Effect of drip irrigation and nitrogen management on inorganic nitrogen content and nitrous oxide emission in maize-planting soil
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摘要:目的
获得玉米种植土壤氧化亚氮(N2O)减排的滴灌施肥模式,揭示不同滴灌灌水量和施氮比例下土壤无机氮含量对土壤N2O排放的影响。
方法在移动防雨棚内开展2季玉米3种滴灌灌水量(W60、W80和W100分别为田间持水量的50%~60%、70%~80%和90%~100%)和2种滴灌施氮比例(等N量为180 kg · hm−2,其中,F55为50%氮肥作基肥土施、50%氮肥作滴灌施肥,F37为30%氮肥作基肥土施、70%氮肥作滴灌施肥)的田间试验,测定生育期内土壤N2O通量和不同生育时期土壤无机氮含量,计算不同生育时期和全生育期土壤N2O排放量,分析土壤N2O通量与土壤无机氮含量之间的关系。
结果2季玉米土壤的N2O排放规律相似;相同施氮比例下,W100水分处理下土壤N2O排放通量在多数玉米生育时期高于W60和W80,表明高水分处理下土壤N2O排放通量高于中、低水分处理;相同水分处理下,除夏季玉米苗期外,土壤N2O排放通量施氮比例F55比F37更低。从整个生育时期土壤N2O累积排放量来看,春季玉米种植土壤W60F55处理N2O累积排放量低于其他处理,W80F55次之,夏季玉米种植土壤则是W60F37和W80F55处理的N2O累积排放量均较低。另外,2季玉米的土壤N2O通量与硝态氮和亚硝态氮含量之间显著相关,相关系数分别为0.433~0.579和0.396~0.532。
结论W80F55处理(田间持水量的70%~80%,以及50%氮肥作基肥土施,50%氮肥作滴灌施肥)降低种植玉米的土壤N2O排放。此外,土壤硝态氮和亚硝态氮含量显著影响土壤N2O排放。
Abstract:ObjectiveThe objectives of this study were to obtain a rational drip fertigation mode for reducing nitrous oxide (N2O) emission in maize-planting soil, and reveal the effects of soil inorganic nitrogen content on N2O emission under different drip irrigation amount and nitrogen fertigation ratios.
MethodIn the mobile rainproof shelter, two-season maize experiments with three drip irrigation amount (W60, W80 and W100 were 50%−60%, 70%−80% and 90%−100% of field water holding capacity, respectively) and two nitrogen fertigation proportions (F55: 50% nitrogen fertilizer applied to soil as basal fertilizer, and 50% nitrogen fertilizer as fertigation, F37: 30% nitrogen fertilizer applied to soil as basal fertilizer, and 70% nitrogen fertilizer as fertigation; Both of F55and F37 had the equal nitrogen rate of 180 kg·hm−2) were carried out. The soil N2O flux over the whole growth stage and soil inorganic nitrogen content at different growth stages were measured. Soil N2O emissions at the different growth stages and over the whole growth stage were calculated and the relationships between soil N2O flux and soil inorganic nitrogen content were analyzed.
ResultThe N2O emission fluxes of corn soil in two seasons were similar. Under the same nitrogen application ratio, soil N2O emission fluxes under W100 water treatment were higher than those under W60 and W80 in most maize growth periods, indicating that soil N2O emission fluxes under high water treatment were higher than those under medium and low water treatment. Under the same water treatment, soil N2O emission flux ratio of F55 was lower than that of F37 except in summer maize seedling stage. During the whole growth period, the cumulative emission of soil N2O under W60F55 treatment in spring was lower than that under other treatments, followed by W80F55, while those under W60F37 and W80F55 treatments in summer were lower. In addition, in two seasons, soil N2O flux was significantly correlated with nitrate nitrogen and nitrite nitrogen contents, with correlation coefficients ranging from 0.433 to 0.579 and 0.396 to 0.532, respectively.
