Effect of Compound (NPSB) Fertilizer Type on Yield and Nutrient use Efficiency of Maize ( Zea mays L.) at Beko Village in Yeki District, Southwest Ethiopia

– Farmer in different parts of Ethiopia uses a similar type of fertilizer and amounts that are below the crop requirements, even the low soil fertility which limits crop production in general. To solve the over-blanket fertilizer application over different agroecology Ethiopian Soil Information System (EthioSIS) mapped the soil fertility and recommended types of fertilizer for a specific location. A NPSB type of fertilizer where recommended for Beko village, but the rate of this fertilizer type was not studied so far. So, this field experiment was conducted to determine the rate of NPSB fertilizer type and nutrient use efficiency of maize during the 2018 cropping season. A total of eight treatments with four replications were laid out in a factorial randomized complete block design. Treatments were control (zero fertilizer), previously blanket recommended nitrogen and phosphorus (92 N+ 69 P2O5) kg/ha, 150 NPSB +100 urea +100 K2O kg/ha, 200 NPSB +100 urea + 100 K2O kg/ha, 250 NPSB +100 urea +100 K2O kg/ha, 150 NPSB +150 urea +100 K2O kg/ha, 200 NPSB +150 urea +100 K2O kg/ha and 250 NPSB +150 urea +100 K2O kg/ha. Data were statistically analyzed by statistical analysis system (SAS) and mean treatment differences were compared by least significant differences (LSD). An analysis of variance indicated that application of NPSB fertilizer was not influenced plant height, ear height, ear length, cob length, number of ears per plant, thousand seed weight, harvest index, and shelling percentage as compared to the previously blanket recommended Nitrogen and Phosphorus (NP) fertilizer but grain and above-ground dry biomass were influenced except the application of 150 NPSB +100 urea. Application of 250 NPSB + 100 urea gave the highest maize grain yield (8828.2 kg/ha). Application of NPSB fertilizer improved the nitrogen and phosphorus use efficiency of maize compared to the previously blanket recommended NP. The highest N use efficiency (64.75 kg/ha) was obtained from the application of 200 NPSB +100 urea, while the lowest N use efficiency (23.89 kg/ha) was from the previously blanket recommended NP fertilizer. As economic analysis indicated that the application of 150 NPSB +100 urea is recommended for the study area.


I. INTRODUCTION
Maize (Zea mays L.) is one of the most important food crop in Ethiopia as well as in Sheka zone. Its average productivity is below 3.67 t/ha [1] when compared to the national average to 4.7 t/ha [2] and lower than the world average yield which about 5.21 t/ha [3]. Low soil fertility is one of the bottlenecks for sustaining maize production and productivity in Ethiopia [4; 5). Continuous crop production without improved farming practices has resulted in several deplete nutrients and soil organic matter which affect agricultural production [6; 7]. Lower biomass production and increasing demand of local organic matter of fuel and fodder also accelerate the declining of soil fertility [8; 9] In Ethiopia farmers use similar fertilizer types commonly known as urea and DAP in different agro-ecology as a blanket recommendation [10]. Urea and DAP fertilizer provide only nitrogen and phosphorus plant nutrients [46,47]. Plants require a specific amount of certain nutrients in some specific form at appropriate times for their growth and development. The role of both macro and micronutrients are crucial in crop nutrient and thus important for obtaining higher yields [11; 12; 13] In a past decade Ethiopian Soil Information System (EthioSIS) where mapping soil fertility status of the country. Accordingly, in addition to nitrogen and phosphorus plant nutrients other nutrients like, potassium (K), Sulfur (S), boron (B), copper (Cu), manganese (Mg), iron (Fe), and zinc (Zn) where deficiencies are widespread in Ethiopian soil [14;15;16].
Four types of fertilizer (NPS, NPSB, NPSBCa and NPSCa) are suggested for Yeki District. However, the map is suggested type of fertilizer but, the rate of those fertilizer in respective to crop type is not studied [45]. With this back ground, the present study was designed to evaluate the effect of NPSB fertilizer type on grain yield, nutrient use efficiency of maize and economic feasibility in Yeki district at Beko village Southwest of Ethiopia.

A. Description of the study area
The experiment was conducted in Sheka Zone Yeki District at Beko village during 2018 main cropping season. The Yeki located in Southwest Ethiopia in South West people of Ethiopia regional state at an elevation of 1200 m.a.s .l, latitude of 7 o 10'54.5'' and longitude of 35 o 25'04.5 '' East of Ethiopia and approximately 611km far from the capital city of Addis Ababa, Ethiopia. The average maximum and minimum annual temperatures is 29.7 o C and 15.5 o C respectively. The annual rainfall in the area is unimodal distribution with average of 1559mm. The area is dominated by Nitisols [17].

