Effects of NPSB Fertilizers Rate on the Yield of Common Bean ( Phaseolus vulgaris L. ) at Tocha District, Southern Ethiopia

: Use of balanced nutrition means supplying other essential plant nutrients in adequate amount and proportion along with N and P. This implies N and P fertilizers are not the only yield determining nutrients but also S, B, and Cu nutrients are important nutrient for crop production. A trial was conducted in Tocha District to evaluate the rate of blended fertilizers to improve Common bean yield during main cropping season of 2019 and 2020. The experiment consists of seven treatment including (1) control, (2) NPSB: 18.9-37.7-6.95-0.1 (3) NPSB: 28.35-56.55-10.425-0.15 (4) NPSB: 37.8-75.4-13.9-0.2, (5) NPSB: 18.9-37.7-6.95-0.1+0.4kgCu, (6) NPSB: 28.35-56.55-10.425-0.15+0.4kgCu and (7) NPSB: 37.8-75.4-13.9-0.2+0.4kgCu. Soil physic chemical properties of the experimental site had moderately acidic, moderate level of OC and total N, high level of exchangeable K, very high level of CEC, low level of available P and clay loam textural class. In generally, application of blended fertilizer yielded better when compared with control. NPSB with the ratio of 37.8-75.4-13.9-0.2 (200kg NPSB) gave significantly optimum yield (4368.83 kg ha -1 ) compared to other treatments and also the highest net benefit (18725 ETB/ha) was obtained with acceptable marginal rate of return (MRR) (375.91%) which is more than the minimum acceptable MRR (100%) considered in this experiment. Similarly, NPSB 18.9-37.7-6.95-0.1 gave considerable net benefit with acceptable MRR. Therefore, based on the yield response and economic indicators, 200kg NPSB (37.8-75.4-13.9-0.2) is recommended as the best option and 100kg NPSB (18.9-37.7-6.95-0.1) as an alternative option for common bean producers at Tocha district and areas with the same soil conditions and agro-ecology.


Introduction
Common bean (Phaseolus vulgaris L.), is herbaceous annual plant domesticated independently in ancient Mesoamerica and in the Andes, and now is grown worldwide for both dry seeds or as a green bean.Thousands of legume species exist but common bean in any form is the most eaten by human beings compared to any other legumes (Broughton et al., 2003).Common bean is highly preferred by Ethiopian farmers because of its fast maturing characteristics that enable households to get cash income required purchasing food and other household needs when other crops have not yet
In Ethiopia common bean crop production land area coverage was about 216,803.91ha and with annual production of 3,727,664.85quintals.From this production SNNPR land area coverage was about 97,694.18haand with annual production of 1,529,627 quintals which was about 45% and 41% of national land coverage and production respectively (CSA, 2017/18).Common bean is one of the major crops grown in mid and low lands of Tocha woreda.2006) also reported that low soil fertility status especially low level of N and P to be the major constraints of common bean production responsible for the loss of grain yield up to 1.2 million tons in Africa.Soil fertility mapping project in Ethiopia recently reported the deficiency of K, S, Zn, B and Cu in addition to N and P in major Ethiopian soils and thus recommend application of customized and balanced fertilizers (ETHIOSIS, 2013).A very recently assessment of the EtioSIS information by ATA highlighted that > 50% NPSBCu and 20-29% NPSB fertilizers were deficient soil nutrients in Tocha woreda.This implies N and P fertilizers are not the only yield determining nutrients such as S, B, and Cu nutrients are important for crop production.Use of balanced nutrition means supplying other essential plant nutrients in adequate amount and proportion along with P. At balanced nutrition, crop yields are maximized and P use efficiency improved (Fageria, 2009).However, no study has been done on response of common bean (P.vulgaris L.) varieties to the rates of blended fertilizer in Tocha district, Southern Ethiopia.Thus, the objectives of this study were to investigate the effect of NPSB fertilizer rates on yield and yield components of common bean and to identify economically feasible rates of this fertilizer's at Tocha woreda, Dawuro Zone, Southern Ethiopia.

