Effects of N and P Fertilizer Application Rates on Yield and Economic Performance of Upland Rice in Tselemti District of N.W Tigray, Ethiopia

ISSN: 2375-4338

Rice Research: Open Access

  • Research Article   
  • J Rice Res 2018, Vol 6(2): 191
  • DOI: 10.4172/2375-4338.1000191

Effects of N and P Fertilizer Application Rates on Yield and Economic Performance of Upland Rice in Tselemti District of N.W Tigray, Ethiopia

Alem Redda*, Hailegebriel K, Yirgalem T, Redae W, Welegerima G and Husien S
Maitsebri Agricultural Research Center, Tigray, Ethiopia
*Corresponding Author: Alem Redda, Maitsebri Agricultural Research Center, Tigray, Ethiopia, Tel: +251-914782436, Email: [email protected]

Received Date: Jan 27, 2018 / Accepted Date: Feb 26, 2018 / Published Date: Mar 01, 2018

Abstract

Rice agronomy plays a great role in increasing and sustaining rice production and productivity. Due mainly to its relatively recent history of cultivation in Ethiopia, the scientific information available with regards to the response of rice to N and P sources of fertilizers for its production is very limited. An experiment was conducted in 2014 and 2015 in Tigray, Ethiopia, with the objectives of determining the economically optimum rates of N & P sources of fertilizer on yield of rice. Five levels of N (0, 23, 46, 69 and 138 kg N/ha) and four levels of P (0, 23, 46 and 69 kg P2O5/ha) Factorial experiment was laid out in a randomized complete block design with three replications. The interaction effects of N and P were significant (P ≤ 0.05) for grain yield, biomass yield, plant height and days to heading but not for days to maturity, harvest index and thousand seed weight. From the view point of the physical (agronomic) yield, the combined results of the experiment revealed that the combination of 138 kg N/ha and 46 kg P2O5/ha recorded maximum grain yield of 5723 kg/ha and the control (i.e. no N and no P) gave the lowest grain yield (1601 kg/ha). Unlike that of the agronomic yield, the economic analysis of the combined result of the experiment with two years and two locations revealed that the profitable mean net return of 22208.63 Birr/ha was obtained for the plot that received 69 kg N/ha and 23 kg P2O5/ha which is 11185.12 Birr more than the net returns obtained from the control (with no urea plus no DAP) which is Birr 11023.51 birr. Therefore, from the economically profitable fertilizer rate use point of view, rice farmers in Tselemti district and similar areas should use the most economically feasible fertilizer rate with highest value of marginal rate of return i.e. 69 kg N/ha with 23 kg P2O5/ha.

Keywords: Agronomic Yield; Economic Yield; Fertilizers; Marginal Rate of Return; Rice; Tigray

Introduction

Rice (Oriza sativa L. ) remains the most important crop grown in the world because of its political, economic, and social significance [1]. Rice agronomy plays a great role in increasing and sustaining rice production and productivity [2]. Soil nutrient application rates, schedule of nitrogen fertilizer application, seed rate, planting methods and rice-based cropping systems are among the major agronomic practices which limit rice productivity and production [3]. Soil nutrient management has a great role in rice production, nitrogen being the most important nutrient for rice.

Rice was introduced to Ethiopia in the 1970s and has been cultivated in small pockets of the country [4]. In spite of its uses as food and feed and adaptable to sub-merged soils, rice was not well known by majority of Ethiopian farmers due mainly to lack of information [5]. But currently, Ethiopia is fast emerging as one of the big rice-producing countries in sub-Saharan Africa [6,7]. Rice has a great potential to food security in Ethiopia due to its better productivity. According to the National Rice Research and Development Strategy of Ethiopia [6], the trend in the number of rice producing farmers, area allocated and production showed high increase especially since 2006. Area rose from 6,000 ha in 2005 to nearly 222,000 ha in 2010 and paddy production from 15,460 tons to 887,400 tons, at the same time, the number of rice farmers increased from 18,000 to more than 565,000 [6]; and out of the total national production of rice in 2009, 43.9% is produced in the Amhara regional state, 3.4% in Tigray region, 6.5% in Benshangul-Gumz, 8.3% in Oromia, and 8.5% in Gambella, 10.7% in Somalia, 18.7% Southern region. Rice is one of the strategic cereal crops of Ethiopia in alleviating poverty and insuring food security and got the nick name “Crop of the Millennium” [7]. In the near past, rice production system in Ethiopia has focused mainly on the introduction of improved varieties (mainly, the NERICA (new rice for Africa) varieties) from a range of different sources. However, as a new rice growing country, it is also important to know how rice reacts to the physical environment, farming system and to the socioeconomic livelihoods [7].

