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Effect of foliar application of urea on leaf nutrient status and yield of ‘Kew’ pineapple
Scientia Horticulturae, 18 (1982/83) 225--230
225
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
EFFECT OF FOLIAR APPLICATION OF UREA ON LEAF NUTRIENT STATUS AND YIELD OF 'KEW' PINEAPPLE
B.M.C. REDDY, H.C. DASS, G.S. PRAKASH, T.R. SUBRAMANIAN and M.H. RAO
Indian Institute of Horticultural Research, Bangalore-560 080 (India) Contribution No. 1192 (Accepted for publication 8 February 1982)
ABSTRACT
Reddy, B.M.C., Dass, H.C., Prakash, G.S., Subramanian, T.R. and Rao, M.H., 1983. Effect of foliar application of urea on leaf nutrient status and yield of 'Kew' pineapple. Scientia Hortic., 18: 225--230. Field trials were conducted to determine the optimum nitrogen (N) in combinations of foliar and soil application and the concentrations of urea for foliar application in pineapple. No increase in fruit weight and yield was observed in either the plant crop or the ratoon crop with foliar application of urea compared to soil application. This lack of yield response from foliar application was further substantiated by leaf N status. Leaf N content was found to be significantly different in the "D" leaf but not in the base leaf. Under the conditions of the trial, where fertilizer N was applied in split doses, soil application seemed to be as good as foliar application.
INTRODUCTION
Of the 3 major nutrients nitrogen (N), phosphorus (P) and potash (K), the maximum response in pineapple has been observed from N (Shrivastava, 1969; Tay, 1972). Under Indian conditions, the optimum N requirements of pineapple were determined under irrigated and rain-fed conditions, and 16 g per plant under rain-fed conditions and 12 g per plant under irrigated conditions were optimum for obtaining high yields (Teotia and Pandey, 1964; Singh et al., 1977). Due to the global energy crisis and consequent escalating cost of N fertilizers in recent years, it has become imperative to minimise its use without affecting productivity. Foliar application of N is one of the important means of economising N fertilization. This has been practiced successfully in several countries such as Australia (Cannon, 1960; Mitchell and Nicholson, 1965), China (Su and Huang, 1956) and French Guinea (Py, 1962). In pineapple, foliar application is of special importance due to the presence of thorns on the leaves and high plant population densities. At present, soil
0304-4238/83/0000--0000/$03.00
© 1983 Elsevier Scientific Publishing Company
226 application of nutrients to pineapple is still quite c o m m o n in India. The present studies were therefore, carried out to find the relative efficacy of soil vs. foliar application of N. The study also attempts to determine the optimum concentration of urea for a foliar spray. MATERIALS AND METHODS Plants. -- Field trials were c o n d u c t e d at the Horticultural Experiment Station
of the Indian Institute of Horticultural Research at Hessaraghatta, from 1973 to 1977, with the plant crop as well as the ratoon crop of the pineapple 'Kew.' S o i l a n d foliar a p p l i c a t i o n . -- A field trial was laid o u t in a split plot design
with N levels (8, 12, 16 or 20 g N/plant) as main plots, and methods of application as sub-plots (all N through soil, 75% N through soil + 25% foliar~ 50% N through soft + 50% foliar, 25% N through soil + 75% foliar, or all foliar). Foliar application of N was done with c o m m o n l y available urea containing 1--1.5% biuret. The number of sprays and the interval of spraying increased as the amount of N increased through foliar application. Soil application of N was done in 4 split doses. The total application of N (soil or foliar) was completed before flower initiation. A planting density of 43 000 plants per ha was adopted using a 30 X 60 × 90-cm spacing. Applications of P2Os and K~O were kept constant at the rate of 100 and 500 kg/ha, respectively. The experiment was replicated 4 times and each treatment consisted of 80 plants. Data on the number of leaves per plant, leaf area index, fruit weight, yield, etc., were recorded. Total soluble solids (T.S.S.) were recorded with the help of a refractometer and acidity was expressed as citric acid in 100 cc of juice by titrating 5 ml of juice with N/10 NaOH, using phenolphthalein as an indicator. Urea f o r foliar a p p l i c a t i o n . -- One hundred and t w e n t y plants per treatment were used. The total quantity of N was kept at 16 g/plant, of which half was fed through the soil in 3 split doses and the other half through the leaves in different concentrations o f urea, viz. 2, 4, 6, 8 or 10%. The experiment was replicated 6 times and randomized layout was adopted. Data on leaf and fruit characteristics were taken as above. L e a r N d e t e r m i n a t i o n . -- " D " leaves were collected at the 6th and 10th month
after planting. There were 2 types o f samples: (1) the middle one-third to one-half of the basal portion; (2) the remainder of the " D " leaf. These were expressed as "base" and "leaf", respectively. The preparation of samples and analytical procedures o f Subramanian et al. (1974) and Rao et al. (1977) were adopted.
