Determination of Inorganic N and P Fertilizers on Fruit Yield and Yield Components of Pineapple (Annanas comosus MERR L. Var. Smooth cayanne) at Gojeb, South Ethiopia

Tewodros M. Getachew E, Neim S. Getachew W, Mesfin S

Jimma Agricultural Research Center, P.O. Box 192, Jimma, Ethiopia

*Corresponding Author E-mail: tewodrosmulualem@gmail.com

ABSTRACT:

The study was conducted at Gojeb Horizan plantation farm of South Ethiopia, for two cropping seasons (2012-2014 and 2015-2017 as a ratoon crop). The aim of the study was to determine the appropriate inorganic NP fertilizer amount required for high yield and quality of pineapple (variety Smooth cayenne) for production. Four levels of N (0, 93.6, 108 and 281 kg ha-1) and four levels of P (0, 134.8, 269.6 and 404.4 kg P2O5 ha-1) weresourced from Urea and DAP arranged in RCBD with three replications. Different yield, quality and yield related traits collected and subjected to data analysis. The result revealed that, the highest fruit yield obtained from application rate of 281 kg N ha-1 and 134.8 kg P2O5 ha-1. The rate of application of nitrogen of 281 kg ha-1 significantly increased the fresh fruit yield of pineapple up to 26.86% than the control. Likewise, application of phosphorus rate of 134.8 kg P₂O5 ha-1 increased the fresh fruit yield of pineapple by 8.93% than the control. Similarly, the quality (TSS content) of pineapple significantly decreased when the applied nitrogen beyond 93.6 kg N ha-1 rate. Apply treatments beyond 93.6 kg N ha-1, similarly, the quality (TSS content) declined by 5.67%. The economic analysis also revealed that the highest net benefit of 18305.0 Ethiopian Birr/ha (ETB/ha) with marginal rate of return of 705.4% was obtained by the application of 281 kg N ha^-1. Likewise, the net benefit of 131774.0 ETB/ha with marginal rate of return of 5431.74% were obtained by the application of 134.8 kg P₂O₅ ha^-1. Based on the above results, a combined application of 281 kg N ha^-1 and 134.8 kg P₂O₅ ha^-1 are optimum and economically better for pineapple production at Gojeb plantation and its surroundings.

KEYWORDS: Determination, Nitrogen; Phosphorus; Pineapple, Quality, Variety.

INTRODUCTION:

Pineapple [Ananas comosus (L.) Merr.] is an important representative of the Bromeliaceae family and widely cultivated throughout tropical and subtropical regions (Tewodros et. al, 2018). It is the second most important fruit crop after bananas and contributing over 20 % of the world tropical fruits production (Mohamed and Ahmad. 2004) and 51% of world global fruit market (FAO, 2008).

Pineapple fruits are consumed freshly as table fruit or in desserts and are an important source of essential mineral elements, nutrients and vitamins. The suitability of pineapple as food stores on ships and medical ingredients greatly facilitated their distribution throughout the world. Presently, Annanas is a pan tropical genus and different species have been independently domesticated across continents.

In Ethiopia, pineapple successfully grows in South, Southwestern and Western parts as small scale farming and the average yield of the crop is low about 50 tons/ha (Tewodros et. al, 2018) as compared to global average fruit yield of 63 t/ha (Samuels et al., 1960). Different factors that contribute directly and indirectly for low yield: low fertility status of the soil when the pineapple was grown, resulting from depletion by proceeding crops (Hermann et al., 2013), lack of improved pineapple technologies adapted for diverse environmental conditions, longer maturity, poor marketing system, presence of diseases and insect pests, and lack of improved post harvest handling technologies are few to mention (Tewodros et al., 2014). Besides, lack of sufficient information on the nutritional requirement of pineapple cultivation, leads low productivity (IAR, 1996). According to Khalid and Rashid (2009), pineapple requires nutrients such as nitrogen (N), phosphorus (P) and potassium (K) for fertility maintenance and crop production. These nutrients are specific in function and must be supplied in sufficient quantity to plant at the right time (Omotoso and Akinrinde, 2013). According to the reported of Spironello et al., (2004), fruit yield of pineapple is very responsive to NPK fertilization. In fruit crops, it is known that applications of NPK fertilizer are vital for fruit yield and quality (Vho, 1999). Besides, NPK plays an important role in the growth and development of the plant (FAO, 2000). On the other hand, excessive application of K in the soil results in low uptake of NH₄+, Ca++ and Mg++ (Ludders, 1980). Thus, a balanced application of K not only improves the yield and quality of pineapple, but it also increases the fertilizer use efficiency of other nutrients.