The impact of increased fertilizer use on crop production has been large [8,9]. The addition of any amount of fertilizer is interesting to farmers if and only if it is profitable through the enhancement of either yield or quality [10]. However, maximum profits are rare at maximum yields because the last increment of fertilizer to produce a little more yield may cost more than the yield increase is worth. Therefore, fertilization needs to be rationally used and economically profitable because unwise application of fertilizers negatively affects the soil fertility, future crop productivity and farmers' economy [11]. Rice has got wider adoption by Ethiopian farmers due mainly to social, economic, and environmental perspectives [5]. However, the production and productivity of the crop under farmers’ field conditions is low (about 2600 kg/ha on the average) compared to its yield levels under farmers’ conditions in other parts of the world [12]. Apparently, low soil fertility and inadequate nutrient management are among the major factors determining its yield level.

Since Tselemti wereda is rice basket of the region, detailed information on how rice reacts to fertilization and identifying the pros and cons of the rice production system is important. Besides, Maitsebri Agricultural Research Center (MyARC) was established in this district and is conducting rice research as a regional rice research coordinating center, the information contained in this study could also partially fill the gap in rice production and the questions of future productivity of the crop regarding its fertilizer needs and economic aspects of farmers in general and the poor farmers in particular. Moreover, no research has been done in this area of interest regarding the economically feasible rate of N and P fertilizers in rice production in Tigray. Therefore, this research was conducted to study the effects of different rates of N and P fertilizer on yield and yield components of rice and to determine the economically profitable rate of N and P fertilizers in rice production.

Despite its relatively recent history of cultivation, rice in Tigray is considered to be one of the strategic crops of the region in alleviating poverty mainly due to its better yield and versatile uses. However, application of fertilizer to mitigate problems of nutrient limited yields in Tigray has been based on conventional blanket recommendations. Furthermore, farmers are arguing that the price of the inorganic fertilizers is getting up. Therefore, it is important to evaluate the effects of different rates of N and P fertilizers on yield of rice and check the profitable rates.

rice-research-Tselemti-District-Tigray

Figure 1: Location map of the experimental site, Tselemti District and Tigray region in Ethiopia (Source: Tigray Regional Meteorological Agency, Mekelle, Tigray, Ethiopia).

Materials and Methods

Description of the study area

Tigray, located in the northern tip of Ethiopia is bordered with Afar region in the East, Sudan in the West, Eritrea in the North and Amhara region in the South. It extends from 12013' to 14054' North latitude and from 36027' to 40 018' East longitudes. The study district is found in north western zone of Tigray and is 400 km west of Mekelle and 190 km north of Gonder. The field experiment was conducted at two locations: one at the research station of Maitsebri Agricultural Research Center which lies at 13005’ North Latitude and 38008’ East Longitude and has an altitude of 1350 masl and the other at Boroke village which has an altitude of 1111 masl Figure 1. The mean annual temperature ranges from a minimum of 18.3°C (November-January) to an average annual maximum of 30.9°C (February-May). It has an average (10 years) annual rainfall of 1106.16 mm. Rainfall starts in June and ends in September. Regarding the soil of the study site it is deep heavy black soil that cracks (shrink) when dry and swells when moistened.

Soil sampling and analysis

Pre-planting soil samples were randomly collected from twenty spots diagonally from a depth of 0-30 cm. The samples were composited, bagged, labeled and about 1 kg of the sample were given to Soil Laboratory for determination of selected physico-chemical properties of the soil. The texture of the soil was determined using Bouyoucos hydrometer method [13] and pH at 1:2.5 soils to water ratio was determined using a glass electrode attached to pH digital meter [14]. Soil organic carbon was determined using Walkley and Black [15] wet digestion method and total N were determined using Kjeldhal method as described by Jackson [16]. For determination of available P, the Olsen et al. [17] method was used and the cation exchange capacity (CEC) was measured using 1M-neutral ammonium acetate [16].

