Soil moisture in the root zone and its relation to plant vigor assessed by remote sensing at management scale

Abstract

Vegetation index derived from satellite data can be indirectly utilized for obtaining information on moisture in the soil root zone in cropped areas, considering that the soil profile moisture in many regions of the world is the main factor controlling plant vigor. In this context, the aims of this work were: (i) to verify the relationship between moisture in the soil profile (until 100-cm depth) and the vigor of the plant, as measured by Vegetation Index EVI-2, (ii) to identify which is the plant vigor response time delay for soil moisture at different depths of the profile, (iii) to propose linear equations for estimating soil moisture by EVI-2, and (iv) to test the hypothesis that is possible to identify, with the aid of the EVI-2, which soil depth can be considered the effective depth of water absorption by plants. Data were collected in a coffee crop area at São Roque de Minas, Upper São Francisco River basin, Minas Gerais state, Brazil. The soil moisture was measured with a multi-sensor capacitance (MCP) probe, from March to December, 2010, and the coffee plant vigor was evaluated by Vegetation Index EVI-2. It was verified a correlation between vegetative vigor of coffee plants and soil moisture in the root zone. Linear equations were generated to estimate soil moisture in this zone using vegetation indexes at soil management scale (soil profile explored by the crop). There is a response time delay of coffee vigor to soil moisture, and this time varies according to depth and water content in the soil profile. The highest correlation was obtained at a depth of 60 cm, indicating that this depth is the one that best reflects the plant's water status.