ConclusionW80F55 treatment (70%−80% field water holding capacity, 50% nitrogen fertilizer as basal fertilizer and 50% nitrogen fertilizer as fertigation) reduces N2O emission from maize-planting soil. In addition, soil nitrate nitrogen and nitrite nitrogen contents significantly affect soil N2O emission.
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Keywords:
- Drip fertigation /
- Nitrate nitrogen /
- Nitrite nitrogen /
- Cumulative N2O emission
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液压压榨过程中蓖麻籽可视为非线性粘弹塑性流变体[1],流变特性是蓖麻压榨理论研究的主要内容之一.目前国内外相关学者在油料力学特性方面取得了一些研究成果,张亚新等[2]建立了葵花籽压榨过程中的塑性模型,Bargale等[3]研究了大豆出油率和压榨时间的关系,但均未给出流变模型;郑晓等[4]基于蠕变试验建立了菜籽、花生和芝麻的非线性粘弹塑性模型,但并不适用于松弛试验中蓖麻籽的流变特性.本文根据蓖麻籽应力松弛试验结果,建立了蓖麻籽压榨过程中非线性粘弹塑性流变模型,并验证了模型的可靠性,从而为榨油工艺中蓖麻油流出时间的确定提供理论依据.
1. 蓖麻籽瞬时力学特性试验
1.1 试验装置与材料
该试验采用单轴压榨试验装置(图 1)、电子万能试验机和上位工控机.湖南省林业科学院培育的“湘蓖一号”蓖麻籽作为试验原料.蓖麻籽直径为6~8 mm.
1.2 试验方法
将蓖麻籽装入单轴压榨试验装置,每组试验装入蓖麻籽高度为75 mm,共3组.利用电子万能试验机加载单轴压榨试验装置,加载速度为55 mm·min-1, 并用上位机读取万能试验机的压力值及试验装置柱塞的位移.
1.3 试验结果与分析
由轴向应力σ与轴向应变ε定义有:
式中F为电子万能试验机加载压力(N),A为柱塞面积(1 194.6 mm2),H0为压榨前蓖麻籽原始高度(mm),ΔH单轴压榨试验装置柱塞位移(mm),代入试验数据得瞬时轴向应力与应变关系曲线, 见图 2.
从图 2可知,该3组试验重复性较好;压榨过程中,蓖麻籽在应变小于0.55时,应力与应变基本呈线性关系;应变大于0.55时,蓖麻籽发生塑性变形且伴随着油脂的渗出,加载过程中由于油脂不能及时流出而加快了应力增加速度,因此轴向应力与应变呈现幂次增长关系;在此定义屈服应变为系统达到屈服状态时的应变[5].蓖麻籽屈服应变(εs)为0.55,对应的屈服应力约为3.5 MPa;为更好地获取应力松弛等时曲线,由图 2可确定应力松弛试验加载应变水平分别为0.20、0.30、0.40、0.50、0.55、0.60、0.65、0.70和0.75.
2. 蓖麻籽流变试验
在流变试验中,应力松弛试验和蠕变试验是等价的,松弛和蠕变是同一物理性质的不同表现形式[6],蠕变试验条件是应力恒定,而松弛试验则是应变恒定,对于油料压榨过程,恒定应变能更容易实现,为提高数据的可靠性, 本研究采用应力松弛试验.
2.1 试验方法
试验装置及试验材料与瞬时力学特性试验相同.应用分别加载试验方法[7-8],利用电子万能试验机对每组装有蓖麻籽的单轴压榨试验装置分别进行加载(加载速度与上述力学特性试验相同),使每组试验应变分别达到0.20、0.30、0.40、0.50、0.55、0.60、0.65、0.70、0.75,各应变水平保持30 min不变,每间隔3 min读取电子万能试验机的压力值.