Experimental treatments, design and procedures

The fertilizer treatments considered in the study consisted of five levels of N (0, 23, 46, 69 and 138 kg N/ha) and four levels of P (0, 23, 46 and 69 kg P2O5/ha). The source of N was urea whose chemical formula is CO(NH2)2; and the source of P was TSP (Triple Superphosphate) and its chemical formula is Ca(H2PO4)2. The experiment was conducted using a 5 × 4 factorial experiment laid out in a randomized complete block design in three replications and a total of 20 treatments. The field was oxen plowed three times before laying the experimental plots on the field. A 2 m × 3 m (6 m2) plot size was used as an experimental unit. The blocks were separated by 1.5 m whereas the plots within a block were separated by 1 m. The rice variety called Maitsebri-1 (released by the center in 2014) was used as a testing material. Planting was made by hand drilling the seeds at a seed rate of 70 kg/ha and row spacing of 20 cm. Nitrogen was applied in three equal splits, i.e. the first one-third as basal at planting; the second one-third top dressed at maximum tillering and the final one-third top dressed at the panicle initiation. Unlike N, the total dose of P was applied basal as Triple Super Phosphate (TSP, 20% P) at planting. All data collected from the net plot size were subjected to analysis of variance (ANOVA) following a procedure appropriate to RCBD [18] using GenStat statistical software; GenStat, 2009 [19].

Yield and agronomic data collection and analysis

Days to heading (DH) was done by counting the number of days from the time of sowing to 50% heading whereas days to maturity (DM) was done by counting the number of days from the time of sowing to 85% physiological maturity. Plant height (PH) was measured using a meter from the soil level to the tip of the top spike on the panicle on 10 random plants at physiological maturity. Biomass yield was determined after harvesting the plots close to the ground level by hand using sickles and weighing them using a sensitive balance. Grain yield was determined after threshing the plants harvested from the net (1.6 m by 2.6 m) plots to avoid border effects after air drying at the field. Thousand seed weight was determined by counting 1000 seeds from the grain yield of each plot and weighing using a sensitive balance in gram basis. Analysis of variance was carried out for the yield and yield components studied following statistical procedures appropriate for the experimental design using GenStat computer software (GenStat 16th version). Whenever treatment effects were significant, the means were separated using Duncan’s Multiple Range Test (DMRT) procedures. Second year data for the Boroke experiment was not included because there was high erosion over the experiment due to excessive rainfall.

Results and Discussion

Physical and chemical characteristics of soil

Soil texture, pH, total N, cation exchange capacity, organic carbon, and exchangeable cations were determined for the composite soil samples collected from the experimental field at 0-30 cm depth before sowing of rice and also after harvesting of rice. Analytical results of the composite surface soil before sowing of rice indicated that the soil was clay in texture with 10% sand, 23% silt and 67% clay. The pH of the soil was pH 6.3 (Table 1) which is slightly acidic and highly suitable for rice production, as rice can grow well over a relatively wide pH range of 5 to 7.5, although the best soil is with slightly acidic pH of 5.5 to 6.6 [12]. Tekalign et al. [20] classified soil N availability of <0.05% as very low, 0.05-0.12% as poor, 0.12-0.25% as moderate and >0.25% as high. The Netherlands commissioned study by Ministry of Agriculture and Fisheries (1995) also classified soil contents as follows: 1) for total N (%) >0.300, 0.226-0.300, 0.126-0.225, 0.050-0.125 and <0.050 as very high, high, medium, low and very low, respectively, 2) for OC contents (%) >3.50, 2.51-3.5, 1.26-2.50, 0.60-1.25 and <0.60 as very high, high, medium, low and very low, respectively. Accordingly, taking into consideration the respective limits set by the Netherlands commissioned by the Ministry of Agriculture (1995) and Tekalign et al. [20], the total N, organic carbon and C:N ratio of the soil in the study area is low.

Soil characteristics Values Rank Reference
pH (1:2.5 H2O) 6.3 Slightly acidic [20]
Total N (%) 0.094 Low [20]
OC (%) 0.983 Low [20]
C: N Ratio 10.15 Low [20]
Available P 3.8 Very low [17]
CEC (cmol/kg) 65.2 High [21]
Na (cmol/kg) 123 High [21]
Mg (cmol/kg) 11.5 High [21]
K (cmol/kg) 123 High [21]
Ca (cmol/kg) 4.1 High [21]

Table 1: Major chemical properties of soil at the main station site (before planting).

Analytical results of the composite surface soil after harvest of rice indicated that the soil was clay in texture (max 68%, min 56%). It was slightly acidic (max pH 6.12, min 5.46), low in total N (max 0.070%, min 0.063%), and low in organic carbon (max 0.973%, min 0.470%). The C:N ratio (max 13.9:1, min 7.46:1) was within the range of normal agricultural soils.

