李红颖(1991—),女,河北唐山人,博士研究生,主要从事农业资源利用与环境效应研究。E-mail:
过量施肥引起的氮磷流失是影响三峡库区水环境的重要因素。以三峡库区砂质土生草覆盖梯田橘园为研究对象,开展了不同施肥水平下的小区试验,连续2年对地表径流和渗漏液中的氮磷流失情况进行了观测。结果表明:(1)小区水分主要通过渗漏流失,地表径流系数低,土壤侵蚀弱。(2)深穴埋施施肥对地表径流氮磷流失无显著影响。(3)渗漏损失是小区氮磷流失的主要途径,分别占全氮和全磷总流失量的99.0%和76.9%。(4)氮磷流失量占施肥量的34.5%和6.4%,其中渗漏流失的氮磷分别占施肥量的34.3%和5.1%。(5)施肥引起的渗漏液氮流失量(
Citrus production is one of the main income of farmers in the Three Gorges Reservoir area. The loss of nitrogen and phosphorus caused by excessive fertilizer in the Three Gorges Reservoir area present negative impacts on the aquatic environment.
In this study, sandy soil citrus orchard with natural grass mulching was chosen. The amount of nitrogen and phosphorus loss from surface runoff and leaching was observed for two consecutive years by plot experiment at six levels of fertilization. The pathways of nitrogen and phosphorus losses in the citrus orchard and the effects of different fertilization levels on nitrogen and phosphorus losses were investigated. Seven treatments were set in the experimental plot, with an average row and plant spacing of 4.7 m × 3.4 m; with no fertilizer application (T1) as the control, the application rates of nitrogen, phosphorus and potassium fertilizer for the T3, T4, T5, T6 and T7 treatments were 1.67, 2.33, 3.00, 3.67 and 4.33 times those of T2, respectively. During the growth season of navel orange in 2016—2017, rainfall and atmospheric deposition of nitrogen and phosphorus were monitored. Surface runoff water, sediment, and infiltration water were sampled for total nitrogen (TN) and total phosphorus (TP) content.
Under the ecological protection mode of grass mulching, the surface runoff and soil erosion were effectively controlled. The main pathway of water loss in the rain-fed citrus orchard was leaching with a low coefficient of surface runoff and weak soil erosion. During the study period, the rainfall loss by seepage accounted for 48.9% of the rainfall, and the surface runoff only accounted for 1.73% of the rainfall. The amount of fertilization applied in deep furrow had no effect on the amount of nitrogen and phosphorus loss from the surface runoff. Leaching was the main pathway of nitrogen and phosphorus loss. The average leaching loss of total nitrogen and total phosphorus accounted for 99.0% and 76.9% of the total loss of nitrogen and total phosphorus respectively. Also, the amount of nitrogen loss (