Despite the importance of NPK, the nutrient requirement of pineapple in Ethiopia is poorly understood and leads severe yield losses in major pineapple growing areas of the country. To raise the productivity, better understanding on the growing environment of pineapple in association with its appropriate fertilizer requirements and types are needed to boost pineapple production, which minimize the scarcity and improve the livelihood security of rural households. Therefore, this study was designed to determine the effect of inorganic nitrogen and phosphorus fertilization on the yield and quality traits of pineapple in Gojeb state farm of Southwest Ethiopia.

MATERIALS AND METHODS:

Description of the study areas:

Field experiments were conducted for two consecutive growing seasons (2012-2014 and 2015-2017 as a ratoon crop) at Gojeb state farm, Kaff zone of South Ethiopia. Gojeb state farm is located at latitude 7^o 42.36' N and longitude 36^o 51’66’ E with an altitude of 1553 meters above sea level (m.a.s.l.). The area receives mean annual rainfall of 1430 mm with mean maximum and minimum temperatures of 25.4°C and 10.6°C, respectively. The soil of the study site is sandy loam with p^H of 6.5.

Soil sampling and Analysis:

Fiften nucleus soil samples randomly collected from 0-30cm top soil and bulk to form a composite sample. The collected samples air dried, crushed and allowed to pass through a 2 mm sieve. Particle size distribution carried out by the hydrometer method, while soil p^H in soil solution ratio 1:2 in 0.01M C_aCl₂. Soil organic carbon was determined by the Walkey and Black method and total N by the micro-kjeldahl digestion method (Bremer and Mulraney, 1982). Available P was determined by Bremer and Mulraney, (1982) extraction method. Exchabgeble bases were extracted with neutral 1M NH₄OAC at soil solution ratio of 1:10 and measured by flame photometry. Exchabgeble acidity was determined by titration of 1M KCL extract against 0.05M NaOH to a pink end point using phenolphthalein as indicator (Maclean, 1982). The soil sample analysis was conducted at Jimma Agricultural Research Center (JARC) soil and plant tissue laboratory.

Experimental materials:

Improved variety of pineapple (Smooth cayenne) planted in double row planting system. Treatment consisted on N applied at (0, 93.6, 108 and 281 kg ha^-1 as urea (46% N) and P applied at (0, 134.8, 269.6 and 404.4 kg ha-1) as DAP (46% P₂O₅ and 18% N).

Experimental design and management:

The experiment was laid out in RCBD with three replications. The gross plot size for each treatment was 6m x 4m (24 m²). Plants was field established using double spaced of 30 x 60 x 90cm. Slips of the same size were used as planting material. Both fertilizer rates applied at near root zone of each row. All DAP and 50% of Urea applied at planting. The remaining 50% of Urea applied as side banded after 60 days of planting. One month after planting, seedlings were earthed up, followed by frequent weeding. All other agronomic practices were followed according to the recommendations.

Data collection and analysis:

Data were collected from ten plants from each plot and the average value used for data analysis. The characters that considered for data collection are: plant height (m), leaf length (cm), fruit length (cm), fruit diameter (cm), fruit weight (kg fruit^-1) and TSS (%). Total soluble solid (TSS) in Brix was obtained by a temperature self compensating digital refractometer (AOAC, 2005) at Jimma University, College of Agriculture and Veternery Medicine (JUCAVM) food and nutrition laboratory. A drop of solution was squinted on the prism of refractometer. The percentage of TSS was obtained from the direct reading of the instrument. The collected data were subjected to analysis of variances and treatment means separated by Least Significant Difference (LSD) by using Statistical Analysis System (SAS) package (version 9.0 of SAS Institute Inc, 2000).

Economic evaluation:

Economic evaluation comprising partial budget with dominance and marginal rate of return was carried out. To estimate economic parameters, product (marketable fruit yield) valued based on average market price collected from local markets during the two consecutive years of production when fresh pineapple fruits sold by 25 Ethiopian Birr per kg. Average price of Urea, and DAP were 15.0 and 18.0 Birr per kg, respectively. Some of the concepts used in the partial budget analysis are gross field benefit (GFB), total variable cost (TVC) and the net benefit (NB). The GFB ha^-1 was obtained as the product of the real price and the mean pineapple fruit yield for each treatment. TVC refers to the sum of cost of all variable inputs (fertilizers) were used according to (CIMMYT, 1988).

