Scientia Horticulturae, 14 (1981) 235--244 235 Elsevier Scientific Publishing Company, Amsterdam - - Printed in The Netherlands

EFFECT OF NUTRIENT SPRAYS ON GRANULATION AND FRUIT QUALITY OF 'DANCY TANGERINE' MANDARIN

ROOM SINGH ~ and RANJIT SINGH

Division o f Horticulture and Fruit Technology, Indian Agricultural Research Institute, New Delhi-110012 (India)

1Fruit Research Station, Punjab Agricultural University, Bhatinda 151001, India

(Accepted for publication 25 June 1980)

ABSTRACT

Singh, R. and Singh, R., 1981. Effect of nutrient sprays on granulation and fruit quality of 'Dancy tangerine' mandarin. Scientia Hortic., 14: 235--244.

The efficacy of foliar spray of various macro- and micro-nutrients in different con- centrations on granulation and fruit quali ty in 'Dancy tangerine' (Citrus reticulata Blanco ), a cultivar which suffers badly from granulation, was studied in the research orchard at the Punjab Agricultural University during 1974--75 and 1975--76. The com- bined spray of zinc sulphate 0.5% + copper sulphate 0.5% reduced the incidence of granulation to 45% from 78% in control during 1974--75 (42% reduction over control). Potassium nitrate 1% (included in the second year of experimentat ion) gave the lowest granulation of 50% against 74% in control. The former t reatment followed it closely. Low concentrat ions of boric acid (25 and 50 mg 1-1 ) and calcium hydroxide 2% also markedly reduced the disorder. All these treatments improved the fruit quali ty and gave much more pulp, juice, T.S.S., sugars and ascorbic acid content than control, and they also markedly reduced peel, rag, total acidity and starch during both years. The applicat ion of nutrients is, therefore, considered to be a successful tool in reducing granulation in this cultivar of mandarin.

INTRODUCTION

C i t r u s g r a n u l a t i o n is a s e r i o u s p r o b l e m in m o s t o f t h e c i t r u s - g r o w i n g c o u n t r i e s . I n g r a n u l a t i o n , t h e j u i c e sacs b e c o m e h a r d a n d d r y , t h e f r u i t be - c o m e s u n m a r k e t a b l e , a n d t h e g r o w e r s s u f f e r h e a v y losses . T h e m a n d a r i n c u l t i v a r s ' D a n c y t a n g e r i n e ' a n d ' K a u l a ' , a n d s w e e t o r a n g e c u l t i v a r s ' H a m l i n ' , ' M o s a m b i ' a n d ' B l o o d R e d ' s u f f e r f r o m g r a n u l a t i o n m o r e t h a n o t h e r s . E f f e c t i v e c o n t r o l m e a s u r e s a r e l a c k i n g . A l i m i t e d suc c e s s has b e e n r e p o r t e d b y B a r t h o l o m e w e t a l . ( 1 9 4 1 ) a n d AwaslLhi a n d N a u r i y a l ( 1 9 7 2 ) w i t h c a l c i u m a p p l i c a t i o n .

T h e d e g r e e o f g r a n u l a t i o n w a s f o u n d t o b e h i g h e r o n t r e e s w h i c h w e r e d e f i c i e n t in v a r i o u s m a c r o - a n d m i c r o - e l e m e n t s ( A w a s t h i , 1 9 6 9 ) . F u r t h e r , t h e t r a n s l o c a t i o n o f p h o t o s y n t h a t e s t o w a r d s t h e f r u i t s in g r a n u l a t i o n is

0304-4238/81/0000--0000/$02.50 01981 Elsevier Scientific Publishing Company

236

restricted (Chakrawar, 1975). Boron and potassium have been reported to facilitate this transloca~ion, and these elements are the obvious means to manipulate the translocation process. Thus, in the present s tudy an a t tempt was made to control granulation with the aid of some macro- and micro- nutrients in different concentrations and combinations.

MATERIALS AND METHODS

An experiment consisting of 9 treatments of various nutrients, as specified in Table I, was laid out during 1974--75 on 27 'Dancy tangerine' plants (planted in 1966) in a randomised block design with 3 replications. The nutrients were sprayed 3 times at monthly intervals starting from 10 Sep- tember 1974. Some modifications were made during 1975--76 and 4 appli- cations were given at month ly intervals starting on 7 August 1975. Five new treatments were included and 4 treatments, which were not found effective during 1974--75, were dropped. Thus, 10 treatments were repli- cated 3 times in a randomised block design on 30 trees during 1975--76.

