Evaluation of Blended Fertilizer (NPSZnB) Rates on grain yield, nutrient uptake and economic feasibility of maize (Zea mays L.) in Kolla-Temben, Central zone of Tigrai, Ethiopia

Background: Maize is an important cereal crop grown and consumed in Ethiopia. However, its yield is constrained by low soil fertility and improper utilization of fertilizer. Therefore the objective of this nds was to study the effect of NPSZNb fertilizer rates on grain yield, nutrient uptake and economic feasibility of maize. Methods: A eld experiment was conducted at Bega-Sheka in 2018/19 & 2019/2020 cropping season. The treatments were consisted of six blended fertilizer rates (0, 50, 100, 150, 200 and 250 kg NPSZnB ha -1 ) and recommended p (40 kg ha -1 ). Treatments were arranged in RCBD design with three replications. Result: Analysis of variance indicated that blended fertilizer rate had statistically signicant (p < 0.005) effect on plant height, ear length, number of seeds per row, grain and biomass yield. However, it did not have a signicant effect on phonological traits, number of grain rows and 1000-grains weight. Application of NPSZnB fertilizer ranging from 150 to 250 kg ha-1 and 200 kg ha-1 of DAP gives the highest grain and biomass yields. Hence the higher nutrient uptake of N and P was recorded from the maximum rate of NPSZnB and P fertilizer, respectively. The MRR value showed that the highest MRR of 529% was obtains from 150 kg NPSZnB ha -1 . Conclusions: From the result of the study, application of 150 kg NPSZnB ha -1 increases yield and yield component of maize and give maximum return from unit investment which can be recommended for the study area.


Background
Maize is one of the pillar cereal crops ranking rst in total production and productivity in Ethiopian agriculture, and second to tef in area coverage (FAOSTAT, 2017). In spite of the large area coverage under maize, the national (Ethiopia) and regional (Tigray)average grain yields reached about 3.6 t ha-1( FAOSTAT, 2017) these yields were certainly below the world's average yield which was about 6 .2 t ha-1(CSA, 2015).
In Tigray, maize crop production is one of the high priority food security crops and the vision portends the intention of the government to transform the agricultural sector from a rural based economy to commercial and industry oriented sector to boost agricultural productivity. As the result it involves in extensive area.
However, the yield obtained by the farmers in the study areas is low due inappropriate agronomic practice, lack of stable high yielder varieties, drought, soil erosion and poor essential soil nutrient (ATA, 2014). Deteriorating soil fertility, shallow soil depth, high run-off and low in ltration capacity of the soil are the major restriction for supportable agricultural production in Kolla-Temben. So something is done to repair soil fertility rst to increase crop production.
Chemical fertilizers have been the important tools to overcome soil productiveness problems and they are also responsible for a large part of the food production increases worldwide (Sanchez, A. P. and R. B.
Leakey, 1997). It has been estimated about 50% of crop yield increment is attributable to application of commercial fertilizers (Stewart et al., 2005). Low soil fertility is highly affects the growth and development of maize as compared to other crops. As the result, it is often said "maize speaks" implying that maize cannot produce maximum yields unless su cient nutrients are available (Delorite, R. J. and H. L. . The correct application rates of plant nutrients are determined by knowledge about the nutrient requirement of the crop and the nutrient supplying power of the soil (Foth, H. D. and B. G. Ellis, 1997). Unblended fertilizer use favored the emergence of multi nutrient de ciency in Ethiopian soils Wassie and Shiferaw, 2011) and resulted in low crop production.
To overcome this problem of nutrient de ciency balanced fertilizers containing N, P, S, B, Fe and Zn have been recommended for site speci c nutrient de ciency and thereby increase crop production and productivity, water and labor productivity. The major recently recommended blended fertilizers for Bega-Sheka by ATA is NPSZnB (ATA, 2014) but the optimum rates of the recommended blended fertilizer for maize crops is not yet identi ed for Kolla-Temben district. Therefore, the main objective of the study was to evaluate the effects of NPSZnB fertilizer rates on grain yield, nutrient uptake and feasibility of maize at Bega-Sheka