Table 1. Physico-chemical properties of top soil (0-30cm) of experimental field of Gojeb state farm experimental sites.

S. No	Physical composition	Gojeb state farm
1	% Sand	60
2	% Silt	18
3	% Clay	22
4	Textural class	Sandy loam
5	p^H(H₂O) (1:2:5)	6.50
6	Organic carbon	3.215
7	Available P (ppm)	0.561
8	Total N (g/kg)	0.641
9	Available K (meq/100g)	1.083
10	%Organic matter	5.946
11	Exchangeable acidity (meq/100g)	0.134
12	CEC (meq/100g)	23.12
13	Exchangeable AL⁺⁺⁺(meq/100g)	Trace

Table 2. The analysis of variance of nitrogen and phosphorus on yield and yield related traits of pineapple 2012-2014 grown at Gojeb state farm

Treatments	PH	LL	FL	FDi	FFW	Brix
0kg/ha N x 0kg/ha P₂O5	54.17^cde	49.60^cdef	10.64^cde	8.66^abc	0.88cd	15.16^abc
134.8 Kg P₂O5	54.49^cde	47.85^edf	10.43^de	8.99^ab	1.01bcd	15.33^abc
269.6 Kg P₂O5	59.81^bcde	53.87^abcde	12.6^abcde	6.15^c	0.94cd	13.5^c
404.4 Kg P₂O5	65.09^ab	56.91^abcd	12.7^abcde	10.37^ab	1.08^abcd	14.66^bc
93.6 Kg N	59.06^bcde	51.62^bcdef	13.43^abc	9.13^ab	1.26^abcd	15.83^ab
93.6 Kg N+134.8 Kg P₂O5	67.58^ab	59.25^abc	14.90^a	10.63^ab	1.39^abc	15.16^abc
93.6 Kg N+269.6 Kg P₂O5	69.94^a	63.47^a	14.85^a	10.7^ab	1.26^abcd	15.00^abc
93.6 Kg N+404.4 Kg P₂O5	53.13^de	44.18^f	11.8^bcde	9.35^ab	1.47^ab	15.33^abc
108 Kg N	54.68^cde	47.4^edf	11.79^cde	9.00^ab	0.85^d	16.00^ab
108 Kg N+134.8 Kg P₂O5	66.25^ab	60.14^ab	13.1^abcd	10.30^ab	1.12^abcd	14.23^bc
108 Kg N+269.6 Kg P₂O5	67.94^ab	54.39^abcde	14.17^ab	11.18^a	1.57^a	15.93^ab
108 Kg N+404.4 Kg P₂O5	60.8^abcde	56.69^abcd	12.2^bcde	9.81^ab	1.05^abcd	13.83^c
281.6 Kg N	63.64^abc	57.02^abcd	13.31^abc	9.97^ab	1.19^abcd	14.66^bc
281.6 Kg N+134.8 Kg P₂O5	61.87^abcd	54.57^abcde	12.2^abcde	10.05^ab	1.15^abcd	15.00^abc
281.6 Kg N+269.6 Kg P₂O5	59.04^bcde	52.06^bcdef	12.2^abcde	9.94^ab	0.96^bcd	16.83^a
281.6 Kg N+404.4 Kg P₂O5	52.12^e	45.74^f	11.5^bcde	8.54^bc	0.9^cd	14.33^bc
Mean	60.60	53.42	12.40	9.55	1.13	15.05
CV (%)	9.67	10.08	2.83	2.59	0.52	1.93
LSD (<0.05)	0.96	0.11	0.14	0.16	0.28	0.77

PH= Plant height (cm), LL= Leaf length (cm), FL= Fruit length (cm), FDi= Fruit diameter (cm), FW= Fruit fresh weight (kg/fruit) and Brix= TSS (%)

Table 3. The analysis of variance of nitrogen and phosphorus on yield and yield related traits of pineapple ratoon crop grown at Gojeb state farm