The incidence of granulation was expressed as percentage of fruits affected by the disorder. The degree of granulation (severity of disorder in the gran- ulated fruit) was based on the visual estimation of the affected portion of the fruit. It was placed in one of 5 categories: < 10;10--25; 25--50; 50--75; 75--100%. These observations were recorded at the time of harvest, during January of each year, by cutting 50 randomly selected fruits. Twenty fruits were used to determine the peel, pulp, juice and rag percentage on fresh- weight basis.

The total soluble solids (T.S.S.) were determined with a hand-refractometer and the readings corrected for temperature. The total acidity, sugars and ascorbic acid contents were estimated with the methods given in A.O.A.C. (1970). The starch was determined colorimetrically (McCready et al., 1950). Ca, Mg, K, Zn, Cu and B were not determined.

RESULTS

G r a n u l a t i o n ( T a b l e I) . - - The minimum incidence of granulation was obtained in the combined spray of zinc sulphate 0.5% + copper sulphate 0.5%, reduc- t ion being 42% over control during 1974--75. Boric acid 50 and 200 mg 1-1 and calcium hydroxide 2% also decreased the incidence of granulation to a satisfactory ievel (27--31% reduction). In t h e following year, potassium nitrate :1% gave the lowest granulation and it reduced the disorder by 32% over control. This t reatment was followed by zinc sulphate 0.5% + copper sulpl~ate 0.5%, boric acid 25 mg 1-1 and calcium hydroxide 2%, which treat- ments gave almost similar results.

With regard to the degree of granulation (part of the fruit affected), the combined spray of zinc sulphate 0.5% ÷ copper sulphate 0.5% gave the lowest value. The reduction was 30% over control. This t rea tment was followed by

237

c a l c i u m h y d r o x i d e 2%. D u r i n g 1 9 7 5 - - 7 6 , t h e l a t t e r t r e a t m e n t gave t h e l o w e s t d e g r e e o f g r a n u l a t i o n , t h e r e d u c t i o n b e i n g a b o u t 54% o v e r c o n t r o l . B o r i c a c i d 2 5 mg1-1 a n d t h e c o m b i n e d s p r a y o f z i n c s u l p h a t e 0 .5% + c o p p e r s u l p h a t e 0 . 5 % a l so m a r k e d l y r e d u c e d t h e d i s o r d e r a n d gave 53 a n d 50% r e d u c t i o n o v e r c o n t r o l , r e s p e c t i v e l y .

TABLE I ::

Effect of nutrient sprays on granulation in 'Dancy tangerine'. C.D. = Confidence difference (LSD). NS = not significant

Treatment and Incidence of granulation Degree of granulation concentrat ion (%) (%)

1974--75 1975--76 1974--75 1975--76

Control (water) 78 74 31 34 Calcium hydroxide 1% - - 61 - - 22 Calcium hydroxide 2% 56 54 23 15 Calcium hydroxide 4% - - 67 - - 27 Magnesium nitrate 1% 73 - - 26 - - Potassium nitrate 1% -- 50 - - 19 Zinc sulphate 0.5% 74 - - 33 - - Copper sulphate 0.5% 77 68 34 24 Zinc sulphate 0.5% + 45 51 22 17

copper sulphate 0.5% Boric acid 25 mg 1-1 - - 53 - - 16 Boric acid 50 mg 1-1 57 62 26 23 Boric acid 100 mg 1 -~ - - 64 - - 25 Boric acid 200 mg 1-1 54 - - 29 - - Boric acid 500 mg 1-1 67 - - 32 -- C.D. at 5% 8.5 9.7 7.2 5.5 C.D. at 1% 11.7 13.3 NS 7.5

Peel, pulp, juice and rag (Table II). -- M o s t o f t h e t r e a t m e n t s m a r k e d l y re- d u c e d t h e p e e l a n d i n c r e a s e d t h e p u l p c o n t e n t d u r i n g b o t h y e a r s . I n 1 9 7 4 - - 75 , t h e c o m b i n e d s p r a y o f z i n c s u l p h a t e 0 .5% + c o p p e r s u l p h a t e 0 . 5 % p r o - d u c e d t h e l o w e s t p e e l % a n d t h e h i g h e s t p u l p %. B o r i c a c i d 50 m g 1-1 a n d c a l c i u m h y d r o x i d e 2% gave a l m o s t s i m i l a r r e s u l t s . H o w e v e r , in t h e f o l l o w i n g y e a r , p o t a s s i u m n i t r a t e 1% gave t h e l o w e s t p e e l % a n d t h e h i g h e s t p u l p %. T h e c o m b i n e d s p r a y o f t h e s u l p h a t e s o f z inc a n d c o p p e r , 0 . 5% e a c h , a n d b o r i c a c i d ( 2 5 m g 1-1) f o l l o w e d c l o s e l y a n d gave a l m o s t s i m i l a r r e s u l t s .

