Abstract:
Abstract: For developing citrus drought resistance and water saving cultivation techniques in karst mountainous area, the 12 years old Newhall navel orange was used as the testing material to study the effects of cave irrigation, surface irrigation and no irrigation (CK) on the growth of new shoot and fruit, nutrient element contents in the leaves, fruit yield and quality in karst mountainous area. The results showed that the sprouting period of navel orange under cave irrigation and surface irrigation was 30 d earlier than that of no irrigation. The spring shoot growing period and flowering period of navel orange under cave irrigation was 3-7 d earlier than that of surface irrigation and 30 d earlier than that of no irrigation. Under the same irrigation amount, cave irrigation and surface irrigation both could obviously improve the spring shoot growth of navel orange. However, cave irrigation was the best at increasing the number, length, diameter of spring shoot, the number of spring shoot leaf and its leaf area. Its effect on improvement of navel orange spring shoot growth was more obvious than that of surface irrigation. The navel orange leaf age was 26 and 25 months in cave irrigation and surface irrigation respectively. Old leaves fell off in late March to the middle of April and early March to late March in each year in cave irrigation and surface irrigation respectively. Cave irrigation was the best at maintaining leaf healthy and extending leaf life. Leaf life in no irrigation was the shortest, which old leaves fell off in middle of December to late December in each year and the leaf age was only 20 months. The fruits of cave irrigation matured in normal times. The fruit-coloring beginning period of surface irrigation was about 7 to 10 d earlier than that of cave irrigation. The fruit-coloring beginning period of no irrigation was more than 18 and 22 d earlier than that of cave irrigation and was more than 9 and 13 d earlier than that of surface irrigation. Cave irrigation could obviously improve the nutritional condition in navel orange tree. The contents of N、P、K、Mg、Fe、Mn、Zn and B in navel orange leaf under cave irrigation increased a lot. By comparison of the leaf analysis nutrition diagnosis classification standard of citrus, the contents of all kinds of nutrient elements in navel orange leaves reached the optimum values levels under cave irrigation. Cave irrigation could improve fruit growth and quality more obviously compared with surface irrigation and no irrigation. The average weight per fruit, contents of soluble solids and total soluble sugar in sarcocarp and percentage of fruit juice were the highest in cave irrigation. There was significant difference between cave irrigation and surface irrigation, no irrigation (p<0.05). Under the same irrigation amount, cave irrigation played a best role in effectively using water, improving navel orange grow, increasing the yield, improving the quality and nutritional status in navel orange tree. This study can provide a reference for citrus water-saving irrigation in karst mountainous area.