The disclosure provides systems and methods of use pertaining to irrigating and thermally protecting a field of crops. One embodiment provides a semi-closed circuit irrigation and thermal-protection system that circulates heated irrigation fluid from a storage reservoir, through a fluid distribution system associated with each crop in the field, and back to the reservoir. The fluid distribution system incorporates a number of expandable, porous vessels associated with the crops. The vessels receive a large volume of irrigation fluid and, while slowly releasing the fluid into the soil to raise soil-saturation levels, transfer heat from the fluid directly to the crops and to the ambient environment. The system may be activated in discrete bursts to irrigate the crops or activated over a prolonged duration to heat the crops during a freeze or frost event. Other embodiments are also disclosed.