Soil moisture measurement for agriculture

Chapter 2. Whilst infrastructure projects have often focused on improving the supply of water for agriculture, there has been much less focus on managing or reducing the agricultural water demand. The net effect of increasing supply, without managing demand, is that agricultural water (and energy) consumption increases, without necessarily increasing food production. Improved agricultural Water Use Efficiency (WUE) can help address this issue, as well as contributing to reducing the pressures on water resources (NITI Aayog 2019). This chapter outlines how recent improvements in large area measurement of soil moisture and the availability of high-resolution Soil Moisture Deficit information at a fine scale can provide actionable guidance to farmers. Practical methods, demonstrated in farm pilot studies, to manage irrigation demand are discussed, along with considerations of efficient irrigation methods, with the objective of improving WUE

The Indian COSMOS Network (ICON): validating L-band remote sensing and modelled soil moisture data products

Availability of global satellite based Soil Moisture (SM) data has promoted the emergence of many applications in climate studies, agricultural water resource management and hydrology. In this context, validation of the global data set is of substance. Remote sensing measurements which are representative of an area covering 100 m2 to tens of km2 rarely match with in situ SM measurements at point scale due to scale difference. In this paper we present the new Indian Cosmic Ray Network (ICON) and compare it’s data with remotely sensed SM at different depths. ICON is the first network in India of the kind. It is operational since 2016 and consist of seven sites equipped with the COSMOS instrument. This instrument is based on the Cosmic Ray Neutron Probe (CRNP) technique which uses non-invasive neutron counts as a measure of soil moisture. It provides in situ measurements over an area with a radius of 150–250 m. This intermediate scale soil moisture is of interest for the validation of satellite SM. We compare the COSMOS derived soil moisture to surface soil moisture (SSM) and root zone soil moisture (RZSM) derived from SMOS, SMAP and GLDAS_Noah. The comparison with surface soil moisture products yield that the SMAP_L4_SSM showed best performance over all the sites with correlation (R) values ranging from 0.76 to 0.90. RZSM on the other hand from all products showed lesser performances. RZSM for GLDAS and SMAP_L4 products show that the results are better for the top layer R = 0.75 to 0.89 and 0.75 to 0.90 respectively than the deeper layers R = 0.26 to 0.92 and 0.6 to 0.8 respectively in all sites in India. The ICON network will be a useful tool for the calibration and validation activities for future SM missions like the NASA-ISRO Synthetic Aperture Radar (NISAR)