By 2050, the world's population will reach 9 billion with demand for agricultural products expected to rise by 50%. To meet this growing global food demand, agricultural production must increase, but without depleting scarce resources such as land and water. Agriculture production consumes more than 70% of the world's water, mainly for irrigation. With water use efficiency less than 50%, the challenge is to ensure adequate agricultural production while achieving maximum efficiency of irrigation water use. Climate smart irrigation practices such as monitoring soil moisture offer improvements to help to meet this challenge and ensure availability for future generations. For example, using moisture sensors can provide crucial information to help farmers decide when and how much to irrigate. However, accurate measurement of soil moisture, even at field level, calls for a large number of sensors which can increase cost. On the other extreme, remote sensing satellites can measure soil moisture on a very large scale, but often it's too large for agricultural purposes. Between these two scales, the Cosmic Ray Neutron sensor fills the gap. It measures soil moisture at field and landscape scales, with the added advantage that it does not disturb agricultural operations in the field. Here is how it works. Incoming Cosmic Rays interact with elements of the Earth's atmosphere and produce fast high energy neutrons that eventually penetrate the soil and then scatter back into the atmosphere. These scattered neutrons lose energy due to collisions, mainly with hydrogen atoms, which come mostly from soil moisture and become low energy neutrons. The Cosmic Ray Neutron sensor measures these low energy neutrons near the soil surface. Because the neutrons are spatially distributed and scatter across large distances in the air, they can monitor soil moisture over vast areas. The joint FAO IAEA division is working with scientists in many member states to introduce the use of Cosmic Ray Neutron sensors for efficient agricultural water management at both field and landscape levels. Using these sensors to validate remote sensing imagery predictions for irrigation and drought management is essential for the development of climate smart agricultural practices that foster global food security.