The problem of nutrient loss; leaching nitrogen loss in citrus orchards, in particular, should be given more attention. To reduce nutrient loss and achieve efficient utilization, nutrient management should be further optimized.
以三峡库区为核心的长江中上游沿江区域是我国重要的柑橘产地之一[
我国已有农田养分流失研究多针对周年或季节性的农作物[
试验点位于三峡库首的湖北省秭归县茅坪镇九里村(110°57′51.9″ E,30°48′21.8″ N)。地处亚热带湿润季风气候,年平均气温16~19℃,降水量1 100 mm左右[
供试土壤基本理化性质
Basic physical and chemical properties of tested soil
土壤类型 |
pH | SOM |
TN |
AN |
AP |
AK |
机械组成Soil texture/% | ||
2~0.05 mm | 0.05~0.002 mm | < 0.002 mm | |||||||
注:SOM代表有机质;TN代表全氮;AN代表碱解氮;AP代表速效磷;AK代表速效钾。机械组成采用激光衍射法测定(Mastersizer 2000,Malvern Instruments,Malvern,UK)。Note:SOM stands for soil organic matter;TN stands for total nitrogen;AN stands for alkaline nitrogen;AP stands for available phosphorus;AK stands for available potassium. The mechanical composition was determined by laser diffraction(Mastersizer 2000,Malvern Instruments,Malvern,UK). ①Yellow soil. | |||||||||
黄壤① | 5.3 | 12.03 | 0.66 | 92.05 | 11.70 | 48.45 | 85.30 | 9.68 | 5.02 |
试验选择的柑橘品种为枸橘砧弗罗斯特,定植于2001年,树龄15年。柑橘树体处于树势扩展与结果同步期,植株间无枝叶交叉。在定植前为改善根际土壤性状,提高底层土壤养分水平,采用表土深翻,将养分含量较丰富的表层土壤深翻入底;并在离地面50 cm处施用一层鸡粪,平均每棵树施用20 kg。选择土壤条件、植株长势一致的个体作为试验用树,共选择3排梯田21棵。每个处理的田面坡度保持一致。试验小区设置7个处理,3个重复,平均行株距为4.7 m×3.4 m。其中T1处理为不施肥对照小区。T2、T3、T4、T5、T6和T7处理小区的氮磷钾施肥量如
不同处理小区的施肥量
Fertilization amount in different treatment plots/(kg·hm–2)
处理 |
施肥量 |
2016 | 2017 | ||||||
FC | ED | Tot | FC | ED | ED | Tot | |||
注:FC代表保果肥;ED代表膨大肥,Tot代表总量。Note:FC stands for fruit conserving fertilizer;ED stands for expanding fertilizer,Tot stands for total. | |||||||||
T2 | N | 75.0 | 37.5 | 112.5 | 75.0 | 37.5 | 37.5 | 150.0 | |
P2O5 | 37.5 | 18.75 | 56.25 | 37.5 | 18.75 | 18.75 | 75.0 | ||
K2O | 37.5 | 75.0 | 112.5 | 37.5 | 37.5 | 75.0 | 150.0 | ||
T3 | N | 125.0 | 62.5 | 187.5 | 125.0 | 62.5 | 62.5 | 250.0 | |
P2O5 | 62.5 | 31.25 | 93.75 | 62.5 | 31.25 | 31.25 | 125.0 | ||
K2O | 62.5 | 125.0 | 187.5 | 62.5 | 62.5 | 125.0 | 250.0 | ||
T4 | N | 175.0 | 87.5 | 262.5 | 175.0 | 87.5 | 87.5 | 350.0 | |
P2O5 | 87.5 | 43.75 | 131.3 | 87.5 | 43.75 | 43.75 | 175.0 | ||
K2O | 87.5 | 175.0 | 262.5 | 87.5 | 87.5 | 175.0 | 350.0 | ||
T5 | N | 225.0 | 112.5 | 337.5 | 225.0 | 112.5 | 112.5 | 450.0 | |
