TWO FIELD experiments were conducted at Giza Agriculture Research Station during the two growing seasons of 2015 and 2016. The investigation was carried out to study the effect of different irrigation intervals, i.e., two weeks and three weeks in combination with different sowing dates, i.e., 1st April ,15th April , 1st May and 15th May on Guar forage crop (Cyamopsis tetragonoloba L.,var. Shandaweel 1 ) crop - water relations, yield and yield components under middle Egypt conditions. The main results could be summarized as follows:-
The number of applied irrigations and seasonal water consumptive use (CU) were increased with decreasing irrigation interval days which the shortage irrigation interval (irrigation every 15 days) recorded the maximum CU under all sowing date with an overall average being 442 and 453 mm for first and second season, respectively. The same trend was found with sowing date, with plant sown in 1st April consumed more water than the other sowing dates. The lowest water use efficiency (WUE) was recorded under longer irrigation interval (irrigation every 21days) comparable to (irrigation every 15 days) and values of WUE differed due to sowing date, which the S4 (sowing at 15th May) gave the lowest WUE while, S1( sowing at 1st April) obtained the highest value. The crop coefficient (Kc) values started small and increased to reach their maximum values in mid season under all sowing dates, then decline again until the crop maturity under all sowing dates.
All yield and yield component traits were markedly affected by sowing date and irrigation interval. Most of the studied traits except leaves/stem ratio as well as fiber %, decreased by delaying sowing date from 1st April to 15th May. Decreasing irrigation interval days from 21 to 15 days significantly increased plant height, number of branches/plant, fresh and dry yield ton fad-1, while leaves/stem ratio and crud fiber% which increased by increasing irrigation intervals from 15 to 21 days.