与土壤大部分养分含量呈显著负相关,表明土壤氮素功能群活性易受土壤养分状况的影响,可以灵敏地反映土壤肥力质量变化。
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DOI:10.3969/j.issn.1674-5906.2008.01.071URL [本文引用: 4]
提高氮肥利用效率，减少氮肥过量施用对环境造成的污染，是保障国家粮食生产和生态环境安全的关键。文章以甘肃河西灌区为试验地点，在0、300、450kg．hm^-2氮水平下，探讨了小麦（Triticum aestivum L．），玉米（Zea mays L．）和蚕豆（Hcia faba L．），玉米间作对土壤硝态氮累积和分布的影响。结果表明：随氮肥用量增加，0-60cm土层土壤硝态氮相对累积量增加，100～200cm土层降低。在3个氮水平下，蚕豆间作土壤硝态氮含量和累积量都低于单作。小麦间作在300kg·hm^-2氮水平下土壤硝态氮累积量都低于单作，但在0和450kg·hm^-2氮水平下，小麦收获后间作与单作近似，玉米收获后小麦间作土壤硝态氮累积量都低于单作。与小麦和蚕豆间作的玉米在300kg·hm^-2氮水平下土壤硝态氮累积量都低于单作玉米，在0和450kg·hm^-2氮水平下则表现不同。在300kg·hm^-2氮水平下，两种间作氮肥当季利用率都明显高于相应的单作，施氮量增加到450kg·hm^-2时，则表现不一样。
DOI:10.3969/j.issn.1674-5906.2008.01.071URL [本文引用: 4]
提高氮肥利用效率，减少氮肥过量施用对环境造成的污染，是保障国家粮食生产和生态环境安全的关键。文章以甘肃河西灌区为试验地点，在0、300、450kg．hm^-2氮水平下，探讨了小麦（Triticum aestivum L．），玉米（Zea mays L．）和蚕豆（Hcia faba L．），玉米间作对土壤硝态氮累积和分布的影响。结果表明：随氮肥用量增加，0-60cm土层土壤硝态氮相对累积量增加，100～200cm土层降低。在3个氮水平下，蚕豆间作土壤硝态氮含量和累积量都低于单作。小麦间作在300kg·hm^-2氮水平下土壤硝态氮累积量都低于单作，但在0和450kg·hm^-2氮水平下，小麦收获后间作与单作近似，玉米收获后小麦间作土壤硝态氮累积量都低于单作。与小麦和蚕豆间作的玉米在300kg·hm^-2氮水平下土壤硝态氮累积量都低于单作玉米，在0和450kg·hm^-2氮水平下则表现不同。在300kg·hm^-2氮水平下，两种间作氮肥当季利用率都明显高于相应的单作，施氮量增加到450kg·hm^-2时，则表现不一样。
URL [本文引用: 4]
【Objective】 The aim of this paper was to study the mechanisms of interspecific nitrogen facilitation and transfer in the relay-planting systems of wheat/maize/soybean and wheat/maize/sweet potato. 【Method】 The methods of root barrier and 15N-isotope dilution were used to investigate the nitrogen transfer, nitrogen uptake and utilization in the two relay-planting systems.【Result】 Comparing the no barrier with solid barrier, the results showed that the 15N total uptake and crop recovery rate of wheat were highly remarkable and 15N% abundance and N% content of soil was lower obviously than that of solid barrier. In the wheat/maize/soybean system with no barrier, the 15N total uptake, 15N grain uptake, 15N crop recovery rate, soil 15N% abundance and N% content of maize increased by 17.62%, 24.52%, 17.63%, 13.9% and 10.1%, respectively. But in the wheat/maize/sweetpotato system with no barrier, the value of above index reduced by 50.19%, 42.58%, 33.42%, 29.6% and 5.2%, respectively. For soybean, the 15N total uptake, 15N grain uptake, and 15N crop recovery rate reduced, but the soil N% content increased by 6.06%. For sweetpotato, the 15N total uptake and crop recovery rate increased, but soil 15N% abundance and N% content reduced by 0.9% and 4.95%. 【Conclusion】 There existed nitrogen interspecific competition and facilitation and nitrogen transfer in the two relay-planting systems. In the wheat/maize/soybean system, the nitrogen uptake from fertilizer, soil fertility remaining and sustainable crop production were better than the system of wheat/maize/sweetpotato.
URL [本文引用: 4]
【Objective】 The aim of this paper was to study the mechanisms of interspecific nitrogen facilitation and transfer in the relay-planting systems of wheat/maize/soybean and wheat/maize/sweet potato. 【Method】 The methods of root barrier and 15N-isotope dilution were used to investigate the nitrogen transfer, nitrogen uptake and utilization in the two relay-planting systems.【Result】 Comparing the no barrier with solid barrier, the results showed that the 15N total uptake and crop recovery rate of wheat were highly remarkable and 15N% abundance and N% content of soil was lower obviously than that of solid barrier. In the wheat/maize/soybean system with no barrier, the 15N total uptake, 15N grain uptake, 15N crop recovery rate, soil 15N% abundance and N% content of maize increased by 17.62%, 24.52%, 17.63%, 13.9% and 10.1%, respectively. But in the wheat/maize/sweetpotato system with no barrier, the value of above index reduced by 50.19%, 42.58%, 33.42%, 29.6% and 5.2%, respectively. For soybean, the 15N total uptake, 15N grain uptake, and 15N crop recovery rate reduced, but the soil N% content increased by 6.06%. For sweetpotato, the 15N total uptake and crop recovery rate increased, but soil 15N% abundance and N% content reduced by 0.9% and 4.95%. 【Conclusion】 There existed nitrogen interspecific competition and facilitation and nitrogen transfer in the two relay-planting systems. In the wheat/maize/soybean system, the nitrogen uptake from fertilizer, soil fertility remaining and sustainable crop production were better than the system of wheat/maize/sweetpotato.
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DOI:10.1073/pnas.0600359103URL [本文引用: 2]
DOI:10.1038/srep20700URL [本文引用: 2]
DOI:10.1016/j.jclepro.2014.10.002URL [本文引用: 2]
