A field trait was conducted at Nubaria Agricultural Research Station, EL-Behira Governorate, Egypt during two winter successive growing seasons of 2013/2014 and 2014/2015 on fodder beet (Beta vulgaris L.) variety Voro-shenger. The aim was to study the effect of three drip irrigation regimes i.e. Irrigation with amount of water equal 100% (I1), 80% (I2) and 60 %( I3) of potential evapotranspiration (ETp) and potassium fertilization at rates of 0, 57.12, 114.24 and 171.36 Kg K2O/ha.
Results of combining analysis revealed that increasing irrigation levels led to significant increase in crop growth rate (CGR) at (90-120) and (120-150) DAS, leaves and root fresh weight Kg/plant, leaves and root dry weight g/plant, root length and diameter as well as root, total yield ton/ha and total chlorophyll of leaves. Dry treatments significantly reduced the percentage of potassium (K %), crud protein (CP %), digestive crud protein (DCP %) and crud fiber (CF %). Whereas, the percentage of total soluble solid (TSS %) and total digestible nutrients (TDN %) significantly increased. The maximum percentage of Relative water content (RWC %) was obtained from wet treat-ment, while medium treatment at 80% of ETp give the maximum values of water utilization efficiency (WUtE).
Adding 171.36 KgK2O/ha significantly increased CGR at (90-120) and (120-150) DAS, Leaves fresh weight Kg/plant, leaves and root dry weight, root length and diameter, root and foliage yields as well as total yield ton/ha, total chlorophyll of leaves, DCP% and K%. While adding 171.36 and 114.3 KgK2O/ha significantly increased root fresh weight Kg/plant, CP% and CF% with insignificant difference. However, TDN% decreased by increasing potas-sium fertilization. Maximum RWC% and WUtE were obtained when plants received 171.36 KgK2O/ha.
The interaction between irrigation regimes and potassium fertilization levels had significant effect on all traits under study except CGR at (90-120) DAS, root diameter, foliage yield ton/fed, total chlorophyll of leaves, K% and TSS%. The highest values of CGR (120-190), Leaves Fresh weight Kg/plant, leaves and root dry weight g/plant, CP%, CF% as well as DCP% and RWC were achieved from wet treatment (100% of ETp) in combination with 171.36 KgK2O/ha. While irrigation with 100%, 80% of ETp and 171.36 KgK2O/ha gave the highest values for root length, root and total yield ton/ha as well as WUtE with insignificant difference. However irrigation with 100% of ETp combined with 114.24 and 171.36 have the highest values for root fresh weight Kg/plant with insignificant dif-ference. The maximum TDN% obtained from dry treatment (60% of ETp) without potassium fertilization.
According to profitability assessment, the highest net income and investment ratio as an average of two growing seasons were obtained when plants watered by amount of water equal 80% of ETp and received 171.36 KgK2O/ha.