Municipal solid waste and NPK fertilizer effects on soil physical properties and maize performance in Nsukka , Southeast Nigeria

A study was carried out in the experimental farm of the Department of Crop Science, University of Nigeria, Nsukka to determine the effect of composted Municipal Solid Waste (MSW) on some soil physical properties and also the effect of combined application of MSW and NPK 20:10:10 fertilizer on maize. Four rates of MSW; 0, 1000, 1500 and 2000 kg/ha and four rates of NPK fertilizer; 0, 100, 200 and 300 kg/ha were tested. These were laid out in a 4 × 4 factorial experiment in randomized complete block design (RCBD). The result shows that the application of MSW did not cause significant improvement in some soil physical properties such as soil aggregate stability, saturated hydraulic conductivity, bulk density and porosity. Maize yield was significantly increased by the application of MSW. Combined application of MSW and NPK fertilizer resulted to higher yield in maize than sole application of either MSW or NPK fertilizer. The highest grain yield was realized from the combined application of 2000 kg/ha of MSW and 300 kg/ha of NPK fertilizer. The result shows that combined application of MSW with NPK performed better than sole application of either MSW or NPK fertilizer. Combination of 2000 and 300 kg/ha performed better than other treatment combinations and was found satisfactory to improve maize performance in sandy loam ultisol in Nsukka.


INTRODUCTION
The physical condition of a soil is one of the fundamental factors affecting crop growth, development and yield.This is because the soil physical properties have very high degree of correlation with crop production and have high influence on soil fertility and crop performance (Nnaji, 2009).
According to Wallace and Wallace (1986), to obtain high crop yield, the soil must have the proper physical properties and unless the physical nature of soils is improved, and high plants-nutrient-use efficiency will not be achieved (Parr et al., 1986).One way of improving soil physical properties is by application of organic matter to the soil.Application of biosolids help to replenish soil organic matter levels, supply nutrients such as N, P and K, and other essential micronutrients to plants and improve soil structure and water holding capacity, and have beneficial effects on microbial biomass and activity (Barry et al., 2004;Bell et al., 2004;Eriksen et al.,1999;Leifield et al., 2002).Municipal Solid Waste (MSW) is defined as household waste and other waste which because of its nature or composition is similar to household waste which undergoes anaerobic or aerobic decom-*Corresponding author.E-mail: Nikejahp@yahoo.com,nikejahp@gmail.com.position, including green MSW from gardens and parks such as tree cuttings, branches, grass and wood (European Commission, 2001).Ghaly and Alkonik (2010) defined MSW as wastes that constitutes portion of solid waste stream originating from household, insti-tutions, commercial and service establishments, offices and public facilities.Several authors have assessed the positive effects of compost municipal solid waste application on the environment.These include the reduction of weed germination and number of plant pathogens, increase in crop yield, increase in organic matter content, decrease in erosion rates and improves moisture content and decrease in soil bulk density (Elherradi et al., 2005;Sharma and Campbell, 2003;Silva et al., 2007).Soil amendment with manures, municipal biosolids, and other organic wastes has been found to improve the physical and chemical properties of soil (Barzegar et al., 2002;Mkhabelaa and Warmanb, 2005;Šimon et al., 2013;Unagwu et al., 2013).Beneficial effects of organic soil amendments include decreased soil bulk density and increased waterholding capacity, aggregate stability, saturated hydraulic conductivity, water infiltration rate and biochemical activity (Martens and Frankenberger, 1992;Turner et al., 1994).Roe et al. (1997) studied the effect of green peppers and cucumbers in a sandy soil fertilized with compost or mineral fertilizers application and found that, yields were usually higher when compost was combined with mineral fertilizers.
Integrated use of organic nutrient sources with inorganic fertilizer has been reported to increase the potential of organic fertilizer (Heluf, 2002) and improve the efficiency of inorganic fertilizer.Dutta et al. (2003) reported that the application of both organic manure and chemical fertilizers, compared to application of only organic fertilizers had a higher positive effect on microbial biomass and soil health.Incorporation of chemical fertilezers in composted materials improves its efficiency and reduces yield losses (Gua and Geta, 1993).High and sustained crop yield can be obtained with judicious balance of NPK fertilization combined with organic matter amendment.The objectives of the work were to evaluate the effect of MSW on some soil physical properties in a sandy loam ultisol and to determine the response of maize to MSW and NPK fertilizer application.