P2O5 | 112.5 | 56.25 | 168.8 | 112.5 | 56.25 | 56.25 | 225.0 | ||
K2O | 112.5 | 225.0 | 337.5 | 112.5 | 112.5 | 225.0 | 450.0 | ||
T6 | N | 275.0 | 137.5 | 412.5 | 275.0 | 137.5 | 137.5 | 550.0 | |
P2O5 | 137.5 | 68.75 | 206.3 | 137.5 | 68.75 | 68.75 | 275.0 | ||
K2O | 137.5 | 275.0 | 412.5 | 137.5 | 137.5 | 275.0 | 550.0 | ||
T7 | N | 325.0 | 162.5 | 487.5 | 325.0 | 162.5 | 162.5 | 650.0 | |
P2O5 | 162.5 | 81.25 | 243.8 | 162.5 | 81.25 | 81.25 | 325.0 | ||
K2O | 162.5 | 325.0 | 487.5 | 162.5 | 162.5 | 325.0 | 650.0 |
本试验于2015年5月开始野外布设。在垂直植株滴水线的地下60 cm深度位置埋设渗漏液收集装置(
渗漏装置示意图
Diagram of lysimeter and sampling system
采用SPECTRUM公司的WatchDog观测站,实时观测干湿球温度、辐射、气压、风向、风速和降雨量等气象数据和不同深度土壤含水量。WatchDog的水分传感器分别安装于橘园内地下5 cm、20 cm、30 cm、40 cm、60 cm和70 cm深度,其中60 cm以上为土层,60 cm以下为岩石或碎屑物。采用联合国粮食及农业组织(FAO)推荐的彭曼(Penman-Monteith)模型,利用气象参数计算参考作物蒸散量ET0,然后利用作物系数
阶段降雨渗漏量(
式中,
降雨产流后,首先用标尺测量每个小区径流桶的水深,在每个径流桶不同位置测量三次取平均值,为最终的水深,根据径流桶直径计算地表径流量。然后将桶中水沙充分搅匀,采集1 L水沙混合样。待泥沙全部沉入桶底,将水排出,采集径流泥沙样,带至室内风干待测。
采集到的径流水沙混合样静置30 min后采集250 mL上清液用以测定TN和TP浓度,剩下的样品用滤纸过滤后,105℃烘干后称重测定泥沙含量[
经Excel 2010整理实验数据后,采用SPSS 21.0统计学分析软件对数据进行单因素方差分析,最小显著差异方法(LSD)对数据进行多重检验和皮尔森相关性分析(Pearson correlation),采用Origin2020作图。
降水产流是氮磷流失的驱动因子和载体,岩土结构的砂壤土不仅地表径流造成氮磷流失,入渗形成的渗漏在岩土交界面形成的侧向流也会带走氮磷等营养盐。观测表明,2016年降水(
研究期脐橙园水分收支情况
Water budget of the citrus orchard in the research period
日期 |
降水量 |
地表径流 |
蒸散发 |
渗漏 |
2016-01-01—2016-05-05 | 283.3 | 0 | 169.5 | 73.8 |
2016-05-06 —2016-06-05 | 187.9 | 0 | 69.8 | 104.3 |
2016-06-06—2016-08-14 | 679.0 | 14.1 | 212.2 | 453.5 |
2016-08-15—2016-10-19 | 19.3 | 0 | 103.9 | 0 |
2016-10-20—2016-11-18 | 140.3 | 5.1 | 28.3 | 77.5 |
2016-11-19—2016-12-31 | 29.3 | 0 | 20.3 | 0 |
总量Total | 1 339 | 19.2 | 604.0 | 709.1 |
2017-01-01—2017-02-19 | 19.8 | 0 | 25.6 | 0 |
2017-02-20—2017-03-27 | 98.5 | 0 | 43.4 | 30.0 |
2017-03-28—2017-06-13 | 284.6 | 0 | 181.5 | 52.3 |
2017-06-14—2017-08-03 | 2.6 | 0 | 83.4 | 0 |
2017-08-04—2017-08-18 | 76.0 | 8.9 | 52.0 | 3.5 |
2017-08-19—2017-10-20 | 408.5 | 9.2 | 106.9 | 255.7 |
2017-10-21—2017-12-31 | 11.6 | 0 | 39.8 | 0 |
总量Total | 881.8 | 18.1 | 507.0 | 395.1 |
2016—2017年研究期橘园大气沉降氮和磷总输入分别为38.2 kg·hm–2和0.4 kg·hm–2。对于水体而言,大气干湿沉降是面源污染的一个组成部分;而在橘园,干湿沉降形成氮磷输入是橘园系统氮磷营养盐输入的一部分。本项试验各处理小区(T1对照除外)施肥氮输入和磷输入分别介于262.5~1 138 kg·hm–2和57.3~248.2 kg·hm–2。平均施氮肥输入分别占总氮收入的87.3%~96.8%;平均施磷肥输入分别占总磷输入的99.3%~99.8%。因此,橘园绝大部分的氮磷收入来源于施肥,干湿沉降所占比例很低。
