Bangladesh Agron. J. 2025, 28(1): 23-28 FERTILIZER RECOMMENDATION FOR CHILLI - ONION INTERCROPPING SYSTEM I. S. M. Farhad1*, H. M. Naser1, E. Jahan2, M. M. Masud1 and M. S. Bhuiyan3 1Soil Science Division, Bangladesh Agricultural Research Institute, Gazipur-1701, Bangladesh 2Regional Laboratory, Soil Resources Development Institute, Tangail, Bangladesh 3On-Farm Research Division, Bangladesh Agricultural Research Institute, Coxsbazar, Bangladesh *Corresponding author, E-mail: farhadsau@gmail.com (Received: 12 October 2025, Accepted: 21 November 2025) Keywords: Benefit cost ratio, chilli equivalent yield, intercropping, optimum fertilizer Abstract An experiment was conducted at Central Research Farm, BARI, Gazipur during Rabi season of 2021-22, 2022-23 & 2023-24 to develop a fertilizer recommendation for chilli with onion intercropping system. Six treatment combinations viz. T1= 100% RDCF of chilli + 0% RDCF of onion, T2= 100% RDCF of chilli +10% RDCF of onion, T3= 100% RDCF of chilli + 20% RDCF of onion, T4= 100% RDCF of chilli +30% RDCF of onion, T5= 100% RDCF of chilli +40% RDCF of onion and T6= 100% RDCF of chilli +50% RDCF of onion were tested. The experiment was laid out in randomized complete block design with 3 replications. Both chilli and onion significantly influenced by different treatment combinations. Significantly the highest yield of chilli (12.18 t ha-1) and onion (8.13 t ha-1) were obtained from T6 treatment (100% RDCF of chilli +50% RDCF of onion) which was statistically similar with T5 treatment (100% RDCF of chilli +40% RDCF of onion). Chilli equivalent yield (CYI) progressively increases with the increase of inorganic fertilizers. The results showed that T6 provided the highest CEY (21.93 t ha-1) followed by T5 (21.88 t ha-1). The highest net return (430005 Tk ha-1) as well as BCR (4.67) were obtained from T5 treatment (100% RDCF of chilli +40% RDCF of onion) whereas the lowest net return (364411 Tk. ha-1) as well as BCR (4.28) were observed in T1 treatment (100% RDCF of chilli + 0% RDCF of onion).Though T6 treatment gave higher yield over all the treatments yet it showed lower BCR compared to T5 treatment due to higher cost involvement for inorganic fertilizer. Introduction In Bangladesh, the majority of farmers practice monoculture rather than intercropping. However, intercropping uses nutrients more efficiently and provides greater yield stability than monoculture (Seran and Brintha, 2010). Furthermore, mixed or intercropping can maximize land utilisation and boost productivity when compared to single crops (Launay et al., 2009; Mucheru- Muna et al., 2010). In highly populated countries with limited per capita land for agricultural production, intercropping is a crucial strategy for increasing productivity per unit area by intensifying the use of land. One of the major spices grown in Bangladesh is chilli, which is often grown as sole crop on char land. Farmers of different region especially char areas grow chilli as a sole or sometimes intercropping with onion. From the previous research findings of Begum et al. (2015), chilli with onion intercropping system found very productive and profitable for the char land. For the intercropping system of chillies with onions, there is currently no suggested fertilizer dosage. Fertilizer management is the most logical approach to increase overall productivity in order to obtain the highest return and crop yield. So, it is necessary to find out the optimum fertilizer dose for chilli with onion intercropping system. 24 Farhad et al. Materials and Methods A field experiment was conducted at Central Research Farm, BARI, Gazipur (AEZ-28) during Rabi season of 2020-21, 2021-22 & 2022-23 to develop a fertilizer recommendation for chilli with onion intercropping system. The experiment confined with intercropping where chilli was transplanted as main crop and onion was transplanted as companion crop. The variety of chilli and onion were BARI Morich-4 and BARI Piaj-4, respectively. Before conducting the experiment, initial composite soil samples at a depth of 0-15 cm from the experimental plots were collected and analyzed following standard methods (Table 1). Table 1. Chemical properties of initial soil (0-15 cm depth) of the experimental field at Central Research farm, BARI, Joydebpur, Gazipur during Rabi season The experiment was laid out in a randomized complete block design with three replicates. The unit plot size was 4.0 m  3.0 m. Chilli (30 days old seedlings) and