1. Mixture of Saline and Non-Saline Irrigation Water Influences Growth and Yield of Lettuce Cultivars under Greenhouse Conditions A. A. Alsadon, M. A. Wahb-allah, and S. O. Khalil. Department of Plant Production, College of Food and Agricultural Sciences, King Saud University P.O. Box 2460, Riyadh 11451, Saudi Arabia

3.  In arid and semi-arid climates, most of water require- ments for crops are supplied through irrigation water which normally contains large amounts of dissolved salts.  Therefore, salinity control is often considered a major objective of irrigation management. INTRODUCTION  When water resources are limited and the cost of non- saline water becomes high, crops of moderate to high salt tolerance can be irrigated with saline water.

4. Introduction (Continued)  There are two water management strategies to utilize saline water for irrigation: 1.Blending: (Mixture of saline with non-saline water at different ratios). 2.Cyclic: (Alternative irrigation with saline and non-saline water).

5.  Cyclic management of good quality water with saline water is easier than mixing water from different sources because it does not require reservoirs. Introduction (Continued)

6.  Lettuce (Lactuca sativa L.) is the most popular amongst the salad vegetable crops and has high cash value.  One of the major factors influencing growth and yield of lettuce is water quality.  Lettuce is classified as moderately sensitive to salinity.  Salinity affects both vegetative growth and head quality.

9.  The objectives of this study were: OBJECTIVES b)To evaluate salinity tolerance of lettuce cultivars under cyclic irrigation treatments. a)To determine the effect of cyclic irrigation treatments on growth and yield of crisp head lettuce cultivars.

11.  This study was conducted during the two winter seasons of 2005 and 2006 at the Agricultural Research and Experiment Station in Dirab near Riyadh, Saudi Arabia. MATERIALS & METHODS  Seeds of three crisp head lettuce cultivars; namely Sahara, Sharp Shooter and Summer Time were sown in plastic trays.  Four-weeks old seedlings, uniform in size, were transplan- ted into soil in the fiberglass greenhouse.

12. Materials & Method (Continued)  Two sources of irrigation water were used: a)Well water with EC 4.5 dS.m-1 (saline water). b)Desalinized water with EC 0.5 ds.m-1 (non-saline water).

14. Materials & Method (Continued) Table 1. Chemical analysis of the two sources of irrigation water. CharacteristicsWell waterDesalinized water EC (ds m -1 ) pH Ca + + meq l -1 Mg + + meq l -1 Na + meq l -1 K + meq l -1 HCO 3 – – meq l -1 Cl- meq l -1 NO 3 – ppm SO 4 – – meq l -1 SAR 4.50 7.1 11.0 10.5 14.65 0.56 4.7 12.9 5.2 14.61 4.66 0.50 6.47 0.73 0.16 3.5 0.1 0.325 1.85 2.69 0.9 5.11

15. Materials & Method (Continued)  Drip irrigation system was applied six days per week using cycling water management strategy.  Irrigation treatments started 5 days after transplanting.

16. Materials & Method (Continued) No.Treatment T1Irrigation with desalinized water for the whole growth period. T2 Irrigation with desalinized water for four days and with well water for two days. T3 Irrigation with desalinized water for three days and with well water for three days. T4 Irrigation with desalinized water for two days and with well water for four days. T5 Irrigation with desalinized water for one day and with well water for five days. T6Irrigation with well water for the whole growth period.  Six irrigation treatments were applied:

17. Materials & Method (Continued)  Plot area was 4 m 2 and included 32 plants. Planting distance was 25 cm and 50 cm between plants and rows, respectively.  Irrigation treatments were randomly allocated to the main plots while cultivars were arranged in the sub-plots.  The experimental layout was split-plot in randomized complete blocks design with four replications.

19.  Eighty days after starting the irrigation treatments, yield of crisp head lettuce of each sup-plot was harvested and weighted with and without outer leaves then converted into kg m -2 to determine total and net (marketable) yield.  Ten heads were randomly selected from each treatment to measure the following traits: head diameter and length, stalk length, bolting %, leaf dry mater %, average head weight, number and weight of outer leaves. Materials & Method (Continued)

21. RESULTS & DISCUSSION Influence of cyclic irrigation water treatments

22. Fig. 1. Influence of cyclic irrigation treatments on outer leaf number of lettuce cultivates over the two seasons 2005 and 2006 under greenhouse conditions. Results and Discussion (Continued)

