Effects of Planting Density on Water Use and Productivity of Pearl Millet (Pennisetum Typhoides) Grown on Stored Water. II. Water Use, Light Interception and Dry Matter Production

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Abstract
Pearl millet was grown on stored water at Niamey, Niger, using three row spacings. Water extraction based on neutron probe readings was compared with crop transpiration using a porometer and allied measurements. Between 23 and 52 days after sowing, plants at the narrow and medium spacings used about 77 and 100 mm of water, respectively, and those at the wide spacing used between 59 and 75 mm. Estimates of seasonal crop evaporation from leaf resistances and from the green leaf area index (GLAI) of the crops were 103, 130 and 123 mm for the narrow, medium and wide spacings, respectively. The water use per unit of dry weight produced was similar for both narrow and medium spacings but water was used more efficiently in the wide spacing. Dry weight increased in proportion to intercepted radiation with the same efficiency (1·3 g MJ−1) irrespective of spacing.