李静, 闫金垚, 胡文诗, 李小坤, 丛日环, 任涛^,*, 鲁剑巍^*华中农业大学资源与环境学院 / 农业农村部长江中下游耕地保育重点实验室, 湖北武汉 430070

Effects of combined application of nitrogen and potassium on seed yield and nitrogen utilization of winter oilseed rape (Brassica napus L.)

LI Jing, YAN Jin-Yao, HU Wen-Shi, LI Xiao-Kun, CONG Ri-Huan, REN Tao^,*, LU Jian-Wei^*College of Resources and Environment, Huazhong Agricultural University / Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture and Rural Affairs, Wuhan 430070, Hubei, China

通讯作者: ^*任涛, E-mail: rentao@mail.hzau.edu.cn

收稿日期:2018-11-9接受日期:2019-01-19网络出版日期:2019-03-20

基金资助:

本研究由国家自然科学基金项目.31872173 国家现代农业产业技术体系建设专项.CARS-12 中央高校基本科研业务费专项基金(2662018PY077)资助.

Received:2018-11-9Accepted:2019-01-19Online:2019-03-20

Fund supported:

This study was supported by the National Natural Science Foundation of China.31872173 the China Agriculture Research System.CARS-12 the Fundamental Research Funds for the Central Universities (2662018PY077)..

作者简介 About authors
E-mail:ljing@webmail.hzau.edu.cn,Tel:027-87288589。









摘要
实际生产中氮钾肥投入不平衡严重限制了氮肥肥效及作物的产量潜力。为了探明不同施氮量下钾肥施用对油菜产量及氮素利用的影响, 于2016—2017年及2017—2018年在湖北省武穴市开展连续2年的田间试验, 采用氮钾两因素完全试验设计, 设氮0、90、180、270 kg N hm ^-2和钾0、60、120、180 kg K₂O hm ^-2各4个水平。在油菜成熟期取样测定产量、地上部氮钾积累量以及氮肥利用率。结果表明, 在钾供应不足时(K₀和K₆₀), 冬油菜施用氮肥的平均增产率为113.7%, 而在钾供应充足的条件下(K₁₂₀和K₁₈₀), 施用氮肥的平均增产率高达172.9%; 与K₀处理相比, K₁₂₀处理冬油菜氮肥回收利用率平均提高了16.6%, 继续增施钾肥对不同施氮量下冬油菜氮肥回收利用率的进一步提高无显著影响; 达到区域平均产量时, 钾供应充足较低钾(K₆₀)投入平均降低33.9%的氮肥用量。综上所述, 氮钾配施显著提高了冬油菜产量和氮肥利用率, 在冬油菜实际生产中除了重视氮肥施用外, 应增加钾肥投入, 通过优化氮钾肥配施比例可进一步提高油菜产量, 实现冬油菜高产和养分高效。
关键词： 冬油菜;氮钾配施;产量;氮肥利用率

Abstract
The imbalance inputs of nitrogen (N) and potassium (K) fertilizer in current agricultural production severely restricts fertilizer use efficiency and crop yield potential. In order to estimate the influence of K fertilizer application on rapeseed yield and N fertilizer use efficiency under different nitrogen application rates, field experiments using two-factor experimental design were conducted at Wuxue county, Hubei province in 2016/2017 and 2017/2018 winter oilseed rape growing seasons. Four levels of N and K fertilizer application rates were set up, which were 0, 90, 180, 270 kg N ha ^-1 and 0, 60, 120, 180 kg K₂O ha ^-1, respectively. Seed yield, shoot N and K accumulation and N fertilizer use efficiency were measured at the harvest of winter oilseed rape. When K supply was insufficient (K₀ and K₆₀), the average increase rate of seed yield was 113.7%, while under sufficient K supplies (K₁₂₀ and K₁₈₀), the average seed yield increase rate was 172.9%. In contrast to the K₀ treatment, the K₁₂₀ treatment increased N fertilizer use efficiency by 16.6% on average; nevertheless, further increase K fertilizer application rate played minor role in the improvement of N fertilizer use efficiency. Considering the regional average rapeseed yield, adequate K supply could reduce the N fertilizer application rate with the average of 33.9% compared with insufficient K fertilization (K₆₀). Consequently, the combined application of N and K fertilizers could significantly enhance rapeseed yield and N fertilizer use efficiency. In practices, besides paying more attention to N fertilizer application, K fertilizer input also should be strengthened. Optimizing N and K fertilizer application could be beneficial to further achieving higher seed yield and higher fertilizer use efficiency.
Keywords：winter oilseed rape (Brassica napus L.);combined application of nitrogen and potassium;seed yield;nitrogen use efficiency


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本文引用格式
李静, 闫金垚, 胡文诗, 李小坤, 丛日环, 任涛, 鲁剑巍. 氮钾配施对油菜产量及氮素利用的影响[J]. 作物学报, 2019, 45(6): 941-948. doi:10.3724/SP.J.1006.2019.84146
LI Jing, YAN Jin-Yao, HU Wen-Shi, LI Xiao-Kun, CONG Ri-Huan, REN Tao, LU Jian-Wei. Effects of combined application of nitrogen and potassium on seed yield and nitrogen utilization of winter oilseed rape (Brassica napus L.)[J]. Acta Crops Sinica, 2019, 45(6): 941-948. doi:10.3724/SP.J.1006.2019.84146