227 RESULTS Foliar application
of urea
The results in Table I clearly show that with increasing levels of N there was a significant increase in the number of leaves per plant, the average fruit weight and the yields/ha. No adverse effect was observed on the quality of the fruit (T.S.S., acidity} due to higher levels of N. However, in different methods of application, when part or the whole amount of N was applied to foliage in the form of urea, no increase in yield or fruit weight was obtained over the all-soil application.
Plant crop. --
TABLE I E f f e c t of v a r i o u s levels a n d m e t h o d s o f a p p l i c a t i o n o f N o n vegetative and fruit characteristics in the plant c r o p o f ' K e w ' p i n e a p p l e . A n y p a i r o f t r e a t m e n t s h a v i n g at least 1 l e t t e r in c o m m o n d o n o t d i f f e r signific a n t l y , CD a t 5%. A b s e n c e o f letters d e n o t e s n o s i g n i f i c a n t differences Treatments
Plant crop
R a t o o n crop
N u m b e r of leaves/plant 12 m o n t h s after p l a n t i n g
Average fruit weight with crown (kg)
Estimated y i e l d in tonnes/ha with crown
T.S.S. (° B)
Acidity (%)
Average f r u i t weight with crown (kg)
N l e v e l / p l a n t (g) 8 12 16 20
32.51 35.03 34.01 35.34
1.290 1.394 1.466 1.492
a ab b b
57.31 61.95 65.14 65.28
a ab b b
12.86 12.90 12.96 13.38
0.83 0.81 0.79 0.76
1.204 1.283 1.298 1.361
Method of application All in soil 75% in soil + 2 5 % foliar 50% in soil + 50% foliar 2 5 % in soil + 75% foliar All foliar
34.38 34.91 34.56 33.68 33.59
1.450 1.415 1.350 1.389 1.447
b b a ah b
64.42 62.89 59.98 61.74 64.31
b b a ab b
12.99 12.85 12.83 13,18 13.28
0.79 0.82 0.81 0.78 0.78
1.406 1.378 1.292 1.203 1.152
a b ab b
c c b a a
c r o p . - - Data for average fruit weight (Table I) showed that the increase in fruit weight was not significant. Regarding the methods of application, fruit weight decreased as the amount of foliar-applied N increased {Table I). Ratoon-crop data further substantiated that foliar application of N had n o t been found useful in increasing fruit weight. Ratoon
s t a t u s . ~ Leaf N was measured in 2 samplings~ i.e. at the 6th and 10th m o n t h {Table II). The "base" N content was only significantly affected by the N levels in the 2nd sampling, and no significant differences were observed due to the various methods of application. Leaf N content was n o t significantly affected by N levels in the 1st sampling. However, in the second sampling it was significantly affected. Leaf N was also n o t significantly affected by m e t h o d of application in either of the samplings of the "base". LearN
228 TABLE II Leaf N contents in 'Kew' pineapple as affected by N levels and foliar applications of N. Details as Table I Treatments
Sampling I
Sampling II
Base N
Leaf N
Base N
Leaf N
N level/plant (g) 8 12 16 20
1.098 1.196 1.242 1.210
1.160 1.129 1.157 1.157
1.210 1.230 1.300 1.360
1.290 1.320 1.370 1.470
a a a b
Methods of application All in soil 75% in soil + 25% foliar 50% in soil + 50% foliar 25% in soil + 75% foliar All foliar
1.161 1.125 1.189 1.220 1.247
1.129 1.088 1.176 1.148 1.229
1.340 1.280 1.330 1.420 1.450
ab a ab bc c
b a d c e
a ab bc c
1.264 1.326 1.229 1.268 1.291
Concentration o f urea for foliar application Data on the vegetative and fruit characteristic after various concentrations o f u r e a as a f o l i a r s p r a y w e r e r e c o r d e d . H o w e v e r , n o d a t a f r o m 0 - - 1 0 % u r e a p r o d u c e d s i g n i f i c a n t d i f f e r e n c e s . T h e e x p e r i m e n t was c o n t i n u e d i n t h e r a t o o n crop, and the data recorded confirmed those with the plant crop.