Treatments	PH	LL	FL	FDi	FFW	Brix
0kg/ha N x 0kg/ha P₂O5	61.93^a	62.86^a	12.08^abc	9.55^a	0.91^ab	14.93^abcd
134.8 Kg P₂O5	56.62^ab	61.01^a	12.33^abc	9.73^a	1.22^ab	15.33^abcd
269.6 Kg P₂O5	56.62^ab	59.67^a	11.06^c	9.87^a	0.89^ab	14.06^bcd
404.4 Kg P₂O5	56.76^ab	58.12^a	12.15^abc	10.0^a	0.94^ab	15.1^abcd
93.6 Kg N	58.66^ab	56.09^a	12.05^abc	9.73^a	0.88^ab	16.06^ab
93.6 Kg N+134.8 Kg P₂O5	57.36^ab	58.46^a	10.86^c	9.43^a	1.34^a	14.83^abcd
93.6 Kg N+269.6 Kg P₂O5	56.53^b	54.68^a	11.7bc	9.29^a	0.84^ab	15.06^abcd
93.6 Kg N+404.4 Kg P₂O5	58.86ab	54.05^a	11.4c	9.06^a	1.19^ab	15.83^abc
108 Kg N	60.7^ab	62.46^a	12.01^abc	9.36^a	1.02^ab	16.66^a
108 Kg N+134.8 Kg P₂O5	61.2^ab	60.76^a	11.9^abc	9.55^a	0.92^ab	16.66^a
108 Kg N+269.6 Kg P₂O5	61.33^ab	61.8^a	11.58^c	9.46^a	0.83^b	14.23^bcd
108 Kg N+404.4 Kg P₂O5	59.65^ab	62.0^a	11.18^c	9.6^a	1.06^ab	15.26^abcd
281.6 Kg N	61.13^ab	61.63^a	13.66^ab	9.90^a	0.87^ab	13.83d
281.6 Kg N+134.8 Kg P₂O5	60.83^ab	56.26^a	11.7^bc	9.55^a	0.84^ab	15.83^abc
281.6 Kg N+269.6 Kg P₂O5	60.62^ab	63.13^a	13.86^a	9.57^a	0.76^b	15.16^abcd
281.6 Kg N+404.4 Kg P₂O5	61.16^ab	63.21^a	10.96^c	9.29^a	0.80^b	16.16^ab
Mean	59.37	59.76	11.90	9.56	0.96	15.12
CV (%)	5.32	10.69	2.04	0.99	0.50	2.15
LSD (<0.05)	0.54	0.11	0.10	0.62	0.32	0.85

PH= Plant height (cm), LL= Leaf length (cm), FL= Fruit length (cm), FDi= Fruit diameter (cm), FW= Fruit fresh weight (kg/fruit) and Brix= TSS (%)

RESULTS AND DISCUSSION:

Soil physic chemical characteristics:

The result of the soil physico-chemical properties of Gojeb state farm is presented in Table 1. The data Gojeb state farm revealed, the p^H of the soil was 6.5 in water, 0.641 g kg^-1 N, 3.215 g kg^-1 organic C. 0.561 ppm available P, 1.083 meq/100g K, 5.946 % Organic matter, 0.134 meq/100g exchangeable acidity and 23.12 meq/100g CEC. Particle size distributions were 60% sand, 22% clay and 18% silt. The soil physic chemical properties of the tested sites are conducive for pineapple production.

Plant growth, fruit yield and quality characteristics of pineapple:

The results of analysis of variance (ANOVA) indicated, plant height, leaf length, fruit length, fruit diameter, fruit fresh weight and TSS of pineapple plants influenced significantly by rates of nitrogen and phosphorus in main and ratoon crop at Gojeb state farm (Table 2 and Table 3).

The effect of NP fertilization on yield and quality traits of pineapple:

The effects of NP fertilizer on yield and quality traits of pineapple at Gojeb state farm are presented in Table 4. The result revealed plant height is an important growth character directly allied with fruit yield, which is positively correlated with productivity of the crop (Babatola et al., 2002). In this study, the effects of N fertilizer rates had significant effects on the height of pineapple (Table 4). The tallest plant (63.95cm) was obtained from 281 kg N ha^-1 and 63.87cm at rates of 269.6 kg P₂O₅ ha^-1 at Gojeb. Pineapple treated at a control, the height became lowest (58.19cm and 58.82 cm) N and P₂O₅rates, respectively. The trends of N application of 281 kg N ha^-1 gave 9.0% and 0.57% increases over the control in main plant and ratoon crops (Table 4). This result is consistent with the report of Delali, (1995) who reported, increasing the levels of N application was observed to increase the height and the yield of pineapple. The application of P₂O₅ showed similar trends like as N application on plant height. The tallest plant was obtained by application rate of 269.6 kg P₂O₅ ha^-1. Similarly, the advanced rates of N and P₂O₅ from 93.6 kg N ha^-1 to 108kg N ha^-1 and 269.6 kg P₂O₅ ha^-1 to 404.4 Kg P₂O₅ ha^-1 resulted in a corresponding increasing in plant height, leaf length, fruit length and fruit fresh weight, however, the opposite result was observed on fruit diameter and brix (TSS) contents, when the higher rates of N and P (Ademar et al., 2004). Leaf length of a plant is an important growth character and directly associated with the yield potential of pineapple and positively correlated with plant productivity through dry matter accumulation (Omotoso and Akinrinde, 2013). Pineapple tested with 108 kg N ha^-1and 404 kg P₂O₅ ha^-1 had longest (54.31 cm and 53.50cm) leaf length.

Table 4. Effect of nitrogen and phosphorus on yield and yield related traits of pineapple and ratoon crop 2012-2014 and ratoon crop grown at Gojeb state farm

Treatment	2012/2014
Treatment	PH	LL	FL	FDi	FW	Brix
Nitrogen (Kg/ha)
0	58.19^ab	53.35^a	12.42^a	9.61^a	0.94^a	14.66^b
93.6	60.21^a	54.19^a	12.61^a	9.77^a	1.08^a	15.79^a
108	60.02^a	54.31^a	12.96^a	9.52^a	1.15^a	14.89^ab
281	63.95^a	51.83^a	11.62^a	9.28^a	1.34^a	14.85^ab
SE±	7.89	8.55	2.34	1.79	0.32	1.20
Phosphorous (P₂O₅Kg/ha)
0	60.44^ab	52.46^ab	12.48^ab	8.61^ab	1.02^ab	14.70^ab
134.8	59.38^ab	52.54^ab	11.87^b	9.48^a	1.12^a	15.22^a
269.6	63.87^a	55.19^a	13.36^a	10.26^a	1.13^a	15.56^a
404.4	58.70^ab	53.50^a	11.89^b	9.63^a	1.19^a	14.70^ab
Interaction N x P	NS	NS	NS	NS	NS	NS
CV%	13.03	16.00	18.92	18.78	28.70	8.03
Ratoon crop
Treatment	PH	LL	FL	FDi	FW	Brix
Nitrogen (Kg/ha)
0	58.82^a	57.89^a	12.22^a	9.69^a	0.80^a	15.05^ab
93.6	60.40^a	60.02^a	12.07^a	9.59^a	0.96^a	15.00^ab
108	59.11^a	59.48^a	11.61^a	9.52^a	0.99^a	15.72^a
281	59.16^a	61.67^a	11.70^a	9.43^a	1.08^a	14.70^a
SE±	3.47	7.20	1.80	0.72	0.34	1.31
Phosphorous (P₂O₅Kg/ha)
0	58.64^a	58.56^a	11.68^ab	9.38^ab	0.81^b	15.02^b
134.8	59.23^a	59.12^a	12.59^a	9.64^a	0.95^av	15.11^ab
269.6	59.64^a	59.98^a	11.00^b	9.46^ab	0.97^av	15.10^ab
404.4	59.98^a	61.80^a	12.35^ab	9.74^a	1.10^a	15.35^a
Interaction N x P	NS	NS	NS	NS	NS	NS
CV%	5.84	12.04	15.56	7.62	36.30	8.71

PH= Plant height (cm), LL= Leaf length (cm), FL= Fruit length (cm), FDi= Fruit diameter (cm), FW= Fruit fresh weight (kg/fruit) and Brix= TSS (%)

