Effects of Integrated Use of Calcite and Inorganic Fertilizer on Soil Physicochemical Properties and Maize (Zea mays l.) Yield and, Economic Feasibility on the Nitisols of Northwestern Ethiopia

Background: Understanding the soil reaction (pH) is relevant for improving crop productivity. Soil acidity is one of the restraining factors to crop production in the highlands of Ethiopia. This study was carried out on the nitisols of Burie District to examine the effect of integrated use of Calcite and Nitrogen fertilizer on soil physico-chemical properties. Treatments were two levels of lime (0 and 0. 50 t ha -1 ) and ve-level of nitrogen (0,100, 200, 300, and 400 kg ha -1 ). The experiment was laid out in randomized complete block design (RCBD) with ten treatments replicated three times. Before and after harvest, both disturbed and undisturbed soil samples were collected. Analysis of variance (ANOVA) and bivariate correlations was employed using SAS statistical package program version 9.0. After harvesting thirty soil samples were collected from each treatment and then ten composite soil samples within a block were arranged for laboratory analysis. Result: The result indicated that among the soil properties before planting the crop soil bulk density (BD), pH, organic carbon (OC), total nitrogen (TN), available P and CEC were 1.43g cm -3 , 5.2 (strongly acidic), 1.32% (very low), 0.12% (low), 8.86 mg kg -1 (very low), and 19.57 cmol c kg -1 (medium), respectively. After harvesting, most of the surface physico-chemical properties except bulk density increased. The lowest soil BD was 1.21 g m -3 from plots treated with 0.5 t ha -1 lime and 400 kg ha -1 urea. The maximum soil pH (6.85) was obtained from plots treated with 400 kg ha -1 N and 0.5 t ha -1 lime. The maximum soil CEC (35.38 (cmol c kg -1 ) was obtained from plots treated with 400 kg ha -1 N and 0.5 t ha -1 lime. Level of lime, nitrogen fertilizer and interaction effects of lime and nitrogen fertilizer (L*N) signicantly affected maize yield (p<0.001). Yield of maize have positive correlations with most soil physico-chemical properties but negative with BD (r=-0.543).The adjusted yield and net benet was 6,410.20 kg ha -1 and 58,891.47 Ethiopian Birr (ETB), respectively. Conclusion: Inherent physicochemical properties of the soil is changed either by sole or combined use of lime and N fertilizer. Soils tilled with 0.5 t ha -1 lime and 138 kg ha -1 nitrogen was found in maximum net benet. Residual long-term effects should be researched. Thus, liming should be given emphasis in acidic soil amelioration. Moreover, the government may facilitate the supply of calcite (CaCO 3 ) and urea fertilizer to the farmers.


Experimental Materials used
Plant , fertilizer and lime The maize variety H-661 (Bako Hybrid-661) which is adapted to the agro-ecology and registered at the national level was collected from Amhara Seed Enterprise and used as a test crop.
As a feretilizer urea (46% N) was applied at ve different rates (0,100,200,300, and 400 kg ha -1 ) and was applied in one dose at knee height sage. This fertilizer was applied by banding at a distance 2 to 3 cm away from the plant and at 20 cm depth and covered immediately with soil.The recommended rate of NPS (19% N, 38% P 2 O 5 , and 7% S) fertilizer was uniformly applied to all plots at the time of planting.
Liming material in the form of calcium carbonate (CaCO 3 ) passed a 100-mesh was applied. According to Burie district Agricultural O ce Manual (2019), there are two ways of lime application. First, during seed sowing (i.e row application) if the lime is a powder, and the secondis broadcasting application for granular type of lime. First, during seed sowing one fourth (20 t ha -1 ) of the recommended rate of broadcasting (i.e 0.5 t ha -1 lime) was applied. Broadcasting application is recommended to apply one or two months before seed sowing (BDAO, 2019). Lime was added as the district agricultural o ce manual, based on the soil pH of the experimental site. According to BDAO (2019) unpublished mannual, if the pH (H 2 O) value of the soil is between 5.14 to 5.32, the recommended lime rate for broadcasting application method is 20 t ha -1 . For row application method, 0.5 t ha -1 of the recommended rate for broadcasting method was used. Since the soil pH of experimental site was 5.20, the amount of lime rate added during maize sowing was 0.5 t ha -1 .