自20世纪50年代以来, 农业生产中化学氮肥的施用量急剧增加^[1], 在许多农业集约化产区, 为了提高作物产量, 往往施用大量氮肥, 导致氮肥利用率明显下降。过量的氮素进入环境中造成水体富营养化、土壤酸化、温室气体排放加剧、氮沉降量增加等一系列严重的环境问题^[2,3,4]。与氮肥施用相比, 钾肥的施用在农业生产中一直被忽视, 我国钾肥用量远低于氮肥用量^[5]。钾肥投入不足导致农业生态系统中的钾素失衡和产量停滞, 将随着时间的推移更加明显^[6], 在中国不同的种植系统和农业生态区内, 钾素亏缺广泛存在, 导致了土壤中钾的不断枯竭^[7]。Khan等^[8]在小麦上的研究表明, 随着施氮、钾量的增加, 小麦的生物量和产量均显著提高, 小麦对钾施用量的响应随着施氮量的增加而增加, Jackson等^[9]在玉米上最新研究结果表明, 缺钾既限制了玉米产量, 也限制了玉米对氮肥的响应能力, 而氮钾肥施用显著增加了玉米籽粒产量, 且钾供应充足时玉米对氮肥的响应更高。由此可见, 合理的氮钾肥配比有利于作物的生长, 增加作物产量, 提高肥料利用率。

油菜是世界第二大油料作物, 在气候温和地区广泛种植^[10]。油菜为我们提供了优质的植物油, 菜籽油占我国国产油料作物产油量的57.2%^[11], 因此, 油菜高产和稳产对于保证我国食用油供给具有重要的意义。作为油菜高产和稳产的重要措施, 我国冬油菜合理施用氮肥和钾肥的平均增产率分别为42.5%和16.1%^[12]。但据调查, 在我国油菜主产区的长江流域, 冬油菜生产中氮肥平均用量为175 kg N hm^-2, 而钾肥施用量仅为42 kg K₂O hm^-2, 甚至有22.8%农户在实际生产中并不施用钾肥^[13]。农民往往重视氮肥, 而忽视钾肥的施用, 氮钾肥不协调施用已经成为限制油菜产量及肥料利用率的重要因子。重氮轻钾是我国农业生产中的突出问题, 为了达到2020年化肥零增长, 走资源节约、环境友好型现代农业发展之路的目标, 实现油菜生产减肥增效、绿色增产增效, 本研究在冬油菜主产区开展了连续2年的氮钾配施田间试验, 旨在探明氮钾配施对油菜产量及氮素利用的影响, 为冬油菜生产中氮钾肥合理配施实现油菜的高产、高效提供理论支撑。

1 材料与方法

1.1 试验点概况

湖北省武穴市梅川镇(30°06'N, 115°36'E), 供试土壤为花岗片麻岩母质发育的水稻土, 0~20 cm耕层土壤pH 5.76, 含有机质32.1 g kg^-1、全氮1.75 g kg^-1、速效钾54.5 mg kg^-1、速效磷3.4 mg kg^-1、有效硼0.48 mg kg^-1。试验点前茬作物为水稻。

1.2 试验设计

采用氮钾两因素完全试验设计, 氮、钾各设置0、90、180、270 kg N hm^-2和0、60、120、180 kg K₂O hm^-2 4个水平, 记做N₀、N₉₀、N₁₈₀、N₂₇₀及K₀、K₆₀、K₁₂₀、K₁₈₀。共16个处理, 每个处理3次重复, 完全随机区组排列, 小区面积为20 m²。

各处理磷硼肥用量相同, 分别为90 kg P₂O₅ hm^-2、硼沙15 kg hm^-2。供试肥料分别为尿素(含N 46%)、过磷酸钙(含P₂O₅ 12%)、氯化钾(含K₂O 60%)和硼沙(含B 11%)。氮肥按基肥∶越冬肥∶薹肥 = 6∶2∶2比例分3次施用, 其他肥料均一次性基施。

2016年9月至2018年5月2年试验供试油菜品种均为华油杂9号, 采用育苗移栽的方式。在每年的9月中下旬播种育苗, 选取4~5片叶(苗龄约45 d)大小均一的油菜幼苗移栽到试验田, 移栽的密度为11.25×10⁴ plants hm^-2。所有试验小区布置完成后在整个试验外围设保护区, 保护区内亦种植移栽油菜, 在试验过程中, 所有的田间管理, 包括除草剂施用和病虫害的防治等, 均采用当地的栽培管理方法。

1.3 测定项目与方法

1.3.1 土壤样品的采集与分析 土壤基础样品在前茬水稻收获后油菜基肥施用前采集。以整个试验田块为采样单元, 在试验田块内以“S”形均匀布点15个, 取0~20 cm耕作层土壤, 实验室风干磨细过20目和100目筛, 供理化分析用。按常规方法测定土壤基本理化性质^[14]。按水土比2.5︰1.0, 后用pH计测定土壤pH; 采用重铬酸钾容量法测定有机质; 采用半微量开氏法测定全氮; 采用1 mol L^-1 NH₄OAc浸提火焰光度计测定速效钾; 采用0.5 mol L^-1 NaHCO₃浸提钼锑抗比色法测定速效磷; 采用热水回流姜黄素比色法测定有效硼。

1.3.2 成熟期样品采集与测定 收获前2~3 d调查移栽冬油菜所有试验处理的产量构成因素, 包括单位面积角果数(通过单株角果数和移栽密度换算)和每角粒数(角果中油菜籽的个数, 每株随机选取30个角果, 计平均值), 及收获后的千粒重(采用千粒板随机测定2000粒风干后油菜籽的质量)。每个试验处理3次重复, 选取每个小区10株有代表性的植株进行调查, 各项指标取平均值作为调查结果。

油菜成熟后从各小区随机取样6株, 齐地收割地上部, 放入网袋内悬挂风干脱粒后分别测定籽粒、茎秆和角壳干重, 各部位样品经烘干、磨细、过筛后供养分含量测定分析用。籽粒产量以各小区实收风干重计量。浓H₂SO₄-H₂O₂联合消煮后, 用流动注射分析仪(AA3, SEAL, Germany)测定全氮含量, 火焰光度计测定全钾含量。

1.4 参数计算与统计分析

植株各部位氮、钾积累量为植株地上部不同部位干物质量与相应部位氮、钾养分含量之积; 参考彭少兵等方法^[15,16]用氮肥回收利用率表征氮肥利用率:

氮肥回收利用率(nitrogen fertilizer recovery efficiency, RE_N, %), 反映作物对施入土壤中肥料氮素的回收效率, 即RE_N = (U-U₀) × 100/F, 其中U为施氮区作物收获时地上部氮总积累量, U₀为不施氮区作物收获时地上部氮总积累量, F为施氮量。

本研究对不同施钾量下油菜产量对氮肥响应的2个施肥模型(线性加平台和二次多项式模型)^[17,18]进行比较, 选取最小残差平方和^[19]的模型拟合肥料用量和作物产量间的关系。采用Microsoft Excel 2013软件计算处理试验数据, 利用SPSS 18.0软件进行统计分析, 采用Origin Pro 8.5软件作图。

2 结果与分析

2.1 不同氮钾肥用量对冬油菜产量及产量构成的影响

2年油菜产量存在明显差异(F=15.9^**), 但籽粒产量对氮肥和钾肥施用的响应趋势相似, 钾肥用量在0~120 kg K₂O hm^-2范围内, 油菜产量随钾肥用量的增加显著增加, 继续增施钾肥增产效果不显著; 随着钾肥用量的增加, 氮肥肥效明显增加, 在钾供应不足时(K₀和K₆₀), 冬油菜施用氮肥的平均增产率为113.7%; 而在钾供应充足的条件下(K₁₂₀和K₁₈₀), 施用氮肥的平均增产率高达172.9%。施氮不施钾时油菜产量严重下降, 特别在N₂₇₀K₀时产量降幅最多达1345 kg hm^-2; 施氮处理具有较高F值, 表明氮肥施用对油菜产量的贡献大于钾肥, 氮钾配施对油菜产量形成具有显著交互作用(表1)。

Table 1
表1
表1不同氮肥和钾肥用量对2016-2017和2017-2018年油菜产量的影响
Table 1Effects of different nitrogen and potassium fertilizer application rates on rapeseed yield in 2016-2017 and 2017-2018 growing season

处理 Treatment		年份 Year		平均 Average (kg hm-2)
		2016/2017	2017/2018
N0	K0	833 c	750 b	791
	K60	977 b	909 ab	943
	K120	1051 ab	956 ab	1003
	K180	1125 a	1088 a	1106
	平均 Average	996	926	961
N90	K0	1220 c	1284 c	1252
	K60	1618 b	1594 b	1606
	K120	2038 a	1988 a	2013
	K180	2116 a	2138 a	2127
	平均 Average	1748	1751	1749
N180	K0	1904 c	1659 c	1782
	K60	2590 b	2278 b	2434
	K120	3038 a	2981 a	3009
	K180	3366 a	3281 a	3323
	平均 Average	2724	2550	2637
N270	K0	1720 c	1406 c	1563
	K60	2781 b	2372 b	2576
	K120	3320 a	3162 a	3241
	K180	3550 a	3478 a	3514
	平均 Average	2843	2605	2724
方差分析 ANOVA		F值 F-value
氮肥 Nitrogen (N)		761.1**
钾肥 Potassium (K)		296.1**
年份 Year (Y)		15.9**
N×K		29.2**
N×Y		3.2*
K×Y		1.3ns
N×K×Y		0.5ns

N₀, N₉₀, N₁₈₀, and N₂₇₀ indicate that the application rates of N fertilizer are 0, 90, 180, and 270 kg N hm^-2; K₀, K₆₀, K₁₂₀, and K₁₈₀ indicate that the application rates of K fertilizer are 0, 60, 120, and 180 kg K₂O hm^-2; Values followed by different lowercase letters under the same N treatment in the same year are significantly different between different K fertilizer treatments by LSR test (P<0.05); ^* and ^** represent P<0.05 and P<0.01, respectively; ^ns means no significant difference.
N₀、N₉₀、N₁₈₀、N₂₇₀表示氮肥施用量为0、90、180、270 kg N hm^-2; K₀、K₆₀、K₁₂₀、K₁₈₀表示钾肥施用量为0、60、120、180 kg K₂O hm^-2; 标以不同小写字母的值在相同年份同一施氮量下不同钾处理间差异达5%显著水平; ^*表示P<0.05, ^**表示P<0.01; ^ns表示无显著差异。

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氮钾配施对油菜产量构成因子的影响2年表现出相似的变化趋势, 氮钾配施主要增加了移栽油菜单位面积角果数, 从而增加油菜产量, 氮肥施用对油菜单位面积角果数形成的影响大于钾肥, 钾肥施用对每角粒数增加的贡献大于氮肥, 氮肥施用对千粒重的影响大于钾肥, 同一施氮量下不同钾处理间籽粒千粒重无显著差异(表2)。

Table 2
表2
表2不同氮肥和钾肥用量对2016-2017和2017-2018年油菜籽产量构成因素的影响
Table 2Effects of different nitrogen and potassium fertilizer application rates on yield components of rapeseed in 2016-2017 and 2017-2018 growing season