Description of the Study Area
The study was conducted for two consecutive years during 2019 to 2020 main cropping seasons at Tocha district in south western Ethiopia.Tocha is one of the woredas in the Southern Nations, Nationalities, and Peoples' Region of Ethiopia.Part of the Dawro Zone, Tocha is bordered on the south by Isaraand Kechi woreda, on the west by the Kechi and Tarcha zuria woreda]], on the north by Tarcha zuria woreda and on the east by Mareka.Towns in Tocha include Tocha.Tocha was disintegrated into Kechi and Tarcha zuria woredas.(Wikipedia, n.d).

Figure1. The Map of Tocha Woreda at South West Ethiopia Soil Sampling and Methods of Analyses
Composite soil samples were collected from each experimental farm before planting during the initial year and subsequent next year.A 5 cm diameter auger was used to sample five randomly selected spots per farm in depth of 0-20cm.These sub-samples were thoroughly mixed, homogenized, air dried under shade, ground and passed through a 2 mm sieve.The samples were analyzed for soil texture, pH, available P, total N, organic carbon, exchangeable K + and cation exchange capacity (CEC) using standard analytical technique outlined Sahlemedhin and Taye.et al (2000).The physical parameter such as bulk density and texture were analyzed by using cylindrical shaped core sampler for former and hydrometric analysis for later.The soil pH in soil to water suspension in 1:2.5 ration and read macro processor pH , organic carbon in acid digestion(wackily and blackly ,1934), Total nitrogen in keldjal digestion, available phosphorus in Olsen methods (Olsen,1954) ; K and CEC and in 1N ammonium acetate leachate and former read in flame photometer and liter in keldjal distillation followed by titration .

Statistical and Economic Analysis
Analysis of variance was conducted for each year separately and combined analysis over the two years.Analyses of variance were performed by using General Linear Model (GLM) procedure using the Statistical Analysis System (SAS) statistical program (SAS V9.2, SAS Institute Inc., Cary, NC, USA).The differences between treatment means was compared by using Least Significant Difference (LSD) test at 5% level of significance when the ANOVA showed the presence of significant difference.
Economic analysis with partial budget, dominance and marginal analyses was performed to investigate the economic feasibility of the new blended fertilizers for wheat production.The average yield was adjusted downwards by 10%, assuming that farmers could get 10% less yield.The average open market price (Birr kg-1) for wheat and the official prices of N, P and the new blended fertilizers were used for analysis.For a treatment to be considered a worthwhile option to farmers, 100% rate of return (MRR) was considered.

Properties of the Experimental Site Soil
The physicochemical properties of composite soil in experimental site were analyzed by standard analytical techniques.The physical parameter BD of composite sample was 1.3 g/cm3 and less compacted soil because its BD density was below 1.4g/cm3 and particle size distribution of site had 36 % sand, 39% clay and 25% silt and fall at clay loam textural class using textural class triangle.From analysis the soil pH was 5.78 implies soil of study area was moderately acidic and satisfactory for most crop production (Tekalign.et al, 1991, McKenzie et al. 2004).The percentage of soil organic carbon and total nitrogen were 1.67 and 0.15 respectively which was moderate (Tekalign.et al, 1991).The available Phosphorus (P) level was 8.83 ppm shows; the concentration of P was low at the experimental site (Olsen, 1954).The concentration of exchangeable K and CEC was 0.9 and 44.8 meq/100g of soil and implies that experimental site had high level of exchangeable K (Berhanu.et al, 1980) and very high level of CEC (Booker, 1991) respectively.The available sulfur and boron of soil was analyzed by turbid metric and dilute HCl methods respectively and the result was 10.76 ppm and 0.41 ppm (Table 1).The result of sulfur and boron at experimental site implies the soil was deficient in sulfur and boron nutrient , so the addition of mineral fertilizer which containing sulfur and boron was necessary to improve yield of common bean as well as other crop at study areas and also current was in line with report of ETHIOSIS at 2016 (ATA, 2016).The textural class of the site was analyzed by hydrometer and percentage of sand, clay and silt was 36%, 39% and 25% respectively and textural class was clay loam according world textural class triangle of soil.Note: pH: power of hydrogen; OC: organic carbon; P: available phosphorus; K: exchangeable potassium; CEC: cation exchange capacity.