Yield and yield components of rice

Grain yield: Analysis of variance for two factors (N and P) randomized complete block design (Table 2) revealed significant difference (P ≤ 0.01) due to the main effects of the levels of N and P application for the mean yield of rice. For the 2014 Experiment (Table 3), the main yield components of rice i.e. grian yield, biomass yield and plant height are brought significantly different due to the different levels of N and P. The highest yields obtained for the two locations (i.e. on station and Boroke) were 4901 and 7524 kg/ha when 138 kg N/ha was combined with 69 kg P2O5/ha. Again, the minimum agronomic yield obtained were 1368 for the on station and 2897 kg/ha for the Boroke area respectively (for N0P0, i.e. no Urea and no DAP). Here, we clearly see that there is higher yield of rice for the Boroke study area due to higher water holding capacity of the soil. For the 2015 experiment (Table 4), the maximum yield obtained was 4535 kg/ha and the minimum were 938 kg/ha for the main station; the secondyear experiment for Boroke location was failed due to flooding caused by excessive rainfall.

Source of Variation df DH (days) DM (days) PH (cm) GY (kg/ha) BY (kg/ha) HI TSW (g)
Rep 2 5.68 40.53 27.8 4843 3154 6.05 3.9
N 4 268.39** 182.52ns 4394.8** 56230** 1841** 329** 10.6ns
P 3 347.39** 257.18ns 120.8ns 44198ns 1385ns 29ns 9.6ns
N × P 12 82.86** 143.66ns 13.5** 9499** 3377** 10.5ns 2.2ns
Residual 158 1721 6551 167.3 24834 8041 20.5 8
Total 179              

Note: DH= days to heading; DM= Days to maturity; PH= Plant Height; BY=above ground biomass yield; GY=Grain yield; HI=Harvest index; TSW=thousand seed weight; df=degrees of freedom, * significant at p<0.05, ** significant at P<0.01; ns non-significant.

Table 2: Mean squares for DH, DM, PH, GY, BY, HI and TSW of rice, 2014-15.

SN Rxs trt Comb On Station, 2014 Boroke, 2014
PH (cm) GY (kg/ha) BY (kg/ha) Pl Ht (cm) GY (kg/ha) BY (kg/ha)
1 T1 N0P0 64.31hi 1368.05i 3929.16j 73.93hi 2897.22gh 7609.02gh
2 T2 N1P0 67.10ghi 2120.83ghi 5187.49hij 87.87fg 4219.44fj 9816.65efg
3 T3 N2P0 69.62efghi 2912.5cdefg 6849.99defg 95.40cdef 4995.83ef 11363.18cde
4 T4 N3P0 72.92cdeef 2894.44defg 6756.93defg 104.20abcd 6548.60bcd 13138.17abc
5 T5 N4P0 76.04bcde 3040.27cdef 7370.82bcdef 110.33ab 7040.27abc 13613.17abc
6 T6 N0P1 65.61ghi 1569.44i 4181.94j 70.27i 2039.58h 6615.96h
7 T7 N1P1 68.40efghi 2481.94fgh 5936.10fgh 89.07fg 4919.44ef 10255.54def
8 T8 N2P1 72.25defgh 2844.44efg 6538.88efgh 94.73def 4908.33ef 10085.40efg
9 T9 N3P1 78.90abcd 3756.94bc 8566.65bc 99.20cde 5859.71cde 11938.87cde
10 T10 N4P1 82.24ab 3698.61bcd 8666.65b 110.00ab 7297.21abc 13503.45abc
11 T11 N0P2 63.77i 1427.78i 3945.83j 81.67gh 3765.27fg 8579.15fgh
12 T12 N1P2 68.55efghi 2437.50fgh 5908.32fgh 90.73efg 5061.10def 10288.18def
13 T13 N2P2 75.23bcdef 3323.61cde 7547.21bcde 96.00cdef 5816.66cde 11919.43cde
14 T14 N3P2 81.21ab 3552.77bcde 7936.10bcde 104.87abc 7093.04abc 12657.62bcd
15 T15 N4P2 84.34a 4340.27ab 10615.26a 111.07a 8412.49a 15443.73a
16 T16 N0P3 68.05fghi 1741.6hi 4352.77ij 82.47gh 3202.77gh 7981.24fgh
17 T17 N1P3 69.03efghi 2390.27fgh 5773.60ghi 95.47cdef 5019.44ef 11160.40cde
18 T18 N2P3 72.85cdefg 3130.55cdef 7070.82cdefg 101.20bcd 6340.27bcde 12633.31bcd
19 T19 N3P3 80.59abc 3672.2bcde 8247.21bcd 102.53abcd 5958.32cde 11633.31cde
20 T20 N4P3 86.15a 4901.38a 11287.48a 110.07ab 7524.99ab 14992.34ab
Mean 73.36 2880.27 6833.46 95.55 5446 11261.41
SEM 2.8 255.95 524.24 3.42 524.6 1509.02
CV% 6.6 15.4 13.3 6.2 16.7 13.4
LSD (<0.05) 7.97 732 1500.8 9.76 1499 2491

