学术论文

      低场核磁探测水稻田改蔬菜地土壤水分的相态变化

      Phase change of soil water of vegetable field transformed from paddy field by low field nuclear magnetic resonance

      摘要:
      为了解水稻土转变为设施蔬菜地后土壤水分的相态变化,该研究在田间土壤调查的基础上,结合低场核磁测氢技术,评价了田间状态的水稻土和不同转化年限设施蔬菜地土壤水分的相态分布情况。结果表明:随着转化时间的延长,耕层土壤大孔隙吸持的自由水比重下降,土壤小孔隙吸持的束缚水比重上升,犁底层土壤水分的相态分布却无明显变化,土壤水分吸持性能在转化时间序列上呈现下降的趋势,但长期施用有机肥可以优化耕层质量,提升土壤大孔隙吸持自由水的能力,改善土壤水分供释性能;水稻土转化为设施蔬菜地土壤2 a后,出现新犁底层,使得原有的耕层土壤变薄,土壤水分吸持性能下降。核磁共振作为一种新的技术手段,可以实现实时、快速、准确地检测土壤水分的相态变化,可为设施农业的可持续管理提供新的技术支持。
      Abstract:
      Soil pore water is the important part of terrestrial water resource and the basis for plant survival. Furthermore, it is in charge of heat and solute transportation throughout soil profile. This study aimed to identify the variations of soil moisture under land use change from paddy field to greenhouse vegetable field at different time frameworks. To do so, soil samples were taken at the saturated condition of moisture capacity from both paddy and greenhouse plots. The selected greenhouse vegetable site was located in the urban area of Nanjing, China. In this region the main soil type is paddy soil coming from many-year rice-wheat rotation. A new method called low field nuclear magnetic resonance (LF-NMR) technology was adopted to acquire soil samples’ transverse relaxation time (T2)spectrum. Based on this 4 treatments were chosen, which included a long-term paddy field and 3 greenhouse vegetable sites with different transformation time. Accordingly, the paddy field was supposed to be beginning point (0 year) (PS0), and the conversion ages of the greenhouse vegetable fields were 2, 6, and 8 years (GVS2, GVS6 and GVS8, respectively). Based on the previous survey, greenhouse field in the pakchoi (Brassica campestris L. ssp. chinensis) plantation was selected as the research site in this study. Results of soil profile survey indicated that paddy soil profile (0-30 cm) was divided into 2 layers: a plough horizon (0-15 cm) and plow pan (>15-30 cm). Since a new firm structural layer was observed in the lower part of the plough layer, we divided greenhouse vegetable soils’ profile (0-30 cm) into 3 layers: plough horizon, new plow pan, and old plow pan. Soil physicochemical properties including soil organic matter, bulk density, pH value and particle size composition were measured for selected sampling sites. The results showed that: 1) Water flow in topsoil macro pores decreased from 29.7% in PS0 to 14.9% in GVS6. In contrast, slight changes occurred in water flow across deep layers; 2) the average annual rate of organic fertilization in PS0, GVS2, GVS6 and GVS8 were 0, 46.5, 36 and 144 t/hm2, respectively. The organic fertilizer added to GVS8 was 3.1 and 4 times that of GVS2 and GVS6, respectively. Therefore, it suggests that an improvement in plough layer quality caused by heavy application of organic fertilizer can increase water flow and prevent further soil degradation; 3) Land use transformation from paddy field to greenhouse vegetable field for 2 years decreased water holding capacity due to the emergence of new plow pan. In conclusion, the findings of this study confirm that LF-NMR method can be more directly and accurately used to monitor changes in soil moisture content of each phase instantly, and hence it may provide new theoretical and technical support for scientific management of facility agriculture.
      作者: 孔超 [1] 王美艳 [2] 史学正 [2] 郭乃嘉 [1] 于全波 [1]
      Author: Kong Chao [1] Wang Meiyan [2] Shi Xuezheng [2] Guo Naijia [1] Yu Quanbo [1]
      作者单位: 土壤与农业可持续发展国家重点实验室 中国科学院南京土壤研究所,南京 210008; 中国科学院大学,北京 100049 土壤与农业可持续发展国家重点实验室 中国科学院南京土壤研究所,南京,210008
      刊 名: 农业工程学报 ISTICEIPKU
      年,卷(期): 2016, 32(24)
      分类号: S152
      在线出版日期: 2017年1月16日
      基金项目: 国家自然科学基金项目(41401240;41571209);中国科学院南京土壤所“一三五”计划和领域前沿专项基金(ISSASIP1627)。