付江鹏, 贺正, 贾彪^,*, 刘慧芳, 李振洲, 刘志宁夏大学农学院, 宁夏银川 750021

Critical nitrogen dilution curve and nitrogen nutrition diagnosis of maize with drip irrigation

FU Jiang-Peng, HE Zheng, JIA Biao^,*, LIU Hui-Fang, LI Zhen-Zhou, LIU ZhiSchool of Agriculture Ningxia University, Yinchuan 750021, Ningxia, China

通讯作者: 贾彪, E-mail: jiabiao2008@163.com

收稿日期:2019-04-19接受日期:2019-08-9网络出版日期:2019-09-02

基金资助:

本研究由国家自然科学基金项目.31560339 宁夏高等学校科研项目资助.NGY2017025

Received:2019-04-19Accepted:2019-08-9Online:2019-09-02

Fund supported:

The study was supported by the National Natural Science Foundation of China.31560339 the Ningxia Higher Education Research Project.NGY2017025

作者简介 About authors
E-mail:fjp951208@126.com。








摘要
旨在建立宁夏引黄灌区滴灌玉米临界氮稀释曲线模型, 探讨氮营养指数(NNI)用于实时诊断和评价玉米氮素营养状况的可行性, 为实现滴灌玉米合理施用氮肥提供理论依据。以天赐19为试验材料, 采用滴灌水肥一体化技术, 设6个氮肥水平, 利用2年定位试验构建并验证了临界氮稀释曲线模型。结果表明: (1)在一定范围内, 滴灌玉米干物质积累量随施氮水平的提高而增加, 根据方差分析结果, 将玉米各生育时期的地上部生物量分为限氮和非限氮2类; (2)滴灌玉米植株氮浓度均随着施氮量的增加而提高, 但随生育期的推进和地上部干物质量的增加, 玉米植株氮浓度均呈下降趋势; (3)滴灌玉米临界氮浓度(N_c)、最大氮浓度(N_max)和最小氮浓度(N_min)稀释模型与地上部干物质累积量之间均呈现幂函数关系, 其决定系数R²分别为0.982、0.907、0.918, 利用均方根误差(RMSE)和标准化均方根误差(n-RMSE)的验证表明, 该模型稳定性好, 误差范围小; (4)氮素营养指数模型(NNI)可衡量滴灌玉米氮素营养状况, 滴灌水肥一体化条件下, 宁夏引黄灌区玉米以270 kg hm ^-2为最佳施氮量; (5)根据模型推算, NNI与相对吸氮量(RN_upt)、相对地上部生物量(RDW)和相对产量(RY)均极显著相关。本研究所建立的滴灌玉米临界氮稀释曲线模型和氮营养指数模型, 能够精准地预测水肥一体化条件下玉米小喇叭口期至成熟期的氮素营养状况, 为优化玉米的氮素管理提供指导。
关键词： 水肥一体化;玉米;植株氮浓度;临界氮稀释曲线;氮营养指数

Abstract
The objective of this study was to establish the critical nitrogen dilution curve of maize in Yellow River irrigation area of Ningxia province, China, and to study the feasibility of the nitrogen nutrition index model (NNI) for real-time diagnosing and evaluating nitrogen nutrition in maize, which would provide theoretical basis for rational nitrogen fertilization of drip-irrigated maize. The research was carried out with ‘Tianci 19’, using the integrated technology of drip irrigation and fertilizer with six nitrogen levels. The critical nitrogen dilution curve model was constructed and verified by a 2-year fixed position experiment. Within a certain range, the dry matter accumulation of drip-irrigated maize increased with the increase of nitrogen application rate. According to the variance analysis, the aboveground biomass in maize growth period was divided into two types: nitrogen limited and nitrogen non-limited. The nitrogen concentration of drip-irrigated maize plant increased with the increase of nitrogen application rate, while decreased with the extension of growth period and the increase of aboveground dry matter weight. The critical nitrogen concentration (N_c), maximum nitrogen concentration (N_max) and minimum nitrogen concentration (N_min) dilution models of drip irrigated maize showed a power function relationship with the aboveground dry matter accumulation, with the determination coefficient R² of 0.982, 0.907, and 0.918, respectively. The verification using root mean square error (RMSE) and normalized root mean square error (n-RMSE) showed that the model had good stability and small error range. NNI can be used to measure the nitrogen nutrition status of drip-irrigated maize. Under the integration condition with drip-irrigation and fertilizer, the optimal nitrogen application rate for maize grown in Yellow River irrigation area of Ningxia should be 270 kg hm ^-2. According to the model calculations of, NNI with relative nitrogen uptake (RN_upt), relative aboveground biomass (RGW) and relative yield (RY) reached extremely significant levels. The critical nitrogen dilution curve model and nitrogen nutrition index model established in this study can accurately predict the nitrogen nutrition status of maize from the bell stage to the maturity stage under the integrated condition with water and fertilizer, so as to provide guidance for optimizing the nitrogen management of maize.
Keywords：water-fertilizer integration;maize;plant nitrogen concentration;critical nitrogen dilution curve;nitrogen nutrition index


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本文引用格式
付江鹏, 贺正, 贾彪, 刘慧芳, 李振洲, 刘志. 滴灌玉米临界氮稀释曲线与氮素营养诊断研究[J]. 作物学报, 2020, 46(2): 290-299. doi:10.3724/SP.J.1006.2020.93027
FU Jiang-Peng, HE Zheng, JIA Biao, LIU Hui-Fang, LI Zhen-Zhou, LIU Zhi. Critical nitrogen dilution curve and nitrogen nutrition diagnosis of maize with drip irrigation[J]. Acta Agronomica Sinica, 2020, 46(2): 290-299. doi:10.3724/SP.J.1006.2020.93027


