A field experiment was carried out at Ismailia Agricultural Research Station, Agricultural Research Center, Ismailia governorate (Lat. 30° 35' 30" N, Long. 32° 14' 50" E, 10 m a.s.l.), Egypt, during 2018/2019 and 2019/2020 growing seasons to determine the suitable rate of potassium silicate that could mitigate the effect of irrigation water deficiency on productivity of both faba bean and sugar beet under intercropping system. Three irrigation treatments (I1 (120% ETo), I2 (100% ETo) and I3 (80% ETo)) and three rates of sprayed potassium silicate (Si0 unsprayed-control), Si1 (200 ppm) and Si2 (300 ppm)) were used. The results showed the highest intercropped faba bean and sugar beet yields and their components were attained under spraying with Si1 under the three irrigation treatments in both growing seasons. Furthermore, spraying intercropped faba bean and sugar beet with Si1 under I2 and I3 relieved water deficiency and increased the yields, compared to no spraying. The 2-year average values of applied irrigation water to sugar beet intercropping system were 9252, 7730, 6184 m3/ha under I1, I2 and I3, respectively. Using cereal units analysis revealed that the highest values WUE and WP were found under application of I3, namely 0.29 CU/mm and 0.36 CU/mm for WUE and 0.24 CU/mm and 0.25 CU/mm for WP in the first and second seasons, respectively. The highest values of WER were 1.41 and 1.42 obtained from the interaction between irrigation with I2 and spraying with Si1 in the first and second season, respectively. Thus, it could be concluded that to mitigate the effect of irrigation deficiency applied to faba bean intercropped with sugar beet, spraying with 200 ppm of potassium silicate should be applied.
Keywords: Deficit irrigation, potassium silicate, Cereal Units analysis, water use efficiency, water productivity, waterequivalent rati