处理 Treatment		单位面积角果数 Number of pods per unit area (No. m-2)		平均 Average	角粒数 Seed number (No. pod-1)		平均 Average	千粒重 1000 seed weight (g)		平均Average
		2016/2017	2017/2018		2016/2017	2017/2018		2016/2017	2017/2018
N0	K0	1245 b	1059 b	1152	24.7 a	24.4 b	24.5	3.3 a	2.9 a	3.1
	K60	1444 ab	1160 b	1302	25.4 a	24.7 ab	25.0	3.2 a	3.1 a	3.2
	K120	1575 a	1290 ab	1432	26.1 a	25.4 ab	25.8	3.1 a	3.1 a	3.1
	K180	1679 a	1503 a	1591	25.8 a	25.8 a	25.8	3.1 a	3.1 a	3.1
	平均 Average	1486	1253	1369	25.5	25.1	25.3	3.2	3.0	3.1
N90	K0	2981 c	2272 c	2626	24.1 b	23.4 b	23.8	3.2 a	2.9 a	3.1
	K60	3408 bc	2742 b	3075	25.7 ab	26.3 ab	26.0	3.4 a	2.9 a	3.1
	K120	3591 ab	3250 a	3421	25.1 ab	25.1 ab	25.1	3.2 a	2.9 a	3.1
	K180	4114 a	3479 a	3796	26.3 a	26.6 a	26.4	3.1 a	2.9 a	3.0
	平均 Average	3523	2936	3230	25.3	25.4	25.3	3.2	2.9	3.1
N180	K0	3649 c	2662 c	3156	24.3 c	22.7 b	23.5	3.2 b	3.0 a	3.1
	K60	4508 b	3593 b	4051	26.3 b	26.3 a	26.3	3.4 ab	3.0 a	3.2
	K120	4720 a	4838 a	4779	27.5 a	26.8 a	27.1	3.5 a	3.0 a	3.3
	K180	4751 a	5024 a	4888	27.7 a	27.0 a	27.4	3.3 b	3.0 a	3.1
	平均 Average	4407	4029	4218	26.5	25.7	26.1	3.4	3.0	3.2
N270	K0	3455 c	2151 d	2803	24.0 c	22.7 b	23.4	3.4 a	3.2 a	3.3
	K60	4791 b	3626 c	4209	26.2 b	27.3 a	26.8	3.5 a	3.1 a	3.3
	K120	5406 ab	5138 b	5272	27.5 ab	26.0 a	26.8	3.3 a	3.2 a	3.2
	K180	5953 a	5710 a	5832	28.1 a	27.4 a	27.7	3.3 a	3.0 a	3.2
	平均 Average	4901	4156	4529	26.4	25.9	26.2	3.4	3.1	3.3
方差分析 ANOVA		F值 F-value
氮肥 Nitrogen (N)		491.6**			6.3**			9.6**
钾肥 Potassium (K)		119.2**			50.4**			2.9*
年份 Year (Y)		57.2**			4.9*			92.5**
N×K		14.9**			3.7**			1.0ns
N×Y		3.1*			0.9ns			2.9*
K×Y		6.9**			2.3ns			2.2ns
N×K×Y		1.7ns			0.7ns			1.7ns

Values followed by different lowercase letters under the same N treatment in the same year are significantly different between different K fertilizer treatments by LSR test (P<0.05); ^* and ^** represent P<0.05 and P<0.01, respectively; ^ns means no significant difference. Treatments are the same as those given in Table 1.
标以不同小写字母的值在相同年份同一施氮量下不同钾处理间差异达5%显著水平; ^*表示P<0.05, ^**表示P<0.01; ^ns表示无显著差异。处理同表1。

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2.2 氮钾配施对油菜地上部氮钾积累量的影响

氮钾配施显著增加了油菜地上部氮钾积累量(图1)。同一施氮量下, 施钾显著增加油菜地上部氮积累量, 且钾肥用量在0~120 kg K₂O hm^-2范围内, 油菜地上部氮积累量随钾肥用量的增加显著增加, 继续增施钾肥, 地上部氮积累量增加不显著; 不同施氮量下, 施钾对油菜地上部氮积累量的增幅作用不同, 不施氮(N₀)或低氮(N₉₀)下, 施钾地上部氮积累量平均增加18.4%和26.4%, 供氮充足时(N₁₂₀和N₁₈₀), 施钾地上部氮积累量平均增幅高达41.9%和60.9%; 成熟期油菜地上部氮主要累积在籽粒中, 且同一施氮量下, 随施钾量的增加籽粒氮积累量占地上部氮积累量的比例逐渐增加。与氮积累不同, 油菜地上部钾主要积累在茎秆和角壳中, 施钾显著增加了油菜地上部钾积累量, 低钾条件下施氮对地上部钾积累量的增幅作用明显小于供钾充足时的增幅作用, 氮、钾及氮钾交互对成熟期油菜地上部钾吸收产生极显著影响。

图1

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图1氮钾肥配施对2016-2017和2017-2018年收获期地上部氮钾积累量的影响

标以不同小写字母的柱值在相同年份同一施氮量下不同钾处理间差异达0.05显著水平; *表示P < 0.05, **表示P < 0.01。处理同表1。
Fig. 1Effect of combined application of N and K fertilizer on shoot N and K accumulation at harvest during 2016-2017 and 2017-2018 growing season

Bar superscripted by different letters under the same N treatment in the same year are significantly different between different K fertilizer treatments by LSR test (P < 0.05); * and ** represent P < 0.05 and P < 0.01, respectively. Treatments are the same as those given in Table 1.

2.3 氮钾肥施用对氮肥利用的影响

钾肥施用显著提高了氮肥回收利用率(图2), 与K₀处理相比, K₁₂₀处理冬油菜氮肥回收利用率平均提高了16.6%, 继续增施钾肥对不同施氮量下冬油菜氮肥回收利用率的进一步提高无明显作用; 不同施氮量下, 施钾对氮素回收利用率的提升作用不同, 整体表现为N₂₇₀>N₁₈₀> N₉₀, 氮肥和钾肥施用对冬油菜氮素回收利用率产生显著影响。

图2

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图2氮钾肥配施对2016-2017和2017-2018年冬油菜氮素利用效率的影响

标以不同小写字母柱值在相同年份同一施氮量下不同钾处理间差异达0.05显著水平; *表示P < 0.05, **表示P < 0.01; ns表示无显著差异。处理同表1。
Fig. 2Effect of combined application of N and K fertilizer application rates on N use efficiency of winter oilseed rape during 2016-2017 and 2017-2018 growing season

Bar superscripted by different letters under the same N treatment in the same year are significantly different between different K fertilizer treatments by LSR test (P < 0.05); * and ** represent P < 0.05 and P < 0.01, respectively; ns means no significant difference. Treatments are the same as those given in Table 1.

