An experiment was conducted during summer 2015 at the research farm of the Afghanistan National Agricul- tural Science and Technology University, Kandahar, to assess the effect of variable levels of phosphorus on growth and productivity of maize (Zea mays L.) under semi-arid conditions of Kandahar, Afghanistan. The experi- ment was laid out in a randomized complete, block design with 3 replications, having a plot size of 4.25 m 5.60 m with row-to-row distance of 0.60 m and plant-to-plant distance of 0.25 m. The levels of phosphorus were 0 (con- trol), 15, 30, 45, 60, 75 and 90 kg P O /ha. Different levels of phosphorus significantly influenced all growth param- 2 5 eters of maize, viz. plant height, leaf area index, number of green leaves per plant, dry-matter accumulation, leaf area duration, crop growth rate and net assimilation rate; and yield. The application of 75 kg P O /ha resulted in 2 5 the maximum plant height (200.6 cm), higher leaf area index (6.41), greater dry matter accumulation (222 g/plant), net assimilation rate (10.9 g/m2/d) and grain yield (6.51 t/ha) compared to the control. Thus, P may be applied at the rate of 75 kg P O /ha for getting higher grain yield and income in the agro-ecological conditions of 2 5 Kandahar, Afghanistan.