氮素是玉米生长过程中必不可少的营养元素之一, 也是提高产量和改善品质的重要限制因素之一。氮肥施用量对玉米形态建成、生长速度及干物质积累等有很大的影响。目前在玉米生产中, 氮素的过量施用和低效利用严重污染农田生态环境^[1,2], 制约农业可持续发展^[3]。因此, 明确滴灌玉米在不同生育时期的适宜施氮量, 对提高氮肥利用效率和保护环境具有重要的意义。

临界氮浓度是作物最大生长所需的最小氮浓度^[4], 确定临界氮浓度值可以实现对作物氮素营养状况的快速诊断^[5]。Greenwood等^[6]提出了关于C₃和C₄作物的临界氮浓度通用模型, 后经Lemaire等^[7]通过田间试验校正和完善。近年来, 相继有诸多国内外****分别构建了水稻^[8,9]、小麦^[10,11]、马铃薯^[12]、棉花^[13]、番茄^[14]等作物临界氮曲线模型, 较好地描述了地上部干物质量与氮浓度的关系。国内外****分别在法国^[15]、德国^[16]、加拿大^[17]、中国华北地区^[18,19]、中国陕西关中地区^[20,21]和中国豫中地区^[22]构建并验证了玉米相关的临界氮浓度模型, 这些研究均表明利用临界氮浓度模型可以很好地预测本地区玉米临界氮含量。从前人构建临界氮浓度模型结果来看, 因地区、作物、土壤、品种和环境条件不同而存在一定的差异。宁夏引黄灌区玉米在氮肥管理方面, 由于多年采用大水漫灌模式, 难以实现追施氮肥, 习惯播种前和拔节期, 而灌浆期不施肥, 前重后轻的施肥方式往往使玉米生育前期植株发育过旺后期倒伏风险加大, 进而影响产量^[23]。滴灌水肥一体化技术是宁夏地区近年来推广的一项农业生产新技术, 将施肥与灌水融合为一体。国内外****围绕水肥一体化条件下作物生长与养分运输、分配和产量等^[24]方面进行了大量研究, 但是对玉米大田生育时期的需氮量动态变化及其临界氮浓度模型鲜有报道。因此, 构建宁夏引黄灌区滴灌玉米临界氮浓度稀释曲线模型及氮素营养诊断模型很有必要。

本研究通过2年田间定位试验, 构建了宁夏引黄灌区滴灌玉米临界氮变化曲线和氮营养指数诊断模型, 进而探讨是否可利用该模型来诊断滴灌玉米氮素营养, 以期为水肥一体化条件下优化玉米氮肥管理和精准评估氮素营养状况提供理论依据。

1 材料与方法

1.1 试验地概况

宁夏农垦平吉堡农场位于贺兰山东麓(38°N, 106°E)。海拔高度为1100 m, 多年平均温度、降水量和蒸发量分别为8.6℃、272.6 mm和2325 mm, 玉米生育期基本气象条件如图1所示。供试土壤为轻壤土, 基础土壤肥力状况如表1所示。

图1

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图1玉米生育期气象条件

Fig. 1Meteorological conditions during the growth period of maize



Table 1
表1
表1试验地土壤基础肥力
Table 1Foundation fertility of soil at experimental fields

年份 Year	pH	有机质 OM (g kg-1)	全氮 Total N (g kg-1)	全磷 Total P (g kg-1)	碱解氮 Avail. N (mg kg-1)	速效磷 Avail. P (mg kg-1)	速效钾 Avail. K (mg kg-1)
2017	7.98	11.45	0.80	0.51	37.37	19.04	102.52
2018	7.65	12.82	0.75	0.48	36.82	17.37	95.31

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1.2 试验设计

供试玉米品种为“天赐19”。氮肥处理设6个, 分别为0、90、180、270、360、450 kg hm^-2, 以N0、N90、N180、N270、N360、N450表示, 小区面积为67.5 m², 重复3次, 随机区组排列。种植密度约为9万株 hm^-2, 采用宽窄行种植, 宽行70 cm, 窄行40 cm。

玉米全生育期内采用水肥一体化滴灌施肥技术。用潜水泵将水通过75 mm PE管抽送到试验小区, 于管接口处安装水表准确计量, 以32 mm PE管做支管连接到16 mm毛管。肥料由施肥罐随水施入, 窄行玉米中间设置1根滴灌带, 2行玉米由1根滴灌带控制, 滴灌带滴头间距为 30 cm, 滴头流量2.5 L h^-1, 滴头工作压力0.1 MPa, 为保证灌水与施肥的均匀性, 采用横向供水方式。灌水以作物蒸发蒸腾量ET_c为基础, ET_c = K_c × ET_o, ET_o为参考作物蒸发蒸腾量, K_c为作物系数, 依据2006—2016年气象数据按Penman Monteith修正公式计算^[25]取平均值。K_c前期为0.7 (苗期-拔节期), 中期为1.2 (吐丝期-灌浆期), 后期为0.6 (乳熟期)^[25]。灌水总量为400 mm, 苗期、拔节至大喇叭口期、抽雄吐丝期、灌浆期和成熟期灌水量和次数分别为20 mm (1次)、100 mm (3次)、140 mm (2次)、120 mm (3次)和20 mm (1次)。

整个生育期共施肥8次, 分别为苗期1次、拔节至大喇叭口期3次、抽雄吐丝期1次、灌浆期3次, 每次施肥量占总施肥量的比例分别为苗期10%、拔节期45%、抽雄吐丝期20%和灌浆期25%。供试氮肥为尿素(含氮量≥46.4%), 磷钾肥为P₂O₅ 138 kg hm^-2和K₂SO₄ 120 kg hm^-2。2017年4月26日播种, 9月16收获; 2018年4月28日播种, 9月18日收获。

1.3 测定项目与方法

1.3.1 干物质量 于玉米拔节期(V₇)、小喇叭口期(V₁₀)、大喇叭口期(V₁₃)、吐丝期(R₁)、乳熟期(R₃)、蜡熟期(R₅)和成熟期(R₆)(播种后45 d、55 d、65 d、85 d、95 d、105 d、115 d)共计破坏性取样7次, 从每个小区选取长势一致的3株, 分成为茎、叶和穗3个部分, 采用干燥法测定器官干物质量。

