Sprinkler irrigation in lowland rice: Crop yield and its components as a function of water availability in different phenological phases

Efficient water use in agriculture is a global demand, and in this context, the implementation of a sprinkler irrigated rice system has become a reality. Besides saving water, proper management of a sprinkler irrigated system can maintain high levels of productivity. This study aimed to determine the effect of soil water tension on rice crop production, in both vegetative and reproductive stages, as well as to evaluate the effect of soil water availability and physicochemical attributes on biometric and reproductive characteristics associated to rice grain yield under sprinkler irrigation. The experiment was carried out at the Lowland Experimental Station, Embrapa Clima Temperado, Capao do Leao - Rio Grande do SW, Brazil, during two growing seasons, in an area irrigated by a lateral-move sprinkler irrigation system. The following irrigation managements were evaluated: irrigation, when the mean soil water tension was i) 10 kPa; ii) 20 kPa; iii) 40 kPa; iv) 40 kPa on vegetative and 20 kPa on reproductive stages and v) 40 kPa on vegetative and 10 kPa on reproductive stages. Under sprinkler irrigation, rice plant development was impaired as soil water tension increased, evidenced by a reduction in plant heights. Soil water tension of 10 kPa was adequate to manage the sprinkler irrigation in rice, especially in the reproductive stage and when using cultivars developed for flooded environments. Rice development and yield were affected by increasing soil bulk density and acidity. Rainwater represented approximately 40 % of the water used by sprinkler irrigated rice during the crop cycle, contributing with the reduction of irrigation water use.