2.4 不同氮钾肥用量下油菜籽产量效应及适宜氮钾肥用量

采用线性加平台模型对不同氮钾肥用量下油菜籽粒产量和相应氮肥用量进行拟合, 由图3可知, 在氮钾肥投入不均衡时, 油菜产量潜力受到极大的限制, 而随着钾肥用量的增加, 达到平台产量前, 单位氮肥增产率逐渐增加, 单位氮肥增产率增幅逐渐减小, 说明在油菜生产中钾供应充足时, 氮肥可更好发挥其增产效应, 而偏施氮肥或钾肥要达到一定目标产量所需的代价逐渐增大; 同时, 随着钾供应量的增加, 不同施氮量下油菜产量增幅逐渐减小, 在不同钾肥用量下, 当氮肥用量大于208 kg N hm^-2时, 油菜产量不再增加, 结果表明, 在油菜生长中存在较强的氮、钾相互作用, 但过量施用氮钾肥油菜产量不会进一步增长; 目前长江流域冬油菜主产区氮磷钾肥配合施用后, 油菜籽平均产量为2562 kg hm^-2, 以油菜籽粒产量2500 kg hm^-2为目标产量时, 钾供应充足较低钾(K₆₀)投入平均降低33.9%的氮肥用量; 当以3000 kg hm^-2为区域高产量水平时, 钾肥用量为120 kg K₂O hm^-2, 氮肥用量为179 kg N hm^-2, 当钾肥用量提高到180 kg K₂O hm^-2时, 达到相同目标产量氮肥用量降低10.1%。

图3

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图3不同施钾量下油菜产量对氮肥的响应及与目标产量对应的最佳施氮量

图中虚线表示产量为2500 kg hm^-2时的氮钾肥用量, 点划线表示产量为3000 kg hm^-2时的氮钾肥用量; 黑色实心点为2016-2017年平均产量, 空心点为2017-2018年平均产量。处理同表1。
Fig. 3Rapeseed yield responses to N fertilizer application under different K fertilizer application rates and the optimal N and K fertilizer application rate for corresponding target seed yield

The dashed line in the figure shows the N and K fertilizer application rate when the yield is set as 2500 kg hm^-2, The dot dash line in the figure shows the N and K fertilizer application rate when the yield is set as 3000 kg hm^-2; the black solid point is the average yield of 2016-2017, and the hollow point is the average yield of 2017-2018. Treatments are the same as those given in Table 1.

3 讨论

3.1 氮钾配施对冬油菜产量的影响

当作物供钾充足时, 可充分发挥氮肥的增产作用, 而钾素供应不足则严重限制氮肥肥效。本研究中, 氮钾配施显著增加了冬油菜产量, 随着钾肥用量的增加, 氮肥肥效明显增加。钾供应不足时(K₀和K₆₀), 冬油菜施用氮肥的平均增产率为113.7%; 而在钾供应充足的条件下(K₁₂₀和K₁₈₀), 施用氮肥的平均增产率高达172.9%, 而施氮不施钾时, 油菜产量严重下降, 特别在N₂₇₀K₀时产量降幅最多达1345 kg hm^-2, 这与小麦上高氮低钾供应时产量反而下降的结果一致^[20]。Johnston等^[21]研究了不同速效钾含量土壤上春大麦对施氮量的响应, 发现当土壤钾素供应充足时, 适当增施氮肥可进一步提高作物的产量。Brennan等^[22]在油菜上的研究结果也表明, 要达到高产随着氮肥用量的增加, 油菜对钾肥的需求量逐渐增加, 在2年不同梯度氮钾配施试验中, 高钾时氮肥增产率显著高于低钾时的氮肥增产率, 可见氮钾配施是提高油菜产量的关键。而油菜籽产量取决于单位面积角果数、每角粒数和千粒重, 氮素主要影响冬油菜的分枝数、角果数和角粒数^[23], 钾素对各项产量构成因素的影响较小, 而主要影响单株角果数和角粒数^[24]。本研究中, 在钾素供应充足时, 施氮对油菜单位面积角果数的增幅显著高于低钾供应时, 说明氮钾配施主要通过增加油菜单位面积角果数来增加油菜产量, 钾素对油菜每角粒数的影响大于氮素。

3.2 氮钾配施对地上部养分积累及氮素利用的影响

连续2年试验结果表明, 氮钾配施对地上部氮素积累量具有显著影响, 施钾可以促进地上部氮积累量的增加, 提高氮素回收利用率, 且供钾充足时促进作用更加明显。研究表明, 作物对施氮量的响应受土壤钾肥力差异的影响^[25], Duncan等^[26]在小麦上的研究表明, 氮钾配施显著影响作物根系以及地上部生长, 进而提高作物氮素吸收和氮肥利用率。油菜是典型的旱地作物, 施用的氮肥经过水解、硝化等过程最终转化为NO₃^--N被油菜吸收利用, NO₃^-从根向地上部运输过程中往往以K⁺作为陪伴离子, NO₃^-和K⁺同化和利用存在明显正相关^[27,28]; 此外, 施钾可以提高叶片碳酸氢酶和硝酸还原酶的活性, 从而诱导光合作用及蛋白质合成所需的初级含氮有机分子的形成, 促进氮在地上部的同化^[29], 提高作物地上部氮积累量和氮肥利用率。

3.3 氮钾配施时冬油菜生产适宜的氮钾肥用量

本研究结果表明, 氮钾肥配施是油菜生产获得高产的先决条件, 达到区域平均产量时, 氮钾配施可显著降低氮肥用量。据我国冬油菜主产区农户氮肥施用情况及推荐施肥调查结果显示, 农户氮肥用量平均变幅为152~255 kg N hm^-2, 产量平均变幅为1722~2360 kg hm^-2, 长江流域油菜生产推荐施氮量平均变幅为140~190 kg N hm^-2, 产量平均变幅为2265~2751 kg hm^{-2 [30]}。在本研究中, 达到区域平均产量, 氮钾配施钾肥用量为60~120 kg K₂O hm^-2, 氮肥用量为134~191 kg N hm^-2, 较农户施氮降低4.4%~33.5%, 处于区域氮肥推荐用量范围内; 同时, 钾供应充足较低钾(K₆₀)投入平均降低33.9%的氮肥用量; 本研究以3000 kg hm^-2为区域高产量水平, 达到高产水平时钾肥用量为120 kg K₂O hm^-2, 氮肥用量为179 kg N hm^-2, 这与长江流域冬油菜生产高产推荐氮钾肥用量^[31]接近。本研究推测区域施氮变幅较大的原因可能是由生产中氮钾肥施用不协调引起的, 由此可见, 氮钾配施在油菜生产中具有重要作用, 氮钾肥平衡施用可以最大限度发挥氮肥肥效, 减少因氮素过多带来的负面效应。

The authors have declared that no competing interests exist.