The result obtained from this study was consistent with the report of (Babatola et al., 2002) who reported, 58cm and 52 cm of pineapple from application of 200 kg N ha^-1and 180 kg P₂O₅ha^-1. The longest leaf as a result of N application is indicative of the role of N in promoting vigorous foliage growth and more intense physiological activities in the plant which favored the synthesis of more assimilates for fruit development. Likewise, nitrogen increases the chlorophyll contents of the leaves, thereby promote the photosynthetic capacity of the plant, plays a part in the manufacture of dry matter and responsible for high fruit yield in pineapple (Tewodros et. al, 2018). On the other hand, phosphorous promotes CO₂ assimilation and energy for the translocation of carbohydrates from leaves to the fruits of crops, where carbohydrates are the main storage material (Abu, 2015). Similarly, fruit length, fruit diameter and fresh fruit yield followed similar trends as plant height. The control plots (0 Kg N and 0 Kg P₂O₅) showed the shortest plants with the lowest fruit length and fruit fresh weight. Fruit length and diameter had highest at application of 108 kg N ha^-1rates were statistically similar (Table 4). Fruit length and diameter/fruit were significantly increased by P₂O₅ application up to the 269.6 kg ha^-1 rate and not beyond. Although, the rate of application of N from 0 up to 108 kg ha^-1, increased the length of fruit by 4.17 %, whereas, the application of P₂O₅ up to 269.6 Kg ha^-1, gave corresponding value of 6.58% than the control. Fruit length and diameter followed similar trends as increased the N and P₂O₅ rates from 0 kg N ha^-1 to 108 kg N ha^-1 and 0 kg P₂O₅ ha^-1 to 269.6 kg P₂O₅ ha^-1, respectively. The superior growth attributes was obtained at high rates of N and P₂O₅ in this study has been reported by other researchers (Babatola et al., 2002; Mohamed and Ahmad. 2004). The positive response of growth characters to the applied plant nutrients is attributable to their role in cell division, multiplication and photosynthesis which gave rise to increase in size and length of leaves, fruit and stems.

Furthermore, the positive response shown by yield parameters to N and P₂O₅ could be directly linked to the well developed photosynthetic surfaces and increased physiological activities leading to more assimilates being produced and subsequently translocation of assimilates and utilized for fast fruit development. In this regard, Ayoola and Makinde, (2007) reported, both N and P₂O₅ are necessary for root initiation, elongation, and increase in fruit length, diameter and fruit yield. Total fruit fresh weight obtained at 281 kg N ha^-1 rates showed an increase of 29.85% over that of 0 kg N ha^-1 rate, whereas, increasing P₂O₅ rates from 0 to 269.6 kg ha^-1, increase fresh fruit weight by 5.53%; further increase P₂O₅ application up to 404.4 kg ha^-1 decreased fruit fresh weight by 1.03 percent. On contrary, the results obtained from this study is higher than the reported value of 127.04 kg N ha^-1and 65 kg P ha^-1 with fruit fresh weight of 16.72 t ha^-1 (Suminarti et al., 2016). The observed disparity between the results could be explained on the basis of the soil fertility difference and the environmental conditions upon which the plant was grown. Besides, Ademar et al., (2004), also reported significant differences on fruit yield of pineapple due to N, P₂O₅and K application. This result was consistent with the report of Orluchukwu and Adedokun (2015) who suggested that the maintenance dressing of 270 kg N ha^-1and 280 kg P₂O₅ ha^-1per cropping season may be adequate for continuous pineapple production in Nigeria.

The effect of N fertilizer rates on fruit quality of pineapple are presented in Table 4. The TSS content increased significantly as N rates increased. According to Bussi and Amicot (1988) and Omotoso and Akinrinde (2013) reported, high N fertilizer application had significant positive effect on the TSS content. In this study, the highest TSS content (15.79%) and (15.72%) was obtained at N rates of 108 kg N ha^-1in plant and ratoon crops, respectively. Apply treatments beyond 108 kg N ha^-1, the TSS content declined by 5.95%. This result was consistent with the report of Ademar et al., (2004) who reported, high N application had positive effect on fruit yield, but decreased quality (TSS) contents significantly.

Table 5. Marginal rate of return and sensitivity analysis for NP fertilizer at Gojeb stations