1.3.2 植株氮浓度 将各处理的干样粉碎、研磨和过筛, 采用微量凯氏定氮法测定植株含氮量, 计算出植株氮浓度^[9]。

1.3.3 产量 于玉米收获期从每小区随机选取植株完整的长方形地块(1 m × 3 m)进行样方取样, 把样方内的所有玉米果穗带回实验室脱粒, 折合为14%含水量的籽粒产量。

1.4 模型描述

1.4.1 临界氮浓度模型建立 根据Justes等^[26]提出的临界氮浓度稀释曲线计算方法, 结合梁效贵等^[19]针对华北地区玉米临界氮浓度的建模思路, 本研究建模步骤为: (1)对不同施氮处理下的地上部干物质积累量进行方差分析, 将其分为2类, 即限氮和非限氮; (2)对于玉米生长受氮素影响的氮素水平, 将其地上部干物质积累量与对应的氮浓度值进行曲线拟合; (3)对于玉米生长不受氮素影响的氮素水平, 其干物质量的均值代表最大干物质量; (4)采样日的临界氮浓度值为以上线性曲线与以最大干物质量为横坐标的垂线的交点的纵坐标决定。按Greenwood等^[6]对临界氮浓度定义的描述:

(1) ${{N}_{\text{c}}}=a\text{D}{{\text{M}}^{-b}}$
式中, N_c代表临界氮浓度值(g kg^-1); DM代表干物质量的最大值(t hm^-2), a和b均为模型的参数。

1.4.2 临界氮浓度模型验证 采用均方根误差RMSE (root mean square error)和标准化均方根误差(n-RMSE)^[27,28]对模型验证。

(2) $\text{RMSE}=\sqrt{\frac{\sum\nolimits_{i=1}^{n}{{{({{P}_{i}}-{{O}_{i}})}^{2}}}}{n}}$
(3) $n-\text{RMSE}(%)=(\text{RMSE}/S)\times 100$
式中, P_i、O_i分别为临界氮测定值和模拟值; n为样本量; S为实测数据的平均值。参照Jamiesom等^[29]提出的标准来衡量模型稳定性, n-RMSE < 10%, 模型稳定性极好; 10% < n-RMSE < 20%, 模型稳定性较好; 20% < n-RMSE < 30%, 模型稳定性一般; n-RMSE > 30%, 模型稳定性较差。

1.4.3 氮营养指数模型 根据Lemaire等^[30]描述的氮素营养指数(nitrogen nutrition index, NNI)模型,

NNI = N_a/N_c (4)

式中, N_a为实测氮浓度值(g kg^-1), N_c为临界氮浓度值。若NNI<1, 表明氮素不足; NNI=1, 表明氮素恰好适量; NNI>1, 表明氮素过盛。

1.4.4 相对氮吸收量、相对地上部生物量和相对产量计算 相对吸氮量(RN_upt) = 吸氮量/同一生育时期各处理吸氮量最大值; 相对地上部生物量(RDW) = 地上部生物量/同一生育时期各处理地上部生物量的最大值; 相对产量(RY) = 各处理实际产量/各处理产量的最大值。

1.5 数据处理

采用Microsoft Excel 2013数据整理与计算, 用SPSS 22.0进行单因素方差分析和多重比较, 采用Origin 2018软件绘图。采用2018年数据建立模型, 2017年数据验证。

2 结果与分析

2.1 滴灌玉米地上部干物质积累量动态变化与筛选分组

如表2所示, 玉米干物质量随着生育进程呈逐渐上升趋势。不同年际、施氮水平和取样时期, 玉米植株地上部干物质积累量在1.24~16.08 t hm^-2之间。同一生育时期随氮素水平的提高, 干物质量呈逐渐增加趋势, 施氮效果显著, 但同一取样时期N360和N450处理之间地上部干物质积累量基本没有显著差异, 说明施氮过量并不能提高地上部干物质积累量。

Table 2
表2
表2滴灌玉米地上部干物质积累量动态变化
Table 2Dynamic changes of dry matter accumulation in aboveground parts of drip irrigation maize

年份 Year	生育时期 Growing period	地上部生物量Aboveground biomass (t hm-2)
		N0	N90	N180	N270	N360	N450
2017	V10	1.24±0.24 c	1.31±0.18 bc	1.52±0.76 bc	1.75±0.56 abc	2.19±0.11 ab	2.53±0.57 a
	V13	3.05±0.80 d	3.56±0.39 cd	3.64±0.32 cd	3.96±0.09 bc	4.59±0.17 ab	4.77±0.21 a
	R1	4.43±0.89 c	4.9±0.30 bc	5.04±0.43 bc	6.21±1.11 ab	7.34±1.19 a	7.66±0.88 a
	R3	6.43±0.47 c	6.58±0.36 c	7.40±0.67 c	8.95±0.64 b	10.44±0.50 a	11.02±0.84 a
	R5	8.99±0.61 c	9.75±0.12 c	11.80±0.12 b	12.08±0.93 b	13.40±0.43 a	13.12±0.55 a
	R6	10.88±0.74 d	12.93±0.32 c	14.04±0.76 b	15.11±0.09 a	15.42±0.86 a	15.14±0.14 a
2018	V10	1.35±0.21 b	1.50±0.29 b	1.51±0.06 b	1.57±0.17 b	1.73±0.93 a	1.74±0.32 a
	V13	1.89±0.29 c	2.48±0.44 b	2.53±0.10 b	2.86±0.19 b	3.26±0.06 a	3.48±0.08 a
	R1	4.95±0.40 d	5.79±0.65 cd	6.25±0.61 bc	6.62±0.48 ab	7.78±0.92 ab	8.76±0.89 a
	R3	6.27±0.61 d	7.16±0.59 c	8.80±0.17 b	8.92±0.12 b	10.91±0.46 a	10.79±0.42 a
	R5	8.92±0.91 c	9.91±0.51 bc	10.44±1.11 bc	11.21±0.89 b	13.26±1.08 a	12.91±0.76 a
	R6	10.03±0.52 e	11.06±0.29 d	12.55±0.73 c	13.47±0.13 b	16.08±0.47 a	14.82±0.45 a

