Dry matter and grain production of rice, using a line source sprinkler in drought studies

Abstract A line-source sprinkler was assessed as a means for testing rice cultivars in the field, and various aspects of crop growth were examined in relation to drought screening techniques. The experiment consisted of seven rice cultivars and four replications where the line source sprinkler provided the plots with a water supply that diminished linearly with distance from the line. Up to the time of panicle emergence two tall upland cultivars produced more dry matter than lowland cultivars, particularly at lower rates of water application. Soil water measurements for one upland and two lowland cultivars, however, showed that this was due to increased water extraction from the soil profile, and that dry matter production until panicle emergence was a function of water used. There were no differences between these three cultivars in water use efficiency. Heavy rains at and after panicle emergence replenished the soil water. The lowland rice IRI529-430-3 was the most efficient in grain production, with the highest harvest index. The two tall upland cultivars Kinandang Patong and IAC 47 were shown to have deeper root systems, but their relative grain yield at low compared to high water supply was poorer than for IRI529-430-3. Other experiments have shown that this lowland rice has a stable yield across a range of upland environments, and the implications of this are discussed with reference to techniques of selecting for drought resistance. It is emphasised that vegetative assessments used in drought screening must be interpreted in relation to grain yield.