Water requirements and irrigation

This chapter addresses itself to water requirements, direct and indirect measurement thereof, and factors which affect them. Use of the term water requirement, particularly by agricultural engineers, is the amount of water from rainfall and irrigation necessary to meet specific production or performance needs. Turfgrass water use rate is defined as the total amount of water needed for plant growth which includes water lost by the transpiration and evaporation from soil and plant surfaces. The basic factors affecting turfgrass water use rate will be reviewed: (i) evaporative demand of the air surrounding the sward; (ii) the quantity and quality of the water with which the sward is supplied; and (iii) transpiration and evaporation levels typical of the specific type of sward and soil in response to evaporative demands. The driving force for evaporative demand is solar radiation. Amounts and effectiveness of solar radiation are functions of climate, season, altitude, and latitude.