-Scientia Horticulturae, 7 (1977) 329--337 329 Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

I N F L U E N C E O F P L A N T D E N S I T Y A N D TIME OF F E R T I L I Z E R APPLI- C A T I O N ON G R O W T H C H A R A C T E R I S T I C S , N U T R I E N T U P T A K E A N D Y I E L D OF T O M A T O

M.O.A. FAWUSI

Department of Agronomy, University of Ibadan, Ibadan (Nigeria)

(First received 14 April 1977; in revised form 28 June 1977)

ABSTRACT

Fawusi, M.O.A., 197~ Influence of plant density and time of fertilizer application on growth characteristics, nutrient uptake and yield of tomato. Scientia Hortic., 7: 329--337.

In a factorial experiment to investigate the combined effects of plant density and time of split application of fertilizer, 4 spacings and 3 fertilizer treatments were employed. Plant populations were varied between 24,000 and 54,000 per ha. Equal amounts of NPK were applied in different split applications and at specific physiological stages.

Time to 50% flowering was delayed by fertilizer application as well as by wide within- row spacing. Total leaf N and P content declined with all treatments between flowering and mature-green stage of fruits, but increased again at table-ripe stage. Leaf K content remained constant throughout the growth period.

Two-split applications of NPK, one at 2 weeks after transplanting to the field and the other at fruit set, were more beneficial than either no fertilizer or 3-split applications of equal amount of fertilizer, when the third application was at mature-green stage. This was indicated by higher fruit yields with 2-split applications.

Highest fruit yields were obtained when tomatoes were planted either at 30.5 cm × 91 cm single-row spacing, or at 45.5 cm X 122.0 cm, double-row spacing, both giving 36,000 plants per hectare. Fruit yields were reduced at lower and higher population densities.

INTRODUCTION

Studies in p lan t popu la t ion densi ty deserve more investigations, par t icular ly in developing countr ies . Cur ren t high-ferti l izer c o n s u m p t i o n and improved plant p ro t ec t i on should be accompan ied by higher p lan t popu la t ion for effec- tive ut i l iza t ion of p lant nutr ients . In t radi t ional agriculture, p lan t spacings are t oo wide apar t to benef i t f r o m improved fertil izer consumpt ion . In m o s t t ropical areas, harvest ing is done by hand. Hence a suitable p lan t configura- t ion tha t will maximize yield should be evolved. Fo r direct-seeded crops, a square a r rangement was r epo r t ed to give higher yields than row p l a n t i n g (Bleasdale, 1963; Mack and Hatch, 1968). But Wiggans (1939) r epor t ed tha t emphasis should be p laced on u n i f o r m plant dis t r ibut ion. Fo r tomatoes , spacings r e c o m m e n d e d have varied be tween 91.5 cm X 91:5 cm (3 ' X 3 ' ) and 2 .44 m X 2.44 m (8' × 8 ' ) (Rosa, 1922) . More recent ly in Nigeria, Majaro

330

(1970) recommended a 61 cm X 61 cm (2'X 2') spacing. Average yield of tomatoes in Nigeria is about 5 t /ha (Sobulo et al., 1975). Poor knowledge of some of the necessary cultural practices and nutrient requirements, and dis- ease problems might have contributed to this low yield.

Tomatoes respond well to N and P fertilization in the tropics (Sobulo et al., 1975), but N application has been reported to delay fruit matur i ty and ripening (Uzo, 1970).

Important considerations in determining a particular spacing for tomato should include plant morphology, level of soil fertility and added fertilizer (Paul and Jayasundora, 1938).

Little has been reported on the combined effects of plant spacing and timing of fertilizer application on tomato yields. Hence this work was under- taken to obtain information on nutrient utilization by tomatoes at various physiological stages of growth and at various plant densities, and the influence of these phenomena on fruit yields.

MATERIALS AND METHODS

This work was carried out between 1975 and 1976 in 3 plantings at the University of Ibadan Teaching and Research Farm. Ibadan is on latitude 7°N and longitude 3°45'E. Temperatures range between 21°C and 32°C. Annual rainfall is between 1150 mm and 1220 mm. There is a bimodal pattern of rainfall. The heavier rains begin in April and last until early August, while the lighter rains start late in August and last until October. November to March are usually dry months.

The experiments were s i ted on a loamy sand soil, belonging to the order Alfisol of the 7th Approximation (U.S.D.A., 1960). The nursery soil was ob- tained from a spot that had not carried tomatoes for over 5 years. Chemical and mechanical analysis of both nursery and field soils prior to cropping with tomatoes are shown in Table 1.

Lycopersicon esculentum Mill. cultivar 'Ife I' seedlings were raised in nursery trays for 4 weeks before transplanting to the field.