T h e h i g h e s t j u i c e % w a s o b t a i n e d a f t e r t h e c o m b i n e d s p r a y o f z i n c s u l p h a t e 0 . 5 % + c o p p e r s u l p h a t e 0 .5% a n d i t gave 1 2 . 5 % i n c r e a s e o v e r c o n t r o l d u r i n g 1 9 7 4 - - 7 5 . C a l c i u m h y d r o x i d e 2% a n d b o r i c a c i d 5 0 m g 1-1 i n c r e a s e d t h e j u i c e c o n t e n t b y o v e r 9 .3%. T h e f o r m e r t r e a t m e n t ( Z n + Cu) gave t h e h i g h e s t j u i c e p e r c e n t a g e , w i t h a n i n c r e a s e o f 1 4 % in t h e f o l l o w i n g y e a r a l so . C a l c i u m h y d r o x i d e 2%, b o r i c a c i d 25 m g 1-1 a n d p o t a s s i u m n i t r a t e 1% i n c r e a s e d t h e j u i c e p e r c e n t a g e b y 1 0 - - 1 1 % o v e r c o n t r o l . T h e r e was n o m a r k e d r e d u c t i o n

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in the rag con ten t of the fruit during 1974--75. In the following year, zinc sulphate 0.5% + copper sulphate 0.5% gave the lowest rag %, the reduct ion being 16% over control.

Total soluble solids and sugars (Table III). The T.S.S., total, reducing and non-reducing sugars were highest in the combined spray of zinc sulphate 0.5% + copper sulphate 0.5% during 1974 75. This t rea tment increased the T.S.S. by 9.5%, total sugars by 18.8%, reducing sugars by 13.3% and non- reducing sugars by 24.2% over control. [t was followed by calcium hydroxide 2% for T.S.S. (6.3% increase), for total sugars (13.4% increase) and for non- reducing sugars (21.1% increase). Boric acid 50 mg 1 -~ was the next best t rea tment for reducing sugars (9.6%increase). Some newly included treat- ments gave promising results. The highest values for T.S.S. and total sugars were obtained from potassium nitrate 1%. An equal amount of total sugars was given by zinc sulphate 0.5% + copper sulphate 0.5%. The increase over control was 13.7% in T.S.S. and 19.2% in total sugars. Potassium nitrate 1% was fol lowed by calcium hydroxide 2% and the combined spray of zinc sulphate 0.5% + copper sulphate 0.5%, with an increase of about 11% in T.S.S. For total sugars, the next best t reatments were boric acid 25 mg 1 -~ and calcium hydroxide 2%, which gave about 16% increase over control. However, the highest % of reducing sugars was produced by the combined spray of zinc sulphate 0.5% + copper sulphate 0.5% and by boric acid 25 mg 1-1, with an increase of 26%. Potassium nitrate 1% was the next best t rea tment (23% increase for reducing sugars). Calcium hydrox ide 2% was the best t rea tment for non-reducing sugars and gave 23% increase over con- trol. Potassium nitrate 1% followed with an increase of 16%.

Total acidity, T.S.S. : acid ratio, ascorbic acid and starch content (Table IV). -- During 1974 75, the lowest acidity and starch and the highest T.S.S. : acid ratio and ascorbic acid were recorded in the combined spray of zinc sulphate 0.5% + copper sulphate 0.5%. This t rea tment reduced the total acidity by 33.4% and starch by 40.7% over control. The T.S.S. : acid ratio and ascorbic acid were mcreased by 61.9 and 31.6% over control , respec- tively. The nex t best t reatments were calcium hydroxide 2% and boric acid 50 mg 1-1. In the following year also, the combined spray of zinc sulphate 0.5% + copper sulphate 0.5% gave the lowest acidity and starch, reducing them by 38.2 and 35.3% over control , respectively. The highest T.S.S. : acid ratio was found in the same t rea tment ; 81.7% increase over control . The next best t rea tments were calcium hydroxide 2%, potassium nitrate 1% and boric acid 25 mg 1 -~ for T.S.S. : acid ratio. The highest ascorbic acid conten t was recorded after boric acid 25 mg 1-1; 50% more than control . Potassium nitrate 1% and zinc sulphate 0.5% + copper sulphate 0.5% followed The latter 2 t reatments increased the ascorbic acid content by 47 and 40% over control , respectively.

