Some effects of f oliar spray of zinc sulphate on growth, yield and fruit quality of guava (Psidium guajava L.) J. S. ARORA and J. R. SINGH College of Agriculture, Banaras Hindu University, Varanasi-5, India Summary Responses on various characters of guava trees recovery was observed with zinc spray. The zinc due to foliar spray of zinc were studied in the field spray also significantly reduced the time for fruit trial. The guava trees were sprayed with 0.0%, maturity and increased fruit yield significantly. 0.2% and 0.4% zinc sulphate solutions during July The significant improvement was also recorded on 1966 and 1967. Significant improvement in growth fruit weight, length, diameter, reducing sugars, characters, i.e., elongation of terminal shoot, number Vitamin C, pectic substances and total soluble solids, of leaves, leaf area per shoot and chlorophyll and significant reduction in acidity. Introduction The correction of zinc deficiency by foliar application has been the subject of several investigations in past years8, 6, 8, 9,1 "4,17,18 working with guava16'20~, it was observed that spray of zinc sulphate in summer was useful in controlling the deficiency. Beneficial effects of zinc spray on growth2,8'9'19, yield1'5'8,16,17,21~ and quality of fruits1,7,8,11,12> have also been recorded. Therefore, present investigation was undertaken with the objective of determining the effects of zinc spray on growth, yield and quality of guava fruits. Materials and Methods The present experiment was conducted on guava var. `Allahabad Saf eda' during 196667 and 196768 in the Horticultural Garden. The age of trees was five years and selected trees were uniform in size, vigour and bearing condition. The selected trees were sprayed with three concentrations of zinc sulphate, i. e., 0.0%, 0.2% and 0.4% with half amount of hydrated lime on 11th July 1966 and 11th July 1967 from 10.00 A. M. to 5.00 P. M. The treatments were replicated three times. In the present experiment only winter crop (main crop) was taken and rainy season crop was omitted by withholding irrigation and hand picking of flowers. The growth characters were recorded upto only 15th January after the treatment in both the years at the interval of two months, i. e., 15th September, 15th November and 15th January. Elongation of terminal shoots (cm), number of leaves and leaf area per shoot were recorded of 10 shoots per tree. For the percentage of chlorosis, 50 leaves were selected at random per tree and were classified into two categories, green and chlorotic, and percentage was calculated. For statistical analysis, the averages of two years were used. Period of maturity, the difference in days required for maturity, was recorded and yield of fruits was recorded on the basis of total number of fruits harvested from the tree at maturity which was judged by the colour and softness. Received for publication March 27, 1970. 1
208 Jour. Japan. Soc. Hort. Sci. 39 (3) The data on physicochemical composition of fruits at harvest are based on the analysis of ten fruits of average size and maturity, plucked from four sides of the tree at random. The fruit weight, length and diameter were recorded. The acidity was determined by titrating against N/10 NaOH solution, using phenolphthalein as an indicator. Sugars were determined by Fehling solution method, using methylene blue indicator13~. The ascorbic acid (vitamin C) was estimated by the 2 : 6 dichlorophenolindophenol dye method and the content of pectic substances was estimated by the method described by Carre and Haynes4~. Total soluble solids were determined by hand ref ractometer and values were corrected for 20 C. For statistical analysis, year was included as age factor. Results 1. Effect of zinc spray on growth characters. Elongation of terminal shoots was significantly increased by zinc spray. Maximum increase (50.5%) over control was exhibited by 0.4% spray. The age factor also produced significant effect and it was significantly reduced with the advancement of season. The per cent distribution of the season showed that 43.3% elongatton of terminal shoot took place upto 15th September, whereas 33.8% and 22.9% upto 15th November and 15th January, respectively (Table 1). The number of leaves per shoot was significantly improved by zinc spray. The maximum increase (41.0%) in number of leaves was obtained under the influence of 0.4% spray. The age factor showed a similar trend as for elongation of terminal shoot. Table 1. Effect of zinc concentrations and age on growth characters of guava.
