Effects of deficit irrigation and organic matter on growth and yield of cotton cultivated in three gypsiferous soil types

Agricultural land and the abundance of irrigation water are among the main resources on which food security and the national economy depend, but the limited fertile soils and the deterioration of the characteristics of many types of soils, especially gypsum soils and the scarcity of irrigation water represent a major challenge to sustainable agricultural expansion, especially in arid and semi-arid regions such as Iraq. That's why a study was conducted in Kirkuk Governorate, Hawija District, Riyadh area, using plastic pots to explore the effects of deficit irrigation levels, 50 %, 75 % and 100 % of field capacity (FC), organic fertilisation using sheep manure at 3 concentrations 0, 0.5 and 1 % and gypsum content (5 %, 10 % and 20 %) on the growth, yield and yield components of cotton plants. The previous 3 treatments were distributed according to a completely randomized design (CRD) for the distribution of factorial experiments, with 3 repetitions and the results showed that: the soil amended with 10 % gypsum resulted in superior plant height (68.62 cm), leaf area (3777 cm²), number of bolls (2.41 per plant) and floral cotton yield (38.27 g). The use of 1 % organic fertiliser further improved plant growth and yield, reaching 65.47 cm in height and 38.16 g yield per plant. Full irrigation (100 % FC) recorded the highest values for plant height (69.7 cm), leaf area (3879 cm²) and yield (40.37 g), while 50 % irrigation significantly reduced all measured parameters. The combination application of 10 % gypsum, 1 % organic fertiliser and 100 % FC irrigation produced the best overall performance and productivity under gypsiferous soil conditions.