onion (40 days old seedlings) transplantation were done on last week of December in all the three consecutive years. One row of onion was sown in between two rows of chilli. Line to line spacing of chilli was 40 cm and chilli to onion spacing was 20 cm. Plant to plant spacing of chilli and onion was 40 cm and 10 cm, respectively. The experiment was set up with six treatments viz. T1= 100% recommended dose of chemical fertilizer (RDCF) of chilli + 0% RDCF of onion, T2= 100% RDCF of chilli +10% RDCF of onion, T3= 100% RDCF of chilli + 20% RDCF of onion, T4= 100% RDCF of chilli +30% RDCF of onion, T5= 100% RDCF of chilli +40% RDCF of onion and T6= 100% RDCF of chilli +50% RDCF of onion. Recommended fertilizer dose was estimated based on the soil test value. Recommended dose of chemical fertilizer for chilli was N99.5 P32.6 K64 S9.5 Zn0.2 B0.9 kg ha-1 and onion was N108.8P28.5 K75.2S19.6 B1.3kg ha-1. Cowdung (5 t ha-1) were applied as a basal in all the plots. The whole amounts of organic manure, phosphorus, sulphur, zinc, boron, half of nitrogen and potassium were applied as basal during final land preparation. Remaining nitrogen and potassium were applied in two equal installments at 30 and 60 days after transplantation from 10- 12 cm away from the base of the plant which could be beneficial for the growth and yield of onion. All the intercultural operations such as irrigation, weeding, insect control etc. were done as and when necessary. Chilli was harvested five times at 15 days interval starting from 3rd week of March and onion was harvested in its maturity on 1st week of April in all the three years. Ten plants from each plot were tagged at random to take records on different agronomic parameters of chilli and onion. Data on yield and yield contributing parameters were recorded and statistically analyzed with the help of statistical package statistix 10 (Analytical Software. Tallahassee, Fla, USA) and mean separation was tested by Duncan’s Multiple Range Test (DMRT) (Steel and Torrie, 1960). Chilli Equivalent Yield (CEY) was calculated after Bandyopadhyay (1984): Sample pH OM Total N K Ca Mg P S Zn B Cu Fe Mn (%) (%) meq 100 g soil−1 µg g−1 soil Average 6.1 1.36 0.08 0.18 3.8 2.2 12 16 1.6 0.17 4.0 72 8 Critical level - - 0.12 0.12 2.0 0.5 7 10 0.6 0.2 0.2 4.0 1.0 Interpreta tion Slight ly acidic Low Very Low Low Med ium Very high Med ium Me diu m Opti mu m Low Very high Very high Very high Fertilizer recommendation for chilli - onion intercropping system 25 Chilli Equivalent Yield (kg/ha) = Yield of onion (kg/ha )× Price of onion (Tk./kg) Price of chilli (Tk./kg) Methods of chemical analysis Soil pH was measured by a combined glass calomel electrode (Jackson, 1958). Organic carbon was determined by wet oxidation method (Walkley and Black, 1934). Total N was determined by modified Kjeldahl method. K, Ca and Mg were determined by NH4OAc extraction method. Cu, Fe, Mn and Zn were determined by DTPA extraction followed by AAS reading. Boron was determined by CaCl2 extraction method. Phosphorus was determined by Bray and Kurtz method (Acid soils) and S was determined by CaH4 (PO4)2. H2O extraction followed by turbidimetric method with BaCl2. Results and Discussion Chilli The effect of chemical fertilizers on the yield and yield parameters of chilli are summarized in the Table 2. Green chilli yield and yield attributes like plant height, number of branches plant−1, number of fruits plant-1 and average fruit weight plant-1 of chilli were significantly influenced by different nutrient packages in this study. The significantly highest plant height (69.5 cm) was obtained from T6 treatment (100% RDCF of chilli +50% RDCF of onion) which was statistically similar with T5 treatment whereas the lowest plant height (64.0 cm) was obtained from T1 treatment (100% RDCF of chilli + 0% RDCF of onion). That similar to all other treatments except T5 and T6. Table 2. Yield and yield components of chilli as influenced by different treatment combinations at Gazipur during Rabi season (Pooled data of 3-years) Treatments Plant height (cm) Number of branches plant−1 Number of fruits plant−1 Average fruit weight plant−1 (g) Chilli yield (t ha−1) T1 64.0c 8.5c 130.0d 181.7e 10.10e T2 64.4c 9.3bc 134.6d 204.2d 10.48d T3 65.7c 9.6ab 139.5c 211.4c 10.90c T4 66.5bc 9.6ab 145.3b 217.3b 11.40b T5 69.0ab 10.0ab 157.7a 233.6a 12.15a T6 69.5a 10.2a 159.4a 236.2a 12.18a SE (±) 1.38 1.21 2.98 2.80 0.23 CV (%) 6.37 5.83 3.87 3.26 9.21 Means followed by same letter (s) do not differ significantly at 5% level of significance. T1= 100% RDCF of chilli + 0% RDCF of onion, T2= 100% RDCF of chilli + 10% RDCF of onion, T3= 100% RDCF of chilli + 20% RDCF of onion, T4= 100% RDCF of chilli + 30% RDCF of onion, T5= 100% RDCF of chilli + 40% RDCF of onion and T6= 100% RDCF of chilli + 50% RDCF of onion Number of branches plant−1 positively affected by different fertilizer treatment. Significantly the highest number of branches plant−1 (10.2) was obtained from T6 treatment whereas the lowest number of branches plant−1 (8.5) was recorded in T1 treatment. Number of fruits plant−1 progressively increases with the increase of inorganic fertilizers. The maximum number of fruits plant−1 (159.4) was obtained from T6 treatment which was statistically similar with T5 treatment while the minimum number of fruits plant−1 (130.0) was obtained from T1 treatment. The significantly highest average fruit weight plant−1 (236.2 g) was obtained from T6 treatment which was statistically similar with T5 and superior to all other treatments. The lowest average fruit weight plant−1 (181.7 gm) was recorded in T1 treatment. 26 Farhad et al. Yield of chilli progressively increases with the increase of inorganic fertilizers. Significantly the highest yield of green chilli (12.18 t ha−1) was obtained from T6 treatment (100% RDCF of chilli + 50% RDCF of onion) which was statistically similar with T5 treatment (100% RDCF of chilli +40% RDCF of onion) and superior to all other treatments. The lowest yield of green chilli (10.10 t ha−1) was observed in T1 treatment (100% RDCF of chilli + 0% RDCF of onion). The result was similar to the findings of Farhad et al. (2022) in chill + garlic intercropping system and in maize + potato intercropping system. Onion The effect of chemical fertilizers on the yield and yield parameters of onion are summarized in the Table 3. The results indicated that all of the yield attributes of onion were significantly influenced by different treatment combinations. The highest plant height (55.4 cm) was obtained from T6 treatment (100% RDCF of chilli +50% RDCF of onion) which was statistically at par with T3 and T4 treatment whereas the lowest plant height (50.3 cm) was obtained from T1 treatment (100% RDCF of chilli + 0% RDCF of onion), also similar with T2 and T3 treatments. Table 3. Effect of different treatments on the yield and yield attributes of onion at Gazipur during Rabi season (Pooled data of 3-years) Treatments Plant height (cm) Number of leaves plant-1 Bulb length (cm) Bulb diameter (cm) Individual bulb weight (g) Bulb yield (t ha-1) T1 50.3b 8.2e 4.37c 4.10d 36.1c 7.44d T2 51.5b 8.5de 4.38c 4.16c 36.4c 7.50d T3 52.1b 8.7cd 4.43bc 4.19c 37.6b 7.77c T4 54.4a 9.1bc 4.48ab 4.25b 38.7ab 7.93b T5 55.3a 9.4ab 4.54a 4.30a 39.5a 8.11a T6 55.4a 9.6a 4.56a 4.32a 39.8a 8.13a SE (±) 1.29 1.13 0.08 0.05 0.72 0.06 CV (%) 5.80 8.72 5.81 3.91 4.81 8.12 Means followed by same letter (s) do not differ significantly at 5% level of significance. T1= 100% RDCF of chilli + 0% RDCF of onion, T2= 100% RDCF of chilli + 10% RDCF of onion, T3= 100% RDCF of chilli + 20% RDCF of onion, T4= 100% RDCF of chilli + 30% RDCF of onion, T5= 100% RDCF of chilli + 40% RDCF of onion and T6= 100% RDCF of chilli + 50% RDCF of onion The maximum number of leaves plant−1 (9.6) was obtained from T6 treatment which was statistically similar with T5 treatment whereas the minimum number of leaves plant−1 (8.2) was obtained from T1 treatment (100% RDCF of chilli + 0% RDCF of onion). Both of bulb length and bulb diameter are progressively increases with the increase of fertilizers. The highest bulb length (4.56 cm) and bulb diameter (4.32 cm) were obtained from T6 treatment (100% RDCF of chilli + 50% RDCF of onion) which was statistically similar with T5 treatment (100% RDCF of chilli + 40% RDCF of onion). The lowest bulb length (4.37 cm) and bulb diameter (4.10 cm) were obtained from T1 treatment (100% RDCF of chilli + 0% RDCF of onion). Individual bulb weight and yield of onion progressively increases with the increase of inorganic fertilizers. Significantly the highest individual bulb weight (39.8 g) and bulb yield (8.13 t ha−1) of onion were obtained from T6 treatment (100% RDCF of chilli + 50% RDCF of onion) which was statistically similar with T5 treatment (100% RDCF of chilli + 40% RDCF of onion) and superior to all other treatments.The lowest individual bulb weight (36.1 g) and bulb yield (7.44 t ha−1)were obtained from T1 treatment (100% RDCF of chilli + 0% RDCF of onion). Chilli Equivalent Yield Chilli equivalent yield (CEY) was progressively increased with the increase of inorganic fertilizers. The result showed that T6 provided the highest CEY (21.93 t ha−1) that was15.29% higher over T1 (Fig. 1). The treatment T5 also gave higher CEY (21.88 t ha−1) followed by T4, T3 Fertilizer recommendation for chilli - onion intercropping system 27 and T2. The higher CEY was mainly attributed due to additional yield advantage resulted from fertilizer effect in chill-onion intercropping. The result was similar to the findings of Farhad et al. (2022) who observed that there was a trend of increase in CEY with the increase of inorganic fertilizer level and the CEY was decreased considerably towards lower fertilizer levels in chilli with onion intercropping system. Begum et al. (2016) also reported PEY increased towards higher fertilizer rates in potato-hybrid maize intercropping system. Fig.1. Chilli equivalent yield (CEY) and % CEY increase over T1 in different treatment combinations Cost and return analysis Cost and return of chilli with onion intercropping have been described in the Table 4. Among the treatments, the highest net return (430005 Tk. ha-1) as well as BCR (4.67) were obtained from T5 treatment (100% RDCF of chilli + 40% RDCF of onion) whereas the lowest net return (364411 Tk. ha-1) as well as BCR (4.28) were observed in T1 treatment (100% RDCF of chilli + 0% RDCF of onion). Though T6 treatment gave higher yield over all the treatments yet it showed lower BCR compared to T5 treatment due to higher cost involvement for inorganic fertilizer. Table 4. Cost and return analysis of chilli with onion intercropping system as influenced by different fertilizer treatment combinations at Gazipur during Rabi season (Pooled data of 3-years) Treatments Yield (t ha-1) Chilli equivalent yield (t ha-1) Gross return (Tk. ha-1) Total cost (Tk. ha-1) Net return (Tk. ha-1) Benefit cost ratio (BCR) Chilli Onion T1 10.10 7.44 19.02 475500 111089 364411 4.28 T2 10.48 7.50 19.48 487000 112566 374434 4.32 T3 10.90 7.77 20.22 505500 114042 391458 4.43 T4 11.40 7.93 20.91 522750 115520 407230 4.52 T5 12.15 8.11 21.88 547000 116995 430005 4.67 T6 12.18 8.13 21.93 548250 118472 429778 4.62 Input and output price per Kg: Urea = Tk. 16, TSP = Tk. 22, MoP = Tk. 15, Gypsum = Tk. 12, Zinc sulphate =Tk.150, Boric acid Tk. = Tk.220, chilli seed =Tk.600, onion seed =Tk.900, Chilli selling price = Tk. 25 and Onion selling price = Tk. 30 28 Farhad et al. Conclusion From the present study, it may be concluded that treatment package consists of 100% recommended doses chemical fertilizers of chilli along with 40% recommended doses chemical fertilizers of onion is most profitable for chilli with onion intercropping system in the study area (AEZ-28). References Bandyopadhyay, S.K. 1984. Nitrogen and Water Relations in Grain Sorghum Legume Intercropping Systems. Ph. D. Dissertation, Indian Agricultural Research Institute (IARI), New Delhi- 110012, India. Begum, A.A., M.S.U. Bhuiya, S.M.A. Hossain, A. Khatun and S.K. Das. 2016. Effect of fertilizer management on productivity of Potato-Hybrid Maize intercropping system. Bangladesh J. Agril. Res. 41(4): 633-645. Begum, S.A., M.S. Zaman and A.S.M.M.R. Khan. 2015. Intercropping of root crops with chilli in charlands of Mymensingh. Prog. Agric. 26: 109-114. Farhad, I. S. M., E. Jahan, R. Sen, M. M. U. Chowdhury and S. Akhter. 2022. Fertilizer Recommendation for Chill-Garlic Intercropping System. Bangladesh Agron. J. 25(1): 7-14. Jackson, M.L. 1958. Soil Chemical Analysis. Prentice Hall Inc. Engle-wood, Cliffs, N.Y. Launay, M., N. Brisson, S. Satger, H. Hauggaard-Nielsen, G. Corre-Hellou, E. Kasynova, R. Ruske, E.S. Jensen and M.J. Gooding. 2009. Exploring options for managing strategies for pea-barley intercropping using a modeling approach. Eur. J. Agron. 31: 85-98. Mucheru-Muna, M., P. Pypers, D. Mugendi and B. Vanlauwe. 2010. A staggered maize-legume intercrop arrangement robustly increases crop yields and economic returns in the highlands of Central Kenya. Field Crops Res. 115: 132-139. Seran, T.H. and I. Brintha. 2010. Review on maize-based intercropping. J. Agron. 9(3): 135-145. Steel, R.G.D. and Torrie, A.H. 1960. Principles and Procedures of Statistics with Special Reference to the Biological Sciences. McGraw Hill, New York, 187-287. Walkley, A. and I.A. Black. 1934. An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method. Soil Sci. 37: 29-38.