2.2 试验结果与分析
将上位机采集试验数据代入轴向应力定义式,得到蓖麻籽应力松弛试验结果,各个应变水平轴向应力与时间关系如图 3所示.
通过对图 3分析可知,蓖麻籽应力松弛过程大致由快速松弛、缓慢平稳松弛2个阶段构成,快速松弛阶段蓖麻籽承受较大的外力,蓖麻籽在榨筒中滑动,且伴随着油脂流出榨筒,随着滑动和油脂的流出,应力逐渐减小,从而导致滑动和油脂流动减缓,因此应力在该阶段松弛较快,后阶段松弛比较平稳缓慢,且随时间推移呈现基本水平趋势;同时可知,在应变小于屈服应变时,等时长内应力松弛量(即轴向应力变化量)较小,反之较大,这是由于在应变大于屈服应变后,蓖麻籽开始破裂渗出油脂,油脂随油道流出单轴压榨试验装置导致应力松弛量较大,且应变越大,应力松弛量越大.通过对图 4应力应变等时曲线分析可知,在应变小于屈服应变时,应力应变基本呈现出线性关系,应变大于屈服应变时,应力应变呈现出非线性特征,这与瞬时力学特性试验结果基本吻合.
3. 蓖麻非线性流变本构模型
为使模型既能描述非线性问题又具有一定物理意义,本研究采用半理论半经验法建立非线性流变模型.对于线性段,利用模型理论建立线性粘弹性模型;对于非线性段,利用经验模型建立非线性粘塑性模型;根据流变模型并联应力叠加原理[9]可得非线性流变模型.
3.1 非线性粘弹塑性模型的建立
根据上述瞬时力学特性试验结果和流变试验应力应变等时曲线分析结果,可知在应变小于屈服应变0.55时,应力与应变基本是线性关系,该阶段可利用线性粘弹性模型描述.因松弛试验是恒应变,采用并联式模型将有利于分析研究,在并联式模型中广义Maxwell模型被广泛用于固体材料应力松弛表述,且能较为真实反映其应力松弛特性[10].同时由松弛试验结果可知该阶段应力松弛量较小,残余应力小且不为0,可采用三元件广义Maxwell模型模拟该线性段,如图 5所示.
根据试验结果,在应变大于屈服应变0.55时,应力与应变呈现出明显非线性关系.但广义Maxwell模型只能描述线性阶段流变特性,并未含有塑性元件,不能描述压榨过程中塑性阶段的应力应变关系,同时也不能描述屈服后的应力应变的非线性关系,因此需要对模型进行改进,需加入塑性元件使其能表述材料塑性特性,加入经验模型使其能描述非线性应力应变关系.
根据应力松弛试验方法,可见试验过程中控制的变量是应变,因此加入的塑性元件也需要与应变为变量.根据屈服应变的定义,以及类似应力型塑性元件的定义[9],在此定义应变型塑性元件为系统应变达到屈服应变时便开始产生塑性应力的模型,其本构方程如下:
当达到屈服时,应力型塑性元件的应变等于其并联支路的应变[9],应变型塑性元件的应力等于与该元件串联支路的应力.根据模型元件串并联原理[9],加入塑性元件及经验模型得改进后的广义Maxwell模型(图 6).根据应变型塑性元件的性质可知,当应变小于屈服应变时,该模型塑性元件应力为0,经验模型未受力,图 6所示模型可视为图 5的广义Maxwell模型;当应变大于屈服应变时,该模型塑性元件应力不再为0,模型加入了经验模型,此时图 6所示模型能描述应力应变非线性关系.
3.2 模型本构方程及其参数求解
根据上述模型的建立过程可知,除经验模型环节以外,图 6非线性粘弹塑性模型中的参数可由图 5线性阶段粘弹性模型求解出;对于经验模型环节,根据试验结果回归得到经验公式参数.在应变小于屈服应变的线性粘弹性阶段,图 6非线性模型等效于图 5所示广义Maxwell模型,设其E1、E2对应支路应力分别为σ1、σ2,由并联叠加原理可得图 5所示系统总应力:
同理,对于应变大于屈服应变的非线性粘弹塑性阶段,图 5所示系统的总应力为:
式中σJM为经验模型应力值.