Description Of The Study Area
The study area (Bega-Sheka) is considered as one of the most important place in Kolla Temben district, Tigray Region (Northern Ethiopia) (( Fig. 1 :) for the production of maize. It is located between 13°36.0'-13°39.0' N and 38°53.0' − 38°59.0' E. Total annual rainfall of the area ranges from 500-800 mm.
The mean annual temperature of the area is 24°c, with a minimum of 17°c and a maximum of 30°c at an altitude of 1898 m.a.s.l on the site. It is categorized as a Dry Weina-Dega zone.

Experimental Design And Treatment
The experiment was xed in randomized complete block design (RCBD) arrangement with three replications. The experiment consisted seven treatments including recommended blanket P fertilizer with an amount of 40 kg P ha-1 . The blended fertilizer rates were consisted of six levels of NPSZnB which is (0, 50, 100, 150, 200 and 250 kg ha) and were adjusted with N to N of the recommended N since the N content of blended fertilizer of NPSZnB is smaller as compared to P 2 O 5 which the N content of 100 kg NPSZnB is about 17 kg. This revealed that all treatments except contro received 69 kg ha-1. A full dose of blended fertilizer was applied at planting time close to seed drilling line, while the remaining N was applied in split, half at 35 and 65days after planting in the form of urea. The gross plot size was 16 m 2 (3.75m × 4 m) that accommodated ve rows as an experimental unit with 9 m2 (2.25m × 4 m) net plot. A high yielder maize variety of Gibe-III was used as a test crop on the sites that was spacing of 75*20 cm among rows and plants, respectively. Two seeds of maize were planted per hill and after; thinned to one plant per hill. Hence, 9 m2 of net plot size was used for the data collection.

Soil Sampling And Analysis
A disturbed composite soil sample f the study site were collected from 0-20 cm depth before planting for analysis. Soil texture was determined using the Bouyoucos hydrometer method (Bouyoucos, 1962). The pH of the soil was measured in the supernatant suspension of a 1:2.5 soil to water ratio using a PH meter (Rhoades,1982). Organic carbon (%) was determined by method as described by (Walkely and Black 1934). Available P (ppm) was analyzed by employing the Olsen method using ascorbic aci as the reducing agent (Olsen et al., 1954). Total nitrogen was measured using Kjedahl method as describe by (Bremner and Mulyaney,1982). CEC in cmol (+) kg-1soil was determined by ammonium acetate method Number of seeds per rows: was counted on ve representative ears and the average value was recorded for each plot. Number of seed rows per cob: was counted on ve representative ears and the average value was recorded for each plot.1000 Seed Weight (SSW) (g): One thousand seeds per sample was counted using electronic counter and then weighed using sensitive balance. Grain Yield (GY): Grain was manually harvested from central rows and converted to kg ha − 1 after adjusting the moisture content to 12.5%. Biomass Yield (BY): was estimated as the sum of stover weighed and grain yield. Harvest index (HI): Is the ratio of grain yield to total biomass yield which was estimated by dividing grain yield by total biomass.

Plant Tissue Sampling And Analysis
Grain and straw yield nutrient uptake were calculated by multiplying nutrient with respective straw and grain yield ha-1 : NU=(NC*Y)/100 ; where, NU,NC and Y stand for nutrient uptake ,nutrient concentration of gran or straw, and grain yield or straw, respectively.

Statistical Analysis
The collected data were subject to analysis of variance (ANOVA) using SAS computer program following the procedures described by (Gomez, KA.and A.A. Gomez, 1984). Mean separation of signi cant treatment were carried out using the least signi cant difference (LSD) test at P ≤ 0.05 level..

