基于小麦长势遥感监测的土壤氮素累积估测研究

    Estimation of soil nitrogen accumulation based on remotely-sensed monitoring of winter-wheat growth status

    • 摘要: 农田长时间被植被所覆盖给遥感直接监测农田土壤养分及其动态带来巨大难度。由于不同的土壤条件和施肥量会在一定程度上引起作物长势的差异,并最终反映在作物冠层光谱反射率的差异,因此,通过遥感监测作物长势动态实现农田土壤养分与环境质量将是遥感监测土壤质量的一个重要方法。该文利用追肥前后两期高光谱航空影像提取反映小麦长势状况的归一化植被指数NDVI,并结合小麦种植前后的土壤采样数据,分析了追肥前后NDVI及其增量与小麦种植前后土壤碱解氮增量之间的关系。研究结果表明:与追肥前后NDVI绝对增量相比,追肥前的NDVI能够较好地估测小麦生育期内土壤碱解氮增量,追肥前后NDVI绝对增量与追肥前的NDVI的比值是估测小麦生育期内土壤碱解氮增量的最好指标,而追肥后的NDVI与土壤碱解氮增量之间没有显著的相关关系,不能用于土壤碱解氮增量的估测。

       

      Abstract: Covered by vegetation results in the difficulty to monitor soil nutrition and its accumulation of farmland during crop's growing season by remote sensing, however, crop's growth status and growing speed directly reflect the soil fertility and fertilization, so it is a feasible method for monitoring soil nutrition and its accumulation of farmland based on remotely-sensed monitoring of crop's growth status. Two temporal NDVI were derived from hyper-spectral imageries collected at reviving stage and elongation stage, and two temporal grid-sampling data were interpolated to raster soil nutrition data using Ordinary Kriging analysis. The first soil sampling was processed before seeding, and another was after harvest time. It analyzed the correlation among remote sensing parameters, that is, NDVI(Normalized Different Vegetation Index), the absolute increment of NDVI around fertilization (⊿NDVI), the ratio of ⊿NDVI to NDVI obtained pre-fertilization(R_⊿ NDVI1), and the ratio of ⊿NDVI to the summery of NDVI around fertilization(R_⊿ NDVI2), and the increment of alkali-hydrolysable nitrogen in soil(⊿N) during winter wheat growing season. Results show that, compared with ⊿NDVI, NDVI obtained before fertilization can well estimate the increment of alkali-hydrolysable nitrogen in soil, and R_⊿ NDVI1 is the best index for estimating nitrogen accumulation during crops growth period, while NDVI obtained after fertilization is the worst.

       

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