3.2.1 线性阶段本构方程的求解
根据上述分析可知,当应变小于屈服应变时,线性阶段模型可用如图 5所示的三元件广义Maxwell模型表示,该模型由1个Maxwell模型和1个弹性元件并联组成,其中Maxwell模型的本构方程为:
松弛试验中应变恒定不变,解得Maxwell模型应力松弛方程为:
弹性元件E2支路方程为:σ2(ε)=E2ε.
线性阶段应力松弛本构方程为:
式中,t为松弛试验恒定应变保持时间,E(t)为松弛模量,由上式得:
根据线性阶段本构方程式可知,E(t)等于图 4中相应时间t对应的应力应变等时曲线中直线段的斜率(即应变小于屈服应变0.55的直线段),根据应力松弛试验直线段数据拟合得到如表 1所示的各等时曲线直线段斜率,表中拟合相关系数都在0.88以上,可知线性段应力应变高度线性相关.
表 1 各等时曲线中直线段拟合斜率Table 1. The fitted slope of linear segment of each isochronous curve根据松弛模量表达式,代入松弛模量试验值(即表 1中斜率)和对应时间,按最小二乘法构建目标函数,并利用Levenberg-Marquardt算法[11-12]求解目标函数从而得到弹性模量E1和E2分别为1.893 0和5.403 5MPa,粘性系数η1为16.553 4MPa·min;同时可得松弛模量试验值与松弛模式表达式模拟值的对比关系如图 7所示,由图可知该回归算法精度较高,同时也验证了松弛模量表达式能较好模拟线性段的松弛模量.
3.2.2 非线性阶段经验模型
为求解经验模型,将非线性模型中经验模型支路从非线性粘弹塑性模型中分离出来,如图 8所示.
由图 8和应变型塑性元件性质可知,当达到屈服后有:
由流变试验等时曲线,可知应力为瞬时应力值与应力松弛量之差,即可设:
式中,σJM0为t=0时瞬时应力值,σJMt为非零时刻t对应应力松弛量.
根据瞬时力学特性试验结果及流变试验等时曲线,应力应变非线性发生在应变大于屈服应变段,且在此段轴向应力较大,蓖麻籽之间间隙基本被变形的蓖麻籽填充,因此这段与粉体压制成型相似,可利用粉体压制成型过程中应力应变经验模型来建立蓖麻散体在高压段非线性模型.其中川北压制模型在模拟粉体压制过程应力和应变关系时有着较高的精度[13-14],故利用川北压制方程并根据塑性元件性质得瞬时应力为:
由流变试验结果可知,应力松弛量是应变ε和时间t的函数,故可设非零时刻t应力松弛量为:
式中a、b、c、d、n为经验模型参数.
联立总应力公式,Maxwell模型应力松弛方程和弹性元件E2支路方程并代入流变试验数据可得经验模型应力σJM(ε, t)值.根据以上公式并利用线性段参数求解算法和基于最小二乘法的多元非线性回归[12]可解得经验模型参数a、b、c、d、n的值分别为0.012 6、0.044 0、0.066 6、0.158 2和0.398 1.同时也可得到非零时刻t应力松弛的σJMt值(图 9).
综上,得蓖麻籽压榨过程中非线性流变本构模型:
根据模型推导过程中运用到川北压制方程可知,该模型适用于描述蓖麻籽压榨应变达到相对较大时的流变过程.
3.3 非线性流变模型的验证
利用非线性流变模型分别模拟蓖麻籽压榨应变水平为0.65、0.67、0.70、0.73、0.75的应力松弛规律,模拟结果如图 10所示.为提高验证的合理性,做2组应变水平分别为0.67和0.73的流变试验结合前面所做试验数据与模拟结果对比,如图 10所示.