A randomized complete block design with a factorial arrangement was used in the field. Main plots were the 4 plant densities, while the sub-plots were the 3 fertilizer applications. There were 3 replications of each treatment. Plant spacings and densities were as follows: 30.5 cm X 91.5 cm, in single-row arrangements, giving 36,000 plants/ha; 45.5 cm X 91.5 cm, in single-row arrangement, giving 24,000 plants/ha; 30.5 cm X 122 cm in double arrangement, giving 54,000 plants/ha; 45.5 X 122 cm, double-row arrangement, giving 36,000 plants/ha.

Equal amounts of NPK fertilizer (360 kg/ha) were applied to each sub-plot, but the applications were split as follows: (a) Three equal applications of NPK 15--15--15, thus:

120 kg/ha 2 weeks after transplanting; 120 kg/ha at flowering-stage; 120 kg/ha at mature-green stage.

331

TABLE 1

Soil analysis before cropping with tomatoes

Soil analysis Nursery soil Field soil

pH 6.80 6.85 Organic carbon (%) 1.96 0.20 Total N (%) 0.09 0.06 Available P (p.p.m.) 10.90 6.80 Exchangeable K (meq/100 g) 0.64 0.20 Exchangeable Ca (meq/100g) 3.73 1.20 Previous site history Under Has carried

permanent cassava grass for 4 years

Mechanical analysis 0--15 ins

Sand (%) 83 87 Silt (%) 6 3 Clay (%) 10.6 9.3

(b) Two equal applications of NPK 15--15--15, thus: 180 kg/ha 2 weeks after transplanting; 180 kg/ha at fruit set.

(c) Control. No added fertilizer. All cultural operations were carried out uniformly, including spraying

for fungus control with Dithane M 45 at 0.03% from 2 weeks after trans- planting.

P l a n t s a m p l i n g t e c h n i q u e s . - - To determine nutr ient uptake pat tern under various fertilizer t reatments, the fif th leaf f rom the top of the tomato plant (Sobulo et al., 1975) was sampled. However, leaf samples were taken at 5 definite physiological stages, viz. pre-flowering stage, early-flowering stage, 50% fruit set, 50% mature-green stage, and at fruit ripening (table-ripe). The leaf samples were dried in an oven at 60°C for 48 h, ground with a porcelain mortar and pestle, and were used for the determinat ion of total N by the micro-Kjeldahl method, total P by the Vanodo-molybdate method, and K by the flame pho t ome t ry method.

RESULTS

F l o w e r i n g . - - Taken at t ime to 50% flower, flowering occurred earlier in the unferti l ized plots than in the fertilized ones (Table 2) Flowering was observed 4 weeks after transplanting to the field (8 weeks f rom sowing) in the unfer- tilized plots, regardless of spacing, and 5 weeks in the fertilized plots. There

332

TABLE2

Effect of plant spacing and time of fertilizer application on flowering in tomato. Days to 50% flower and 50% fruit set were average no. of days from 1st and 3rd plantings that were rain-fed throughout the growth periods.

Spacing/fertilizer Days to 50% flower after transplanting to the field

Days to 50% fruit set after transplanting to the field

(a) 3-split fertilizer application

• 30.5 cm × 91.5 cm single:row 36 30.5 cm × 122 cm double-row

45.5 cmx 91.5 em single-row 43 45.5 cruX 122 cm double-row

(b) 2-split fertilizer application

30.5 cm X 91.5 era single-row 36 30.5 cmx 122 cm double-row

45.5 cm X 91.5 cm single-row 42 45.5 cmx 122 cm double-row

(c) No fertilizer added 30

42

52

42

52

36

was an in te rac t ion be tween fer t i l izat ion and wi th in- row spacing. The wider wi th in- row spacing (45.5 cm) de layed f lowering c o m p a r e d with the closer wi th in- row spacing (30.5 cm). The be tween- row spacing did n o t inf luence t ime to flowering.

F r u i t c h a r a c t e r i s t i c s . - - NPK appl ica t ion increased size of fruits, bu t de layed f ru i t -co lour deve lopment . When the fruits were harvested at the mature-green stage and kep t at r o o m tempera tu re , the deve lopmen t o f table-ripe co lour t o o k 5 days with fruits f rom fert i l ized plots and 3 days with fruits f rom un- ferti l ized plots.

When mature-green t o m a t o fruits were s tored at 13 ° C, no ro t t ing occur red for 15 days, regardless o f the ferti l izer t r ea tment . But at 25 ° C, ro t t ing s tar ted 5 days af ter harvest ing in all t rea tments .

Frui t yields were higher at the 36 ,000 plants per hec tare at 2-split applica- t ion than ei ther at 24 ,000 or 54 ,000 plants per hectare , bu t the highest frui t yields were ob ta ined regardless o f the p lant ing-conf igura t ion . The lowest frui t yields were ob ta ined w i t h o u t added fertil izer (Table 3).

