YOUSSEF, K.M.R.; ASHRY, M.R.K.; FARRAG, F.R.M. and ABDOU, S.M.M.( 2013). (Crop-water relations and yield of cotton as affected by irrigation water and nitrogen fertilization management) Minufia J. Agric. Res. Vol. 38 No. (4): 985- 996, August 2013.
Abstract: A field experiment was carried out at Tameia Agric, Res. Station, Fayoum Governorate during 2011 and 2012 summer seasons. The study aiming at determining the effect of different irrigation regimes, i.e. irrigation at 30, 50 and 70% available soil moisture depletion (ASMD) and three nitrogen fertilization levels ( 55, 70 and 85 kg N/fed) and interaction on seed cotton yield , yield components and some crop - water relations. The adopted treatments were assessed in a split –plot design with four replicates where irrigation regimes were represented in the main plots while the sub ones were assigned to N levels. The main obtained results could be as follows:
•Seed cotton yield was significantly affected by irrigation regimes, N fertilization levels and interaction, while most studied yield components exhibited similar trend in both seasons of study.
•The highest values of seed cotton yield were recorded under irrigating at 30 ASMD% regime. In addition, the highest N level resulted in the highest seed cotton yield. The highest seed cotton yields( 1140.65 and 1090.74 kg / fed in 2011 and 2012 seasons, respectively ) were obtained with 30 ASMD% regime as interacted with 85 kg N/fed level. Irrigating at 30 ASMD% regime and / or 85 kg N/fed level exhibited the highest values of yield components in the two seasons of study..
• Seasonal evapotranspiration (ETC), as a function of irrigation regimes and N fertilization levels averaged 92.54 and 90.96 cm in 2011 and 2012 seasons, respectively. Either Irrigation at 30% ASMD regime or 85 kg N/ fed level gave the highest ETC values which amounted to 96.81 and 95.04cm and 95.0 and 93.76cm in 2011 and 2012 seasons, respectively. Interaction of irrigating at 30% ASMD regime and 85 kg N/ fed level exhibited the highest ETC values which reached to 99.05 and 97.78cm in 2011 and 2012 seasons, respectively.
• The daily mean of ETC (mmday-1) increased from march and reached its peak values during June and July, then declined during August. The crop coefficient (Kc) as a mean of the two seasons were 0.57, 0.84, 0.91 .1.04, 1.14 and 0.80 during March, April, May, June, July and August, respectively.
•The highest water use efficiency values ( 0.247 and 0.266 kg seed cotton / m3 water consumed in 2011 and 2012 seasons, respectively ) were recorded under irrigating cotton crop at 30 % ASMD and applying 85 kg N/fed level interaction.
•Based on the obtained WUE results, it is advisable to irrigate cotton crop at 50% ASMD regime and applying N - fertilizer at 75 or 85 kgfed-1 levels in order to accomplish acceptable water productivity and cotton seed yield figures under Fayoum Governorate conditions.
Keywords: (Irrigation regimes, N-fertilization levels, cotton crop , water relations, Water use efficiency, crop coefficient . )