L e a f N status. -- L e a f N i n t h e " b a s e " a n d l e a f p o r t i o n s o f t h e " D " l e a f was d e t e r m i n e d in 2 samplings at the 6 t h a n d 1 0 t h m o n t h (Table III). Base N c o n t e n t i n t h e f i r s t s a m p l i n g w i t h d i f f e r e n t c o n c e n t r a t i o n s o f u r e a was s i g n i f i c a n t l y s u p e r i o r t o t h e c o n t r o l . A m o n g s t d i f f e r e n t c o n c e n t r a t i o n s , no significant differences were observed. In the second sampling, there were no significant differences amongst various treatments, there being no TABLE III Effect of different concentrations of urea used as a folar spray on leaf N content in 'Kew' pineapple Spray treatment
Control (water) 2% urea 4% urea 6% urea 8% urea 10% urea
Sampling I
Sampling II
Base N
Leaf N
Base N
Leaf N
1.00 1.12 1.10 1.19 1.14 1.19
0.93 1.03 0.96 1.02 1.10 1.03
1.17 1.31 1.33 1.28 1.23 1.29
1.03 1.17 1.14 1.09 1.09 1.12
a b b b b b
a c bc ab ab bc
229
advantage in respect of " b a s e " N from foliar application. The t r e a t m e n t differences regarding leaf N were n o t significant in the first sampling. In the second sampling, urea spray treatments registered a significantly higher leaf N level over the control, b u t amongst spray treatments there were no significant differences, except for the 2% spray. DISCUSSION
In the experiment where different levels of nitrogen and methods of application were involved, significant effects on average fruit weight and yield were observed only in respect of levels of N. Similar results were obtained by Singh et al. (1977). However, among the methods of application, where a portion or the full a m o u n t of N was applied as a foliar spray of urea, no increase in fruit weight and yield was observed, compared to full soil application. The trend of results in the ratoon crop was similar to that in the plant crop. This was further substantiated in the experiment where half the N was applied in different concentrations of urea spray. No increase in fruit weight and yield was observed over the control in the plant crop or in the ratoon crop. A beneficial effect of foliar spray of urea on fruit weight of pineapple has been observed by Py (1962) and by Mitchell and Nicholson (1965). However, in the present studies no advantage was observed from the foliar spray based on yield and fruit weight. Page (1971) observed leaf burn and negative growth response from foliar application of urea. Sanford et al. (1954) observed biuret toxicity to pineapple plants. The fact t h a t there were no adverse visual s y m p t o m s due to the higher percentage of urea spray showed that, at the levels tried, biuret did not seem to be a factor. In previous studies (Rao et al., 1977), the " b a s e " N c o n t e n t was f o u n d to be a more reliable index of yield, and this was n o t affected by the m e t h o d of application in the present trials. However, leaf N c o n t e n t was significantly affected by the m e t h o d of application where a portion or full N was applied as a foliar spray of urea. Foliar application of nutrients is a c o m m o n practice in Australia, Hawaii and the Philippines, and in these countries it has probably done more for labour saving than for increasing yield. The absence of any beneficial effect on yield due to foliar application of urea probably shows that under the conditions of the experiment with split applications, the availability of N in the soil was adequate for pineapple plants, with the result that foliar application had no advantage Over soil application.