N0: 0 kg N hm^-2; N90: 90 kg N hm^-2; N180: 180 kg N hm^-2; N270: 270 kg N hm^-2; N360: 360 kg N hm^-2. V10: small trumpet period; V13: big bell period; R1: silking; R3: milk stage; R5: ripening period; R6: maturity. The data is the average of three replicates ± standard error. Values within the same column followed by data indicate that the and significantly different lowercase letters different at P < 0.05.
N0: 0 kg N hm^-2; N90: 90 kg N hm^-2; N180: 180 kg N hm^-2; N270: 270 kg N hm^-2; N360: 360 kg N hm^-2。V10: 小喇叭口期; V13: 大喇叭口期; R1: 吐丝期; R3: 乳熟期; R5: 腊熟期; R6: 成熟期。数据为3个重复的平均值±标准误, 同列数据后不同小写字母表示在P<0.05水平差异显著。

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由于2017—2018年玉米播种后45 d (七叶展时期)地上部干物质积累量小于1 t hm^-2, 故舍弃此部分数据。从整个生育期来看, N0、N90、N180和N270地上部干物质积累量之间显著; N360和N450之间不显著, 说明玉米地上部干物质积累量并不随施氮水平的提高而增加。参照Justes等^[26]建立临界氮浓度稀释曲线模型的方法, 对玉米植株地上部干物质积累量进行方差分析, 即每次取样日地上部干物质积累量呈显著差异的施氮处理为限氮组, 反之, 则为非限氮组。由表2可知, 限氮组数据为N0、N90、N180、N270处理的取样值, 而非限氮组数据为N360、N450处理的取样值。

2.2 滴灌玉米地上部植株氮浓度动态变化

如图2所示, 滴灌玉米植株氮浓度随着地上部干物质积累量的增加呈逐渐下降趋势。不同年际、同一取样时期植株氮浓度均随着施氮量的增加呈上升趋势, 但从整个生育期来看, 玉米植株氮浓度随生长进程和干物质量的增加均呈下降趋势。2017年和2018年植株氮浓度的变化范围分别为9.13~ 29.86 g kg^-1和9.95~30.26 g kg^-1。同一施氮水平下的植株氮浓度变化趋势基本一致。

图2

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图2滴灌玉米植株氮浓度动态变化

缩写同表2。
Fig. 2Dynamic changes of nitrogen concentration in maize plant widen drip irrigation

Abbreviations are the same as those given in Table 2.

2.3 滴灌玉米临界氮浓度稀释曲线模型构建

由1.4.1模型构建方法, 得到每次取样日的临界氮浓度, 并与地上部干物质量拟合, 得到滴灌玉米临界氮浓度稀释曲线(图3)。模型的决定系数R²为0.982, 达到极显著水平, 说明该模型可以很好地解释滴灌玉米临界氮浓度与地上部干物质积累量之间的关系。

图3

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图3滴灌玉米临界氮浓度稀释曲线

Fig. 3Dilution curve of critical nitrogen concentration in drip irrigation maize



从图3可以看出, 在相同地上部生物量的情况下, 氮浓度值变异性很大, 采用每个采样日最大(N_max)和最小(N_min)氮浓度值可拟合得到最高氮浓度稀释模型(N_max = 40.516 DM^-0.314, R²=0.907)和最低氮浓度稀释模型(N_min = 22.108 DM^-0.395, R² = 0.918), 其结果也同样符合模型(1)。

2.4 滴灌玉米临界氮浓度稀释曲线模型验证

如图4所示, 利用2017年各取样时期地上部干物质量和植株氮浓度单独拟合来验证模型的精度和可靠性。将2017年干物质积累量实测值分别带入上述模型, 计算得到临界氮浓度模拟值, 比较模拟值与2018年的实测值, 均方根误差(RMSE)为1.13 g kg^-1, 标准化均方根误差(n-RMSE)为6.20%, 小于10%, 说明模型稳定性极好, 进一步表明可用于滴灌玉米的氮营养估测。

图4

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图4滴灌玉米临界氮浓度稀释曲线模型验证

Fig. 4Model verification of dilution curve of critical nitrogen concentration in drip irrigation maize

2.5 滴灌玉米氮营养指数模型的建立

如图5所示, 不同年际、同一取样时期, NNI随着施氮量的增加而增大。整体来看, N0、N90、N180处理在播种后55~115 d内NNI均小于1, 说明N0、N90和N180水平下出现了氮供应不足状况, 使玉米的生长受到了氮素的限制; N360和N450处理, NNI均大于1, 说明出现了氮肥供应充足甚至过量; N270处理的NNI在1附近波动, 说明在N270处理氮素供应达到最佳适宜量。因此, 由NNI可以判定出该地区在水肥一体化条件下玉米的施氮量以270 kg hm^-2为宜。

图5

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图5滴灌玉米氮营养指数动态变化

NNI: 氮营养指数。缩写同表2。
Fig. 5Dynamic changes of nitrogen nutrition index in drip irrigation maize

NNI: nitrogen nutrition index. Abbreviations are the same as those given in Table 2.