MATERIALS AND METHODS
The field experiment was carried out at the Department of Crop Science Teaching and Research Farm, University of Nigeria, Nsukka which is located by latitude 06° 52 1 N and longitude 07° 24 1 E with a 447 m altitude above sea level.During the period of the study, the experimental area received mean annual rainfall of 1614 mm, maximum and minimum mean monthly temperature were 33 and 19°C, respectively.It is within the low -land humid tropical agro -ecology of Nigeria.The municipal solid waste used for the study was generated from waste bins found within University of Nigeria, Nsukka campus.The biodegradable materials were properly sorted before the materials were composted aerobically.The composted material included: food waste, paper, vegetable scrap, plant leaves, Onwudiwe et al. 69 banana, cassava and pawpaw peelings and plant cuttings.The composted product used in the study was free of odour and dark in colour -but with small amount of foreign materials as defined by CCME (2000).The chemical fertilizer used was NPK (20:10:10) which was sourced from ENADEP depot in Nsukka.The soil samples were subjected to laboratory analysis.Bulk density was determined by core method as described by Blake and Hartge (1986).Saturated hydraulic conductivity (K sat ) was calculated using Darcy's equation as outlined by Young (2011): Where Q = steady state volume of outflow from the entire soil column (cm 3 ), L = the length of soil column (cm), A = the interior cross-sectional area of the soil column (cm 2 ), H = the change in hydraulic head pressure difference causing the flow (cm), T = the time of flow (s).
Mean weight diameter (MWD) was calculated using the method described by Kemper and Rosenau (1986).A 25 g of < 4.75 mm air-dried soil sample was placed in the topmost nest of sieves 2.00, 1.00, 0.50 and 0.25 mm mesh sizes and left for 5 min.Thereafter, the nest of sieves and its contents were oscillated vertically in water for 65 times using 4 cm amplitude at the rate of one oscillation/second.Thereafter, the different soil aggregates were oven-dried for 48 h and weighed: Where, Xi = the mean diameter of each sieve (mm) size or fraction, Wi = the proportion of total sample weight in the corresponding size fraction and n = number of samples.
Particle size analysis of the soil was determined using the Bouycous hydrometer method as described by Gee and Bauder (1986).Organic carbon was determined using Walkley and Black dichromate method as described by Nelson and Sommer (1982).This was corrected to soil organic matter by multiplying with a correction factor of 1.724 (Nelson and Sommers, 1996).Total nitrogen was determined using the Kjeldhal method as described by Bremner and Madison (1996); soil pH was determined using a hand pH meter in a soil solution ration of 1: 2.5.The experimental design was a 4 × 4 factorial in randomized complete block design (RCBD).The two factors: MSW compost (0, 1000, 1500 and 2000 kg/ha) and NPK 20:10:10 (0, 100, 200 and 300 kg/ha) were combined to produce 16 treatment combinations (Table 1) which was replicated three times.Two weeks after planting (WAP), the treatments were applied to the plots accordingly.The treatments were applied in a ring form (10 to 15 cm from the plant) and properly mixed with the soil at the base of the plant.The following parameters were measured: plant height, leaf area at 4 and 8 WAP respectively as well as grain yield and harvest index were measured.Data was subjected to analysis of variance (ANOVA); means were separated using fisher's least significant difference (F-LSD) procedure as described by Obi (2002).Test of significance was done at 5% probability level.

Harvest index
This was obtained by using the formula: Seed weight (g/plant) Total dry matter of plant material (g/plant)