REFERENCES Cannon, R.C., 1960. Save on costs of fertilizer for pineapples. Queensl. Agric. J., 86: 473-475. Mitchell, A.R. and Nicholson, M.E., 1965. Pineapple growth and yield as influenced by urea spray schedules and potassium levels at three plant spacings. Queensl. J. Agric. Anim. Sci., 22: 409--417.
230 Page~ P.E., 1971. Nitrogen uptake by pineapple from urea foliage sprays. Queensl. J. Agric. Anita. Sci., 28: 195--197. Py, C., 1962. Foliar spraying with urea as applied to pineapples. Fruits Outre Mer, 17: 285--287. Rao, M.H., Subramanian, T.R., Srinivasa Murthy, H.K., Singh, H.P., Dass, H.C. and Ganapathy, K.M., 1977. Leaf nitrogen status as influenced by varying levels of nitrogen application and its relationship with yield in 'Kew' Pineapple. Scientia Hortic., 7: 137-142. Sanford, W.G., Growing, D.P., Young, H.Y. and Leeper, R.W., 1954. Toxicity of pineapple plants of biuret found in urea fertilizers from different sources. Science, 120: 349-350. Shrivastava, S.S., 1969. NPK nutrition in relation to the growth and chemical composition of pineapples. Madras Agric. J., 8 : 7--11. Singh, H.P., Dass, H.C., Ganapathy, K.M. and Subramanian, T.R., 1977. Nitrogen requirement of pineapple under irrigated and rainfed conditions. Indian J. Hortic., 34: 377-384. Su, N.R. and Huang, C.R., 1956. Effect of foliar fertilization after the initiation of floral induction of pineapples. J. Agric. Assoc. China, 14 : 30--37. Subramanian, T.R., Chadha, K.L., Melanta, K.R. and Srinivasa Murthy, H.K., 1974. Studies on nutrition of pineapple. III. Effect of varying levels of NPK on leaf nutrients status in var. Kew in high fertility soil. Indian J. Hortic. 31: 219--222. Tay, T.H., 1972. Quantitative assessment of the relative importance of N.P.K. and their interactions in the nutrition of pineapple. Malays. Pineapple, 2: 33--39. Teotia, S.S. and Pandey, I.C., 1964. A manurial trial on pineapple (Ananas comosus L. Merr) var Giant Kew. I. Effect of nitrogen, phosphorus and potash on yield, flowering and growth. Kanpur Agric. Coll. J., 24: 27--39.
225
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
EFFECT OF FOLIAR APPLICATION OF UREA ON LEAF NUTRIENT STATUS AND YIELD OF 'KEW' PINEAPPLE
B.M.C. REDDY, H.C. DASS, G.S. PRAKASH, T.R. SUBRAMANIAN and M.H. RAO
Indian Institute of Horticultural Research, Bangalore-560 080 (India) Contribution No. 1192 (Accepted for publication 8 February 1982)
ABSTRACT
Reddy, B.M.C., Dass, H.C., Prakash, G.S., Subramanian, T.R. and Rao, M.H., 1983. Effect of foliar application of urea on leaf nutrient status and yield of 'Kew' pineapple. Scientia Hortic., 18: 225--230. Field trials were conducted to determine the optimum nitrogen (N) in combinations of foliar and soil application and the concentrations of urea for foliar application in pineapple. No increase in fruit weight and yield was observed in either the plant crop or the ratoon crop with foliar application of urea compared to soil application. This lack of yield response from foliar application was further substantiated by leaf N status. Leaf N content was found to be significantly different in the "D" leaf but not in the base leaf. Under the conditions of the trial, where fertilizer N was applied in split doses, soil application seemed to be as good as foliar application.