2.6 氮营养指数与相对吸氮量、相对地上部干物质量和相对产量之间的关系

2017—2018 2年分别研究了NNI与RN_upt、RDW和RY的关系。从图6可以看出, 玉米不同生育时期的NNI-RN_upt均表现为线性相关, RN_upt随NNI的增加而增加, 各生育时期R²分别为0.836、0.768、0.846、0.811、0.804和0.861, 均达到极显著水平。从图7可以看出, 玉米不同生育时期的 NNI与RDW 均表现为线性相关, RDW随着NNI的增加而增加, 各生育时期方程决定系数分别为0.456、0.647、0.579、0.667、0.753和0.759, 均达到极显著水平。从图8可以看出, NNI与RY二者呈二次函数关系, 即相对产量随NNI 的增加先升高后降低, 决定系数0.796, 达到极显著水平。该试验条件下, NNI为0.990时, RY获得最大值, 为0.970。

图6

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图6滴灌玉米氮营养指数与相对吸氮量的关系

NNI: 氮营养指数; RN_upt: 相对吸氮量。缩写同表2。
Fig. 6Relationship between NNI and relative nitrogen uptake RN_upt in drip irrigation maize

NNI: nitrogen nutrition index; RN_upt: relative nitrogen uptake. Abbreviations are the same as those given in Table 2.

图7

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图7滴灌玉米氮营养指数与相对地上部生物量的关系

NNI: 氮营养指数; RDW: 相对地上部生物量。缩写同表2。
Fig. 7Relationship between nitrogen nutrition index and relative dry matter of drip irrigation maize

NNI: nitrogen nutrition index; RDW: relative dry matter. Abbreviations are the same as those given in Table 2.

图8

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图8滴灌玉米氮营养指数与相对产量的关系

NNI: 氮营养指数; RY: 相对产量。
Fig. 8Relationship between nitrogen nutrition index and relative yield of drip irrigation maize

NNI: nitrogen nutrition index; RY: relative yield.

3 讨论

3.1 宁夏引黄灌区滴灌玉米临界氮浓度稀释曲线特征

玉米是宁夏地区第一大粮食作物, 播种面积常达3×10⁵ hm²以上^[31], 而引黄灌区和扬黄灌区玉米总产量占宁夏玉米总产量60%以上^[23]。目前在玉米生产中氮肥普遍过量施用和低效利用, 从而污染农业生态环境^[1,2], 制约农业可持续发展^[3]。因此, 建立快速有效的诊断滴灌玉米氮素营养状况的技术显得十分重要。本研究利用2年6个氮素水平的定位试验数据, 建立并验证了宁夏引黄灌区滴灌玉米临界氮浓度稀释曲线模型(图3和图4), 分析了不同施氮量下的NNI (图5), 研究了NNI与RN_upt、RDW和RY的关系(图6、图7和图8)。模型的决定系数均达到显著水平, 在不同年际间也具有较好的稳定性, 可以作为宁夏引黄灌区滴灌玉米氮素营养快速诊断的方法之一。此外, 本研究进一步表明, 水肥一体化条件下NNI与RN_upt (图6)、RGW (图7)和RY (图8)显著相关。因此, 基于N_c曲线的NNI可以用来评价玉米氮素营养状况。

近年来, 梁效贵等^[18]构建了华北地区夏玉米临界氮稀释曲线(N_c = 34.914 DM^-0.413); 李正鹏等^[20]构建了陕西关中地区夏玉米临界氮曲线(N_c = 22.5 DM^-0.27), 研究均表明临界氮浓度稀释曲线模型可用于预测该地区夏玉米临界氮含量。本研究构建了宁夏引黄灌区滴灌玉米临界氮浓度稀释曲线模型(N_c = 35.504 DM^-0.312), 其模型表达式均满足幂函数方程(图3)。从数学角度来讲, 参数a代表生物量为1 t hm^-2时的植株氮浓度, 参数b描述的是随地上部生物量的增加植株氮含量递减关系, 与前人相比, 本研究参数a值偏高, 而b属于中间范畴, 其参数a值偏高的原因是: (1)与李正鹏等^[20]构建模型相比可能受气候状况影响, 宁夏灌区以半干旱温带大陆性气候为主, 玉米生长季节光热资源丰富, 降水量少, 而关中地区属于亚热带季风气候, 夏季高温多雨。依据积温学说原理^[32], 宁夏引黄灌区玉米生育期(143 d)远高于陕西关中地区(110 d), 生育期延长意味着植株吸氮量增加^[33]; (2)与梁效贵等^[18]构建模型相比, 其值也偏高, 原因主要与土壤因素有关, 华北地区供试玉米土壤为冲积型盐化潮土, 而宁夏引黄灌区供试玉米土壤为轻壤土, 土壤肥力比华北地区高, 这可能是导致宁夏引黄灌区玉米临界氮稀释曲线高于华北地区的主要原因。

利用2017年独立试验数据对2018年构建的模型进行验证, 发现此模型不受年际变化影响, 稳定性较好。本研究构建的临界氮浓度稀释曲线模型, 仅是在单一生态区域和品种下构建的, 今后需要通过不同区域和品种来进一步不断完善该模型, 从而实现模型预测的通用性。

3.2 滴灌玉米最佳施氮量的确定和氮营养指数的可行性

NNI是衡量作物氮营养状况的重要指标^[34]。银敏华等^[21]利用NNI对陕西关中地区玉米生育期内氮素营养状况诊断发现2种氮素(尿素和控释氮肥)的NNI 在0.74~1.12之间变化, 且随施氮水平的提高而增大。本研究表明, 滴灌玉米NNI 值随着氮肥施用量的增加不断增大, 在0.60~1.41之间变动(图5), 从而依据NNI确定的滴灌玉米最佳施氮量为270 kg hm^-2。通过NNI确定的最佳施氮量与张富仓等^[35]基于最小二乘法进行回归分析推荐的宁夏滴灌玉米适宜施氮量(210~325 kg hm^-2)基本一致。由此可见, 基于临界氮稀释模型的NNI来评价植株氮营养状况是可靠的。

4 结论

在一定氮素水平下, 滴灌玉米干物质量随施氮水平的提高而增加, 氮浓度随生长天数的增加而降低; 建立并验证了滴灌玉米临界氮浓度稀释曲线模型, 滴灌玉米各生育时期的最大生物量与临界氮浓度之间符合幂函数模型N_c = 35.504 DM^-0.312, 模型稳定性高。基于临界氮浓度稀释曲线模型, 水肥一体化条件下, 玉米以270 kg hm^-2为最佳施氮量。NNI与相对氮吸收量(RN_upt)、相对干物质量(RDW)和相对产量(RY)等指标间存在极显著相关性。NNI可以直观地反映玉米不同生长阶段的氮素盈亏状况。