应变水平0.65、0.67、0.70、0.73、0.75对应的平均相对误差分别为12.27%、3.37%、4.30%、4.44%和3.06%.应变大于0.65后的平均相对误差均小于4.50%,相对都较小,这是由于非线性流变本构模型给出的蓖麻籽压榨非线性流变模型引入了粉体压制方程,在应变大于0.65时应力已大于10 MPa,远大于屈服应力,榨筒中的蓖麻籽之间的间隙已被变形的蓖麻籽填充,此时能更好地近似于粉体压制过程,该非线性流变模型能更好地模拟蓖麻籽该段压榨过程,故该模型适用于描述压榨应变大于0.65时蓖麻籽的流变特性.
4. 结论
综合应力松弛试验结果可知蓖麻籽在压榨过程呈现出非线性流变的性质, 同时在快速松弛阶段,松弛速度较快且其呈现递减趋势,最终松弛速度趋近于0达到平稳松弛阶段,由试验结果可知各应变水平的快速松弛阶段历时约12 min;结合模型验证结果可知,基于改进后的广义Maxwell模型和川北压制方程建立的非线性流变模型,能较好地模拟蓖麻籽散体在压榨应变大于0.65段的应力松弛特性,为后续蓖麻压榨保压问题的研究以及部分榨油机构设计奠定了理论依据.
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图 1 不同处理下春季和夏季玉米土壤N2O通量的变化
图中向下箭头所指为施肥时间;W60、W80和W100分别为田间持水量的50%~60%、70%~80%和90%~100%;F55:50%氮肥作基肥土施、50%氮肥作滴灌施肥;F37:30%氮肥作基肥土施、70%氮肥作滴灌施肥
Figure 1. Changes of N2O fluxes in spring and summer maize soil under different treatments
The downward arrow in the figure represents each fertilization time; W60, W80 and W100 were 50%−60%, 70%−80% and 90%−100% of field water holding capacity, respectively; F55: 50% nitrogen fertilizer applied to soil as basal fertilizer and 50% nitrogen fertilizer as fertigation; F37: 30% nitrogen fertilizer applied to soil as basal fertilizer and 70% nitrogen fertilizer as fertigation
表 1 玉米各生育期不同水肥处理的灌水量1)
Table 1 Irrigation amount at each growth stage of maize in different water and fertilizer treatments
mm 季节 Season 生育期 Growth stage W60F37 W60F55 W80F37 W80F55 W100F37 W100F55 春季 Spring 苗期 Seedling stage 57.9 57.9 90.0 91.3 114.6 115.3 拔节期 Jointing stage 103.1 108.2 142.2 156.6 216.6 214.2 抽穗期 Heading stage 95.1 70.9 117.4 96.0 153.9 153.5 成熟期 Maturing stage 36.3 52.5 84.9 89.2 119.2 119.7 合计 Total 292.3 289.5 434.5 433.1 604.3 602.7 夏季 Summer 苗期 Seedling stage 57.9 57.9 69.4 69.4 81.0 81.0 拔节期 Jointing stage 147.3 139.8 215.3 232.7 283.5 286.9 抽穗期 Heading stage 93.8 105.6 143.2 119.1 199.5 190.3 成熟期 Maturing stage 19.1 11.7 47.7 56.5 70.2 74.4 合计 Total 318.0 314.9 475.6 477.7 634.2 632.7 1) W60、W80和W100分别为田间持水量的50%~60%、70%~80%和90%~100%;F55: 50%氮肥作基肥土施、50%氮肥作滴灌施肥;F37:30%氮肥作基肥土施、70%氮肥作滴灌施肥 1) W60, W80 and W100 are 50%−60%, 70%−80% and 90%−100% of field water holding capacity, respectively; F55: 50% nitrogen fertilizer applied to soil as basal fertilizer and 50% nitrogen fertilizer as fertigation; F37: 30% nitrogen fertilizer applied to soil as basal fertilizer and 70% nitrogen fertilizer as fertigation 表 2 不同处理下玉米各生育期土壤N2O累积排放量及方差分析1)
