Effect of Foliar Application of Kaolin and Different Sources of Potassium on Yield, Growth and Physiological Characteristics of ‘Asgari’ Grapevine Under Rainfed Conditions

Document Type : Full Paper

Authors

• Saied Eshghi ¹
• Abbas Madadi Moghadam ²
• Niloufar Rajaei ³

¹ Department of Horticultural Science, School of Agriculture, Shiraz University, Shiraz, Iran

² Department of Horticultural Science, School of Agriculture, Shiraz University, Shiraz, ,Iran

³ Department of Horticultural Science. faculty of Agriculture, Guilan university, Rasht, Iran.

Abstract

Keywords

• Chlorophyll
• Grape Cluster
• drought
• fruit
• plant adaptation

Main Subjects

• Fruit Science

Extended Abstract

Introduction

Grape is one of the most popular small fruits, which is widely cultivated and consumed in Iran. The Fars province having the largest area under rainfed cultivation and annual production of grape, sits at the first place in the country. Changes in annual rainfall amounts and distributions cause uncertainty and high risk in rainfed cultivation and therefor decrease in rainfed crop production. The high intensity of sunlight and very high temperatures during the summer season are significant problems in many fruit growing regions of Fars province. Furthermore, drought can intensify these conditions and as a result, their adverse effects. To deal with these problems utilizing antiperspirants and improving plant nutrition, particularly with potassium, are applicable methods. As a new solution, spraying kaolin on the crowns of trees can be an effective technique for enhancing light reflection and reducing transpiration. This research was conducted in order to increase the adaptability of ‘Asgari’ grapevine against drought stress in rainfed conditions

Material and Methods

The present investigation examined the response of rainfed ‘Asgari’ grapevine to foliar application of  kaolin (6%) and different sources of potassium (1.5% and 3%) over two years. The study was carried out on 30 years old grapevines grown in commercial vineyard, located in Shiraz region. Potassium nitrate (1.5% and 3%), potassium sulfate (1.5% and 3%), and potassium chloride (1.5% and 3%) were sprayed alone or combined with 6% kaolin. Four replications of 14 treatments were conducted as randomized complete blocks design, with distilled water as the control treatment. Spraying was done in two stages. The first foliar spray was applied after fruit set (June 5) and the second one shortly before the fruit color change (July 25).

Results and discussion

Results showed that different sources of potassium (Potassium Nitrate, Potassium sulfate and Potassium chloride) increased berry weight, cluster weight, total soluble solid, chlorophyll and K content of leaf and fruit compared to untreated vines and had positive effect on relative water content. Whereas, potassium application given in different sources and different doses decreased the antioxidant enzyme activities and leaf  temperature compared to untreated vines. Kaolin treatment decreased berry weight, cluster weight, total soluble solid, total phenol, chlorophyll and relative water content compared to untreated vines. Kaolin treatment had negative impact on K content of leaf and fruit, whereas increased the antioxidant enzyme activities compared to untreated vines.

Conclusion

    This research tried to increase the adaptation of ‘Asgari grapevine’ to rainfed condition by foliar application of potassium in two concentrations or in combination with kaolin. Potassium sources in both concentrations were able to improve the morphological and physiological characteristics of the plant compared to the control treatment. The results showed the greater resistance of ‘Asgari grapevine’ to drought and heat stress, and increase in the yield compared to the control treatment. But the application of kaolin had no positive effect on studied traits, which may have been due to the inappropriate concentration used in the study.