a-jMeans that do not share a letter are significantly different.

Table 3: Effect of NP fertilizer on days to flowering, days to maturity, plant height, stand %, grain yield and biomass yield of upland rice, 2014, on Station.

SN Rxs Rx Comb Urea (Kg/ha) TSP (Kg/ha) DH DM PH (cm) NPP/m2 GY (kg/ha) BY (kg/ha) HI 1000 SW (g)
1 T1 N0P0 0 0 84.0f 104.3de  55.2h 140.3h 938h 2209g 42.6 28.5
2 T2 N0P1 0 50 83.0ef 104.3de 54.3h 163.0gh 1195gh 2785fg 42.9 30.7
3 T3 N0P2 0 100 82.0cdef 102.0abcde 54.8h 161.0gh 1049h 2549g 40.9 27.2
4 T4 N0P3 0 150 81.3abcdef 103.0bcde 53.2h 158.7gh 993h 2375g 42.1 26.8
5 T5 N1P0 50 0 82.3def 104.3de 65.9fg 176.7fgh 1813f 4098ef 44.5 30.2
6 T6 N1P1 50 50 78.0ab 100.3abcd 64.7g 186.7efgh 2084def 4709de 44.3 30.1
7 T7 N1P2 50 100  80.0abcde 102.3abcde 67.0fg 228.3cdef 1750fg 4125ef 42.4 30.7
8 T8 N1P3 50 150 77.3a 100.7abcd 65.2fg 233.7cdef 1903ef 4570de 41.9 26.8
9 T9 N2P0 100 0 81.0abcdef 102.3abcde 69.4fg 244.3cde 2271cdef 5146cde 44.1 28.5
10 T10 N2P1 100 50 78.7abcd 101.0abcd  9.2cde 285.7abc  2639bcd 6028bcd 43.7 29.1
11 T11 N2P2 100 100 78.0ab  98.7a 71.0efg 234.0cdef 2986b 6632bc 45.1 30.5
12 T12 N2P3 100 150  77.7a 99.7abc  74.8def 233.3cdef 2910bc 6757b 42.8 30.0
13 T13 N3P0 150 0 84.7f  105.7e  9.4cde 210.7defg 2507bcde 5688bcd 44.2 24.8
14 T14 N3P1 150 50 78.0abc 100.7abcd 82.4bcd 247.3cde 2882bc 6507bc 44.3 30.3
15 T15 N3P2 150 100 79.3abcde 100.3abcd 79.7cde 261.3bcd 2952b 6848b 43.2 30.0
16 T16 N3P3 150 150 77.7a 99.0ab 80.3cde  272.3bcd 3111b 7119b 43.7 29.3
17 T17 N4P0 300 0 90.3g 105.7e 90.2ab 263.0bcd  2613bcd 5980bcd 44.7 27.1
18 T18 N4P1 300 50 81.0abcdef 103.3bcde 87.1abc 318.3ab 4292a 9431a 45.4 28.1
19 T19 N4P2 300 100  81.0abcdef  102.7abcde 95.1a 287.0abc 4417a  9723a 45.6 29.0
20 T20 N4P3 300 150  78.7abcd 101.7abcde 91.8a 334.0a 4535a 10459a 43.4 28.7
Mean 80.7 102.1 73.0 232 2492 5687 43.6 28.8
SEM 1.186 1.203 3.0 18.64 202.5 464.3 1.5 1.6
CV% 2.5 2 7.1 13.9 14.1 14 4.1 9.7
LSD (<0.05) 3.4 3.445 8.6 53.38 579.5** 1329.3* ns ns

*** significant at p<0.05, ns non-significant; a-h means that do not share a letter are significantly different

Table 4: Effect of NP fertilizer on days to flowering, days to maturity, plant height, stand%, grain yield and biomass yield of upland rice, 2015, On Station.

