Effects of nitrogen application on nitrogen and phosphorus leaching in fluvo-aquic soil on a winter wheat-summer maize rotation farmland
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摘要: 潮土是我国华北地区主要土壤类型之一, 潮土区是我国冬小麦-夏玉米作物的主要产区, 研究不同施氮量潮土氮磷淋溶特征对于指导区域农田面源污染防控具有重要意义。本研究设置3个施肥处理, 即传统施氮(CON)、优化施氮(OPT)和优化再减氮(OPTJ), 利用田间渗漏池法, 研究潮土冬小麦-夏玉米轮作农田硝态氮及总磷淋溶特征。结果表明: 2016—2018年, 冬小麦-夏玉米轮作周年不同施肥处理90 cm土层年淋溶水量79.0~102.5 mm, 不同淋溶事件间土壤淋溶液硝态氮浓度波动较大, CON、OPT和OPTJ处理单次淋溶事件硝态氮浓度分别为18.9~208.7(平均为72.7) mg·L-1、9.0~99.2(平均为33.8) mg·L-1、4.7~55.5(平均为15.4) mg·L-1。本研究区域冬小麦-夏玉米轮作模式的氮素淋溶风险较高, 磷素淋溶风险较低。传统施氮处理(CON)下农田硝态氮的平均淋溶量和表观淋失系数分别为66.4 kg·hm-2和10.3%, 而总磷(TP)为0.06 kg·hm-2和0.04%。氮肥减施会显著降低氮素淋失, OPT和OPTJ处理的氮素淋溶减排率可达56.3%和78.9%。两个年度CON、OPT和OPTJ处理硝态氮平均表观淋失溶系数分别为10.3%、6.2%和4.9%, 随着施氮量的增加, 硝态氮淋失溶系数动态增加。氮淋溶具有较大的年际变化, 降雨量高的2018年比降雨少的2017年硝态氮淋溶量多57.0%。两个年度CON、OPT和OPTJ处理总磷平均淋溶量分别为0.06 kg·hm-2、0.06 kg·hm-2和0.08 kg·hm-2。适量减施氮肥会增加作物产量, OPT处理的作物产量是CON处理的1.08倍。然而, 过量减施则会带来减产风险, OPTJ处理氮肥减施56%, 作物产量比CON处理降低2.0%~8.1%。总之, 潮土区农田硝态氮淋溶风险较大, 适量减施氮肥能够在保证作物产量的基础上显著降低氮素淋失损失。Abstract: Fluvo-aquic soil is predominant in the North China Plain, where a large amount of wheat and corn are grown in China. Understanding the relationship between nitrogen and phosphorus leaching and nitrogen application is important for preventing and controlling nonpoint source pollution in this area. The field seepage pool method was used to explore nitrate nitrogen and total phosphorus leaching in fluvo-aquic soil on a winter wheat and summer maize rotation farmland. Three fertilization treatments were tested: traditional nitrogen application (CON), optimized nitrogen application (OPT), and optimized nitrogen plus nitrogen reduction (OPTJ). The results showed that from 2016 to 2018, the annual leachate volume from the 90 cm soil layer was between 79.0 and 102.5 mm (all treatments). The leached nitrate nitrogen concentrations were 18.9-208.7 (average 72.7) mg·L-1 (CON), 9.0-99.2 (average 33.8) mg·L-1 (OPT), and 4.7-55.5 (average 15.4) mg·L-1 (OPTJ), fluctuating among leaching events. The nitrogen leaching risk was higher, and the phosphorus leaching risk was lower in the fluvo-aquic soil area. The average leaching amount was 66.4 kg·hm-2 and apparent leaching loss coefficient was 10.3% for nitrate nitrogen; these values for total phosphorus were 0.06 kg·hm-2 and 0.04%, respectively. Reducing nitrogen fertilizer decreased nitrogen leaching by 56.3% (OPT) and 78.9% (OPTJ), and the apparent leaching coefficients were 10.3% (CON), 6.2% (OPT), and 4.9% (OPTJ), indicating that nitrate nitrogen leaching increased as nitrogen fertilizer increased. Nitrogen leaching had interannual variation; 2018 had high rainfall, and the leaching amount was 57.0% higher than in 2017, which had low rainfall. During the sampling years, the total phosphorus leached was 0.06 kg·hm-2 (CON), 0.06 kg·hm-2 (OPT), and 0.08 kg·hm-2 (OPTJ). A moderate nitrogen fertilizer reduction increased crop yield; the OPT yield was 1.08 times higher than the CON yield. However, excessive fertilizer reduction decreased yield. OPTJ had 56% less nitrogen than CON, and the yield decreased by 2.0%-8.1%. The partial factor productivities were 25.3 kg·hm-2 (CON), 35.7 kg·hm-2 (OPT), and 57.4 kg·hm-2 (OPTJ) for winter wheat and 28.5 kg·hm-2 (CON), 44.8 kg·hm-2 (OPT), and 62.7 kg·hm-2 (OPTJ) for summer maize. The nitrogen fertilizer partial factor productivities of OPT and OPTJ were significantly higher than that of CON. These results showed that the nitrate nitrogen leaching potential was high in fluvo-aquic soil, and reducing nitrogen fertilizer could significantly reduce nitrogen loss without decreasing crop yield. Considering crop yield and nitrate nitrogen leaching risk together, the optimal nitrogen amount for winter wheat and summer maize farmland in the study area was 465 kg·hm-2. When nitrogen decreased to 285 kg·hm-2, nitrogen leaching sharply decreased, but the crop yield decreased slightly.
