Multi-Temporal Mapping of Soil Total Nitrogen Using Google Earth Engine across the Shandong Province of China

Wu Xiao,Tingting He,Jiwang Guo,Linlin Ruan,Wenqi Chen

doi:10.3390/su122410274

Wu Xiao, Tingting He + Show 3 more

Open Access

https://doi.org/10.3390/su122410274

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Abstract

Nitrogen plays an important role in improving soil productivity and maintaining ecosystem stability. Mapping and monitoring the soil total nitrogen (STN) content is the basis for modern soil management. The Google Earth Engine (GEE) platform covers a wide range of available satellite remote sensing datasets and can process massive data calculations. We collected 6823 soil samples in Shandong Province, China. The random forest (RF) algorithm predicted the STN content in croplands from 2002 to 2016 in Shandong Province, China on the GEE platform. Our results showed that RF had the coefficient of determination (R2) (0.57), which can predict the spatial distribution of the STN and analyze the trend of STN changes. The remote sensing spectral reflectance is more important in model building according to the variable importance analysis. From 2002 to 2016, the STN content of cropland in the province had an upward trend of 35.6%, which increased before 2010 and then decreased slightly. The GEE platform provides an opportunity to map dynamic changes of the STN content effectively, which can be used to evaluate soil properties in the future long-term agricultural management.

Highlights

Nitrogen is a nutrient element that exists widely in nature and plays an important role in plant growth and development [1]
The result showed that the predictive performance with the first 15 predictor variables was almost the same as that of the model based on 32 predictive variables
The annual maximum reflectance of Band 6 is the most important predictor that affects the spatial distribution of soil total nitrogen (STN) with a contribution rate of 7.28%

Summary

Introduction

Nitrogen is a nutrient element that exists widely in nature and plays an important role in plant growth and development [1]. Imbalances in the nitrogen cycle may produce negative ecological effects, such as water pollution, soil eutrophication, greenhouse effects, and acid rain [4]. The reasonable application of nitrogen fertilizer can effectively increase grain production, so it is widely used in farming [5,6]. The excessive application of nitrogen fertilizers may induce groundwlater and soil pollution [7]. Natural factors and continuous human activities can directly affect the soil nitrogen content in different regions [8]. Due to the high spatial heterogeneity of soil nitrogen at the regional scale, accurately monitoring the spatial distribution of the soil total nitrogen (STN) content is important to balance the nitrogen cycle and for sustainable development in intensive agriculture [9]

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