From this two years experiment, we see that as N and P levels increased, agronomic yield also increased. But this does not necessarily mean the net profit. A research done by Heluf and Mulugeta [12] at Fogera area of Ethiopia also indicated that grain yield of rice was significantly increased with an increase in the level of nitrogen.

From Table 5 below, grain yield of rice showed that the combined result over the 2 years (2014 and 2015) and two locations (on-station and Boroke) experiment showed that, the combination of 138 kg N/ha and 46 kg P2O5/ha resulted in grain yield of 5723 kg/ha and the control (i.e. no N with no P) resulted in the lowest grain yield (1601 kg/ha). Moreover, as N rate increases, yield also increased at all increased N levels but at 138 kg N/ha and 69 kg P2O5/ha the yield began to decline i.e. it reached the turning point of yield (5653.82<5723.26 kg/ha). This agrees with the findings of Mahajan et al. [22], who stated that significant increase in grain yield was observed with increased N supply (with more kg of N/ha) as compared to the control (unfertilized) but will finally reach a point where more fertilizer addition will not bring more yield due to the law of diminishing returns. Increased N application ensured better availability of N to plants at active tillering and panicle growth stage, which might have resulted in more productive tillers and grains.

SN Trt comb N (kg/ha) P2O5 (kg/ha) DH (days) DM (days) PH (cm) GY (kg/ha) BY (kg/ha) HI TSW (g)
1 N0P0 0 0 80.67 109.33 64.47i 1601.19i 4528hgh 38.4 31.84
2 N0P1 0 23 79.67 108.44 63.39i 1734.28hi 4582.23gh 37.11 32.14
3 N0P2 0 46 79.67 108 66.76hi 2080.58ghi 7786.47fgh 40.31 30.9
4 N0P3 0 69 78.56 108 68.13hi 2124.10ghi 8333.24bcde 40.8 31.09
5 N1P0 23 0 81 108.44 73.64ghi 2717.64fghi 8987.88bc 42.69 31.95
6 N1P1 23 23 77.89 107.22 74.07ghi 3161.63efgh 4527.61cdefg 44.65 31.97
7 N1P2 23 46 78.22 107.33 75.42fghi 3082.91efgh 6966.78cdefg 44.31 31.74
8 N1P3 23 69 77.56 106.44 76.56efgh 3104.21efgh 7550.85cdefg 42.69 30.37
9 N2P0 46 0 80.78 108.22 78.15efgh 3393.11defg 9004.33bcde 43.31 31.16
10 N2P1 46 23 79.22 107.56 82.06cdefg 3463.96defg 10533.80bcd 45.27 31.82
11 N2P2 46 46 77.89 106.56 80.75defg 4042.20cdef 5024.60cde 46 31.98
12 N2P3 46 69 78 107.11 84.05bcdefg 4254.24bcde 6773.94bcd 46.48 30.89
13 N3P0 69 0 82.44 111 85.18abcdefg 3906.54cdef 8699.70bcd 45.73 31.56
14 N3P1 69 23 78.78 108.56 86.82abcdef 4671.20abcd 9147.16bcd 45.75 31.26
15 N3P2 69 46 79.33 106.56 88.58abcde 4532.48abcde 11927.33bc 48.07 30.04
16 N3P3 69 69 79 106.78 86.78abcdef 3975.54cdef 5237.79cde 45.87 30.84
17 N4P0 138 0 86.22 113.11 92.20abcd 4231.06bcde 7167.94bcd 45.8 30.35
18 N4P1 138 23 81.78 112.22 93.12abc 5095.94abc 8861.98bc 47.28 30.63
19 N4P2 138 46 80.11 108.11 96.84a 5723.26a 8457.12bcd 47.03 30.73
20 N4P3 138 69 80.44 107 96.01ab 5653.82ab 12246.3a 45.7 29.35
Mean 79.86 108.3 80.65 3627.49 7909.22 44.16 31.13
SEM 1.1 2.2 4.3 525.3 945 1.51 0.94
CV 4.1 5.9 16 24 28 10.3 9.1
LSD (<0.05%) 3.1 ns 12 1467.27 2640 ns ns

Note: DH= Days to heading; DM= Days to Maturity; PH= Plant height BY=above ground biomass yield; GY=Grain yield; HI=Harvest index; TSW=thousand seed weight; ns= non- significant

Table 5: Combined results on the Effect of N and P fertilizer sources on days to heading, days to maturity, plant height, grain yield, biomass yield, Hi and TSW of upland rice, 2014 and 2015.

