干旱区生态环境知识资源中心

The Sultanate of Oman is an arid country (temperature ranges 7 to 50 degrees C) located in the southeast corner of the Arabian Peninsula having a coastal line of almost 1700 km, bordering three seas: the Arabian Gulf, the Sea of Oman and the Arabian Sea. Rainfall (scarce and random) ranges between 50 to 300 mm with an annual mean of less than 100 mm. Irrigation water is highly scarce and groundwater (major part saline) is the main resource which ultimately causes soil salinization resulting in growth and yield losses of crops and desertification. Date palm is the major crop. Abandoning of date palm orchards has increased due to very low yields because of soil and water salinity. The situation required a systematic research. Therefore, this experimental work was conducted to investigate the water salinity tolerance of important date palm varieties. The study was performed to screen tissue derived date palm varieties for tolerance to water salinity [ Treatments: A. Categories of irrigation water: ECiw 3 (Control), 6, 9, 12, 15 and 18 dS m(-1) B. Date palm varieties: 'Khalas', 'Khunaizy' and 'Abunarenjeh']. A uniform dose of N=0.375, P=0.20 and K=0.30 kg plant(-1) year(-1) was applied. Growth parameters: plant height, plant girth, number of new fronds and length of fronds were recorded annually for two years coupled with soil and plant analysis. The research work was undertaken at the Agricultural Research Center (ARC) Rumais, Oman during the years 2006-08 (split plot design with four replications in a low EC sandy loam soil having very good drainage). Fresh water (EC 1.0 dS m(-1)) and the saline water (EC 35-40 dS m(-1)) were mixed in appropriate ratios to get the desired levels of ECiw. Data indicated a significant decrease in growth of all the three date palm varieties during irrigation for two consistent years with saline water of 6-18 dS m(-1) when compared with 3 dS m(-1). However, a 50% decline was recorded only at water EC 18 dS m(-1). Therefore, date palm could be regarded as highly salt tolerant. Much difference between salt tolerance potential of the three varieties was not recorded, only 'Khunaizy' showed a little edge over the other two. A significant increase in leaf Na and decrease in K was observed while Cl remained unchanged. The physiological basis of salt tolerance in date palm was found as a strict control on Na and Cl concentration in leaves and keeping up the K content. It can be recommended that Date palm plants (seedlings of varieties 'Khalas', 'Khunaizy' and 'Abunarinjah') can be irrigated with saline water during vegetative growth. However, a significant decline in growth will be expected when the EC of irrigation water exceeds 9 dS m(-1) that may reach up to 50% with water EC 18 dS m(-1) (in sandy soil with very good drainage). The research has to be continued on irrigation with saline water at later stages of growth; the reproductive, fruit setting and maturity stages.