Impact of substitution of synthetic nitrogen fertilizer with organic fertilizers on nitrogen loss from sloping cropland of purple soil
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摘要: 为明确紫色土有机肥替代化肥的农学与环境效应, 减少紫色土氮素面源污染, 进一步为紫色土化肥“零增长”策略提供科学依据, 利用紫色土坡地养分管理长期试验平台, 结合自由排水采集器(Free-drain Lysimeter)定位观测, 研究紫色土坡耕地小麦-玉米轮作期间(2012—2013年)不同施肥方式下的土壤无机氮动态、作物产量、氮素流失路径与总量。等氮下设置5个施肥处理: 单施化学氮肥(N)、常规化肥(NPK)、猪厩肥(猪厩肥替代100%的化肥氮, OM)、猪厩肥与氮磷钾配施(猪厩肥替代30%的化肥氮, OMNPK)、秸秆还田与氮磷钾配施(秸秆替代15%的化肥氮, CRNPK), 以不施肥(NF)为对照。结果表明, 紫色土坡耕地壤中流流量占总径流量的54.5%~84.6%, 随壤中流淋失的氮占氮流失总量的90.6%, 以壤中流为介导的氮淋失是紫色土坡耕地氮素流失的首要途径, 且氮淋失量高达12.53~76.72 kg(N)·hm−2, 远高于我国其他地区农田氮淋失量, 紫色土地区是氮淋失的热点区域。与常规施肥(NPK)相比, 有机肥替代化肥显著降低紫色土氮素流失量, 其中猪厩肥(OM)、猪厩肥与氮磷钾配施(OMNPK)、秸秆还田与氮磷钾配施(CRNPK)总氮素流失量分别减少32.1% (P<0.05)、27.5% (P<0.05)与21.2% (P<0.05), 其关键机制在于有机肥替代化肥对氮淋失的减控作用, 通过壤中流淋失的氮素分别减少32.0% (P<0.05)、26.7% (P<0.05)与18.0% (P<0.05); 此外, 氮流失系数分别降低44.8%、38.5%及24.3%, 玉米-小麦轮作系统年产量分别增加23.0%、17.8%及4.1%。因此, 长期有机肥替代化肥能在减量施用化肥的基础上保证作物产量, 同时显著降低紫色土坡耕地氮流失风险, 是当前紫色土坡耕地可推荐的减氮增效技术。Abstract: Excessive N fertilizer application not only increases crop productivity, but also induces substantial environmental N losses that cause large environmental pollution risks. This study aimed to examine the effects of substituting synthetic N fertilizers with organic fertilizers on the reduction in environmental N losses from croplands in purple soil areas. Therefore, we conducted a one year field investigation to measure N-loss pathways and fluxes, crop productivity, and soil environmental variables in a wheat-maize rotation system under long-term different fertilization regimes with the same N rate, including the control (no fertilizer; NF); synthetic N fertilizer only (N); pig manure substituting 100% synthetic N fertilizer (pig manure; OM); regular synthetic N, P, and K fertilizer (NPK); combination of pig manure with synthetic N, P, and K fertilizer (OMNPK; pig manure substituting 30% synthetic N fertilizer); and combination of straw residue returned with synthetic N, P, and K fertilizer (CRNPK; straw residue substituting 15% synthetic N fertilizer). The results showed that N losses via surface runoff and sediment were in the range of 1.12–3.52 kg(N)∙hm−2 and 1.48–7.26 kg(N)∙hm−2, respectively. The N leaching losses via interflow ranged from 12.53 to 76.72 kg(N)∙hm−2, which were over 10 times greater than those for surface runoff; nevertheless, N leaching losses accounted for 90.6% of the total hydrological N losses. These results indicate that N leaching via interflow is the predominant pathway of hydrological N losses, thereby highlighting that sloping cropland of purple soil is one of the hotspots of N leaching losses from agricultural soils in China. Compared with that of the NPK treatment, the substitution of synthetic N fertilizer with organic fertilizers (OM, OMNPK, and CRNPK treatments) decreased the total hydrological N losses by 32.1%, 27.5%, and 21.2%, respectively. This was mainly because practices with substitution of synthetic N fertilizer with organic fertilizers significantly decreased N leaching losses via interflow compared with the application of synthetic N fertilizer only. Furthermore, considering the crop yields, the substitution of synthetic N fertilizer with organic fertilizer treatments (OM, OMNPK, and CRNPK treatments) significantly increased the total annual crop yields by 23.0%, 17.8%, and 4.1%, respectively, and decreased the yield-scaled total hydrological N losses by 24.3% to 44.8%. Therefore, the long-term substitution of synthetic N fertilizer with organic fertilizer can not only increase the crop productivity of both wheat and maize, but also decrease environmental N losses, thereby decreasing the risk of agricultural non-point source pollution in the purple soil region. Overall, the substitution of synthetic N fertilizer with organic fertilizers can be recommended as an optimized agricultural N management strategy to reduce synthetic N fertilizer rates and improve N use efficiency in agricultural systems of the purple soil region.
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Key words:
- Purple soil /
- Sloping cropland /
- Interflow /
- Nitrogen loss /
- Nitrogen leaching /
- Organic fertilizer /
- Improved fertilization
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图 2 试验期间常规试验小区的降雨、径流量、气温及表土温度(0~10 cm)
小麦季11月5日施肥，玉米季6月1日施肥。Fertilizer is applied on November 5 in wheat season and on June 1 in maize season, respectively.