Evaluation of changes in soil properties
Before sowing the seed, ten disturbed soil samples were taken at a depth of 0 to 20 cm at different points by vertical insertion of a shovel and mixed to get one composite sample. Similarly, ten representative undisturbed samples were taken for bulk density determination using core sampler. Likewise, 30 disturbed soil sample were collected from each plot within a block and reduced into ten composite sample for soil chemical property analysis. On the other hand, after harvest, 30 undisturbed samples were also collected from each plot within a block for BD determination. The composite surface soil and individual soil samples from each plot after treatment were properly labeled and the lables were placed both inside and outside the plastic bags and were transported to the soil laboratory of Amhara Design and Supervision Works Enterprise.

Analysis of soil physical properties
Soil bulk density was measured from undisturbed soil samples collected using a core sampler (which was weighed at eld moisture) after drying the preweighed soil core samples to constant weight in an oven at 105 0 C as per the procedures described by (Blake 1965). Then soil bulk density was calculated by dividing the masses of the oven-dried soils by their respective total volume of the core sampler.

Analysis of soil chemical properties
The composite soil samples were air-dried, mixed well, and passed through a 2mm sieve for the analysis of selected chemical properties. Soil pH was measured using a pH meter in a 1:2.5 soil: water ratio suspension as outlined by Van (1993). Soil OC was determined by the Walkley and Black wet digestion method (Walkley and Black 1934), and the soil OM was calculated by multiplying the percent organic carbon by a factor of 1.724. Total N was determined using the micro-Kjeldahl digestion, distillation, and titration procedure as described by Bremner and Mulvaney (1982). Available P was determined using the standard Olsen extraction method (Olsen 1954). CEC was measured by ammonium acetate extraction method (Chapman 1665).

Fertilizer application and eld activities
The experimental plot plowed three times; the rst plowing was done on the rst of April with a disc plough. The second and nal plowing was conducted by oxen-driven local plow called "Maresha" at rst and last dates of May. Spacing of maize plants was 75cm between rows and 25cm between plants. The experimental eld was hand weeded twice at 25 and 45 days after planting. A late-emerging weeds were removed by hoeing to avoid mixup between the N applied and non-applied treatments. All other agronomic practices such as fertilization, hoeing, disease, insects, and weeds management were as per the recommendation. Maize plants in the central net plot area were harvested leaving one boarder row from each side of each plot.

Data Analysis
Analysis of variance (ANOVA) was carried out using SAS statistical package program version 9.0 (SAS, 2004). Duncan's Test was used to assess yield differences among treatment means where signi cant differences were obtained by the analysis of variance. Soil physico-chemical properties bivariate correlations on yield of maize was also carried out. Finally, soil physico-chemical properties comparison with critical values was done.