Partial Budget Analysis
Partial budget analysis was done to investigate the economic feasibility of the treatments by using partial and marginal analysis. Marginal rate of return (MRR) was calculated as the change in net bene t (NB) divided by the change in total variable cost (TVC) of the successive net bene t and total variable cost levels (CIMMYT, 1988). The variable cost are application costs and price of each fertilizer that vary for each treatment. The fertilizer cost was (1786 ETB/qt) NPSZnB and DAP and price of the grain yield was 12 ETB /kg on the local market.

Soil Analysis
The result of the soil sample before planting of physical and chemical analysis of the site was done in Mekelle soil laboratory. The soil of the experimental site has a proportion of 30% sand, 56% silt and 14% clay and it is classi ed as silt loam soil according the soil triangle texturally ( Table 1). The organic carbon content of the soil was 0.8% which rated under low, in agreement with the nding of (Tekalign, 1991). The pH valve of the soil result at the experimental site 7.4 was almost neutral. The cation exchange capacity was 35.4 Meq/100 gm soil which is categorized as medium.
The results in (Table 2) indicated that the soil comprised total N of 0.121% and thus the composite soil sample of the experimental area was rated as low (London, 1991). The available P in the experimental soil contains 8.46 ppm. According Olson et al (1954), it has medium level of available P in the experimental site. This is may be due to the cropping history of the area was maize so, maize is not required in as high amounts as N.  Analysis of variance indicated that there is a signi cant effect between the blended fertilizer rates on maize ear length (p ≤ 0.05). The ear length increment with the blended fertilizer application might be attributed to good photo assimilate supply of the blended elements. The highest ear length was recorded from the 100-250 kg of NPSZnB ha -1

Number Of Seeds Per Row
Result of the analysis of variance (p ≤ 0.05) revealed blended fertilizer rates have a signi cant effect on number of seeds per row. The highest number of seeds per row (35.5) was achieved from the treatments 150 kg NPSZnB ha − 1 . On the other hand the similar number of seeds per row (30.8) was recorded from untreated plot(control)..These increments of number of seeds per row with the blended fertilizer could be due to the more plant nutrient contents of blended fertilizer. In agreement with result of this experiment,maize production depends mainly on the availability of essential plant nutrients and application of fertilizers (Adediran, 2003).

Grain Yield
The application of different rate of blended fertilizer showed a highly signi cant (< 0.001) effect on grain yield of maize. The highest grain yield recorded from the application of (150 to 250 kg ha-1 NPSZnB and 200 kg ha-1) DAP did not have statically deference each other. But they have a highly signi cance deference from the other treatments. Whereas, the lowest grain yield was recorded from plots treated with zero (5667 kg ha − 1 ) and 50 kg ha-1 (5687 kg ha-1) NPSZnB fertilizers. The grain yield increment may be bene cial effect of yield contributing character and positive interaction of nutrients in the blended fertilizers. This result in agreement with the current ndings Tekle and Wassie (2018) found that grain yield of tef was found highest in blended fertilizers as compared to control treatment and recommended NP fertilizers. Additionally, Jafer (2018) found better grain yield from application of blended fertilizer compare to recommended NP fertilizer and unfertilized plot.

Biomass Yield
Analysis of the variance showed that, there is a signi cant difference (P ≤ 0.001) between blended fertilizer rates on biomass yield of maize. The highest biomass yield was recorded from the treatment received the heights blended fertilizers rate of 150-250 kg NPSZnB /ha and 200 kg ha-1 DAP (Table 3)  Thousand Seed Weight (gm) Thousand grain weight of maize did not show any signi cant variations (p < 0.05) amongst the blended fertilizer rates. This result is different from tekulu (2019) reported that thousand seeds weight of maize crop were found to be signi cantly affected by blended fertilizer rates compared to the control.