Above ground biomass yield: As is indicated in Table 5, for the combined two years (2014 and 2015) experiment highest biomass yield of 12246 kg/ha was observed at the treatment combinations of 138 kg N /ha and 69 kg/ha of P2O5 and the lowest biomass yield i.e. 4528 kg/ha was observed at the treatment combination of zero nitrogen and zero phosphorous (N0P0) for the two locations.. Likewise, at Boroke the highest rate of N i.e. 138 kg N/ha gave significantly different biomass yields of 8861, 8457, 12246 kg/ha when combined with the P rates of 23, 46 and 69 P2O5; and the control (zero nitrogen with zero P) gave the lowest biomass yield which is 7609 kg/ha in 2014. This result agrees with the findings of Zahir and Ahmad [23] who reported that Urea was indicated as a quick and more potent source of nitrogen for increasing the vegetative growth of agricultural crops.

Yield profitability (economic analysis)

The economic yields and added benefits as influenced by the combined use of N (through urea) and P (through TSP) fertilizers on yield of rice were calculated and presented in Table 6. Based on the principles of economic analysis using Marginal Rate of Return (MRR), the economic analysis was done on the basis of the prevailing prices of varying treatment inputs (Urea and TSP) and outputs (grain and straw) during the cropping seasons using the Ethiopian currency (Birr). One US dollar is about 21.5 Ethiopian Birr. The price of TSP was 1654.5.0 Birr per quintal (i.e. per 100 kg) and Urea was 1327.0 Birr per quintal (i.e. per 100 kg). The prices of output at that cropping season were unhulled grain of rice valued 600 Birr/100 kg and straw=90 birr/100 kg. Unlike that of the physical agronomic yield, the economic analysis of the combined result of the experiment with two years and two locations (Table 6) revealed that the profitable highest mean net return of 22208.63 Birr/ha was obtained for the plot that received 69 kg N/ha (i.e. 150 kg of Urea) and 23 kg P2O5/ha ( i.e. 50 kg DAP) which is 11185.12 Birr more than the net returns obtained from the control (with no N plus no P) which is 11023.51 Birr (Table 6). On the other hand, the lowest net return of 9577.53 Birr/ha was obtained from the use of no N and 46 kg P2O5/ha (i.e. 100 kg of DAP). High net return from the foregoing treatments could be attributed due mainly to high yield and the low net return was attributed due to low yield (Table 6).

SN Combinations (N: P2O5)   N (kg/ha) P2O5 (kg/ha) Gross return (Birr) TVC (Birr/ha)   Net Return (Birr/ha) DA MRR (%) Rank
1 N0P0 0 0 11023.51 0 11023.51  -  
2 N1P0 23 0 16651.9 663.5 15988.4 * 748  
3 N0P2 0 46 10404.78 827.25 9577.53 D    
4 N0P1 0 23 20665.78 1327 19338.78 * 1953 3
5 N3P0 69 0 19035.25 1490.75 17544.5 D    
6 N3P1 69 23 12863.13 1654.5 22208.63 * 2848 1
7 N2P0 46 0 23309.78 1990.5 21319.28 D    
8 N2P1 46 23 20792.67 2154.25 18638.42 D    
9 N2P2 46 46 18546.48 2318 16228.48 D    
10 N4P0 138 0 13214.88 2481.75 10733.13 D    
11 N1P2 23 46 24949.14 2817.75 20131.39 * 2797 2
12 N1P3 23 69 24178.21 2981.5 21196.71 D    
13 N3P3 69 69 18940.22 3145.25 15794.97 D    
14 N3P2 69 46 26645.88 3645 23000.88 * 1441  
15 N4P1 138 23 25221.55 3808.75 21412.8 D    
16 N1P1 23 23 25217.37 3981 21236.37 D    
17 N4P2 138 46 23703.66 4472.25 19231.41 D    
18 N0P3 0 69 30149.26 4808.25 25341.01 * 1818  
19 N2P3 46 69 33934.74 5635.5 28299.24 * 357  
20 N4P3 46 69 33877.75 6462.75 27415 D    

Key: PBA = Partial Budget Analysis; DA= Dominance Analysis; D= Dominated; TVC= Total Variable Cost. Note: Price of fertilizer and unpolished rice is as of 2014/15; Source: CIMMYT [24].