Table 2 Cumulative emissions of N2O at each growth stage of maize under different treatments
g·hm−2 季节 Season 水分处理(W) Water treatment 施氮比例(F) Fertigation proportion 苗期 Seedling stage 拔节期 Jointing stage 抽穗期 Heading stage 成熟期 Maturing stage 总计 Total 春季 W60 F37 45.20±2.94a 32.36±0.60a 23.02±1.17bc 15.01±1.14a 115.59±3.25a Spring F55 22.30±1.66c 24.54±1.22b 14.59±1.96d 11.51±0.86a 72.94±3.91c W80 F37 37.72±2.29ab 21.80±1.90b 27.62±3.24ab 15.59±1.83a 102.74±8.19ab F55 25.18±1.37bc 20.89±1.90b 18.63±0.73cd 14.98±0.23a 79.68±3.46bc W100 F37 50.81±7.95a 24.59±1.99b 29.90±2.20ab 19.02±5.95a 124.31±16.48a F55 42.41±6.53a 23.81±2.82b 34.00±2.60a 13.16±1.52a 113.38±3.37a 夏季 W60 F37 19.09±0.99b 22.66±1.24c 16.14±0.13d 11.80±0.25c 69.69±2.55c Summer F55 21.47±0.33ab 16.05±0.63d 20.59±1.54b 15.89±0.89a 74.01±2.46bc W80 F37 23.21±0.17a 26.34±0.34b 32.11±0.13a 13.00±0.18bc 94.66±0.67a F55 21.38±1.64ab 18.87±0.76d 17.83±0.24cd 10.08±0.06d 68.60±0.89c W100 F37 22.31±1.41ab 32.24±0.58a 20.77±0.03b 16.56±0.23a 91.88±2.01a F55 20.95±0.42ab 22.67±1.55c 19.21±0.38bc 13.79±0.41bc 76.62±1.50b 春季 P W < 0.05 < 0.01 < 0.01 0.569 < 0.01 Spring F < 0.01 0.060 < 0.05 0.155 < 0.01 W×F 0.297 0.141 < 0.05 0.631 0.181 夏季 W 0.120 < 0.01 < 0.01 < 0.01 < 0.01 Summer F 0.883 < 0.01 < 0.01 0.156 < 0.01 W×F 0.136 0.309 < 0.01 < 0.01 < 0.01 1)表中数据为平均值±标准误;相同玉米季的同列数据后,不同小写字母表示处理间差异显著 (P<0.05,Duncanʼs法);W60、W80和W100分别为田间持水量的50%~60%、70%~80%和90%~100%;F55:50%氮肥作基肥土施、50%氮肥作滴灌施肥;F37:30%氮肥作基肥土施、70%氮肥作滴灌施肥 1)The values in the table are means ± standard errors; Different lowercase letters in the same column of the same maize-season indicate significant difference among treatments (P<0.05, Duncan’s test); W60, W80 and W100 were 50%−60%, 70%−80% and 90%−100% of field water holding capacity, respectively; F55: 50% nitrogen fertilizer applied to soil as basal fertilizer and 50% nitrogen fertilizer as fertigation; F37: 30% nitrogen fertilizer applied to soil as basal fertilizer and 70% nitrogen fertilizer as fertigation 表 3 不同处理下玉米各生育期土壤铵态氮含量1)
Table 3 Soil ammonium nitrogen content at each growth stage of maize under different treatments