Seasonal differences in quali ty characteristics (Tables III and IV) might be ascribed to differences in day and night temperatures rather than to differences in crop load.

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DISCUSSION

Nutrients play a vital role in the various physiological functions of the plant and are needed for the development of fruits. Citrus plants which are deficient in certain elements, have more granulation. Different nutrients were tried in the present study to evaluate their effect on granulation and fruit quality in 'Dancy tangerine'.

The combined spray of zinc sulphate 0.5% + copper sulphate 0.5% was the best t reatment in reducing the granulation during 1974--75. Zinc is involved in the biosynthesis of auxin, indole-3-acetic acid. Zinc-deficient plants have shown a marked reduction in auxin content and an increase in peroxidase activity, resulting in accumulation of polysaccharides (Skoog, 1940; Chesters and Rolinson, 1951). Siegel et al. (1960) reported the role of IAA in the plant as an antioxidant in the formation of lignins. The zinc appli- cation in our case may have overcome the ill-effects of auxin deficiency. Copper has been reported to increase the synthesis of simple sugars (Gilbert et al., 1946). Thus the reduction in granulation by zinc + copper becomes understandable; decreasing starch and increasing soluble sugars.

Potassium nitrate 1% was tried in 1975--76 and proved to be the best t reatment in reducing the granulation. A low potassium level results in accumulation of starch and lignin (Nightingale et al., 1930), increased res- piration and low assimilation rate (Eaton, 1952; Gregory and Richards, 1929; Richards, 1932) and decreased sucrose content (Hartt, 1934b). The trans- location of metabolites is interfered with by potassium deficiency (Hartt, 1934a). These symptoms are common in granulated fruits (Singh, 1977). Therefore, the effectiveness of potassium spray in reducing granulation and giving an improvement in the fruit quality is logical.

The application of boric acid 25 and 50 mg 1-1 reduced granulation and improved fruit quality markedly. Boron regulates the translocation of sugars (Dugger and Humphries, 1957). Boron facilitates the movement of sugar in fruits by forming a more permeable boron--sugar complex (Gauch and Dugger, 1953; Sisler et al., 1956). Healthy citrus fruits have been found to have a considerably higher amount of boron than granulated ones (Singh, 1977). Boron deficiency has also been found to be associated with thick rind (Morris, 1938). The thick rind of granulated fruits may be due to boron deficiency in the present material. Therefore, the possibility of boron being associated with the incidence of granulation is strong.

Soluble calcium has been reported to increase the amylase activity and give an increase in sugars (Paleg, 1960). Calcium also affects the translocation of carbohydrates in a manner analogous to that postulated for boron in cot- ton (Joham, 1957). The beneficial effect of calcium application in reducing granulation has been reported by Bartholomew et al. (1941) and Awasthi and Nauriyal (1972). In the present study, 2% calcium hydroxide reduced the granulation markedly and also improved the fruit quality. This is prob- ably due to better translocation of carbohydrates and restoration of amylase activity.

243

I t is a h a p p y s i t u a t i o n t h a t t h e t r e a t m e n t s m o s t e f f e c t i v e in c o n t r o l l i n g g r a n u l a t i o n a l so i m p r o v e d t h e f r u i t q u a l i t y , t h u s m a k i n g t h e e x p l o i t a t i o n o f t h e s e t r e a t m e n t s e c o n o m i c a l l y m o r e f e a s i b l e .

CONCLUSION

T h e p o s s i b i l i t y e x i s t s t h a t g r a n u l a t i o n c a n b e c h e c k e d b y t h e a p p l i c a t i o n o f n u t r i e n t s . However~ t h e r e is n e e d f o r f u r t h e r s t u d y o f t h e t i m e o f a p p l i - c a t i o n . I t is v e r y l i k e l y t h a t t h e f a c t o r s r e s p o n s i b l e f o r d i s t u r b a n c e in t h e n u t r i e n t b a l a n c e a n d c o n s e q u e n t r u p t u r i n g o f t i s sue s in t h e j u i c e sacs m a y be o p e r a t i v e m a n y m o n t h s b e f o r e t h e g r a n u l a t i o n a c t u a l l y a p p e a r s . A c o m - p r e h e n s i v e p r o g r a m m e , w i t h m o r e n u t r i e n t s in d i f f e r e n t c o n c e n t r a t i o n s a n d c o m b i n a t i o n s a t d i f f e r e n t i n t e r v a l s , is u n d e r w a y t o o v e r c o m e th i s p r o b l e m in c i t ru s .

