Abstract
Land use maps specifying up-to-date acreage information on maize (Zea mays L.) cropping patterns are required by many stakeholders in Vietnam. Government statistics, however, lag behind by one year, and the official land use maps are only updated at 5-year intervals. The aim of this study was to apply the Savitzky–Golay algorithm to reconstruct noisy Enhanced Vegetation Index (EVI) time series (2003–2018) from Terra Moderate Resolution Imaging Spectroradiometer (MODIS) Vegetation Indices (MOD13Q1) to allow timely detection of changes in maize crop phenology, and then to employ a linear kernel Support Vector Machine (SVM) classifier on the reconstructed EVI time series to prepare the present-day maize cropping pattern map of Dak Lak province of Vietnam. The method was able to specify the spatial extent of areas cropped to maize with an overall map accuracy of 79% and could also differentiate the areas cropped to maize just once versus twice annually. The by-district mapped maize acreage shows a good agreement with the official governmental data, with a 0.93 correlation coefficient (r) and a root mean square deviation (RMSD) of 1624 ha.
Highlights
Maize (Zea mays L.) crop has an increasing importance in the economy of Vietnam
In the reconstructed Enhanced Vegetation Index (EVI) profile the negative value is no longer present, and since the filter was able to the reconstructed EVI profile the negative value is no longer present, and since the filter was able to identify cropping seasonal changes, a cropping boundary can be set for fitting the whole EVI series identify cropping seasonal changes, a cropping boundary can be set for fitting the whole EVI series based on its annual behavior
The maximum EVI value of 0.68, which was seen at the peak of the maize growing stage, was preserved during the smoothing and upper-envelope process
Summary
According to the latest national statistical survey [1] by 2018 the total maize area cultivated across the country was roughly 1,104,000 hectares, from which close to 10% is located in Dak Lak. Over the past 20 years, the maize cropping area has almost doubled, leaping from 663,000 hectares in 1997 [2]. Over the past 20 years, the maize cropping area has almost doubled, leaping from 663,000 hectares in 1997 [2] This increase was mostly driven by the growing demand from some of the largest animal feed, meat [3] and food companies that have been operating in Vietnam since 1986. In Dak Lak, maize fields are located either on hillslopes or in valleys, depending on the water demand of the crop, which is mostly grown under rainfed conditions. Soils with high fertility and organic matter are used, due to the economic and terrain difficulties faced by farmers to fertilize
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