作者已声明无竞争性利益关系。

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[15] 彭少兵, 黄见良, 钟旭华, 杨建昌, 王光火, 邹应斌, 张福锁, 朱庆森 , Roland B, Christian W. 提高中国稻田氮肥利用率的研究策略
中国农业科学, 2002,35:1095-1103.
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Peng S B, Huang J L, Zhong X H, Yang J C, Wang G H, Zou Y B, Zhang F S, Zhu Q S, Roland B, Christian W . Research strategy in improving fertilizer nitrogen use efficiency of irrigated rice in China
Sci Agric Sin, 2002,35:1095-1103 (in Chinese with English abstract).
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[16] 张福锁, 王激清, 张卫峰, 崔振岭, 马文奇, 陈新平, 江荣风 . 中国主要粮食作物肥料利用率现状与提高途径
土壤学报, 2008,45:915-924.
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Zhang F S, Wang J Q, Zhang W F, Cui Z L, Ma W Q, Chen X P, Jiang R F . Nutrient use efficiencies of major cereal crops in China and measures for improvement
Acta Pedol Sin, 2008,45:915-924 (in Chinese with English abstract).
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[17] 贾良良, 陈新平, 张福锁, 刘宏斌, 吴健繁 . 北京市冬小麦氮肥适宜用量评价方法的研究
中国农业大学学报, 2001,6(3):67-73.
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Jia L L, Chen X P, Zhang F S, Liu H B, Wu J F . Study of optimum N supplying rate in winter wheat in Beijing area
J China Agric Univ, 2001,6(3):67-73 (in Chinese with English abstract).
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[18] 陈新平, 周金池, 王兴仁, 张福锁, 宝德俊, 贾晓红 . 小麦-玉米轮作制中氮肥效应模型的选择——经济和环境效益分析
土壤学报, 2000,37:346-354.
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Chen X P, Zhou J C, Wang X R, Zhang F S, Bao D J, Jia X H . Economic and environmental evaluation on models for describing crop yield response to nitrogen fertilizers at winter-wheat and summer-corn rotation system
Acta Pedol Sin, 2000,37:346-354 (in Chinese with English abstract).
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[19] Wang W N, Lu J W, Ren T, Li X K, Su W, Lu M X . Evaluating regional mean optimal nitrogen rates in combination with indigenous nitrogen supply for rice production
Field Crops Res, 2012,137:37-48.
DOI:10.1016/j.fcr.2012.08.010URL [本文引用: 1]
Nitrogen (N) is an essential nutrient that requires careful management in intensive rice systems, since insufficient amounts might result in yield losses, and excessive application might harm the environment. However, farmers often tend to apply a large excess of N fertilizer to ensure high rice yields, primarily because of the absence of reliable methods to estimate optimal N application rates. Therefore, a large-scale study comprising 514 field experiments for rice was conducted in seven rice regions (totaling 1.253millionha) in Hubei province, Central China. We (i) evaluated yield responses to different N application levels, (ii) established indigenous soil N supply (INS) classification systems for different rice regions by identifying and using the preferable predictor of INS, and (iii) determined the optimal N application rates for each region based on regional mean optimal N rates (RMONR) in combination with INS. In all of the rice regions, rice yields were significantly higher in plots receiving N than in plots without N (termed no-N plots). The highest yields were obtained in plots receiving medium nitrogen (MN) treatment, where the average partial factor productivity (PFPN) and agronomic efficiency (AEN) were 50.4kggrainkg611N and 12.5kggrainkg611N, respectively. Yield responses of rice to N fertilizer were different among different rice regions because of regional variations in climatic conditions and soil fertility. A significant positive relationship between grain yield with and without N fertilizer also proved an important effect of INS on yield response to N fertilizer. On the basis of regression models, relative yields of 90%, 80%, 70%, 60%, and 50% were used as the critical values to obtain INS classifications, which were estimated by the yield of the no-N treatment but not by alkaline hydrolyzable-N. An obvious increasing trend of economic optimum N rate (EONR) with decreasing INS (from Class 1 to Class 6) was found for each rice region. Averaged across all rice regions of Hubei province, EONR was 150kgha611, which was lower than the N application rate for the MN treatment of 171kgha611. The results indicated that the N application rate recommended by local rice technicians could be cut by 12% (1–18% in different rice regions) without any loss of yield. In conclusion, the recommended N fertilizer application, based on RMONR in combination with INS, is feasible for regional rice production in China and other countries that have large numbers of small farmland areas and where agricultural testing equipment is absent or less modern.

[20] Loué A . The interaction of potassium with other growth factors, particularly with other nutrients
IPI Res Topics, 1980,8:67-93.
URL [本文引用: 1]
Results of long-term experiments on the effects of interactions of K fertilizers with other fertilizer nutrients on crop yields in arable rotations, with special emphasis on experiments carried out in France are reported.

[21] Milford G F J, Johnston A E . Potassium and nitrogen interactions in crops production
Nawozy I Nawozenie, 2009,34:143-162.
URL [本文引用: 1]
The potassium (K) status of the soil has a considerable influence on crop uptake and response to nitrogen (N). Yield response to applied fertiliser N is decreased by low concentrations of exchangeable K in the soil. The basis of this interaction is explored using historical and current data from Rothamsted Research's experiments at Rothamsted, Saxmundham, Woburn and Broom's Barn on spring barle...