Fertilizer level	Mean Yield (Kg/ha)	Adjusted Yield (Kg/ha)	Gross Benefit (ETB/ha)	Cost of Urea (ETB/ha)	Cost Of DAP (ETB/ha)	Gross Cost (ETB/ha)	Net Benefit (ETB/ha)	Change gross cost	Change Net benefit	MRR (%)
N(kg ha^-1)
0	41360.0	4136.0	82720.0	0	0	0	103400	-	-	-
93.6	47520.0	4752.0	95040.0	1404.0	0	1404.0	117396	1404	13996	996.866
108	50600.0	5060.0	101200.0	1620.0	0	1620.0	124880	216	7484	3464.81
281	58960.0	5896.0	117920.0	4215.0	0	4215.0	143185	2595	18305	705.394
P(P₂O₅kg ha^-1)
0	44880.0	4488.0	89760.0	0	0	0	112200	-	-	-
134.8	98560.0	9856.0	98560.0	0	2426.0	2426.0	243974	2426	131774	5431.739
269.6	99440.0	9944.0	99440.0	0	4852.8	4852.8	243747.2	2426.8	226.8	-9.345640
404.4	104720.0	10472.0	104720.0	0	7279.2	7279.2	254520.8	2426.4	10773.6	444.0158

Sensitivity analysis

Fertilizer level	Mean Yield (Kg/ha)	Adjusted Yield (Kg/ha)	Gross Benefit (ETB/ha)	Cost of Urea (ETB/ha)	Cost Of DAP (ETB/ha)	Gross Cost (+10%)	Net Benefit (-10%)	Change gross cost	Change Net benefit	MRR (%)
N(kg ha-1)
0	41360.0	4136.0	82720.0	0	0	0	93060.00	-	-	-
93.6	47520.0	4752.0	95040.0	1404.0	0	1544.4	105530.04	1544.4	12470.04	807.43
108	50600.0	5060.0	101200.0	1620.0	0	1782	112246.2	237.6	6716.16	2826.66
281	58960.0	5896.0	117920.0	4215.0	0	4636.5	128487.15	4636.5	16240.95	350.28
P(P2O5 kg ha-1)
0	44880.0	4488.0	89760.0	0	0	0	100980	-	-	-
134.8	98560.0	9856.0	98560.0	0	2426.0	2668.6	219358.26	2668.60	118378.2	4435.968
269.6	99440.0	9944.0	99440.0	0	4852.8	5338.08	218935.72	2669.48	-422.532	-15.828
404.4	104720.0	10472.0	104720.0	0	7279.2	8007.12	228413.59	2669.04	9477.864	355.1038

MRR=Marginal Rate of Return, field price of pineapple = 25 ETB ha^-1, price of Urea= 15ETB ha^-1, price of DAP= 18ETB/kg.

On contrary, adequate supply of P₂O₅is important for energy synthesis and translocation, and it also increases yield and improves the fruit quality (brix contents). Hence, the positive response of fruit yield and yield components to increased rates of N and P₂O₅ could be adduced to high energy synthesis and translocation of assimilates.

The result of economic analysis revealed, the highest change net benefit of 18305.0 ETB/ha with marginal rate of return (MMR) of 705.4% and 1, 31, 774.0 ETB ha^-1 with marginal rate of return of 5431.739% were obtained by growing pineapple with the application of 281 kg N and 134.8 P₂O₅ha^-1, respectively (Table 5). An increase in output will always raise profit as long as the marginal rate of return is higher than the minimum rate of return i.e. 50 to 100%. Result on Table 5 showed that, the marginal rate of return at the nitrogen application rate of 281 kg N ha^-1 was greater than 50% marginal rate of return showed an economically feasible. Besides, the marginal rate of return due to phosphorus application is also more than 50%, application of phosphorus fertilizer is economically profitable up to the rate of 134.8 kg P₂O₅ha^-1. The MRR decreased as the cost increased. Rate of phosphorus fertilizers at 269.6 kg P₂O₅ha^-1 was dominated.

CONCLUSION:

The result of this study revealed that N and P fertilizers sourced from Urea and DAP had significant effect on yield and quality of pineapple. Combined application of 281 kg N ha-1 and 134.8 kg P₂O5 ha-1 had improved the yield and quality of pineapple in tested area. The result of economic analysis indicated that application of 281 kg N ha^-1 and 134.8 kg P₂O₅ha^-1 are economically feasible for pineapple production under Gojeb and its surrounding areas.

ACKNOWLEDGEMENT:

The authors would like to acknowledge Ethiopian Institute of Agricultural Research (EIAR)/ Jimma Agricultural Research Center (JARC), and Gojeb state farm for the financial and experimental site support of this study.

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Received on 09.05.2019 Modified on 30.05.2019

Res. J. Pharmacognosy and Phytochem. 2019; 11(3):160-166.

DOI: 10.5958/0975-4385.2019.00027.X