Effect of Irrigation Interval, Humic Acid and Methanol Foliar Application on Morphological Traits, Yield and Yield Components of Cichorium intybus L.

Iran with mean annual precipitation of 240 mm is considered located in arid zones of the world. Water deficit reduces plant growth and development by affecting various physiological and biochemical processes. Methanol foliar application is a method which increases crop CO2 fixation in unit area. Recent investigation showed that C3 crops yield, and growth increased via methanol spray and methanol may act as C source for these crops. Generally, the major role of this substance is to prevent negative effects of stresses on crops via reduction of photo respiration. The application of organic matters, such as humic substances have inhibitory effects of drought stress by improving the physical and chemical properties of soils, increasing soil water retention and providing the nutrients during plant growth. The objective of the present study was to examine the possibility of increasing water use efficiency and tolerance to water deficit stress by using humic acid and methanol foliar application and also influence of methanol and humic acid application on yield and yield components of Cichorium intybus L. under water deficit stress in Birjand, Iran.

This research was carried out as factorial split-plot layout based on randomized complete block design with three replications in the research farm of Islamic Azad University of Birjand, Iran in 2015. In this research, irrigation interval was considered as main factor with three levels (irrigation after 70, 140 and 210 mm cumulative evaporation from evaporation pan class A), the factorial of methanol spray at two levels (0 and 21 % V/V) and humic acid at two levels (0 and 10 L.ha-1) were considered as sub factor. The texture of the soil in research farm was loam with the pH of 8.2, electrical conductivity of 3.23 dS.m-1 whose organic carbon, total N, P, and K content was 0.3%, 0.033%, 6.8 mg.kg-1 and 133 mg.kg-1 at the depth of 0-30 cm, respectively. All data were analyzed by MSTAT-C statistical software and means were compared by Duncan’s Multiple Range Test at 5% level.

The results showed that irrigation after 210 mm cumulative evaporation compared to irrigation after 70 mm of cumulative evaporation significantly reduced stem diameter, branch number of main stem and 1000-grain weight by 30.6, 46 and 35.5%, respectively. The means comparison showed that 21% V/V methanol spray significantly increased 1000- grain weight by 15.3%. Also, application of 10 L.ha-1 humic acid significantly increased stem diameter, aken number per plant, seed number per plant, 1000- seed weight and water use efficiency by 16.7, 8.9, 10.6, 13.2 and 14.3 % respectively as compared with no application of humic acid treatment. Means comparison of interaction between irrigation and methanol revealed that the highest seed yield (57.2 g.m-2) and biological yield (423.4 g.m-2) were produced under the treatment of irrigation after 70 mm cumulative evaporation with methanol spray. It seems that although methanol application at irrigation intervals after 70 and 140 mm accumulation evaporation from the evaporation pan increased seed and biological yield but methanol application in severe water deficit stress conditions (irrigation interval of after 210 mm cumulative evaporation) probably due to the reduction in stomatal conductance and absorption, has not been able to change dramatically these traits. Also, means comparison of interaction between irrigation and humic acid indicated that highest seed yield (55.5 g.m-2) and biological yield (415.1 g.m-2) were produced under the treatment of irrigation after 70 mm cumulative evaporation with humic acid application. Increasing of low water stress in vegetative growth stage reduces the absorption of water and nutrients, chlorophyll content and relative humidity of leaves, thus decreased vegetative growth, leaf photosynthesis and production of assimilate but humic acid application significantly increases chlorophyll index and relative humidity of leaves. Hence the result of these positive effects of humic acid application was the improvement of yield components and seed and biological yields of chicory, even under conditions of water deficit stress. Moreover, means comparison of interaction between irrigation and methanol showed that the highest water use efficiency for seed production (66.7 g.m-3) belonged to treatment of irrigation after 140 mm of cumulative evaporation and methanol application.

Overall, results of this study showed that treatment of irrigation after 70 mm cumulative evaporation with humic acid application or methanol spray could be suggested for chicory cultivation in Birjand, Iran.