Harvest Index
Analysis of the result revealed that application of the blended fertilizer in compound had signi cant effect (P < 0.05) on harvest index of maize crop. The maximum harvest index was obtain from the application of 50 to 150 kg NPSZnB per ha as compared to the other fertilizer rates. The blended fertilizer might be attributed to positive interaction of nutrients in the blended fertilizer gives more grain weight and have positive relation to grain yield increment. This result agrees with the ndings of Tekulu (2019) who reported that harvest index of maize was found to be highest at the rate of 150 kg NPSZnB per ha as weighed to the control treatment.

Nitrogen Uptake By Grain And Stalk
The results presented in (Table 4) indicated that, the highest N uptake form grain (10 kg /ha) and stover (20.67 kg /ha) was obtained in plot treated by (200 and 250 kg) NPSZnB /ha. While the lowest N uptake by grain (7.59 and 7.56 kg / ha) was recorded in control and a plot treated by the low level. The lowest N uptake by Stover (10.45 kg ha-1) was recorded from the plot treated by 50 kg NPSZnB /ha of blended fertilizer. The maximum N uptake form grain and stover are increased by 24.4 and 49.4 from the minimum uptake which treated by 50 kg ha-1 NPSZnB fertilizer. This study agreed with the ndings of Jones (1996) who reported that agronomic practices affected not only yield, but also seed N contents. The highest yield was associated with highest dry matter production and Stover N uptake increased signi cantly with optimum nutrient application.

Phosphorus Uptake By Grain And Stover
Application of different blended fertilizer rates on P uptake in grain and stover showed high difference and increasing trends. Due to the blended fertilizer treatment (

Partial Budget Analysis
The result displayed in Table 5 reveals that, the partial budget analysis of fertilizer rates revealed that the maximum net bene t (79010.2 ETB/ha) was attained from application of 150 kg NPSZnB ha − 1 and the least net bene t (68662.6 ETB/ha) and (69885.9.ETB/ha) was obtained from the application of 50 kg NPSZnB /ha and unfertilized treatment. The dominance analysis showed that all the treatments, except the treatment with NPSZnB fertilizer rate of 100 kg ha − 1 , and 150 kg ha − 1 were cost dominated.
The highest marginal rate of return (529%) was obtained from the treatment of 150 kg NPSZnB ha − 1 fertilizer followed by (113%) amended with 100 kg NPSZnB ha − 1 fertilizer (Table 5) gave maximum pro t from unit investment. Generally, the analysis of marginal rate of return (MRR) indicated that the application of blended fertilizer on productivity of maize had MRR of greater than 100%. This indicates that maize production is pro table with these all alternatives. According to CIMMYT (1988), application of fertilizer with the marginal rate of return above the minimum level (100%) is economically feasible.

Conclusions And Recommendations
Based on the result of two years eld experiment, the biomass yield, grain yield and nutrient uptake of maize variety (Gibe-III) was signi cantly affected by the application of different blended fertilizer rates.
The highest grain and biomass yields of maize was obtained from the application of 150 to 250 NPSZnB and 200 kg ha-1 DAP fertilizer. The maximum nutrient uptake of N and P also recorded from the treatment received 250 kg NPSZnB ha − 1 and 200 kg DAP ha − 1 fertilizer, respectively. This result indicated that, when the rate fertilizer is increase the chance of NP uptake also rises. On the other hand, the highest marginal rate of return (529%) followed by (114%) was obtained from the treatment of 150 and 100 kg NPSZnB ha − 1 fertilizer amended with enough N. Based on the result of (MRR)shown, application of blended fertilizer on productivity of maize had greater than 100%. Therefore, as the result of two years experiment it was possible to conclude that, in the presence of appropriate rate of N fertilizer; maize is responsive to high yield and maximum net bene t at 150 kg NPSZnB ha − 1 of blended fertilizer. In order to increase the rate of fertilizer application and crop productivity the government should subsidize the cost of fertilizer to make it affordable for farmers. Further study can be important on different varieties and nutritional content. Map of the study area