A field experiment was conducted at the Experimental Farm, El-Mattana, Agriculture Research Station, Luxor, Egypt during spring season of 2013 to determine the effects of water stress on sugarcane yield and its quality as well as its response to potassium application. The experiment was laid out in split-split plots design with three replicates. The main plots were used to express irrigation regimes (0.8, 1 and 1.2 of the cumulative pan evaporation, CPE). The split units were assigned for irrigation manners (all furrows and alternative furrows). Sub split plots were occupied by K levels (25, 50 and 75 Kg K2O/ fed). All the experimental treatments were randomly distributed on the respective plots.
The actual evapotranspiration (ETa) values under alternative furrow irrigation treatments (5215 m3) were less than that under all irrigated furrow treatments (5764 m3) regardless to the effect of irrigation regime or potassium fertilization. The amounts of applied water were 3592.50, 4979.39 and 8134.33 m3/ fed for irrigation regime (CPE) of 0.8, 1 and 1.2, respectively. Irrigation efficiency (IE) was decreased as the percentage of soil moisture depletion increased (at 0.8 CPE). Normal irrigation with 1.2 CPE at 75 Kg K2O/ fed achieved the highest value of IE (86.16%) while the lowest value (57.52%) was recorded at normal irrigation with 0.8 CPE and 50 Kg K2O/ fed. The best treatment was alternative irrigated furrow at 1 CPE when fertilized by 75 Kg K2O / fed since it realized the highest CWUE (8.86 Kg cane /m3 and 1.1 Kg sugar/m3). Cane yield as well as juice purity and sugar concentration declined, resulting in decreased sugar yield as irrigation intervals was increased. Also, cane yield and its quality was increased by increasing potassium fertilization level.