Mechanisms of organic-instead fertilization for coupling nitrogen supply and retention in cropland of purplish soil
文献类型：学位论文
| 作者 | HAMIDOU BAH |
| 答辩日期 | 2020 |
| 授予单位 | 中国科学院大学 |
| 授予地点 | 北京 |
| 导师 | 朱波 |
| 关键词 | 固碳 有机添加 温室气体排放 氮淋失 紫色土 |
| 学位名称 | 博士 |
| 学位专业 | 土壤学 |
| 其他题名 | 有机替代施肥方式下的紫色土氮素供应与保持机制 |
| 英文摘要 | Agricultural activities contribute a wide range of pollutants that have seriously negative environmental impacts, with high potential for global warming consequences. In recent years, the increasing rate of nitrogen oxides (NOx) emissions, ammonia (NH3) volatilization, and hydrological N losses from croplands have raised major concerns due to the recurrent negative influence on air and water quality, especially the implications for global warming. Thus, a method for improving crop productivity while reducing the environmental impacts of these gaseous and hydrological N losses from fertilized agricultural soils could be a best practice for sustainable agriculture. To date, several studies have separately reported soil organic carbon sequestration, gaseous N losses and hydrological N losses pathways and loadings, and soil N mineralization. This has resulted in misunderstanding the mechanisms of coupling N supply and retention in croplands. Although, organic-instead fertilization is highly recommended as a reliable resource for soil nutrient recycling, very few studies have simultaneously quantified N inputs and outputs for determining the N balance under organic-instead fertilization regimes because of complicated N biogeochemical cycling, especially in cropland of purplish soil. More so, few studies have focused on both gaseous and hydrological N loss based on long term organic-instead fertilization experiments. Therefore, it is important to integrate both N inputs and outputs together to understand the mechanisms of coupling N supply and retention in cropland based long term organic-instead fertilization. The main objectives of this study were to understand the mechanisms of coupling nitrogen supply and retention and to find optimal practices of organic-instead fertilization in cropland of purplish soil for diminishing nitrogen losses while maintaining crop yields. This study intended to answer the following key scientific questions: (1) what are the effects of organic-instead fertilization on crop productivity and nitrogen use efficiency? (2) how does organic fertilization mitigate greenhouse gas emissions and hydrological N loss in cropland of purplish soil?. The study provided a scientific base for reactive N loss mitigation through organic-instead fertilization in cropland of purplish soil.Field free-drain lysimeters and incubation experiments were conducted to monitor N supply and retention from 2016 to 2018 in a wheat-maize rotation system. A completely randomized block design of long term fertilization experiment since 2002 with six treatments as, no fertilizer (CK), regular mineral fertilizers (NPK), pig slurry as organic manure (OM), crop residues (CR), and organic manure combined with mineral fertilizers (OMNPK) and crop residues combined with mineral fertilizers (CRNPK) have been used for field monitoring. The applied N rate was 280 kg N ha-1, split in 130 kg N ha-1 for the wheat season, and 150 kg N ha-1 for the maize season. The main results and conclusions were as follows:(1) The leaf photosynthesis rate was not significantly increased by organic-instead fertilization compared to NPK treatment, and was within a range of 4.8 to 45.3 µmol m-2 s-1 for the wheat and -20.1 to 40.4 µmol m-2 s-1 for the maize across elongation stage, heading stage, and grain filling stage. However, higher leaf photosynthesis rate was observed in CR treatment in the wheat season, and in CRNPK in the maize season, showing that the CRNPK application could be beneficial for improving crop leaf photosynthesis rate.(2) The three years' average biomass ranges from 2.8 to 5.9 Mg ha-1 for wheat and 3.5 to 6.4 Mg ha-1 for maize across organic-instead fertilization. While the average grain yield ranges from 1.4 to 3.4 Mg ha-1 and from 2.7 to 5.4 Mg ha-1 for wheat and maize, respectively. Excluding the incorporation of crop straw only, organic-instead fertilization can sustain crop productivity comparably to the NPK treatment. However, crop yield and biomass for organic-instead fertilization were significantly greater than those for NPK. The average wheat N uptake ranges from 32.8 to 82.5 kg N ha-1, and 67.4 to 143.5 kg N ha-1 for maize N uptake. The OM and CRNPK treatments showed greater wheat and maize N uptake, respectively (p < 0.05). Moreover, the agronomic nitrogen use efficiency (NUE) for the maize growing season (27.3 to 37.3 kg kg-1) was higher than those for the wheat season (21.7 to 30.1 kg kg-1). These results indicated that NUE for organic-instead fertilization for OM, OMNPK, and CRNPK treatments was significantly greater compared to those for NPK. (3) The soil CO2 emissions for the maize season range from 203 to 362 g C m-2, and from 118 to 252 g C m-2 for the wheat season for all treatments. The organic-instead fertilization increased annual cumulative CO2 emissions from 30-51% compared to NPK treatment. While the average crop C uptake ranged from174 to 378 g C m-2 and from 287 to 488 g C m-2 for the wheat and maize seasons, respectively, and the organic-instead fertilization increased the crop C uptake by 4-23% compared to NPK treatment. The organic-instead fertilization C balance ranged from -160 to 460 g C m-2 and from -301 to 334 g C m-2 for the wheat and the maize seasons, respectively. The results suggest that organic-instead fertilization can be an effective strategy for increasing C sequestration and sustaining crop productivity in cropland of purplish soil.