Discussion
The results of soil analysis before application of calcite and N fertilizer for maize crop is presented in Table 1. Before harvesting, BD of the soil was 1.42 gcm -3 with clay texture ( Table 1). The high BD value might be due to compactness of the soil and lower OM content that resulted from continuous cultivation and removal of plant roots and residues. Thus, as per the critical value rated by Karltun et al. (2014), the soil of the study area has a higher BD. This is supported by Karltun et al.(2014) reported an increase in bulk density due to compaction and decreasing soil pore space in Ethiopia. Bulk densities of soils are inversely related to the amount of pore space and soil OM (Gupta 2000;Brady and Weil 2008). Any factor that in uences soil pore space will also affect the bulk density. For instance, exhaustive cultivation increases bulk density resulting in a decrease of total porosity (Brady and Weil 2008).
The soil OC contents were 1.32% (Table 1), which is rated as very low (< 1.7%) to low (2-4%) as per the rating of soil test values interpretation by Landon (1991). Based on this result, soil OC of the study area rated as very low compared to the critical value (3%). This might be due to the removal of plant tissues and root residue from the soil. For a soil to be productive, it needs to have OC content in the range of 1.8-3% so as to achieve good soil structural conditions and structural stability (Abera and Wolde-Meskel 2013).
The content of Total Nitrogen (TN) also followed the trend of soil OC which had a value of 0.12% (Table 1). According to Assefa (2009), TN rated as very low (< 0.10%), low (0.1-0.15%) and optimum (0.15-0.30%). Based on these ratings, the study area had lower TN content. These minimum soil OC and TN values are expected in the maize-growing elds of the study area where there is complete removal of biomass from the crop eld, lower application rate of fertilizers, and continuous cultivation that favors rapid rate of mineralization (Abera and Wolde-Meskel 2013).
Available P before the application of lime and urea fertilizer was very low (8.86 mg kg -1 ) in acidic Nitisols of the study area (Table 1). The value is below the critical level of available P on Nitisols of Northwestern Ethiopia for maize is 11.10 mg kg -1 in Al sols as suggested by Yihenew G. Selassie (2016). This might be attributed to P xation due to the acidic nature of the soil and is not readily available to plant uptake. The low application rates of P-containing fertilizers, continuous crop uptake, losses due to erosion and xation by acidic soils in this maize-growing eld of the study area might be linked to the inadequate P levels recorded in the studied soils.
The CEC value of Nitisols of the study area was 19.57 cmolc kg -1 (Table 1), which is rated as a medium as per the ratings of (Karltun et al., 2014). According to this author, soils having CEC of >40, 25-40, 15-25, 5-15, < 5 cmol c kg -1 categorized as very high, high, medium, low, and very low, respectively (Karltun et al., 2014). The level of CEC could be associated with the texture of the soil which is clay. Clay soils have more cations as they have the characteristics of increasing negative surface charges of soil.