B. Experimental Materials
A high yield medium maturity date of hybrid maize variety (BH140) was used as a test crop. Urea fertilizer as source of nitrogen, triple super phosphate (TSP) as phosphorus source, potassium chloride as a source of potassium and NPSB fertilizer were used. Fertilizers' Triple Super Phosphate (TSP) and NPSB were applied at planting while, urea applied in twice equal split half at knee height and the remaining at flag leaf emergence as Tolessa et al. [4] recommendation.

C. Experimental Design
A field experiment was conducted in a factorial randomized block design with eight treatments with four replication, an experimental plot 3.5mx3.75m length and width respectively. The treatments consisted three level of NPSB (150, 200, 250) kg/ha each combined with two levels of urea (100, 150) kg/ha and two checks were added to each block (Control and previously blanket recommended 92 N + 69 P2O5) kg/ha. The details treatment combination were indicated as follow (Table  1).

D. Data collection and Analysis
Before the experimentation composite surface soil samples was collected from the plough layer (0-20 cm) depth across the experimental plot. The composite soil sample was analyzed in laboratory and used for analysis of soil physio-chemical properties; soil texture by Bouyoucos hydrometer method [18], soil reaction (pH) in a 1:2.5 soil water suspension by a glass electrode pH meter [19], total nitrogen by modified Kjeldahl method [20], available phosphorus by Olsen method [21], available potassium by ammonium acetate extracts flame photometer [22], available sulfur and boron by Mehlich-3 method [23], cation exchangeable capacity (CEC) [24], organic carbon by Walkley and Black method [25], organic matter was estimated as organic carbon multiplied by 1.74 assuming the average carbon concentration of organic matter is 58%.
Six plants from each net plot were randomly taken to measure plant height, ear height, ear length, cob length, thousand seed weight, grain yield, above-ground dry biomass, harvest index, shelling percentage of maize. Maize grain was taken to analysis nutrient content for nutrient use efficiency analysis using procedure described by [26]. A partial budget analysis were calculated follow as CIMMTY [27] procedure. The collected data were statistically analyzed as using statistical analysis system (SAS) software package [28]. The mean differences were separated using the least significant difference (LSD) to signify the treatment differences at a 5% level of probability.

A. Pre-plant soil properties
The pre-plant composite soil sample were collected from the experimental field at Beko village, Yeki district. The various soil physio-chemical properties of the experimental site were analyzed under laboratory and the results were presented ( Table  2). B. Effect of NPSB fertilizer application on growth, yield and yield components of maize Application of NPSB fertilizer was none significantly (p>0.05) influenced plant height, ear height, ear length, cob length and number of ear per plant as compared to the previously blanket recommended NP fertilizer (Table 3). Application of NPSB fertilizer was none significantly (p>0.05) influenced thousand grain weight, harvest index and shelling percentage of maize as compared to the previous blanket recommended NP fertilizer, while grain and aboveground dry biomass yield were influenced (Table 4). When compared with the control treatment with other treatments application of NPSB fertilizer influenced thousand seed weight, grain yield, above-ground dry biomass yield, harvest index and shelling percentage of maize. The heaviest thousand seed weight (407.5gm) was recorded from the application of 200 NPSB + 100 urea + 100 KCl. The highest grain yield (8828.2 kg/ha), harvest index (47.65), and shelling percentage (88.51) was recorded from the application of 250 NPSB + 100 urea + 100 KCl fertilizer. The lighter thousand seed weight (300.78gm), grain yield (2968.9 kg/ha), aboveground dry biomass (38.61 t/ha), harvest index (36.61) and shelling percentage (73.79) of maize was recorded from the control treatment followed by the previously blanket recommended NP fertilizer rate. Application of macronutrient S from NPSB and K from KCl and B fertilizer in addition to enough urea contributed for the increment of maize thousand yield, grain yield, above-ground dry biomass yield, harvest index and shelling percentage over the control treatment and split nitrogen application also improve the nutrient use efficiency of the maize.
Maize request the greatest amount of potassium fertilizer. A study by Muhammad et al. [34] indicate that application of 120 kg/ha fertilizer improved maize yield by 24.21% as compared to the control. As a different study showed application of balanced fertilizer improved grain yield of different cereal crops. A study by Dagne [35] and Shiferaw et al. [36] grain yield of maize were improved under the application of blended fertilizer as compared to the control. A study on tef indicate that blended fertilizer with a recommended amount of N and P increased yield as compared with the control treatment [37; 38]. Similarly study on wheat also showed yield increments as blended fertilizer application as compared to the control [39; 40].