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图 1 两个监测年度试验点月降雨量及灌溉量
Figure 1. Monthly rainfall and irrigation in the experiment site during two sampling years
图 2 2017年和2018年不同施肥处理冬小麦-夏玉米轮作周期年淋溶水量
CON:传统施氮; OPT:优化施氮; OPTJ:优化再减氮。不同小写字母表示同一年份不同处理间在0.05水平差异显著。
Figure 2. Annual leachate amounts under different fertilization treatments for winter wheat-summer maize rotation in 2017 and 2018
CON: traditional nitrogen application; OPT: optimized nitrogen application; OPTJ: optimized nitrogen plus nitrogen reduction. Different lowercase letters indicate significant differences among different treatments in the same year at P < 0.05 level.
图 3 2017年和2018年不同处理冬小麦-夏玉米轮作农田土壤淋溶液硝态氮浓度
CON:传统施氮; OPT:优化施氮; OPTJ:优化再减氮。不同小写字母表示同一淋溶次数不同处理间在0.05水平差异显著。
Figure 3. Leachate nitrate nitrogen concentrations under different fertilization treatments for winter wheat-summer maize rotation system in 2017 and 2018
CON: traditional nitrogen application; OPT: optimized nitrogen application; OPTJ: optimized nitrogen plus further nitrogen reduction. Different lowercase letters indicate significant differences among different treatments at the same leaching time at P < 0.05 level.
表 1 不同施肥处理冬小麦和夏玉米季氮磷和钾肥总施用量
Table 1. Total application rates of nitrogen, phosphorus and potassium fertilizers of different fertilization treatments for winter wheat and summer maize seasons
kg·hm-2 处理Treatment 冬小麦Winter wheat 夏玉米Summer maize N P2O5 K2O N P2O5 K2O CON 315.0 90.0 90.0 330.0 67.5 67.5 OPT 225.0 90.0 90.0 240.0 67.5 67.5 OPTJ 135.0 90.0 90.0 150.0 67.5 67.5 CON:传统施氮; OPT:优化施氮; OPTJ:优化再减氮。CON: traditional nitrogen application; OPT: optimized nitrogen application; OPTJ: optimized nitrogen plus nitrogen reduction. 
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表 2 2017年和2018年不同处理冬小麦-夏玉米产量及氮肥偏生产力
Table 2. Yields and average nitrogen partial factor productivities under different fertilization treatments for winter wheat and summer maize in 2017 and 2018
处理Treatment 产量Yield (kg·hm-2) 氮肥偏生产力PFP (kg·kg-1) 小麦(2017) Wheat 玉米(2017) Maize 小麦(2018) Wheat 玉米(2018) Maize 小麦(2017) Wheat 玉米(2017) Maize 小麦(2018) Wheat 玉米(2018) Maize CON 7274.0±399.8a 9008.5±1443.6a 8694.0±243.1a 9791.1±442.0a 23.1±1.3c 27.3.±4.4c 27.6±0.8c 29.7±1.3c OPT 7170.5±292.0a 10 657.5±1254.5a 8885.9±1613.2a 10 831.1±616.2a 31.9±1.3b 44.4±5.2b 39.5±7.2b 45.1±2.6b OPTJ 7400.3±325.6a 9215.0±743.0a 7990.0±415.3a 9596.7±574.6a 54.8±2.4a 61.4±5.0a 59.2±3.1a 64.0±3.8a CON:传统施氮; OPT:优化施氮; OPTJ:优化再减氮。数值表示平均值±标准差。不同小写字母表示不同处理间差异达显著水平(P < 0.05)。CON: traditional nitrogen application; OPT: optimized nitrogen application; OPTJ: optimized nitrogen plus nitrogen reduction. PFP: partial factor productivity from applied N. The data is average value ± standard deviation. Different lowercase letters mean significant differences among different treatments at P < 0.05 level.