Figure 2. Rainfall, runoff, air temperature and topsoil temperature (0−10 cm) in the regular plot during the experimental period
图 3 不同施肥方式下的紫色土表土(0~10 cm)无机氮含量变化
图中各施肥处理分别为单施氮肥(N)、常规施肥(NPK)、猪厩肥(OM)、猪厩肥与氮磷钾配施(OMNPK)、秸秆还田与氮磷钾配施(CRNPK)及不施肥(NF)。图中两个箭头分别指示小麦季(11月5日)和玉米季(6月1日)施肥。
Figure 3. Changes of topsoil (0−10 cm) inorganic nitrogen contents under different fertilization regimes on sloping cropland of purple soil
Fertilization treatments in the figure are: nitrogen fertilizer only (N), regular synthetic nitrogen, phosphorus and potassium fertilizer (NPK), pig manure (OM), combination of pig manure with synthetic nitrogen, phosphorus and potassium fertilizer (OMNPK), combined application of straw residue with synthetic nitrogen, phosphorus and potassium fertilizer (CRNPK). Two arrows in the figures indicate fertilization on November 5 in wheat season and on June 1 in maize season, respectively.
图 4 不同施肥方式下紫色土坡耕地的地表径流、壤中流流量和泥沙量
图中各施肥处理分别为单施氮肥(N)、常规施肥(NPK)、猪厩肥(OM)、猪厩肥与氮磷钾配施(OMNPK)、秸秆还田与氮磷钾配施(CRNPK)及不施肥(NF)。不同小写字母代表施肥处理间差异显著(P<0.05)。
Figure 4. Discharge of overland runoff, interflow and sediment yield under different fertilization regimes on sloping cropland of purple soil
Fertilization treatments in the figure are: nitrogen fertilizer only (N), regular synthetic nitrogen, phosphorus and potassium fertilizer (NPK), pig manure (OM), combination of pig manure with synthetic nitrogen, phosphorus and potassium fertilizer (OMNPK), combination of straw residue with synthetic nitrogen, phosphorus and potassium fertilizer (CRNPK). Different lowercases letters in the figure indicate significant differences among ferilization regimes at P<0.05 level .
图 5 不同施肥方式下紫色土坡耕地氮素流失路径与总量
图中各施肥处理分别为单施氮肥(N)、常规施肥(NPK)、猪厩肥(OM)、猪厩肥与氮磷钾配施(OMNPK)、秸秆还田与氮磷钾配施(CRNPK)及不施肥(NF)。不同小写字母代表施肥处理之间差异显著(P<0.05)。
Figure 5. Nitrogen loss pathways and fluxes from sloping cropland of purple soil under different fertilization regimes
Fertilization treatments in the figure are: nitrogen fertilizer only (N), regular synthetic nitrogen, phosphorus and potassium fertilizer (NPK), pig manure (OM), combination of pig manure with synthetic nitrogen, phosphorus and potassium fertilizer (OMNPK), combination of straw residue with synthetic nitrogen, phosphorus and potassium fertilizer (CRNPK). Different lowercases letters in the figure indicate significant differences among treatments at P<0.05 level.
表 1 不同施肥方式下小麦-玉米轮作系统的作物生物量、产量、总氮流失量及氮流失系数(2012—2013年)
Table 1. Biomass, crop yield, nitrogen loss and nitrogen loss coefficient of wheat-maize rotation system under different fertilization regimes (2012−2013)
施肥方式
Fertilization regime生物量
Biomass (t∙hm−2)产量
Crop yield (t∙hm−2)总氮流失量Total nitrogen loss
[kg(N)∙hm−2]基于单位产量的氮流失系数Nitrogen loss per unit yield (kg∙hm−2∙t−1) 小麦
Wheat玉米
Maize小麦
Wheat玉米
Maize合计
TotalNF 3.12±0.41b 2.51±0.77d 0.84±0.18b 1.84±0.62d 2.68±0.87c 18.26±3.16a 6.81 N 2.19±0.48b 4.89±1.03c 0.81±0.20b 3.23±0.61cd 4.04±0.76c 87.50±8.51b 21.66 OM 7.80±0.18a 10.55±1.01a 2.74±0.26a 7.21±1.38a 9.95±1.41a 53.58±2.69c 5.38 NPK 6.62±1.66a 9.11±0.44ab 2.39±0.36a 5.70±0.32ab 8.09±0.30ab 78.91±3.34b 9.75 OMNPK 7.40±0.90a 9.79±1.17a 2.50±0.11a 7.03±1.37a 9.53±1.47ab 57.20±2.38c 6.00 CRNPK 7.82±0.79a 7.76±0.74b 2.69±0.13a 5.73±1.37bc 8.42±1.39b 62.15±1.25c 7.38 图中各施肥处理分别为单施氮肥(N)、常规施肥(NPK)、猪厩肥(OM)、猪厩肥与氮磷钾配施(OMNPK)、秸秆还田与氮磷钾配施(CRNPK)及不施肥(NF)。不同小写字母代表施肥处理之间差异显著(P<0.05)。Fertilization treatments in the figure are: nitrogen fertilizer only (N), regular synthetic nitrogen, phosphorus and potassium fertilizer (NPK), pig manure (OM), combination of pig manure with synthetic nitrogen, phosphorus and potassium fertilizer (OMNPK), combination of straw residue with synthetic nitrogen, phosphorus and potassium fertilizer (CRNPK). Different lowercases letters in the figure indicate significant differences among fertilization regimes at P<0.05 level. 
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