INTRODUCTION
Of the 3 major nutrients nitrogen (N), phosphorus (P) and potash (K), the maximum response in pineapple has been observed from N (Shrivastava, 1969; Tay, 1972). Under Indian conditions, the optimum N requirements of pineapple were determined under irrigated and rain-fed conditions, and 16 g per plant under rain-fed conditions and 12 g per plant under irrigated conditions were optimum for obtaining high yields (Teotia and Pandey, 1964; Singh et al., 1977). Due to the global energy crisis and consequent escalating cost of N fertilizers in recent years, it has become imperative to minimise its use without affecting productivity. Foliar application of N is one of the important means of economising N fertilization. This has been practiced successfully in several countries such as Australia (Cannon, 1960; Mitchell and Nicholson, 1965), China (Su and Huang, 1956) and French Guinea (Py, 1962). In pineapple, foliar application is of special importance due to the presence of thorns on the leaves and high plant population densities. At present, soil
0304-4238/83/0000--0000/$03.00
© 1983 Elsevier Scientific Publishing Company
226 application of nutrients to pineapple is still quite c o m m o n in India. The present studies were therefore, carried out to find the relative efficacy of soil vs. foliar application of N. The study also attempts to determine the optimum concentration of urea for a foliar spray. MATERIALS AND METHODS Plants. -- Field trials were c o n d u c t e d at the Horticultural Experiment Station
of the Indian Institute of Horticultural Research at Hessaraghatta, from 1973 to 1977, with the plant crop as well as the ratoon crop of the pineapple 'Kew.' S o i l a n d foliar a p p l i c a t i o n . -- A field trial was laid o u t in a split plot design
with N levels (8, 12, 16 or 20 g N/plant) as main plots, and methods of application as sub-plots (all N through soil, 75% N through soil + 25% foliar~ 50% N through soft + 50% foliar, 25% N through soil + 75% foliar, or all foliar). Foliar application of N was done with c o m m o n l y available urea containing 1--1.5% biuret. The number of sprays and the interval of spraying increased as the amount of N increased through foliar application. Soil application of N was done in 4 split doses. The total application of N (soil or foliar) was completed before flower initiation. A planting density of 43 000 plants per ha was adopted using a 30 X 60 × 90-cm spacing. Applications of P2Os and K~O were kept constant at the rate of 100 and 500 kg/ha, respectively. The experiment was replicated 4 times and each treatment consisted of 80 plants. Data on the number of leaves per plant, leaf area index, fruit weight, yield, etc., were recorded. Total soluble solids (T.S.S.) were recorded with the help of a refractometer and acidity was expressed as citric acid in 100 cc of juice by titrating 5 ml of juice with N/10 NaOH, using phenolphthalein as an indicator. Urea f o r foliar a p p l i c a t i o n . -- One hundred and t w e n t y plants per treatment were used. The total quantity of N was kept at 16 g/plant, of which half was fed through the soil in 3 split doses and the other half through the leaves in different concentrations o f urea, viz. 2, 4, 6, 8 or 10%. The experiment was replicated 6 times and randomized layout was adopted. Data on leaf and fruit characteristics were taken as above. L e a r N d e t e r m i n a t i o n . -- " D " leaves were collected at the 6th and 10th month
after planting. There were 2 types o f samples: (1) the middle one-third to one-half of the basal portion; (2) the remainder of the " D " leaf. These were expressed as "base" and "leaf", respectively. The preparation of samples and analytical procedures o f Subramanian et al. (1974) and Rao et al. (1977) were adopted.