2016—2017年观测期地表平均径流水总量和泥沙总量分别为165.9 m3·hm–2和47.1 kg·hm–2。径流量越大,产沙量越多。其中,T4和T6径流量和泥沙量较多(
2016—2017年研究期地表径流水量和泥沙量
Surface runoff and sediment volume during the study period in 2016-2017
处理 |
2016 | 2017 | |||
地表径流 |
泥沙量 |
地表径流 |
泥沙量 |
||
注:T1为不施肥对照处理小区。表中数据为平均值±误差。Note:T1 was the control plot without fertilization. Data are means±SD. | |||||
T1 | 106±92 | 22.5±10.3 | 144±52 | 22.1±4.0 | |
T2 | 161±120 | 27.6±13.2 | 106±41 | 28.9±11.9 | |
T3 | 224±6 | 64.1±34.7 | 148±93 | 27.1±16.0 | |
T4 | 268±145 | 154.0±69.7 | 228±104 | 40.1±14.7 | |
T5 | 57±49 | 21.9±16.8 | 46±25 | 25.2±12.2 | |
T6 | 265±127 | 121.8±46.3 | 321±163 | 53.2±18.8 | |
T7 | 109±75 | 29.5±13.4 | 140±78 | 21.1±14.4 |
分析表明,地表径流全氮平均流失量为3.8 kg·hm–2(
2016—2017年研究期地表径流全氮(a)和全磷(b)流失量
Total nitrogen loss(a)and total phosphorus loss(b)in surface runoff during the study period in 2016-2017
2016—2017年研究期渗漏全氮的平均流失量为376.9 kg·hm–2,其中未施肥的T1小区全氮流失量最小,为172.9 kg·hm–2;施肥量最大的T7小区全氮流失量最大,为603.9 kg·hm–2(
2016—2017年研究期渗漏全氮流失量
Total nitrogen loss in interflow during the study period in 2016-2017/(kg·hm–2)
日期Date(yyyy-mm-dd) | T1 | T2 | T3 | T4 | T5 | T6 | T7 | 显著性Sig |
注:同行数据后不同字母代表处理间差异达显著水平( |
||||||||
2016-01-01—2016-05-05 | 4.5 ±1.3a | 8.3 ±0.3b | 9.0 ±0.4bc | 10.6 ±1.5c | 12.9 ±0.8d | 14.9±1.4de | 16.0±1.3e | 0.000 |
2016-05-06—2016-06-05 | 18.5±4.3a | 23.0±0.9b | 22.9±0.1b | 22.8±0.4b | 22.8±0.4b | 23.3±0.2b | 23.0±1.1b | 0.053 |
2016-06-06—2016-08-14 | 91.7±5.3a | 95.8±0.7ab | 96.9±0.2b | 97.6±0.1b | 98.7±0.1b | 99.1±0.3b | 106.2±6.7c | 0.004 |
2016-10-20—2016-11-18 | 27.1±12.9 | 35.1±0.5 | 35.8±2.0 | 32.7±3.6 | 35.0±0.2 | 35.6±0.5 | 33.7±2.4 | ns |
2017-02-20—2017-03-27 | 1.3±0.3a | 2.1±0.3a | 4.2±2.3ab | 8.3±7.0ab | 6.4±2.7ab | 10.0±1.1 b | 13.7±9.3b | 0.042 |
2017-03-28—2017-06-13 | 7.5±3.0a | 21.0±8.5ab | 34.1±9.0b | 40.2±3.3b | 51.6±4.2bc | 61.6±17.0cd | 71.9±10.8d | 0.000 |
2017-08-04—2017-08-18 | 0.4±0.0a | 1.1±0.4ab | 1.8±0.3bc | 2.2±0.0c | 2.6±0.1c | 3.9±1.1d | 5.6±0.2e | 0.000 |
2017-08-19—2017-10-20 | 21.9±1.3a | 83.4±16.8b | 134.3±11.5c | 144.5±38.8c | 191.0±13.0d | 224.0±14.9d | 333.8±7.2e | 0.000 |
合计Total | 172.9±28.1a | 269.8±26.2b | 339.0±10.5c | 358.9±47.0d | 421.0±16.4e | 472.2±25.6f | 603.9±38.5g | 0.000 |
2016-2017年研究期渗漏全磷流失量
Total phosphorus loss in interflow during the study period in 2016-2017/(kg·hm–2)