g·hm−2 季节 Season 水分处理 Water treatment 施氮比例 Fertigation proportion 苗期 Seedling stage 拔节期 Jointing stage 抽穗期 Heading stage 成熟期 Maturing stage 春季 Spring W60 F37 12.38±0.64c 20.76±0.60c 25.05±0.66d 18.03±0.40c F55 13.43±0.91bc 21.02±0.67c 25.72±0.76d 18.13±0.68c W80 F37 15.11±0.48b 26.86±0.30b 30.12±0.23c 20.87±0.66b F55 14.98±0.86b 27.22±0.63b 33.77±0.25b 20.48±0.79b W100 F37 21.02±0.78a 28.81±1.08a 39.68±0.70a 26.74±0.73a F55 20.11±0.73a 28.46±0.14a 39.70±0.49a 26.92±0.76a 夏季 Summer W60 F37 21.57±0.01d 27.22±0.06d 29.19±0.05f 25.62±0.33d F55 20.40±0.65d 31.82±0.22c 30.95±0.05e 25.72±0.51d W80 F37 23.27±0.37c 32.47±0.32c 39.71±0.46c 37.96±0.58c F55 25.04±0.05b 34.06±0.03b 37.66±0.68d 37.06±1.02c W100 F37 27.60±0.78a 32.74±0.71c 46.59±0.12b 40.87±0.38b F55 27.50±0.77a 39.20±0.44a 50.58±0.21a 44.40±0.31a 1)表中数据为平均值±标准误;相同玉米季的同列数据后,不同小写字母表示处理间差异显著(P<0.05,Duncanʼs法);W60、W80和W100分别为田间持水量的50%~60%、70%~80%和90%~100%;F55:50%氮肥作基肥土施、50%氮肥作滴灌施肥;F37:30%氮肥作基肥土施、70%氮肥作滴灌施肥 1)The values in the table are means ± standard errors; Different lowercase letters in the same column of the same maize-season indicate significant difference among treatments (P<0.05, Duncan’s test); W60, W80 and W100 were 50%−60%, 70%−80% and 90%−100% of field water holding capacity, respectively; F55: 50% nitrogen fertilizer applied to soil as basal fertilizer and 50% nitrogen fertilizer as fertigation; F37: 30% nitrogen fertilizer applied to soil as basal fertilizer and 70% nitrogen fertilizer as fertigation 表 4 不同处理下玉米各生育期土壤硝态氮含量1)
Table 4 Soil nitrate nitrogen content at each growth stage of maize under different treatments
g·hm−2 季节 Season 水分处理 Water treatment 施氮比例 Fertigation proportion 苗期 Seedling stage 拔节期 Jointing stage 抽穗期 Heading stage 成熟期 Maturing stage 春季 Spring W60 F37 4.39±0.21c 4.18±0.07b 2.77±0.03d 2.88±0.08c F55 4.17±0.25c 4.72±0.27b 3.30±0.13c 2.46±0.04d W80 F37 7.69±0.16b 5.70±0.15a 3.90±0.20b 2.35±0.03d F55 8.23±0.16a 6.27±0.08a 5.96±0.01a 2.46±0.06d W100 F37 8.37±0.09a 6.17±0.32a 3.76±0.12b 3.42±0.12a F55 8.33±0.06a 4.50±0.12b 3.95±0.05b 3.19±0.03b 夏季 Summer W60 F37 4.07±0.01c 3.46±0.47d 2.72±0.02c 1.77±0.02e F55 4.31±0.02c 4.06±0.02b 3.00±0.02b 3.09±0.10b W80 F37 4.73±0.10b 4.03±0.02bc 3.24±0.02a 2.89±0.05c F55 6.65±0.12a 3.55±0.01bc 3.27±0.01a 3.37±0.03a W100 F37 6.59±0.12a 4.66±0.02a 2.99±0.03b 2.54±0.02d F55 4.32±0.08c 4.14±0.08ab 2.40±0.08d 2.57±0.05d 1)表中数据为平均值±标准误;相同玉米季的同列数据后,不同小写字母表示处理间差异显著(P<0.05,Duncanʼs法);W60、W80和W100分别为田间持水量的50%~60%、70%~80%和90%~100%;F55:50%氮肥作基肥土施、50%氮肥作滴灌施肥;F37:30%氮肥作基肥土施、70%氮肥作滴灌施肥 1)The values in the table are means ± standard errors; Different lowercase letters in the same column of the same