Quantifying Agricultural Intensification in the US

Abstract

Increases in crop production show increasing trends in agricultural intensification. These trends are predominant in the corn and soybean crop production of the United States' Midwest region. The increase of production and irrigation in the past 20 years is spatially diverse, with some regions in the Midwest intensifying agriculture at faster rates. Measurement of vegetation through the use of satellite remote sensing methods has gained popularity in recent years, with the refinement of existing retrieval algorithms and the development of new ones. Many different indices can be used to study the vegetation, including optical products such as the Normalized Difference Vegetation Index (NDVI) and the Leaf Area Index (LAI). However, the use of microwave remote sensing has some advantages over near optical methods as it is unaffected by weather conditions and can therefore collect data more regularly. Microwave remote sensing methods can retrieve the vegetation optical depth (VOD), a parameter which is related to the intensity of microwave signal extinction by vegetation and can be derived through the use of both passive and active microwave observations. In this study, these microwave remote sensing methods are used to look for evidence of agricultural intensification trends in the Midwest. The spatial distribution and intensity of trends is compared with trends in yield data and LAI. Trend analysis of soybean and corn yield in the Midwest show statistically significant increasing trends in the Western states of South Dakota, Nebraska, and parts of North Dakota. Similar spatial distributions were picked up in LAI and passive microwave data.