23. Fig. 2. Influence of cyclic irrigation treatments on outer leaf weight of lettuce cultivars over the two seasons 2005 and 2006 under greenhouse conditions. Results and Discussion (Continued)

24. Fig. 3. Influence of cyclic irrigation treatments on average head weight of lettuce cultivars over the two seasons 2005 and 2006 under greenhouse conditions. Results and Discussion (Continued)

25. Fig. 4. Influence of cyclic irrigation treatments on total yield of lettuce cultivars over the two seasons 2005 and 2006 under greenhouse conditions. Results and Discussion (Continued)

26. Fig. 5. Influence of cyclic irrigation tratments on marketable yield of lettuce cultivars over the two seasons 2005 and 2006 under greenhouse condition. Results and Discussion (Continued)

27.  Continuous irrigation with well water (T6) significantly reduced total yield by 25 and 19.8% and reduced marketable yield by 27 and 32% in the first and second seasons, respectively. Results and Discussion (Continued)  All traits were less affected by T3 treatment (Irrigation with desalinized water for three days and with well water for three days).

28. Response of lettuce cultivars to cyclic irrigation treatments Response of lettuce cultivars to cyclic irrigation treatments

29. Fig. 6. Outer leaf number of lettuce cultivars as influenced by cyclic irrigation treatments over the two seasons 2005 and 2006 under greenhouse conditions. Results and Discussion (Continued)

30. Fig. 7. Outer leaf weight of lettuce cultivars as influenced by cyclic irrigation treatments over the two seasons 2005 and 2006 under greenhouse conditions. Results and Discussion (Continued)

31. Fig. 8. Average head weight of lettuce cultivars as influenced by cyclic irrigation treatments over the two seasons 2005 and 2006 under greenhouse conditions. Results and Discussion (Continued)

32. Fig. 9. Total yield of lettuce cultivars as influenced by cyclic irrigation treatments over the two seasons 2005 and 2006 under greenhouse conditions. Results and Discussion (Continued)

33. Fig. 10. Marketable yield of lettuce cultivars as influenced by cyclic irrigation treatments over the two seasons 2005 and 2006 under greenhouse conditions. Results and Discussion (Continued)

34.  Sahara showed good performance for average head weight and total yield under all irrigation treatments.  In the first season, Sahara significantly had the highest marketable yield and with no significant differences in the second season, respectively as compared to other culti- vars. Results and Discussion (Continued)

35. Interaction effects between irrigation treatments and lettuce cultivars

36. Results and Discussion (Continued)  The interaction results indicated that T3 (irrigation with desalinized and well water for three days each) was the most efficient treatment for all traits for the three cultivars.  Sahara cultivar is considered more salinity tolerant follo- wed by Summer Time then Sharp Shooter.

37. Total yield (kg m 2 ) and yield reduction (%) as influenced by cyclic irrigation treatments and lettuce cultivars. Cyclic Irrigation Treatments Cultivars SaharaSharp ShooterSummer Time Yield (kg.m 2 ) reduction % Yield (kg.m 2 ) reduction % Yield (kg.m 2 ) reduction % TI15.81204.36504.5180 TI25.7231.54.0826.54.5811.4 TI35.4426.43.9529.44.1089.1 TI44.64720.13.68015.73.93812.8 TI54.21027.63.68115.73.86214.5 TI64.30626.03.28224.83.43424.0 Results and Discussion (Continued)

38. Marketable yield (kg m 2 ) and yield reduction (%) as influenced by cyclic irrigation treatments and lettuce cultivars. Cyclic Irrigation Treatments Cultivars SaharaSharp ShooterSummer Time Yield (kg.m 2 ) reduction % Yield (kg.m 2 ) reduction % Yield (kg.m 2 ) reduction % TI14.88903.35203.4500 TI24.37310.52.88014.13.3931.7 TI34.20114.12.79016.72.91615.4 TI43.52727.82.65220.82.90415.8 TI53.37530.92.45626.72.66822.6 TI63.16835.22.39028.72.66422.8 Results and Discussion (Continued)

40.  The best cyclic irrigation treatment under the condition of this study was the irrigation with non-saline water for three days then followed by another three days with saline water. CONCLUSION  Total yield reduction was only 6.2 and 7.7% and marketable yield reduction was 17.0 and 16.6% at the first and second seasons, respectively and it was accompanied by an acceptable head quality.

41.  Therefore, it is recommended to apply this treatment for greenhouse crisp head lettuce production to reduce the high costs of water desalinization while maintaining high yield quantity and quality. Conclusion (Continued)