N u t r i e n t u p t a k e p a t t e r n

N i t r o g e n . - - Generally, to ta l N in the leaf increased with fert i l ization. There was a general decline in leaf N f r o m f lowering to mature-green frui t stage

333

TABLE 3

Effect of plant population density and time of fertilizer application on tomato fruit yields. Mean separation by Duncan's multiple range test, read horizontally across the row, 5% level.

Spacing and Fertilizer Yields % Yield plant/ha application t/ha increase

45.5 cmx 91 cm No fertilizer 5.6 a -- Single-row 3-split 10.5 b 88 24,000 plants 2-split 10.5 b 88

30.5 cm x 91.5 cm No fertilizer 5.0 a -- Single-row 3-split 9.4 b 71 36,000 plants 2-split 14.6 c 192

45.5 cm × 122 cm No fertilizer 5.0 a -- Double-row 3-split 12.0 b 140 36,000 plants 2-split 15.6 c 212

30.5 cm × 122 cm No fertilizer 6.0 a -- Double-row 3-split 11.8 b 97 54,000 plants 2-split 13.1 b 118

(Fig. l ) . A sharp increase in leaf N was observed af ter the frui t had a t ta ined the mature-green stage. There was no significant d i f ference in leaf N be tween 2-split and 3-split N appl ica t ion unti l the mature-green stage was at ta ined. Af te r this stage, leaf N became significantly higher with the 3-split appl icat ions than with the 2-split appl ica t ion and unfer t i l ized t rea tment . Total leaf N de- clined more in the unfer t i l ized plants be tween frui t set and mature-green stage, w h e n c o m p a r e d with the ferti l ized t rea tments .

P h o s p h o r u s . - - Phosphorus status of the leaf remained high in all t r ea tmen t s unti l f lowering, when it decl ined sharply and s tar ted to increase af ter the fruits had a t ta ined the mature~green stage (Fig.2). There was no significant d i f ference in leaf P be tween plants tha t received 2-split and those t h a t received 3-split appl icat ions at f lower ing and fruit-set stages. But at mature-green stage, leaf P wi th 2-split appl icat ions was higher than b o t h 3-split appl icat ions and the unfer t i l ized plots. B o t h ferti l izer t r ea tmen t s showed higher leaf P c o n t e n t at the table-ripe stage.

P o t a s s i u m . - - Excep t fo r a low K c o n t e n t at f lower ing in 0 NPK, fertiliza- t ion did n o t af fec t leaf K c o n t e n t (Fig.3).

DISCUSSION

Flower ing was de layed in all the ferti l ized t rea tments . This was p r o b a b l y due to the N c o m p o n e n t o f the fertilizer. Uzo (1970) r epor t ed tha t N appli- ca t ion de layed m a t u r i t y in tomatoes , which cou ld be due to delay in flow-

334

6 -

35- v

O3 LId > <% w4- d

(D

Z

Z . j2-- <%

O

0

3- Spl.it NPK

2-Spli t NPK

0 NPK

Ns I TP_o o5

PHYSIOLOGICAL STAGES

Fig.1. Total N content of tomato leaves as influenced by time of fertilizer application. Physiological stages: 1, 2 weeks to flower; 2, flowering; 3, fruit set; 4, mature green; 5, table ripe.

~n 0-5 h i

o 0.4

g I - . -

z o.3-

0.2-

0

• p 3-Sprit NP K ~ 2-Split NPK

~ 0 NPK

'IP:o.0s I I i i i

2 3 4 5

PHYSIOLOGICAL STAGES

T I P = o . 05

Fig.2. Phosphorus content of tomato leaves as influenced by time of fertilizer application. Physiological stages as Fig.1.

335

o

v

O3 I .d

LLI J

O

~ 2 -

O ¸ I - -

Z

A 2-sp it 3 - Split

• 0 NPK

NPK NPK

T P=0.05 ~. NS NS NS

PHYSIOLOGICAL STAGES

Fig.3. Potassium c o n t e n t of t o m a t o leaves as inf luenced by t ime of fert i l izer applicat ion. Physiological stages as Fig.1.

ering. Flowering was also delayed by wide within-row spacing. Reports on the separate effects of within-row spacing in tomato are scanty in the litera- ture. Emphasis has been laid on fruit yield rather than on components of reproductive development. However, delay in flowering observed in this work for wide within-row spacing could be due to reduced plant compet i t ion for light, resulting in less vertical growth, and more N uptake per plant resulting from less roo t interaction.

Highest tomato yields were observed at the 36,000 plant/ha density. Prev- ious workers did no t include configurations that would give slightly higher density than that recommended. Convenient plant arrangements to obtain the 36,000 density per ha are 45 cm X 122 cm (18" X 48" ) double-row and 30.5 cm X 91.5 cm (12" X 36" ) single-row spacings.