[22] Brennan R F , Bolland M D A. Influence of potassium and nitrogen fertilizer on yield, oil and protein concentration of canola (
Brassica napus L.) grain harvested in southwestern Australia. Aust J Exp Agric, 2007,47:976-983.
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[23] Ahmad C, Jan A, Arif M, Jan M T, Shah H . Effect of nitrogen and sulfur fertilization on yield components, seed and oil yields of canola
J Plant Nutr, 2011,34:2069-2082.
DOI:10.1080/01904167.2011.618569URL [本文引用: 1]
Field experiments were conducted to evaluate the effects of nitrogen (N) and sulfur (S) levels and their methods of application on canola. Branches plant611, pods plant611 and biological yield significantly increased with increase in nitrogen level and no significant increase in seed pod611 and seed and oil yields occurred beyond 120 kg N ha611. However, thousand seed weight consistently decreased with increasing level of nitrogen. Pods plant611 and biological yield continually increased with increase in sulfur level. Alternatively, significant increase in branches plant611, seed pod611, seed weight, seed and oil yields was noted with increase in sulfur level up to 40 kg ha611. Applications of sulfur and nitrogen in split significantly decreased seed yield as compared to sole applications. It is concluded that sulfur and nitrogen application as sole at the rate of 40 and 120 kg ha611, respectively performed better than the rest of their levels and method of application.

[24] Amanullah, Hassan M , Malhi S S. Seed yield and yield components response of rape (
B. napus) versus mustard( B. juncea) to sulfur and potassium fertilizer application in northwest Pakistan. J Plant Nutr, 2011,34:1164-1174.
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[25] Bruns H A, Ebellhar M W . Nutrient uptake of maize affected by nitrogen and potassium fertility in a humid subtropical environment
Commun Soil Sci Plant Anal, 2006,37:275-293.
DOI:10.1080/00103620500408829URL [本文引用: 1]
Nitrogen (N) and potassium (K) fertility management of maize (Zea mays L.) in the humid subtropical Mississippi Delta may differ from a temperate climate because of its use in rotation with cotton (Gossypium hirsutum L.), soil temperatures rarely falling to 0°C, and heavy winter rains that facilitate nutrient losses. An experiment to determine the [N] (concentration=[02]), phosphorus [P], [K], calcium [Ca], magnesium [Mg], iron [Fe], manganese [Mn], zinc [Zn], and copper [Cu] and their total contents plant611 of maize grown in rotation with cotton, using N fertility levels of (134, 179, 224, 269, and 31402kg02N02ha611) in combination with K fertility levels of (0, 45, 90, and 13402kg02K02ha611) was conducted in 2000 and 2001 at Tribbett, MS. Ear leaves, immature ears, and husks collected at growth stage R2 and grain and stover collected 21 days after R6 were dried, weighed, and analyzed for nutrient concentration. Plots were also harvested for yield, kernel weight, grain bulk density, and harvest index (HI). Increased [N] values of about 1.302mg02g611 occurred in all organs except the stover between 134 and 31402kg02N02ha611 N fertility. Stover [N] increased approximately 3.002mg02g611 within the same N fertility range. Total N content of ear leaves, grain, and stover increased by about 11.0, 550.0, and 730.002mg plant611, respectively, with N fertility increased from 134 to 31402kg02N02ha611. Yields, kernel weights, grain bulk densities, and harvest indices also increased with added N fertility. Several micronutrient concentrations and contents increased as N fertility increased. Increased K fertility had only limited influence on concentrations of most nutrient elements. The nutrient contents of most elements in the stover increased with added K fertility compared with plots that received no supplemental K fertilizer. These data showed between 139 and 26502kg02N02ha611 was permanently removed by grain harvest and suggest that N fertility recommendations for the Mississippi Delta may be low for maize yield goals above 1002Mg02ha611. Added K fertilizer has minimal benefit to maize when soil test levels are adequate but are important to succeeding cotton crops where K uptake during fruiting can exceed the soil's ability to release K for uptake.

[26] Duncan E G , Sullivan C A O,Roper M M, Palta J, Whisson K, Peoples M B . Yield and nitrogen use efficiency of wheat increased with root length and biomass due to nitrogen, phosphorus, and potassium interactions
J Plant Nutr Soil Sci, 2018,181:364-373.
DOI:10.1002/jpln.201700376URL [本文引用: 1]
Abstract Balanced applications of nitrogen (N), phosphorus (P), and potassium (K) are known to increase grain yield of wheat but the impact of the interactions among N, P, and K on root growth and nitrogen use efficiency (NUE) have not been proven. The aim of this study was to investigate the effect of balanced applications of N, P, and K on the rooting patterns and NUE of wheat. Two glasshouse experiments were conducted. A rhizobox study was used to assess the impact of interactions among N, P, and K fertilisers on total root length, biomass, specific root length, root length density, N use efficiency (NUE), and N uptake efficiency of the shoots (NUpE shoot ) and N nutrition index. In a separate pot study, plants were grown to maturity to confirm the effect of the observed changes in root growth on NUE, NUpE grain , and grain/biomass yield. In the rhizobox experiment when plants were supplied with N+P+K, total root biomass increased approximately six-fold relative to plants grown with N alone or with no fertiliser. Plants exposed to N+P+K had NUpE shoot and NUE values that were five and ten times higher, respectively, than plants that received just fertiliser N. Plants supplied with N+P or N+P+K had N nutrition indices close to one (N-adequate), while plants that only received N had an index of 0.62 (N-deficient). The pot study confirmed that the changes in root length and biomass in plants exposed to N+P+K resulted in significant increases in NUE, NUpE grain , shoot biomass, and grain yield at maturity. Interactions among fertiliser N, P, and K played a critical role in influencing root biomass and length, which was associated with increases in NUE, NUpE shoot and NUpE grain .

