Effects of irrigation water management on yield and water use efficiency of rice in cracked paddy soils

The management of cracking clay soils has important influence on irrigation efficiency. To determine the effects of different irrigation water managements on yield and water use efficiency of rice (Oryza sativa L.) in cracked paddy soils, a field experiment was conducted on a silty clay soil, a typical swelling soil of Guilan province, northern part of Iran. The experiment was a randomized complete block design with factorial arrangement of treatments with three replications. The main treatment was crack width (3-4 mm, 1.5 cm and 2.5 cm) which are called C^sub 0^, C^sub 1.5^ and C^sub 2.5^, respectively. The subtreatment was irrigation (D^sub 0^, irrigation to fill up the cracks and up to the start of ponding; D^sub 2.5^, irrigation to fill up the cracks and up to 2.5 cm of ponding at the soil surface; D^sub 5^, irrigation to fill up the cracks and up to 5 cm of ponding at the soil surface). The results showed that the effects of crack width, depth of irrigation water and their interaction on rice grain yield and water use efficiency were significant at 5% and 1% level, respectively. The highest grain yield (3.279 ton ha^sup -1^) belonged to the D^sub 5^C^sub 0^ and the lowest grain yield (2.04 ton ha^sup -1^) belonged to D^sub 0^C^sub 2.5^. The reduction of depth of ponding (D^sub 0^ vs. D^sub 5^) caused 36.5% improvement in water use efficiency. On cracked paddy soils, based on the development of crack width, the irrigation schedule can be planned to save water without considerable reduction of crop yield. The results of this study can be applied to cracked paddy soils of the study area in order to save irrigation water. Keywords: Deficit irrigation, rice, swelling soils, yield components.

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