227 RESULTS Foliar application
of urea
The results in Table I clearly show that with increasing levels of N there was a significant increase in the number of leaves per plant, the average fruit weight and the yields/ha. No adverse effect was observed on the quality of the fruit (T.S.S., acidity} due to higher levels of N. However, in different methods of application, when part or the whole amount of N was applied to foliage in the form of urea, no increase in yield or fruit weight was obtained over the all-soil application.
Plant crop. --
TABLE I E f f e c t of v a r i o u s levels a n d m e t h o d s o f a p p l i c a t i o n o f N o n vegetative and fruit characteristics in the plant c r o p o f ' K e w ' p i n e a p p l e . A n y p a i r o f t r e a t m e n t s h a v i n g at least 1 l e t t e r in c o m m o n d o n o t d i f f e r signific a n t l y , CD a t 5%. A b s e n c e o f letters d e n o t e s n o s i g n i f i c a n t differences Treatments
Plant crop
R a t o o n crop
N u m b e r of leaves/plant 12 m o n t h s after p l a n t i n g
Average fruit weight with crown (kg)
Estimated y i e l d in tonnes/ha with crown
T.S.S. (° B)
Acidity (%)
Average f r u i t weight with crown (kg)
N l e v e l / p l a n t (g) 8 12 16 20
32.51 35.03 34.01 35.34
1.290 1.394 1.466 1.492
a ab b b
57.31 61.95 65.14 65.28
a ab b b
12.86 12.90 12.96 13.38
0.83 0.81 0.79 0.76
1.204 1.283 1.298 1.361
Method of application All in soil 75% in soil + 2 5 % foliar 50% in soil + 50% foliar 2 5 % in soil + 75% foliar All foliar
34.38 34.91 34.56 33.68 33.59
1.450 1.415 1.350 1.389 1.447
b b a ah b
64.42 62.89 59.98 61.74 64.31
b b a ab b
12.99 12.85 12.83 13,18 13.28
0.79 0.82 0.81 0.78 0.78
1.406 1.378 1.292 1.203 1.152
a b ab b
c c b a a
c r o p . - - Data for average fruit weight (Table I) showed that the increase in fruit weight was not significant. Regarding the methods of application, fruit weight decreased as the amount of foliar-applied N increased {Table I). Ratoon-crop data further substantiated that foliar application of N had n o t been found useful in increasing fruit weight. Ratoon
s t a t u s . ~ Leaf N was measured in 2 samplings~ i.e. at the 6th and 10th m o n t h {Table II). The "base" N content was only significantly affected by the N levels in the 2nd sampling, and no significant differences were observed due to the various methods of application. Leaf N content was n o t significantly affected by N levels in the 1st sampling. However, in the second sampling it was significantly affected. Leaf N was also n o t significantly affected by m e t h o d of application in either of the samplings of the "base". LearN
228 TABLE II Leaf N contents in 'Kew' pineapple as affected by N levels and foliar applications of N. Details as Table I Treatments
Sampling I
Sampling II
Base N
Leaf N
Base N
Leaf N
N level/plant (g) 8 12 16 20
1.098 1.196 1.242 1.210
1.160 1.129 1.157 1.157
1.210 1.230 1.300 1.360
1.290 1.320 1.370 1.470
a a a b
Methods of application All in soil 75% in soil + 25% foliar 50% in soil + 50% foliar 25% in soil + 75% foliar All foliar
1.161 1.125 1.189 1.220 1.247
1.129 1.088 1.176 1.148 1.229
1.340 1.280 1.330 1.420 1.450
ab a ab bc c
b a d c e
a ab bc c
1.264 1.326 1.229 1.268 1.291
Concentration o f urea for foliar application Data on the vegetative and fruit characteristic after various concentrations o f u r e a as a f o l i a r s p r a y w e r e r e c o r d e d . H o w e v e r , n o d a t a f r o m 0 - - 1 0 % u r e a p r o d u c e d s i g n i f i c a n t d i f f e r e n c e s . T h e e x p e r i m e n t was c o n t i n u e d i n t h e r a t o o n crop, and the data recorded confirmed those with the plant crop.