[27] Siebrecht S, Tischner R . Changes in the xylem exudate composition of poplar (Populus tremula × P. alba): dependent on the nitrogen and potassium supply.
J Exp Bot, 1999,50:1797-1806.
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[28] Delaire M, Mauget J C, Beaujard F . Evidence for a strong correlation between season-dependent nitrate and potassium uptake in two deciduous trees
Trees, 2014,28:769-776.
DOI:10.1007/s00468-014-0990-5URL [本文引用: 1]
Key message Nitrate and potassium uptake are strongly correlated in deciduous trees from bud break to leaf fall. A conceptual model for potassium cycling is proposed to explain this result. Abstract We have studied the correlation between nitrate and potassium uptake in spring and autumn in two deciduous tree species: walnut and sycamore maple. Two-year-old trees were transplanted in early spring and cultivated on hydroponic recirculating nutrient solution systems in a greenhouse. Uptake of nitrate and potassium was surveyed daily during three consecutive weeks in mid-spring (i.e. during vegetative growth) and mid-autumn (i.e. during bud dormancy). Nitrate and potassium uptake was expressed per unit tree leaf area to account for tree size effect. Our results show that nitrate was much more absorbed than potassium in both species and its uptake remained nearly the same in spring and autumn. Contrary to this, potassium uptake was strongly reduced in autumn as a consequence of a strong reduction in vegetative growth. Although potassium uptake was strongly affected by seasonal variation in vegetative growth demand in both species, a positive and strong correlation between nitrate and potassium uptake was maintained in both species whatever the season. Essentially, any reduction in nitrate uptake as a consequence of decrease in nitrate availability in nutrient solution induced concomitantly a reduction in potassium uptake even if its concentration in the nutrient solution was sufficient to ensure potassium uptake. The results are discussed in the light of the accompanying role of potassium for nitrate uptake in plants. A conceptual scheme for internal/external potassium cycling in plant is proposed to explain the seasonal variations in nitrate and potassium uptake correlation in both deciduous tree species.

[29] Armengaud P, Sulpice R, Miller A J, Stitt M, Amtmann A, Gibon Y . Multilevel analysis of primary metabolism provides new insights into the role of potassium nutrition for glycolysis and nitrogen assimilation in Arabidopsis roots
Plant Physiol, 2009,150:772-785.
DOI:10.1104/pp.108.133629URL [本文引用: 1]
Potassium (K) is required in large quantities by growing crops, but faced with high fertilizer prices, farmers often neglect K application in favor of nitrogen and phosphorus. As a result, large areas of farmland are now depleted of K. K deficiency affects the metabolite content of crops with negative consequences for nutritional quality, mechanical stability, and pathogen/pest resistance. Known functions of K in solute transport, protein synthesis, and enzyme activation point to a close relationship between K and metabolism, but it is unclear which of these are the most critical ones and should be targeted in biotechnological efforts to improve K usage efficiency. To identify metabolic targets and signaling components of K stress, we adopted a multilevel approach combining transcript profiles with enzyme activities and metabolite profiles of Arabidopsis (Arabidopsis thaliana) plants subjected to low K and K resupply. Roots and shoots were analyzed separately. Our results show that regulation of enzymes at the level of transcripts and proteins is likely to play an important role in plant adaptation to K deficiency by (1) maintaining carbon flux into amino acids and proteins, (2) decreasing negative metabolic charge, and (3) increasing the nitrogen-carbon ratio in amino acids. However, changes in transcripts and enzyme activities do not explain the strong and reversible depletion of pyruvate and accumulation of sugars observed in the roots of low-K plants. We propose that the primary cause of metabolic disorders in low-K plants resides in the direct inhibition of pyruvate kinase activity by low cytoplasmic K in root cells.

[30] 张智, 丛日环, 鲁剑巍 . 中国冬油菜产业氮肥减施增效潜力分析
植物营养与肥料学报, 2017,23:1494-1504.
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Zhang Z, Cong R H, Lu J W . Potential analysis on winter oilseed rape production under reducing nitrogen input and increasing its efficiency in China
J Plant Nutr Fert, 2017,23:1494-1504 (in Chinese with English abstract).
[本文引用: 1]

[31] Ren T, Zou J, Lu J W, Chen F, Wu J S, Li X K . On-farm trials of optimal fertilizer recommendations for the maintenance of high seed yields in winter oilseed rape (Brassica napus L.) production (fertilizers and soil amendments).
Soil Sci Plant Nutr, 2015,61:528-540.
DOI:10.1080/00380768.2014.1003964URL [本文引用: 1]
Mineral fertilizer plays an important role in the maintenance of high rapeseed yields during oilseed rape (Brassica napus L.) production. On-farm experiments at 60 sites throughout the Yangtze River Basin in China were conducted for 202years to evaluate the effects of the recommended fertilization rates (18002kg02N02ha611, 9002kg P2O502ha611, and 12002kg K2O02ha611) on the rapeseed yield, and three indices of soil nutrient supply were adopted to estimate the yield responses to fertilizer recommendation. The results showed that the average contributions of nitrogen (N), phosphorus (P) and potassium (K) fertilizer to seed yield were 40.4, 23.1 and 11.5%, respectively. Compared with the farmers’ fertilization practices (FFP), the recommended fertilization significantly enhanced the seed yield by 29.1% on average. The relationships between plant-available soil nutrient supply, seed yields of the nutrient omission treatments and the yield responses to fertilization were significant, rather than the results of soil testing. With plant-available soil nutrient supplies and seed yields increasing, the yield responses and fertilizer use efficiencies decreased. When the seed yields of no-N and no-P treatments were less than 200002kg02ha611 and 150002kg02ha611, the recommended fertilizer rate was beneficial for achieving high seed yield and high efficiency. As defined in our study, the recommended fertilization rates could be used as the regional mean optimal rates (RMOR) of fertilization for winter oilseed rape in the Yangtze River Basin. Partial adjustments according to crop nutrient uptakes and seed yields of the nutrient omission treatments will be feasible for the sites where they were nonresponsive to RMOR.