Table 6: Partial Budget Analysis (PBA) for the combined two Cropping Season (2 years and 2 locations) at Maitsebri in n.w Tigray, Ethiopia, 2014 and 2015.

According to the principles of MRR, for the combined results of the experiment, the most economically feasible combination was when 69 kg N/ha is used with 23 kg P2O5/ha which has resulted the MRR of 2848%. The treatment with highest grain yield that was using 138 kg N/ha plus 46 kg P2O5 /ha showed no MRR i.e. it was dominated treatment (Table 6). This clearly justifies the fact that highest grain yield does not necessarily mean highest MRR (rate of gain). This agrees with the findings of Kiros [10] who indicated that the addition of any amount of fertilizer is interesting to farmers if and only if it is profitable through the enhancement of either yield or quality; and maximum profits are rare at maximum agronomic yields because the last increment of fertilizer to produce a little more yield may cost more than the yield increase is worth. Regarding the analysis of MRR for the multi-location experiment (on-station and Boroke), higher MRR of 1119.31% was obtained at Boroke area than the on-station experiment which indicates use of inorganic fertilizers (N and P sources) is much profitable in Boroke than the on- station (maximum MRR being 609.08%). This matches with the fact that Boroke is relatively more water-logged and has more soils of with much water holding capacity (WHC) than the on-station (which is relatively drier than Boroke).

Conclusion

Our study demonstrated that the impact of increased fertilizer use on the agronomic yield has been large, but ever-increasing cost of production, for example the price of inorganic fertilizers, is an important constraint for the increased use of them particularly for resource poor farmers. Rice showed significant increase in grain yield as the level of N and P supply increased up to 138 kg N/ha and 46 kg P2O5/ha. From the combined results of the two years and two locations experiment, the maximum yield obtained was 5723.26 kg/ha which is resulted from the application of 138 kg N/ha with 46 kg P2O5/ha and the minimum yield of 1601 kg/ha was found when no N and no P was used. For the two locations, final economic analysis (according to the principle of profitability) showed that farmers must focus relatively on higher N fertilizer levels and less levels of phosphorous fertilizers than the general 100 by 100 kg/ha recommended. There is a significant difference in yield due to different levels of N and highest (though not statistically different) yield of rice was obtained at the rate of 138 kg N/ha combined with 46 kg P2O5/ha and minimum yield was obtained from N0P0. Here we obviously see that as N and P levels increased, yield increased but later it also showed a limit (i.e. yield turning point) i.e. at 138 kg N/ha when combined with 69 kg P2O5/ha. Maximum yield does not necessarily mean highest profit. From the economics analysis, the profitable yield obtained was when 69 kg N/ha was combined with 23 kg P2O5/ha. Therefore, the final of monetary (profit) analysis showed that farmers must focus on N fertilizers and must consider less (up to 23 kg P2O5/ha). The research results also showed that inorganic fertilizers are relatively much profitable in soils with better WHC (water holding capacity). Based on the principle of PBA, Boroke area is much profitable in the use of inorganic fertilizers than the on-station due mainly to better soil with much water holding capacity. When comparing the two locations, Boroke area (with better water-logged soils) has higher MRR (i.e.1119.31%) than that of the onstation (i.e. 609.08%). Therefore, from the economically profitable fertilizer rate use point of view, rice farmers in Tselemti district and similar areas should use the most economically feasible fertilizer rate with highest value of MRR i.e. 69 kg N/ha with 23 kg P2O5/ha, that is 150 kg/ha of Urea and 50 kg/ha of DAP.

Acknowledgments

The authors would like to thank all staff members of the Maitsebri- Shire Agricultural Research Center for their valuable support during data collections and the Fogera National Rice Research and Training Center for its financial support through its East Africa Agricultural Productivity Project (EAAPP).

References

Citation: Redda A, Hailegebriel K, Yirgalem T, Redae W, Welegerima G, et al. (2018) Effects of N and P Fertilizer Application Rates on Yield and Economic Performance of Upland Rice in Tselemti District of N.W Tigray, Ethiopia. J Rice Res 6: 191. Doi: 10.4172/2375-4338.1000191

Copyright: © 2018 Redda Alem, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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