L e a f N status. -- L e a f N i n t h e " b a s e " a n d l e a f p o r t i o n s o f t h e " D " l e a f was d e t e r m i n e d in 2 samplings at the 6 t h a n d 1 0 t h m o n t h (Table III). Base N c o n t e n t i n t h e f i r s t s a m p l i n g w i t h d i f f e r e n t c o n c e n t r a t i o n s o f u r e a was s i g n i f i c a n t l y s u p e r i o r t o t h e c o n t r o l . A m o n g s t d i f f e r e n t c o n c e n t r a t i o n s , no significant differences were observed. In the second sampling, there were no significant differences amongst various treatments, there being no TABLE III Effect of different concentrations of urea used as a folar spray on leaf N content in 'Kew' pineapple Spray treatment
Control (water) 2% urea 4% urea 6% urea 8% urea 10% urea
Sampling I
Sampling II
Base N
Leaf N
Base N
Leaf N
1.00 1.12 1.10 1.19 1.14 1.19
0.93 1.03 0.96 1.02 1.10 1.03
1.17 1.31 1.33 1.28 1.23 1.29
1.03 1.17 1.14 1.09 1.09 1.12
a b b b b b
a c bc ab ab bc
229
advantage in respect of " b a s e " N from foliar application. The t r e a t m e n t differences regarding leaf N were n o t significant in the first sampling. In the second sampling, urea spray treatments registered a significantly higher leaf N level over the control, b u t amongst spray treatments there were no significant differences, except for the 2% spray. DISCUSSION
In the experiment where different levels of nitrogen and methods of application were involved, significant effects on average fruit weight and yield were observed only in respect of levels of N. Similar results were obtained by Singh et al. (1977). However, among the methods of application, where a portion or the full a m o u n t of N was applied as a foliar spray of urea, no increase in fruit weight and yield was observed, compared to full soil application. The trend of results in the ratoon crop was similar to that in the plant crop. This was further substantiated in the experiment where half the N was applied in different concentrations of urea spray. No increase in fruit weight and yield was observed over the control in the plant crop or in the ratoon crop. A beneficial effect of foliar spray of urea on fruit weight of pineapple has been observed by Py (1962) and by Mitchell and Nicholson (1965). However, in the present studies no advantage was observed from the foliar spray based on yield and fruit weight. Page (1971) observed leaf burn and negative growth response from foliar application of urea. Sanford et al. (1954) observed biuret toxicity to pineapple plants. The fact t h a t there were no adverse visual s y m p t o m s due to the higher percentage of urea spray showed that, at the levels tried, biuret did not seem to be a factor. In previous studies (Rao et al., 1977), the " b a s e " N c o n t e n t was f o u n d to be a more reliable index of yield, and this was n o t affected by the m e t h o d of application in the present trials. However, leaf N c o n t e n t was significantly affected by the m e t h o d of application where a portion or full N was applied as a foliar spray of urea. Foliar application of nutrients is a c o m m o n practice in Australia, Hawaii and the Philippines, and in these countries it has probably done more for labour saving than for increasing yield. The absence of any beneficial effect on yield due to foliar application of urea probably shows that under the conditions of the experiment with split applications, the availability of N in the soil was adequate for pineapple plants, with the result that foliar application had no advantage Over soil application.
REFERENCES Cannon, R.C., 1960. Save on costs of fertilizer for pineapples. Queensl. Agric. J., 86: 473-475. Mitchell, A.R. and Nicholson, M.E., 1965. Pineapple growth and yield as influenced by urea spray schedules and potassium levels at three plant spacings. Queensl. J. Agric. Anim. Sci., 22: 409--417.
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