(4) The results revealed that both the wheat and the maize seasons exhibited distinct patterns of temporal and spatial heterogeneity in CH4 and N2O emissions across all treatments. Moreover, the average cumulative annual CH4 flux ranges from -2.60 to -5.60 kg C ha-1, while N2O flux ranges from 0.44 to 10.04 kg N ha-1 in all organic-instead fertilization regimes. The annual GWP for OM and OMNPK treatments was 3.97 and 1.80 Mg CO2-eq ha-1, while their corresponding annual yield-scaled GWP was 533 and 220 kg CO2-eq Mg-1 grain, respectively, were significantly higher than in the other treatments (p < 0.05). On average, except CR treatment, organic-instead fertilization increased the annual GWP by 26-88% and yield-scaled GWP by 19-88% compared to those for NPK treatment. The study indicates that the fertilization strategy for cropland of purplish soil can shift from only NPK to OMNPK and CRNPK treatments, which can help mitigate greenhouse gas emissions and GWP while maintaining crop yields. (5) There were no significant differences in discharges of both overland flow and interflow between organic-instead fertilization and NPK applications. On average, annual total N (TN) loss loadings ranges from 8.3 to 27.6 kg N ha-1, with 1.1 to 5.2 kg N ha-1 of particulate N (PN), and 6.4 to 19.1 kg N ha-1 of nitrate N (NO3--N) loss loadings. The PN and NO3--N losses account for 13-19%, and 63-78% of TN loss loadings, respectively across all treatments. The results indicate an average TN loss reduction of 3.9 to 19.3 kg N ha-1 by organic-instead fertilization compared to NPK treatment. Compared to NPK treatment, organic-instead fertilization regimes significantly decrease TN loss, by 85% via overland flow and 117% via interflow on average. The results showed that organic-instead fertilization can mitigate hydrological N loss and N agricultural non-point source pollution in cropland of purplish soil.(6) The organic N mineralization rate significantly differed among the organic-instead fertilization regimes. The organic N mineralization rates of OM and CRNPK were 47.51 and 46.93 mg kg-1, respectively, which were significantly higher than in the other treatments (p < 0.05). Compared to the NPK treatment, the organic-instead fertilization regimes increased soil organic N mineralization rate by 17-33%; the potential mineralization of soil organic nitrogen (No) by 15-20%; the constant rate for labile N (kN) by 3-27%; and the initial potential rate of N (No x kN) by 18-52%. The study indicates the organic-instead fertilization significantly increases soil N supply and N mineralization kinetics parameters.(7) The annual cumulative NOx fluxes ranged from 0.12 to 1.27 kg N ha-1. The OMNPK and CRNPK treatments decreased the annual NOx fluxes by 45 and 186%, respectively, compared to NPK treatment. Conversely, the annual NH3 fluxes varied from 15.90 to 31.03 kg N ha-1 across all the treatments. The OM, OMNPK, and CRNPK treatments increased the annual NH3 fluxes by 40%, 26%, and 24%, respectively, compared to NPK treatment. The annual N balance ranged from 103.1 to 164.2 kg N ha-1 across organic-instead fertilization regimes. The N balance for CRNPK was significantly higher than those other treatments, indicating a larger amount of N retention in soils in CRNPK compared with NPK treatment (p < 0.05). The optimal organic-instead fertilization regime of CRNPK can be recommended for N supply and retention while maintaining crop yield in cropland of purplish soil.(8) The mechanisms of N supply from organic-instead fertilization methods mainly consist of direct application of mineral N fertilizer and mineralization of organic N. Soil N loss occurred through denitrification, ammonia volatilization, and nitrate leaching. Thus, soil N could be retained by means of reducing soil active N loss particularly nitrate from leaching, and storing more active N in cropland of purplish soil. |
| 语种 | 英语 |
| 页码 | 208 |
| 源URL | [http://ir.imde.ac.cn/handle/131551/55036]  |
| 专题 | 成都山地灾害与环境研究所_山地表生过程与生态调控重点实验室 |
| 作者单位 | 中国科学院成都山地灾害与环境研究所 |
| 推荐引用方式 GB/T 7714 | HAMIDOU BAH. Mechanisms of organic-instead fertilization for coupling nitrogen supply and retention in cropland of purplish soil[D]. 北京. 中国科学院大学. 2020. |
入库方式： OAI收割
来源：成都山地灾害与环境研究所
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