Effect of Calcite and Nitrogen Fertilizer on Soil Physicochemical Properties
Change in soil bulk density Due to the application of lime, bulk density was declined in all plots (Table 2). This could be aggregation of soil and improve soil crusting. However, the highest reduction (from 1.42 to 1.21 g cm -3 ) was recorded in plots treated with 0.50 t ha -1 lime with 400 kg ha -1 urea. This might be due to the increasing effect of soil organic matter (SOM) after harvest that makes the soil less compact and reduces the BD. Similarly, Tesfaye (2017) found a decrease in soil BD as a result of integrated use of soil fertilizers in maize cultivated land at Yilmana Densa district northwestern Ethiopia. The result was also similar to Muhammad (2011) who found lower bulk density as a result of nutrient and crop management on the crops sugarcane, maize, sorghum, and cotton residues at Gatton, Southern Queensland Australia. However, as Bayu (2006)  Change pH of soil Soil pH was affected by integrated nutrient management that increased with the application of lime and N fertilizer (Table 3). In the sole application of urea fertilizer, the highest (5.51) and lowest pH (4.98) were recorded in plots treated with 100 and 400 kg ha -1 urea, respectively (Table 2). Though, nitrogen fertilizers increase crop yield, at the same time they also increase soil acidity. This is because during ammonium is converted to nitrate, and released hydrogen ion which is one of the contributing factors leading to acidi cation. Hence, the application of N fertilizers containing NH 4 + or even adding large quantities of organic matter to the soil can ultimately increase soil acidity and lower the pH Guo (2010). Similarly, Opala et al. (2018) found that the pH of soil treated with inorganic urea fertilizer was 5.21 as compared to the control pH (4.92) on maize cultivated acidic soils of Western Kenya. Conversely, the sole application of lime effectively increased the soil pH from 5.2 to 5.85 (Table 2). This rise in pH of the soil is associated with the presence of basic cations (Ca 2+ ) and anions ) in lime that can exchange H + ions from exchangeable sites to form H 2 O and CO 3 2 . The increase in soil pH resulting from the application of lime provides a more favorable environment for soil microbiological activity which increases the rate of release of plant nutrients, particularly N. Reduced acidity due to liming increased the availability of other plant nutrients mostly P (Dinkecha and Tsegaye 2017).
Similarly, Opala et al. (2018) reported an increase in soil pH (5.26) after the application of lime as compared to the control that had a pH value of 4.92 in acidic soils of Western Kenya. Correspondingly, Demissie et al. (2017) found increased soil pH after the application of lime, where it was changed from extremely acidic pH of 3.8 to medium and neutral pH of 6.63-6.86 in acid Soils of Wolmera district, West Showa Ethiopia. Likewise, Nadir (2005) reported the effect of lime in raising the soil pH and increase the availability of soil P by unlocking the soil xed P into available P for crop use. Lime increases the availability of other nutrient elements mostly basic cations essential to crop use especially Ca which forms plant structure (Dinkecha and Tsegaye 2017).
The combined application of lime and inorganic fertilizer improved soil pH. The highest pH (6.85) was recorded from plots treated with 0.50 t ha -1 lime mixed with 400 kg ha -1 urea ( Table 2). This is due to the dissociation of urea which releases NH 4 + , during plant up take of NH 4 + and the release of HCO 3 that reacts with H + and form H 2 CO 3 acid. This acid is a weak acid and dissociates into H 2 O and CO 2 . Eventually, CO 2 is released to the atmosphere and water stays in the soil increasing pH by decreasing H + ion concentration in the soil solution. Similar increases in pH using integrated soil fertility management have been reported by Whalen et al. (2002); Moreira and Fageria (2010);Buni 2014). This might be due to the synergetic effect of lime integrated with N fertilizers.
Change in soil organic carbon (OC) The maximum SOC content (2.51%) was recorded in plots treated with 0.50 t ha -1 lime with 400 kg ha -1 urea which was an increase by 52.60% from the initial soil OC analysis result (1.32%). The minimum SOC (2.23%) was recorded from plots treated with 0.50 t ha -1 lime and 100 kg ha -1 N ( Table 2). The increase in SOC could be associated with the decomposition of dead plant tissue like roots and leaves that contributed to plant biomass after the addition of lime. The increased microbial activities by liming are likely to increase SOC mineralization when the soils are cultivated and exposed to increased microbial activity Six et al.(2000).
Similarly, Aye et al.(2016) found that the higher OC of the soil after the application of lime integrated with NP fertilizers at Haryana Agricultural University, India. Besides, Antill (2001) also reported greater levels of SOC under integrated treatments of lime with inorganic fertilizer in acidic soil in the western Himalayas on maize crop. In a similar study, Moges (2018) reported increased amounts of OC from 2.23%, to 2.49% after the application of lime with integrated inorganic fertilizers in the malt barley crop in Angolela Tera district Northwestern Ethiopia. However, the sole application of lime reduced SOC from 1.32% to 1.29%. This is supported by Moges (2018) found in the sole application of lime 4 t ha -1 and 6 t ha -1 decreased SOC from 2.12% to 2.07%.

Total Nitrogen content
The maximum TN (0.231%) was recorded in plots treated with 0.5 t ha -1 of lime and 400 kg ha -1 N. The lowest TN (0.205%) was recorded in plots treated with 0.50 t ha -1 of lime and 100 kg ha -1 urea (Table 2). Hence, it is clear that the application of lime with chemical fertilizers increased TN, which may be attributed to the mineralization of N from OM during the decomposition of organic matter. Generally, the combined application of lime and mineral fertilizers at different rates affected the contents of total N in the study area. Similarly, Kebede and Yamoah (2009) reported increased amount of TN in the vertisols of the Central Highlands of Ethiopia after the application of lime with mineral fertilizers. An increase in TN after the application of organic integrated with inorganic fertilizers has also been reported by Muhammad (2011); Agegnehu and Bekele (2005) in different part of Ethiopia.