参考文献 View Option 原文顺序
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Pedosphere, 2014,24:76-83.
URL [本文引用: 3]
The concept of critical N concentration (N-c) has been widely used in agronomy as the basis for diagnosis of crop N status, and allows discrimination between field situations of sub-optimal and supra-optimal N supply. A critical N dilution curve of N-c = 34.0W(-0.37), where W is the aboveground biomass (Mg DM ha(-1)) and Nc the critical N concentration in aboveground dry matter (g kg(-1) DM), was developed for spring maize in Europe. Our objectives were to validate whether this European critical N dilution curve was appropriate for summer maize production in the North China Plain (NCP) and to develop a critical N dilution curve especially for summer maize production in this region. In total 231 data points from 16 experiments were used to test the European critical N dilution curve. These observations showed that the European critical N dilution curve was unsuitable for summer maize in the NCP, especially at the early growth stage. From the data obtained, a critical N dilution curve for summer maize in the NCP was described by the equation of N-c = 27.2W(-0.27), when aboveground biomass was between 0.64 and 11.17 Mg DM ha(-1). Based on this curve, more than 90% of the data for the N deficiency supply treatments had an N nutrition index (NNI) < 1 and 92% of the data for the N excess supply treatments had an NNI > 1.

[19] 梁效贵, 张经廷, 周丽丽, 李旭辉, 周顺利 . 华北地区夏玉米临界氮稀释曲线和氮营养指数研究
作物学报, 2013,39:292-299.
DOI:10.3724/SP.J.1006.2013.00292URL [本文引用: 2]
为了验证玉米临界氮稀释曲线在我国华北地区的适用性，探讨以氮营养指数评价玉米氮营养状况的可行性，以郑单958为材料，设置5个氮肥处理(0、60、120、180和240 kg N hm^-2)，利用2年定位试验数据研究了夏玉米临界氮稀释曲线和氮营养指数。结果表明，一定范围内随着施氮量增加，地上部生物量(W)显著增长。玉米各生育时期不同氮肥处理的生物量和氮浓度数据可经统计分析分为限氮和非限氮两组，据此计算各生育时期临界氮浓度(N_c)并建立了夏玉米临界氮稀释曲线模型(N_c = 34.914W^-0.4134)，模型参数与已有报道具有较好的相似性。根据模型推算的氮营养指数与相对氮累积量、相对地上部生物量和相对产量均具显著相关性。因此，利用临界氮稀释曲线和氮营养指数可以预测华北地区夏玉米植株临界氮含量和表征植株氮营养状况。
Liang X G, Zhang J T, Zhou L L, Li X H, Zhou S L . Study on critical nitrogen dilution curve and nitrogen nutrition index of summer maize in north China
Acta Agron Sin, 2013,39:292-299 (in Chinese with English abstract).
DOI:10.3724/SP.J.1006.2013.00292URL [本文引用: 2]
为了验证玉米临界氮稀释曲线在我国华北地区的适用性，探讨以氮营养指数评价玉米氮营养状况的可行性，以郑单958为材料，设置5个氮肥处理(0、60、120、180和240 kg N hm^-2)，利用2年定位试验数据研究了夏玉米临界氮稀释曲线和氮营养指数。结果表明，一定范围内随着施氮量增加，地上部生物量(W)显著增长。玉米各生育时期不同氮肥处理的生物量和氮浓度数据可经统计分析分为限氮和非限氮两组，据此计算各生育时期临界氮浓度(N_c)并建立了夏玉米临界氮稀释曲线模型(N_c = 34.914W^-0.4134)，模型参数与已有报道具有较好的相似性。根据模型推算的氮营养指数与相对氮累积量、相对地上部生物量和相对产量均具显著相关性。因此，利用临界氮稀释曲线和氮营养指数可以预测华北地区夏玉米植株临界氮含量和表征植株氮营养状况。

[20] 李正鹏, 宋明丹, 冯浩 . 关中地区玉米临界氮浓度稀释曲线的建立和验证
农业工程学报, 2015,31(13):135-141.
URL [本文引用: 3]
基于临界氮浓度稀释曲线推导的氮素营养指数既可以诊断出氮素供应不足也可以诊断出氮肥供应过量。该文在整理分析关中平原8 a氮肥大田试验的基础上，分别构建了关中灌区夏玉米和渭北旱塬春玉米的地上部生物量的临界氮浓度稀释曲线模型。结果表明，关中玉米地上部临界氮浓度与生物量符合幂函数关系。利用独立试验资料对建立的临界氮稀释曲线模型进行检验，结果表明：该模型能准确诊断该区玉米植株的氮营养状况，施肥量和施肥时期对玉米植株的氮素营养状况影响较大，一般随着施氮量的增加氮素营养指数值会增大，只基施氮肥或前期施氮过多都会使玉米在生长过程中营养失衡。该研究建立的关中地区玉米的临界氮稀释模型为该区玉米氮素营养诊断和优化管理提供了较好的技术途径和理论参考。
Li Z P, Song M D, Feng H . Establishment and verification of dilution curve of critical nitrogen concentration in maize in Guanzhong area
Trans CSAE, 2015,31(13):135-141(in Chinese with English abstract).
URL [本文引用: 3]
基于临界氮浓度稀释曲线推导的氮素营养指数既可以诊断出氮素供应不足也可以诊断出氮肥供应过量。该文在整理分析关中平原8 a氮肥大田试验的基础上，分别构建了关中灌区夏玉米和渭北旱塬春玉米的地上部生物量的临界氮浓度稀释曲线模型。结果表明，关中玉米地上部临界氮浓度与生物量符合幂函数关系。利用独立试验资料对建立的临界氮稀释曲线模型进行检验，结果表明：该模型能准确诊断该区玉米植株的氮营养状况，施肥量和施肥时期对玉米植株的氮素营养状况影响较大，一般随着施氮量的增加氮素营养指数值会增大，只基施氮肥或前期施氮过多都会使玉米在生长过程中营养失衡。该研究建立的关中地区玉米的临界氮稀释模型为该区玉米氮素营养诊断和优化管理提供了较好的技术途径和理论参考。