maize-season indicate significant difference among treatments (P<0.05, Duncan’s test); W60, W80 and W100 were 50%−60%, 70%−80% and 90%−100% of field water holding capacity, respectively; F55: 50% nitrogen fertilizer applied to soil as basal fertilizer and 50% nitrogen fertilizer as fertigation; F37: 30% nitrogen fertilizer applied to soil as basal fertilizer and 70% nitrogen fertilizer as fertigation 表 5 不同处理下玉米各生育期土壤亚硝态氮含量1)
Table 5 Soil nitrite nitrogen content at each growth stage of maize under different treatments
μg·hm−2 季节 Season 水分处理 Water treatment 施氮比例 Fertigation proportion 苗期 Seedling stage 拔节期 Jointing stage 抽穗期 Heading stage 成熟期 Maturing stage 春季 Spring W60 F37 13.57±3.83d 22.44±2.39c 18.72±3.48b 4.24±0.51ab F55 35.36±2.41c 46.58±7.07b 14.60±4.68b 3.38±0.08ab W80 F37 113.26±8.24a 22.08±4.26c 24.29±4.95ab 0.00±0.00b F55 114.43±7.68a 47.37±10.22b 2.90±2.50c 0.00±0.00b W100 F37 127.11±7.38a 86.28±4.89a 24.12±2.75ab 5.91±4.9ab F55 72.25±7.70b 98.23±4.15a 34.70±1.23a 9.04±0.88a 夏季 Summer W60 F37 3.03±1.92b 0.00±0.00c 1.74±1.74b 0.00±0.00c F55 0.00±0.00c 72.38±9.67c 1.53±1.53b 0.00±0.00c W80 F37 0.00±0.00c 42.10±16.94b 3.57±1.41b 0.00±0.00c F55 0.00±0.00c 37.97±12.75b 0.00±0.00b 0.00±0.00c W100 F37 15.86±0.22a 83.16±9.73a 21.99±4.22a 27.99±6.69b F55 16.88±0.89a 87.64±0.23a 20.17±7.73a 37.25±0.32a 1)表中数据为平均值±标准误;相同玉米季的同列数据后,不同小写字母表示处理间差异显著(P<0.05,Duncanʼs法);W60、W80和W100分别为田间持水量的50%~60%、70%~80%和90%~100%;F55:50%氮肥作基肥土施、50%氮肥作滴灌施肥;F37:30%氮肥作基肥土施、70%氮肥作滴灌施肥 1)The values in the table are means ± standard errors; Different lowercase letters in the same column of the same maize-season indicate significant difference among treatments (P<0.05, Duncan’s test); W60, W80 and W100 were 50%−60%, 70%−80% and 90%−100% of field water holding capacity, respectively; F55: 50% nitrogen fertilizer applied to soil as basal fertilizer and 50% nitrogen fertilizer as fertigation; F37: 30% nitrogen fertilizer applied to soil as basal fertilizer and 70% nitrogen fertilizer as fertigation 表 6 土壤N2O通量与无机氮含量的相关性分析1)
Table 6 Correlation analysis of soil N2O flux and inorganic nitrogen content
季节 Season 指标 Index 铵态氮 Ammonium nitrogen 硝态氮 Nitrate nitrogen 亚硝态氮 Nitrite nitrogen 春季 Spring N2O通量 N2O flux −0.107 0.579** 0.532** 夏季 Summer N2O通量 N2O flux −0.075 0.433** 0.396** 1) “**”:P<0.01,r0.01=0.300,n=72 -
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