Change in available phosphorus
In the sole application of inorganic fertilizer, the highest and lowest available P was 26.04 and 15.28 mg kg -1 recorded in treatments T5 and T2, respectively (Table 2). After the combined application of lime and urea, the maximum and the minimum values of available P were 30.43 mg kg -1 and 22.84 mg kg -1 in treatments T10 and T7, respectively.
Thus, the combined use of lime and chemical fertilizers increased available P content in the soil by mineralization or solubilizing of the native P reserves in soil Haynes and Naidu (1998). .As a result, soil available P after harvesting was much higher than the initial levels of lime-treated plots. Therefore, the major bene ts of liming acid soils are the increased utilization of residual fertilizer phosphorus by maize crops. This might be due to the mineralization of OM and plant residues. The incorporation of lime has been shown to increase the amount of soluble organic matter which were mainly organic acids that increase the rate of desorption of phosphate and thus improves the available P content in the soil (Zsolnay and Gorlitz 1994). Similarly, Wanjiru (2018) showed an increase in soil available P after the application of lime, combined with manure and P fertilizer. Generally, the application of lime and mineral fertilizer increased P content. Similarly, Ghosh et al. (2019) reported that the combination of compost with chemical fertilizer helped in increasing the available P in the soil by mineralizing or solubilizing the native P reserves in Yilmana Desnsa district, Northwestern Ethiopia.

Change in Cation exchange capacity
After application of mineral fertilizer, the highest CEC was 23.36 cmolc kg -1 in T5 and the lowest 22.19 cmolc kg -1 in treatments T2 (Table 2). This might be due to increased pH, so do the number of negative charges on soil colloids that increased the CEC. Similarly, Tesfaye (2017) found an increase in CEC value after the application of mineral fertilizers in the soils of the Yilmana Desnsa district. After the application of lime alone, CEC increased from 22.17 cmol c kg -1 to 27.25 cmol c kg -1 in treatments T1 and T6. This increase in CEC could be linked to an increase in pH that increased the negative surface charges of soil colloids which subsequently increase the cation holding capacity of the soil. Similarly, Buni (2014) reported higher values of CEC after lime treatment was reported in Sodo Zuria district. Likewise, Yirga (2019) found the highest values of CEC in soils treated with the highest lime rate (3.75 t ha -1 ) in Welmera and Endibir district Southwestern Ethiopia. Besides, in the combined application of lime and N fertilizer, the highest and lowest CEC value was 35.38 cmolc kg -1 and 31.43 cmolc kg -1 recorded in treatments T10 and T7, respectively. This indicates that the combined application of lime and mineral fertilizer increased CEC to hold a higher amount of nutrients and that readily available to plants. The result was similar to Yirga (2019) who found higher CEC value due to integrated nutrient management.

Effects in Grain Yield
The economic analysis result indicates that, the maximum adjusted grain yield (6,410.196kg ha -1 ) was recorded from plot treated with 0.5 t ha -1 ) lime with 300 kg ha -1 N fertilizer while the min mum grain yield (3,177.135 kg ha -1 ) was from the control ( Table 4).The mariginal rate of return value is 805.24%. This could be due to the improvement of soil physicohemical properties. Grain yield has posive correlat -0.543).This is in line with Opala et al. (2018) maximum maize yield (2.35 t ha -1 ) was obtained from application of 2.00 t ha -1 CaCO 3 + 26 kg P + 60 kg N compared with the control (1.38 t ha -1) . Similarly Tolcha (2018) reported that BH 661 maize yield potential varies between 9,500 and 12,000 kg ha -1 at research eld and 6 and 8.50 t ha -1 at farmers' eld under integrated agronomic managements.

Conclusion And Recommendation
Based on the result of this study we can conclude that; inherent physico-chemical properties of the soil changed either by sole or combined use of lime and N fertilizer. Soils with 0.5 t ha -1 lime and 300 kg ha -1 nitrogen fertilizer was found in maximum net bene t. Thus, liming ahould be given more emphasis in acidic soil amelioration. Moreover, the government may facilitate the supply calcite (CaCO 3 ) and urea fertilizer to the farmers. Figure 1 Monthly rainfall (mm), minimum, maximum and average air temperature (0C) of the study area during 2010-2019 Plough depth (0-20cm) soil physicochemical properties before and after harvest