Nutrient content of the leaf was moni tored through 4 definite physiological stages rather than at biweekly intervals. This approach was adopted because of notable metabolic changes taking place at different physiological stages in plants, particularly f rom the onset of the reproductive phase (Went, 1944; Steenbjerg and Jakobsen, 1963). Total N in the leaves tended to increase with increase in fertilizer addition. However, as the plants entered the reproduc- tive phase, a general decline in leaf N was observed. This suggests heavy de- mands by plants for N at this developmental stage, reproductive structures being an extra sink for nutrients and photosynthates (Geiger, 1966).

A significantly higher leaf N was observed in plants that received 3-split fertilizer application at the table-ripe stage compared with those that re- ceived 2-split applications. This suggested that a third application of N ap- plied late (mature-green stage of fruits) was not well utilized by the plants. A 2-split application, first at 2 weeks after transplanting and the second at

336

fruit set, was bet ter utilized. This phenomenon was reflected in greater yields with the 2-split applications. Phosphorus uptake was bet ter with 2-split ap- plications than with 3-split applications. Even though the 2 modes of appli- cation did no t produce any significant difference in leaf P at: flowering and fruit set, the 2-split applications gave a significantly higher leaf P than the 3-split applications f rom after fruit set to mature green.

These observations indicated that 2-split applications, which saved labour and cost, were as good as 3-split applications. Like for N utilization, the leaf P conten t decreased between fruit set and mature-green stages, again indicating demand by fruits at these stages. Indications from these observations are that for maximum N and P utilization by tomato , the fertilizer has to be applied prior to flowering and definitely no t later than fruit set. Sigr ificant responses by tomato plants to K addition to the soil were observed prior to flowering and until fruit set. Thereafter , there were no significant differences in leaf K between the fertilized and unferti l ized plants.

The 54 kg K20/ha used in this work seemed insufficient to offset the very low K reserve of the soil to meet tomato requirements for growth and fruit yields, hence the initial response and later levelling off. Depending on soil type, moisture and natural K reserve in the soil, an opt imum of 20--60 kg K20/,ha and a maximum of 120 kg K20/ha are commonly recommended for tropical environments (Sobulo et al., 1975). It will seem from this work that op t imum K requirements in low K soils should be higher than 54 kg K20/ha.

It can therefore be concluded that t ime to 50% flower, and hence maturi ty, could be adversely affected by time and mode of fertilizer application. With- in-row spacing also affected t ime to flowering.

Focusing on definite physiological stages, particularly the reproduct ive phase, yielded more relevant informat ion that could lead to bet ter timing of nutr ient application and bet ter yields. Assessment of the response of tomato plants to fertilizer t reatments on the basis of final or overall fruit yield seems to have been overemphasized. Furthe~ detai ledinvest igat ion is required on the opt imum and maximum K requirements of tomatoes in different soil types in the tropiCs.

REFERENCES

Bleasdale, J.K.A., 1963. Crop spacing and management under weed-free conditions. In: Crop Production in a weed-free environment. Blackwell, London.

Geiger, D.R., 1966. Effect of sink region cooling on translocation of photosynthates. Plant Physiol., 41: 1667--1672.

Mack, H.J. and Hatch, D.L., 1968.. Effects of plant arrangement and population density on yield of bush snap beans. Proc. Am. Soc. Hortic. Sci., 92: 418-425.

Majaro, O., 1970. Grow tomato for profit. Agric. News, W.S. Nigeria, 1(4): 6--8. Paul, W.R.C. and Jayasundora, E.S., 1938. Spacing and manurial experiment with tomatoes.

Trop. Agric., 91: 203~212. Rosa, J.T., 1922. Better methods of tomato production. Mo. Agric. Exp. Stn., Bull., 194. Sobulo, R.A., Fayemi, A.A. and Agboola, A., 1975. Nutrient requirements of tomatoes

Lycopersicon esculentum in S.W. Nigeria. II. Foliar analysis for assessing NPK require- ments. Exp. Agric., 11: 137--143.

337

Steenbjerg, F. and Jakobsen, S.T., 1963. Plant nutr i t ion and yield curves. Soil Sci., 95: 69--88.

U.S.D.A., 1960. Soil classification: A comprehensive system 7th Approx. U.S.D.A., Washington, D.C.

Uzo, J.O., 1970. Effects of nitrogen, phosphorus and potassium on the yield of tomato Lycopersicon esculentum in the humid tropics. Hortic. Res., 11: 65--74.

Went, F.W., 1944. Plant growth under controlled conditions. III. Correlation between various physiological processes and growth in the tomato plant. Am. J. Bot., 31: 597-- 618.

Wiggans, R.C., 1939. The influence of space and arrangement on the production of soy- bean plants. J. Am. Soc. Agron., 31: 314--321.