INFLUENCE OF WATER DEFICIT DURING GROWTH STAGES AND NITROGEN FERTILIZATION RATES ON PRODUCTIVITY, OIL CONTENT AND SOME WATER RELATIONS OF CANOLA CROP (Brassica napus L.) IN HEAVY CLAY SOILS.

A field investigation was conducted at the experimental farm, Sakha Agricultural Research Station, Kafr El-Sheikh Governorate during the two successive winter growing seasons 2012/2013 and 2013/2014 to investigate the effect of irrigation treatments (water deficit, during the growth stages) and nitrogen fertilization rates on productivity, oil content and some water relations of canola crop in the North Middle Nile Delta region. The station is situated at 31 0 07ˉ N Latitude and 30 0 57ˉ E longitude. It has an elevation of about 6 metres above mean sea level (MSL). A split plot design with three replicates was used in this present study. The main plots were occupied by irrigation treatments which were I1 (traditional irrigation, as practice by local farmers in the studied area, 6 irrigations), I2 (sowing irrigation + first post planting irrigation (mohayaa) + one irrigation during flowering growth stage only, 3 irrigations), I3 (sowing irrigation + mohayaa + one irrigation during seed filling only, 3 irrigations) and I4 (sowing irrigation + mohayaa + one irrigation during flowering growth stage + one irrigation during seed filling only, 4 irrigations), while, submain plots were randomly assigned by nitrogen fertilization rates 15, 30, 45, and 60 kg N/ fed. for N1, N2, N3 and N4, respectively. The main results can be summarized as follows:* The highest values for irrigation water requirements were recorded under irrigation treatment I1 (Traditional irrigation) and the values are 63.16 cm (2652.72 m 3 / fed.) and 62.14 cm. (2609.88 m 3 /fed.). Meanwhile, the lowest values were recorded under irrigation treatment I3 and the values are 34.87 cm. (1464.54 m 3 / fed.) and33.70 cm. (1415.40 m 3 / fed.) in the first and second growing seasons, respectively. Generally, the values of irrigation water requirements in the two growing seasons can be descended in order I1 > I4 > I2 > I3. Concerning, water consumptive use, the highest values were recorded under irrigation treatment I1 and the values are 36.80 cm. (1545.39 m 3 / fed.) and 36.40 cm. (1528.80 m 3 / fed.). Meanwhile, the lowest values were recorded under irrigation treatment I3 and the values are 23.58 cm. (990.15m 3 / fed.) and 23.20 cm. (974.40 m 3 / fed.) in the first and second growing seasons, respectively. Generally, the values of water consumptive use can be descended in order I1 > I4 > I2 > I3 in the two growing seasons. The values of water consumptive use were slightly affected by nitrogen fertilization rates, where, the values can be descended in order N4 > N3 > N2 > N1 in the two growing seasons. *Regarding, consumptive use efficiency (Ecu), water productivity (WP) and productivity of irrigation water (PIW), the highest overall mean values for Ecu were recorded under irrigation treatment I4. Meanwhile, for WP and PIW were recorded under irrigation treatment I3 and the values are 72.41 %, 1.42 kg/ m 3 and 0.97 kg/ m 3 for Ecu, WP and PIW, respectively. Concerning, the effect of nitrogen fertilization Moursi, E. A. et al. 1306 rates, the overall mean values for Ecu, WP, PIW can be descended in order N4 > N3 > N2 > N1. Concerning, seed yield, some yield attributes, seed oil (%),oil yield (kg/ fed.), number of racemes and number of days to 50 % flowering were significantly affected by irrigation treatments except number of racemes in the two growing seasons and 1000 seed weight (g.) in the first season which not significantly affected by irrigation treatments, for all the studied parameters. The highest mean values were recorded under irrigation treatment I1 in comparison with I2, I3 and I4 in the two seasons. Concerning, the effect of nitrogen rates on canola studied characters, it gave highly significant effect in both seasons. Increasing nitrogen rates from 15 to 60 kg N/ fed. increased all characters except seed oil content which decreased by increasing nitrogen fertilization rates in the two seasons. Regarding, the interactions between irrigation treatments (I) and nitrogen fertilization rates (N), there was significant effect on seed yield kg/ fed. , seed yield gm/ plant, number of days to 50 % flowering, seed oil content (%) and oil yield kg/fed. In the second season only and plant height in the two seasons, while, the other studied characters were insignificantly affected by the interaction between (I * N).