[21] 银敏华, 李援农, 谷晓博, 周昌明, 董丽利, 张天乐 . 氮肥运筹对夏玉米氮素盈亏与利用的影响
农业机械学报, 2015,46(10):167-176.
[本文引用: 2]

Yin M H, Li Y N, Gu X B, Zhou C M, Dong L L, Zhang T L . Effects of nitrogen fertilizer management on nitrogen profit and loss and utilization of summer maize
Trans CSAM, 2015,46(10):167-176 (in Chinese with English abstract).
[本文引用: 2]

[22] 安志超, 黄玉芳, 汪洋, 赵亚南, 岳松华, 师海斌, 叶优良 . 不同氮效率夏玉米临界氮浓度稀释模型与氮营养诊断
植物营养与肥料学报, 2019,25:123-133.
[本文引用: 1]

An Z C, Huang Y F, Wang Y, Zhao Y N, Yue S H, Shi H B, Ye Y L . Dilution model of critical nitrogen concentration and nitrogen nutrition in summer maize with different nitrogen efficiency
J Plant Nutr Fert, 2019,25:123-133 (in Chinese with English abstract).
[本文引用: 1]

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DOI:10.3389/fpls.2017.01517URLPMID:28928757 [本文引用: 2]
Precise quantification of plant nitrogen (N) nutrition status is essential for crop N management. The concept of critical N concentration (Nc) has been widely used for assessment of plant N status. This study aimed to develop a new winter wheat Nc dilution curve based on leaf area duration (LAD). Four field experiments were performed on different cultivars with different N fertilization modes in the Yangtze River basin and Yellow River basin in China. Results showed that the increase in LAD with increasing cumulative thermal time took the shape of an &quot;S&quot; type curve; whereas shoot N concentration decreased with increasing LAD, according to a power function. Both LAD and shoot N concentration increased with increasing N application. The new LAD based Nc dilution curve was determined and described as Nc = 1.6774 LAD^-0.37 when LAD &gt; 0.13. However, when LAD ≤ 0.13, Nc was constant and can be calculated by the equation when LAD = 0.13. The validation of Nc dilution curve with dataset acquired from independent experiments confirmed that N nutrition index (NNI) predictions based on the newly established Nc dilution curve could precisely diagnose N deficiency at different plant growth stages. The integrated N nutrition index (NNI_inte), which was obtained by the weighted mean of NNI, was used to estimate shoot N concentration, shoot dry matter, LAD, and yield using regression functions. The linear relationships between NNI_inte and these growth variables were well correlated. These results provided enough evidence that the new LAD-based Nc dilution curve could effectively and precisely diagnoses N deficiency in winter wheat crops.

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Practice-Based Learning and Improvement is a Core Competency for surgical residents. Self-regulated learning (SRL) skills are an important component of this competency, yet are rarely taught in surgical training. Before we can teach SRL skills to residents we must understand the attributes that are essential. The purpose of this study was to develop a framework for SRL for surgical trainees.

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[31] 赵如浪, 杨滨齐, 王永宏, 赵健, 张文杰, 孙发国, 谢铁娜 . 宁夏高产玉米群体产量构成及生长特性研究
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[32] Liu J L, Zhan A, Bu L D, Zhu L, Luo S S, Chen X P, Cui Z L, Li S Q, Hill R L, Zhao Y . Understanding dry matter and nitrogen accumulation for high-yielding film-mulched maize
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Film mulching is a very common technique in agriculture worldwide, but few studies have focused on the dry matter (DM) and N accumulation of mulched crops. Understanding the grain yield (GY) associated with DM and N accumulation is essential for improving crop production. We conducted a 3-yr field experiment with six N fertilizer rates (0, 100, 200, 250, 300, and 400 kg ha(-1)) in the semiarid climate of northwest China to determine the GY and DM and N accumulation of film-mulched maize (Zea mays L.). The results showed that relatively high GYs (13.1-15.1 Mg ha-1) were obtained using N fertilizer rates of 200 to 400 kg ha(-1) in the 3 yr despite large year-to-year differences in rainfall. When the N rate was below 250 kg ha(-1), the GY, DM, and N accumulation increased significantly as the N fertilizer rate increased. A linear-plateau model best described the relationship between the GY and the DM and N accumulation during the pre-silking stage and a linear model the relationship during the post-silking stage. We conclude that optimizing N management to improve DM and N accumulation (especially post-silking) is the key to ensuring a high yield of film-mulched maize.

[33] Yue S, Sun F, Meng Q, Zhao R, Li F, Chen X, Zhang F . Validation of a critical nitrogen curve for summer maize in the North China Plain
Pedosphere, 2014,24:76-83.
URL [本文引用: 1]
The concept of critical N concentration (N-c) has been widely used in agronomy as the basis for diagnosis of crop N status, and allows discrimination between field situations of sub-optimal and supra-optimal N supply. A critical N dilution curve of N-c = 34.0W(-0.37), where W is the aboveground biomass (Mg DM ha(-1)) and Nc the critical N concentration in aboveground dry matter (g kg(-1) DM), was developed for spring maize in Europe. Our objectives were to validate whether this European critical N dilution curve was appropriate for summer maize production in the North China Plain (NCP) and to develop a critical N dilution curve especially for summer maize production in this region. In total 231 data points from 16 experiments were used to test the European critical N dilution curve. These observations showed that the European critical N dilution curve was unsuitable for summer maize in the NCP, especially at the early growth stage. From the data obtained, a critical N dilution curve for summer maize in the NCP was described by the equation of N-c = 27.2W(-0.27), when aboveground biomass was between 0.64 and 11.17 Mg DM ha(-1). Based on this curve, more than 90% of the data for the N deficiency supply treatments had an N nutrition index (NNI) < 1 and 92% of the data for the N excess supply treatments had an NNI > 1.