日期Date(yyyy-mm-dd) | T1 | T2 | T3 | T4 | T5 | T6 | T7 | 显著性Sig |
2016-01-01—2016-05-05 | 0.04±0.02 | 0.08±0.04 | 0.02±0.01 | 0.04±0.03 | 0.04±0.01 | 0.11±0.03 | 0.10±0.06 | ns |
2016-05-06—2016-06-05 | 0.03±0.01 | 0.03±0.02 | 0.07±13.0 | 0.08±0.03 | 0.13±0.10 | 0.05±0.01 | 0.16±0.06 | ns |
2016-06-06—2016-08-14 | 0.09±0.03 | 0.16±0.03 | 0.19±0.16 | 0.41±0.15 | 0.47±0.27 | 0.51±0.30 | 0.95±0.76 | ns |
2016-10-20—2016-11-18 | 0.05±0.03 | 0.17±0.19 | 0.34±0.23 | 0.43±0.12 | 0.09±0.04 | 0.15±0.06 | 0.13±0.07 | ns |
2017-02-20—2017-03-27 | 0.02±0.01 | 0.06±0.03 | 0.06±0.02 | 0.15±0.10 | 0.11±0.01 | 0.06±0.02 | 0.06±0.02 | ns |
2017-03-28—2017-06-13 | 0.06±0.03 | 0.05±0.02 | 0.07±0.04 | 0.10±0.08 | 0.06±0.04 | 0.09±0.07 | 0.07±0.03 | ns |
2017-08-04—2017-08-18 | 0.01±0.01 | 0.01±0.00 | 0.02±0.01 | 0.01±0.00 | 0.02±0.01 | 0.02±0.00 | 0.02±0.00 | ns |
2017-08-19—2017-10-20 | 0.62±0.4 | 1.20±0.43 | 0.69±0.36 | 1.56±0.96 | 2.53±1.02 | 1.77±1.62 | 1.81±0.34 | ns |
合计Total | 0.92±0.39 | 1.76±0.79 | 1.46±0.64 | 2.78±1.00 | 3.45±1.22 | 2.76±1.17 | 3.30±1.31 | ns |
2016—2017年研究期橘园施肥与沉降氮磷输入比例和氮磷流失占输入的比例
The proportion of nitrogen and phosphorus income and the proportion of nitrogen and phosphorus loss in the income of citrus orchard were studied in 2016-2017
试验表明,对照在连续2年不施肥条件下,渗漏氮磷流失量分别为172.9±28.1 kg·hm–2、0.92±0.39 kg·hm–2,可见,试验前土壤中具有一定量速效态氮磷的残存。将各个施肥处理渗漏氮磷的流失量分别扣除T1对照小区渗漏氮磷的流失量,以反映不同施肥量处理对氮磷流失的影响,表示为施肥引起的氮磷流失增量。结果发现,各处理渗漏氮流失增量与施肥量有显著的线性相关关系(
2016—2017年研究期橘园氮磷施用量与渗漏氮磷流失量的关系
The relationship between the NP fertilization and the NP losses in citrus orchards in 2016-2017
由上可见,自然降雨条件下,岩土构型砂质土梯田成年橘园采用留草覆盖的管理模式,降雨除消耗于蒸散发外,主要通过渗漏流失;采用环沟施肥,渗漏形成的氮磷养分流失是氮磷流失的主要途径,且施肥量越高氮素淋失量呈线性增高;不同施肥量对地表径流氮磷流失无显著影响。由于柑橘养分需求大,而退化山地土壤养分贫瘠,施肥仍为必要措施,且容易造成过量施肥,土壤肥料残存量高。试验表明,在不施肥情况下,氮素渗漏损失平均达86 kg·hm–2。此外,现有常规管理年度一般分2~3次施肥,但在自然降雨条件下,土壤水肥难以协调供应,肥料养分利用率低,且不利于增产增收。因此,柑橘园实施配方施肥,改善肥料运筹的同时,需要进一步优化水肥调控,促进养分高效利用。
通过对橘园小区两年的野外试验发现,自然雨养的砂土梯田橘园在生草覆盖生态保护模式下,地表径流和土壤侵蚀已得到有效控制,养分的主要流失途径为渗漏。研究期降水随渗漏流失量平均占降水量的48.9%,地表径流仅占降水量的1.73%。橘园氮磷流失量占施肥量的比例分别为34.5%和6.4%,其中通过渗漏流失,平均分别占施肥量的34.3%和5.1%,氮磷通过地表径流流失量较小。渗漏氮流失量随着施肥量的增多而增大,二者呈显著的线性正相关。因此,砂质土梯田橘园渗漏养分流失,尤其是氮渗漏问题应当引起重视。经过水土流失生态治理后,砂质土壤橘园施肥管理必须注意水肥协调,在实施配方施肥的基础上,改善肥料运筹,根据橘周年营养生理需求,实行水肥同步供应,避免过量养分残存与强降雨相遇造成养分的渗漏损失,从而实现养分高效利用和增产增效,且进一步降低环境负荷。
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