ACKNOWLEDGEMENT

T h e a u t h o r s a c k n o w l e d g e t h e s k i l f u l t e c h n i c a l a s s i s t a n c e o f Mrs . I n d u S h a r m a .

REFERENCES

A.O.A.C., 1970. Official Methods of Analysis of the Association of Official Agricultural Chemists. Association of OfficialAgricultural Chemists. Washington, DC, U.S.A.

Awasthi, R.P., 1969. Studies on granulation in sweet orange. Ph. D. Thesis. Punjab Ag- ricultural University, Ludhiana, India.

Awasthi, R.P. and Nauriyal, J.P., 1972. Effect of foliar sprays of zinc, copper and cal- cium on granulation in sweet orange. Fert . News, 17: 64--65.

Bartholomew, E.T., Sinclair, W.B. and Turrell, F.M., 1941. Granulation of Valencia oranges. Calif. Agric. Exp. Stn. Bull. No. 647.

Chakrawar, V.R., 1975. A study of some aspects of granulation in citrus. Ph .D. Thesis, Indian Agricultural Research Institute, New Delhi, India.

Chesters, C.G.S. and Rolinson, G.N., 1951. The role of zinc in plant metabolism. Biol. Rev., 26: 239--252.

Dugger, W.M., Jr. and Humphries, T.E., 1957. The influence of boron on starch phos- phorylase and its significance in translocation of sugars in plants. Plant Physiol., 32: 364--370.

Eaton, S.V., 1952. Effects of potassium deficiency on growth and metabolism of sun- flower plants. Bot. Gaz., 114: 165--180.

Gauch, H.G. and Dugger, W.M., Jr., 1953. The role of boron in the translocation of sucrose. Plant Physiol., 28: 457--466.

Gilbert, S.G., Sell, H.M. and Drosdoff, M., 1946. The effect of copper deficiency on the metabolism and oil synthesis of the tung tree. Plant Physiol., 21: 290--303.

Gregory, F.G. and Richards, F.J. , 1929. Physiological studies in plant nutri t ion. I. The effect of manurial deficiency on the respiration and assimilation rate in barley. Ann. Bot., 43: 119--161.

Hartt, C.E., 1934a. Some effects of potassium on the growth of sugar cane and upon the absorption and migration of ash constituents. Plant Physiol., 9: 399--452.

Hartt, C.E., 1934b. Some effects of potassium upon the amounts of protein and amino forms of nitrogen, sugars and enzyme activity of sugar cane. Plant Physiol., 9: 453--490.

244

Joham, H.E., 1957. Carbohydrate distribution as affected by calcium deficiency in cotton. Plant Physiol., 32: 113--117.

McCready, R.M., Guggolz, J., Silvieva, V. and Owens, H.S., 1950. Determination of starch and amylase in vegetables. Anal. Chem., 22: 1156--1158.

Morris, A.A., 1938. Some observations on the effects of boron treatment in the control of "hard fruit" in citrus. J. Pomol. Hortic. Sci., 16: 167--181.

Nightingale, G.T., Schermerhorn, L.G. and Robbins, W.R., 1930. Some effects of potas- sium deficiency on the histological structure and nitrogenous and carbohydrate constituents of plants. N.J, Agric. Exp. Stn. Bull. No. 499.

Paleg, L:G., 1960. Physiological effects of gibberellic acid on starch hydrolysing enzymes of barley endosperm. Plant Physiol., 35 : 902--906.

Richards, F.J., 1932. Physiological studies in plant nutrition. 3. Further studies of the effect of potash deficiency on the rate of respiration in leaves of barley. Ann. Bot., 46: 367--388.

Siegel, S., Frost, P. and Porto, F., 1960. Effects of indoleacetic acid and other oxidation regulators on peroxidation and experimental conversion of eugenol to lignin. Plant Physiol., 35: 163--167.

Singh, R., 1977. Some studies on citrus granulation. Ph.D. Thesis. Indian Agricultural Research Institute, New Delhi, India.

Sisler, E.C., Dugger, W.M., Jr. and Gauch, H.G., 1956. The role of boron in the trans- location of organic compounds in plants. Plant Physiol., 31:11--17.

Skoog, F., 1940. Relationship between zinc and auxin in the growth of higher plants. Am. J. Bot., 27: 939--951.