[34] Lemaire G, Gastal F . Nitrogen Uptake and Distribution in Plant Canopies Diagnosis of the Nitrogen Status in Crops
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[35] 张富仓, 严富来, 范兴科, 李国栋, 刘翔, 陆军胜, 王英, 麻玮青 . 滴灌施肥水平对宁夏春玉米产量和水肥利用效率的影响
农业工程学报, 2018,34(22):111-120.
URL [本文引用: 1]
为探讨不同滴灌施肥水平对春玉米产量及水肥利用效率的影响，应用滴灌施肥技术于2016和2017年在宁夏旱作节水科技园区试验站开展大田春玉米小区试验。以"先玉335"为试验材料，设置4个灌水水平（D75：75%ETc、D90：90%ETc、D105：105%ETc、D120：120%ETc，ETc为玉米需水量）和4个N-P2O5-K2O施肥水平：2016年为60-30-30 kg/hm2（F60）、120-60-60 kg/hm2（F120）、180-90-90 kg/hm2（F180）、240-120-120 kg/hm2（F240），2017年为150-70-70 kg/hm2（F150）、225-110-110 kg/hm2（F225）、300-150-150 kg/hm2（F300）、375-180-180 kg/hm2（F375），以1个充分灌水（120%ETc）无肥为对照（CK），共17个处理。研究不同水肥供应对春玉米株高、茎粗、叶面积指数（leaf area index，LAI）、地上部干物质累积量和产量的影响，并分析其水肥利用效率。2 a试验结果表明：灌水量和施肥量单因素对玉米株高、茎粗、LAI都有显著或极显著的影响，灌水量和施肥量耦合效应对玉米株高有极显著的影响；灌水量和施肥量对玉米成熟期地上部干物质的影响随着2 a施肥梯度的不同而有所差异，在低肥梯度的2016年，灌水量和施肥量对地上部干物质累积有显著的影响，其中D120F180处理籽粒地上部干物质最大，为12 691 kg/hm2，在高肥梯度的2017年，随着灌水量和施肥量的增加，75%ETc和105%ETc处理的地上部干物质累积量有先增加后减小的趋势，D90F300处理下籽粒地上部干物质累积量最大，为14 912 kg/hm2；在低肥梯度的2016年，灌水施肥量对春玉米产量有显著影响，D120F240处理产量最高，为14 400 kg/hm2，而在高肥梯度的2017年，D90F300处理玉米产量最高，为16 884 kg/hm2；2 a试验结果表明灌水量和施肥量对春玉米水分利用效率和肥料偏生产力都有极显著影响。基于春玉米产量和水分利用效率最大值的95%为置信区间优化水肥管理方案，兼顾节水节肥，推荐灌水量在323～446 mm、N-P2O5-K2O施肥量在210-104-104～325-163-163 kg/hm2。该研究结果对宁夏春玉米滴灌施肥管理具有重要指导意义。
Zhang F C, Yan F L, Fan X K, Li G D, Liu X, Liu J S, Wang Y, Ma W Q . Effects of irrigation and fertilization levels on grain yield and water-fertilizer use efficiency of drip-fertigation spring maize in Ningxia
Trans CSAE, 2018,34(22):111-120 (in Chinese with English abstract).
URL [本文引用: 1]
为探讨不同滴灌施肥水平对春玉米产量及水肥利用效率的影响，应用滴灌施肥技术于2016和2017年在宁夏旱作节水科技园区试验站开展大田春玉米小区试验。以"先玉335"为试验材料，设置4个灌水水平（D75：75%ETc、D90：90%ETc、D105：105%ETc、D120：120%ETc，ETc为玉米需水量）和4个N-P2O5-K2O施肥水平：2016年为60-30-30 kg/hm2（F60）、120-60-60 kg/hm2（F120）、180-90-90 kg/hm2（F180）、240-120-120 kg/hm2（F240），2017年为150-70-70 kg/hm2（F150）、225-110-110 kg/hm2（F225）、300-150-150 kg/hm2（F300）、375-180-180 kg/hm2（F375），以1个充分灌水（120%ETc）无肥为对照（CK），共17个处理。研究不同水肥供应对春玉米株高、茎粗、叶面积指数（leaf area index，LAI）、地上部干物质累积量和产量的影响，并分析其水肥利用效率。2 a试验结果表明：灌水量和施肥量单因素对玉米株高、茎粗、LAI都有显著或极显著的影响，灌水量和施肥量耦合效应对玉米株高有极显著的影响；灌水量和施肥量对玉米成熟期地上部干物质的影响随着2 a施肥梯度的不同而有所差异，在低肥梯度的2016年，灌水量和施肥量对地上部干物质累积有显著的影响，其中D120F180处理籽粒地上部干物质最大，为12 691 kg/hm2，在高肥梯度的2017年，随着灌水量和施肥量的增加，75%ETc和105%ETc处理的地上部干物质累积量有先增加后减小的趋势，D90F300处理下籽粒地上部干物质累积量最大，为14 912 kg/hm2；在低肥梯度的2016年，灌水施肥量对春玉米产量有显著影响，D120F240处理产量最高，为14 400 kg/hm2，而在高肥梯度的2017年，D90F300处理玉米产量最高，为16 884 kg/hm2；2 a试验结果表明灌水量和施肥量对春玉米水分利用效率和肥料偏生产力都有极显著影响。基于春玉米产量和水分利用效率最大值的95%为置信区间优化水肥管理方案，兼顾节水节肥，推荐灌水量在323～446 mm、N-P2O5-K2O施肥量在210-104-104～325-163-163 kg/hm2。该研究结果对宁夏春玉米滴灌施肥管理具有重要指导意义。