ARORA SINGH : Effects of f oliar spray of zinc sulphate on guava 209 Table 3. Effect of zinc spray on physicochemical composition of guava fruits. There was significant effect of zinc spray on leaf area per shoot and about 100 per cent increase was recorded under 0.4%, whereas only 51.3% was due to 0.2% spray. The age factor showed quite similar trend to elongation of terminal shoot. The interaction between concentrations and age showed that maximum leaf area (188.25 sq. cm) was produced by 0.4% spray on 15th September (Table 1). The most striking and favourable effect was obtained on leaf chlorosis which was controlled successfully. Both concentrations showed significant recovery in chlorosis and maximum percentage recovery (96.1%) was observed under 0.4% spray (Table 1). 2. Period of maturity and yield. Period of maturity was significantly reduced due to the treatment. The fruits from check trees took 78 days to reach the maturity, whereas fruits from sprayed trees took 70 and 66 days under 0.2% and 0.4%, respectively. The most outstanding and promising result was obtained with regard to yield. Both the concentrations of zinc increased the yield of guava fruits significantly and 100 per cent increase in yield under 0.4% spray (Table 2) was recorded. 3. Physicochemical composition. The beneficial effect of zinc spray was recorded on physicochemical composition of fruits at harvest. There was significant increase in weight and length of fruits and maximum percentage of increase was exhibited under 0.4% spray (Table 3). There was no significant effect on diameter of fruits but 5.88% and 8.37% increase was recorded under 0.2% and 0.4% spray, respectively. 3
210 Jour. Japan. Soc. Hort. Sci. 39 (3) The fruit acidity was significantly reduced by zinc treatment and maximum reduction of 17.39% was observed under 0.4% spray. Reducing and non-reducing sugars were also significantly increased by zinc treatment and maximum increase was noted under 0.4%. The vitamin C, pectin and total soluble solids content of fruits were also improved significantly and maximum increase in vitamin C (7.22%) and total soluble solids content of fruits (16.90%) was observed under. 0.4% spray, whereas pectin content (19.29%) was recorded Discussion under 0.2% spray. Present findings revealed the beneficial effects of zinc spray on growth, yield and quality of guava fruits. Elongation of terminal shoot, number of leaves and leaf area per shoot were significantly improved under the influence of 0.4% spray. After long spell of heat, when plants start new growth with the commencement of rains, there is great need of nutrients for luxuriant growth. The limitation of any major or minor element might check the growth and might affect the other physiological and biochemical processes within the plants. Thus, spraying at the critical period might have proved helpful to cause more luxuriant growth. The observations recorded on 15th September indicated that the percentage of chlorotic leaves was diminished from 69.06 to 6.28 or 4.01 by spraying 0.2% and 0.4% zinc sulphate, respectively. This gave clear cut indication that trees became more active by getting recovered from chlorosis and efficient growth started. Similar results have also been recorded in guava16,20, pear2~, fig21), and citrus8~. The period of maturity was significantly reduced and it was due to more hastened fruit development and finally due to earliness in maturity. The most outstanding effect of zinc spray was noted on yield. Though the role of zinc in plants is not very clearly and completely understood but it is universally claimed to be an essential microelement and it is considered indispensable for the growth of all organisms. The radical improvement in yield of grape1'5, pomelo and lemon8), mandarin16> and fig21) due to zinc spray have also been recorded. The physicochemical composition of guava fruits was greatly improved due to zinc spray and maximum effect was produced mainly under 0.4% spray. The spraying of zinc at appropriate time might have helped in early and better start of fruit development due to efficient synthesis of organic compounds. A reduction in acidity might be due to accumulation of reducing and non-reducing sugars. The vitamin C, pectin and total soluble solids contents of fruits were also improved. An improvement in physicochemical composition of apple11, pomelo and lime8~, and orange7,12~ fruits has also been reported. All these effects indicated that zinc played an important role in maintaining a high efficiency of various enzymes and other elements in improving the general health and vigour of guava trees. Acknowledgements The authors are thankful to Dr. K. Matsumoto, Prof. of Citriculture, College of Agriculture, Ehime University, Matsuyama, for his criticism of the manuscript. Supported by ICAR, New Delhi to J. S. Arora. 4
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