C. Effect of NPSB fertilizer application on nitrogen nutrient uptake of maize
Application of 250 NPSB + 100 urea + 100 KCl fertilizer gave the maximum grain N uptake (126.83 kg/ha), straw N uptake (104.16 kg/ha) and total above-ground dry biomass N uptake (230.99 kg/ha), while the minimum N uptake of grain (12.37 kg/ha), straw (13.35 kg/ha) and above-ground dry biomass (25.72 kg/ha was from the control treatment followed by the previously recommended NP fertilizer (Table 5). This N uptake improvement of maize over the control and recommended NP could be due to the mac and micronutrient provided from NPSB, KCl and split application of nitrogen application.
The application of macronutrient improve nutrient uptake of maize both the grain and straw [35]. The N uptake and grain yield has a positive association [26]. Hence, the improved N uptake in grain yield of maize may lead to improved grain yield. A combine application of nitrogen and phosphorus increase the N uptake of maize reported [41]. Total uptake (above-ground dry biomass) =grain + straw uptake D. Effect of NPSB fertilizer application on phosphorus nutrient uptake of maize Application of 250 NPSB + 100 Urea + 100 KCl gave the maximum grain P uptake (64.45kg/ha) and above-ground dry biomass (88.75 kg/ha) yield, while the minimum P uptake (8.02 kg/ha) and above-ground dry biomass P uptake (12.59 kg/ha) was recorded from the control treatment. P uptake was improved as compared to the control treatment.

E. Effect of NPSB fertilizer application on agronomic N and P nutrient use efficiency of maize
Agronomic fertilizer use efficiency of maize was influenced due to the application of NPSB fertilizer type ( Table 6). The highest agronomic fertilizer N use efficiency (64.75 kg/ha) was recorded under the application of 200 NPSB + 100 urea, while the lowest from recommended NP fertilizer (23.89 kg/ha) and it improved by 46.10% as compared to the previously recommended NP fertilizer. Agronomic fertilizer use efficiency of any nutrient can be increased by increasing plant nutrient uptake and the use of nutrients by decreasing nutrient losses from the soil plant system. As Mengel et al. [42] stated the mean value of agronomic fertilizer use efficiency for a nutrient should not be less than 5 kg/ha and according Dobermann [43] in the range of 10 to 30 kg/ha. The agronomic use efficiency of the study area ranged from 23.89 to 57.98 kg/ha which was the optimum range according to Mengel et al [42;43]. In the case of high value of agronomic use efficiency could be good field management system or at which soil N supply is low [43].
The application of NPSB fertilizer was influenced agronomic P fertilizer use efficiencies of maize when compared to the recommended NP fertilizer ( Table 6). The highest agronomic P fertilizer use efficiency (94.44 kg/ha) was recorded from the application of 150 NPSB + 150 urea, while the lowest (31.85 kg/ha) from the recommended NP fertilizer.

F. Economic NPSB fertilizer application analysis
One of the boldly important in fertilizer study is its economic advantage for smallholder farmer. According to CIMMYT, (1988) the minimum rates of return by investing any cost to the acceptable return between 50 to 100%. So, farmers select the best treatment based on minimum acceptable marginal rate of return, highest net benefit with low total variable cost. In this study a partial budget average of eight (8) treatments were calculated from income and expenses based on variable cost. Net benefit (NB) calculated as subtracting the total variable cost (TVC) from the gross field benefit (GFB) for each treatment. A gross field benefit was calculated as multiplying yield obtained by fife which is a local selling price of a kilogram of maize estimated from the average of fife year. The cost of NPSB fertilizer was Ethiopian birr (ETB 13.75 kg/ha, TSP was ETB 12.75/kg, KCl was ETB14.50/kg and urea was ETB 10/kg. The cost of fertilizer transportation was considered as ETB 15 per 100 kg fertilizer and labor cost of fertilizer application ETB 18 per day for 8 hours for 100 kg fertilizer. The yield adjustment to downward by 10% is to indicate the difference between yield obtained from experimental site and the expected yield from farmers' fields [44]. The acceptable marginal rate of return (4.35%) for undominated treatment at the lowest total cost of variable with the highest net (13445.3 ETB/ha) was recorded from the application of 150 NPSB + 150 urea (Table 7). Dominated treatment indicate that any treatment that has net benefits are less than those of a treatment with lower costs that vary. According to this study, application of 150 NPSB + 150 urea along with 100 KCl is recommended for the experimental site. IV. CONCLUSION Application of NPSB fertilizer was significantly influenced maize grain yield and above-ground dry biomass. The highest maize grain yield (8828.2 kg/ha) was obtained from the application of 250 NPSB + 100 Urea + 100 KCl kg/ha, while the lowest grains yield (2968.90 kg/ha) was obtained from the control plot. Application of NPSB and urea improved nutrient uptake and agronomic use efficiency of maize, as compared with the blanket recommended NP fertilizer. The maximum grain N uptake (126.83 kg/ha) was obtained from the application of 250 NPSB + 100 Urea + 100 KCl kg/ha. Economically application of 150 NPSB + 100 urea + 100 KCl kg/ha gives 13445.3 ETB net benefits. Therefore, application of 150 NPSB + 100 urea along with 100 KCl kg/ha fertilizers rate is recommended for maize production in Yeki district at Beko village.