Effects of Fertilizer Rate on the Yield of Common Bean at Tocha District
The mean data of yield and yield components of Common bean were described in table 2 and results of ANOVA indicated that statistically significant differences among treatments were observed in plant height, biomass yield and grain yield data when only compared with control /no fertilizer/ but, between treatments, except control, there was no statistically significant difference was observed due to neither NPSB nor NPSBCu.In case of other parameters namely: number of branching per plant, number of pod per plant and number of seed per pod statistically not significant even if with control.Kedir.etal ( 2020) also reported that number of pod per plant and number of seed per plant were statistically not affected by application of blended and bio fertilizers when compared to control where as significant yield response was observed in case of above ground biomass and grain yield.Numerically, in case of grain yield, T4 (NPSB=37.8-75.4-13.9-0.respectively.When we compare two treatments with and without copper (Cu) having the same dosage of NPSB: T2 with T5 (T2 + 0.4kg Cu), the output of T2 gave better than T5 in all parameters except number of pod per plant and grain yield; T3 with T6 (T3 + 0.4kg Cu), T6 yielded better in all parameters except grain yield.Whereas, T4 with T7 (T4 + 0.4kg Cu), the output of T4 is better in all parameters except number of pod per plant.Note: NS: Non significant; kg ha-1: kilo gram per hectare; LSD: Least significant difference; CV: coefficient of variance: 100kg NPSB=18.9-37.7-6.95-0.1

Economic Analysis
The dominance analysis (Table 3) indicated that treatment 3, 5, 6 and 7 were dominated by the treatments with lower variable cost with higher net benefit.Treatment 2 had lower total variable cost and high net benefit compared with treatment 3, 5 and 6.Similarly, treatment 5 had lower total variable cost with high net benefit than treatment 3 and 6.Also treatment 3 and 4 had lower TVC with higher net benefit when compared with treatment 6 and 7 respectively.Based on the dominance analysis treatment 2 and 4 were potential options (Table 3).Therefore, treatments 3, 5, 6 and 7 were eliminated from further economic analysis and only the dominant treatments were considered further in the partial budget analysis (Table 4).
Based on the partial budget analysis (Table 4), the treatment with the higher net benefit was treatment 4 when compared with treatment 2 with acceptable marginal rate of return (375.91%).However, the marginal rate of return for treatments 2 was 170.54% means that for each 1 ETB investment, the producer can get more than 100%.Since the minimum acceptable rate of return assumed in this experiment was 100%, this treatment can also give an acceptable marginal rate of return for the extra investment.

Conclusion and Recommendation
In generally, application of blended fertilizer yielded better when compared with control.NPSB with the ratio of 37.8, 75.4,13.9, 0.2 (200kg NPSB) gave significantly optimum yield (2140.39 kg ha -1 ) compared to other treatments and also the highest net benefit (18725 ETB/ha) was obtained with acceptable marginal rate of return (375.91%) which is more than the minimum acceptable marginal rate of return (100%) considered in this experiment.Similarly, treatment 2 gave considerable net benefit with acceptable marginal rate of return.Therefore, based on the yield response and economic indicators, 200kg NPSB is recommended as the best option and 100kg NPSB as an alternative option for common bean producers at Tocha district and areas with the same soil conditions and agro-ecology.As a research gap, even if the available P level of experimental site is low, its effect was not addressed with those treatments.So, it needs conducting further study to answer with appropriate treatments.

Table 4 . Economic (Partial Budget and Marginal Rate of Return) Analysis of Fertilizers on Common Bean at Tocha District
Yield adjustment=10%; Kg/ha: kilo gram per hectare; TVC: total variable cost; GFB: gross field benefit; NB: Net Benefit; ETB: Ethiopian birr and MRR: marginal rate of return.