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表 3 2017年和2018年不同施肥处理冬小麦-夏玉米轮作农田硝态氮淋溶量及表观淋失溶系数
Table 3. Nitrate nitrogen leaching amounts and apparent nitrate nitrogen leaching loss coefficients under different fertilization treatments for winter wheat-summer maize rotation system in 2017 and 2018
年度Year 淋溶量Leaching amount (kg·hm-2) 硝态氮表观淋失溶系数Apparent nitrate nitrogen leaching loss coefficient(%) CON OPT OPTJ CON OPT OPTJ 2017 53.8±1.8a 21.3±6.6b 10.0±2.0c 8.3±0.3a 4.6±1.4b 3.5±0.7b 2018 78.9±8.6a 36.7±12.5b 18.0±6.4b 12.2±1.3a 7.9±2.7b 6.3±2.2b 平均Average 66.4 29.0 14.0 10.3 6.2 4.9 CON:传统施氮; OPT:优化施氮; OPTJ:优化再减氮。同行不同小写字母表示不同处理之间差异显著(P < 0.05)。CON: traditional nitrogen application; OPT: optimized nitrogen application; OPTJ: optimized nitrogen plus nitrogen reduction. Different lowercase letters in the same row indicate significant differences at P < 0.05 level among different treatments.
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表 4 试验期不同施肥处理冬小麦-夏玉米轮作农田根层土壤硝态氮残留特征
Table 4. Residue nitrate nitrogen in root zone soil under different fertilization treatments for winter wheat-summer maize rotation system during sampling period
kg·hm-2 土层Soil layer (cm) 2018小麦基肥前Before base fertilizer of wheat in 2018 2018小麦追肥前Before topdressing of wheat in 2018 CON OPT OPTJ CON OPT OPTJ 0~30 117.5±31.1a 111.6±35.1ab 57.2±9.5b 111.8±43.9a 49.1±23.0ab 27.5±8.3b 30~60 150.6±30.8a 95.0±16.5b 33.5±28.9c 76.8±29.5a 50.0±28.6ab 34.9±9.2b 60~90 132.2±25.7a 57.4±5.5b 24.3±12.4c 83.2±21.4a 63.6±17.5ab 39.8±14.9b 合计Total 400.3 264.0 115.0 271.9 162.7 102.3 CON:传统施氮; OPT:优化施氮; OPTJ:优化再减氮。同行不同小写字母表示不同处理之间差异显著(P < 0.05)。CON: traditional nitrogen application; OPT: optimized nitrogen application; OPTJ: optimized nitrogen plus nitrogen reduction. Different lowercase letters in the same row indicate significant differences at P < 0.05 level among different treatments.
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表 5 2017年和2018年不同施肥处理冬小麦-夏玉米轮作农田土壤淋溶液总磷浓度及淋溶量
Table 5. Leachate concentrations and leaching amount of total phosphorus under different fertilization treatments for winter wheat-summer maize rotation system in 2017 and 2018
处理Treatment 总磷浓度Total P concentration (mg·L-1) 总磷淋溶量Total P leaching amount (kg·hm-2) 2017 2018 2017 2018 CON 0.10±0.06a 0.04±0.02a 0.09±0.01a 0.03±0.00a OPT 0.08±0.03a 0.06±0.02a 0.07±0.03a 0.04±0.01a OPTJ 0.10±0.07a 0.06±0.03a 0.12±0.02a 0.04±0.01a CON:传统施氮; OPT:优化施氮; OPTJ:优化再减氮。同列不同小写字母表示不同处理间差异显著(P < 0.05)。CON: traditional nitrogen application; OPT: optimized nitrogen application; OPTJ: optimized nitrogen plus nitrogen reduction. Different lowercase letters indicate significant differences at P < 0.05 level among different treatments.
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