RESULTS AND DISCUSSION
The application of NPK, MSW and their interaction significantly (P < 0.05) influenced plant height at 4 and 8 WAP (Table 2).The 2000 kg/ha of MSW had the highest plant height (Table 2) and was significantly (P < 0.05) higher than for other MSW rates.Similarly, 300 kg/ha NPK had the highest plant height among the NPK rates.The highest result from treatment combination was obtained with the application of 2000 kg/ha MSW with 300 kg/ha NPK which had significantly (P < 0.05) higher plant height than combination of 0 kg/ha MSW with 0 kg/ha NPK (Table 2).The application of NPK, MSW and their interaction significantly (P < 0.05) influenced the leaf area at 4 and 8 WAP (Table 2).Application of 300 kg/ha NPK had the highest leaf area NPK rates while application of 2000 kg/ha MSW significantly (P < 0.05) gave the highest leaf area (Table 2).The highest leaf area was observed when 2000 kg/ha MSW was combined with 300 kg/ha of NPK.The leaf area increased with increasing rate of MSW.The effects of organic fertilization and combined use of chemical and organic fertilizer on crop growth and soil fertility depend on the application rates and the nature of fertilizers used (Jen-Hshuan, 2006).The higher the concentration of treatment rate, the better the performance.Obidebube et al. ( 2012) obtained similar result and reported that higher rates of NPK performed better than lower rates when applied on maize.
Complementary application of MSW with NPK significantly increased the production of maize vegetative traits (plant height and leaf area).This suggests that the presence of MSW (organic manure) could improve soil conditions.Combined application of MSW and NPK fertilizer performed better than sole application (Murwira and Kirchmann, 1993).Furthermore, nutrient use efficiency might be increased through combination of organic manure and mineral fertilizer.The application of NPK, MSW and their interaction had significant (P < 0.05) effect on grain yield per hectare (Table 3).The 300 kg/ha of NPK had the highest grain yield per hectare.Application of 200 and 300 kg/ha NPK was not significant (P < 0.05) but were significantly (P < 0.05) higher than the effect of 0 kg/ha NPK on grain yield.The highest grain yield per hectare was obtained with 2000 kg/ha MSW application and was significantly higher (P < 0.05) than other MSW rates.Combined application of 2000 kg/ha MSW and 300 kg/ha NPK gave significantly (P < 0.05) higher grain yield per hectare than application of 0 kg/ha NPK with 0 kg/ha MSW (Table 3).
NPK, MSW and their interaction significantly (P < 0.05) affected harvest index (Table 3).Application of 300 kg/ha NPK had the highest harvest index among NPK rates.Also, 2000 kg/ha MSW produced the highest harvest index among MSW rates.It was observed that the application of 2000 kg/ha MSW with 300 kg/ha NPK had the highest harvest index among the NPK by MSW interactions (Table 3).This suggested that the increase in rate of MSW resulted to the increase in grain filling and dry matter content of the plant which resulted to increased yield traits.Obidiebube et al. (2012) obtained similar result when NPK at different levels were applied on maize.Combination of 300 kg/ha of NPK and 2000 kg/ha of MSW performed better than other combinations.This suggests that maize requires supplemental dozes of inorganic fertilizers in order to achieve optimum production.Titiloye et al. (1982) observed that complementary application of organic and inorganic manure increased the efficiency of nutrient release than sole application of organic or inorganic fertilizer especially on The chemical analysis of the municipal solid waste (MSW) showed that the MSW was low in organic matter (18.3%), total nitrogen (1.4%), potassium (0.28%) and available phosphorous (0.05%) but had a high pH value (8.3) which is capable of ameliorating the acidic content of the soil (Table 5).It was expected that MSW would have significant effect in the physical properties as was widely reported in literature.However, the results obtained did not show any significant improvement in bulk density, aggregate stability, mean weight diameter, soil porosity and hydraulic conductivity when compared with the control (Table 6).The reason for the nonsignificance could probably be because the rates of MSW used in the study was too small to have any significantly effect on the soil physical properties and this could be main cause of the non-significance observed in the study.Application of inorganic fertilizer and municipal solid waste had no significant effect on the soil porosity.This could be due to the low quantity (< 3 tha -1 ) of MSW applied.This result was similar to the observation by  Głąb and Gondek (2008) who reported that mineral fertilization, compost or sewage sludge did not significantly influence the size or shape of macropores.They however reported significant influence of pig manure and sewage sludges Czernichów treatments on soil porosity and attributed the significance to their higher application rates (above 14 t fresh matter ha -1 ) with respect to other treatments.Their findings were supported by Tester (1990) who report that compost amendment significantly changed physical properties of soil at 240 t ha -1 compost rate.Ezeaku et al. (2006) reported that organic manure application did not produce significant and immediate effect on soil moisture content, bulk density and porosity.Zebarth et al. (1999) observed that annual applications of organic wastes (municipal biosolids, a commercially produced poultry and food waste, composted hog manure solids and a locally mined peat moss) for as long as 4 years at the rate of 45 t ha -1 had no significant increase in the saturated hydraulic conductivity and soil water-holding capacity but significantly increased the soil organic matter content, decreased soil bulk density and soil water retention of the coarse-textured soil.They attributed the significance to the high rate of organic waste applied and the duration of application.The result is in line with the findings of Sort and Alcaniz (1999) who reported that the application of sewage sludge at a rate of 400 t ha -1 significantly increased the soil macroporosity (>50 mm).

Conclusion
The municipal solid waste applied had no significant improvement in the soil physical properties in terms of soil aggregate stability, soil saturated hydraulic conductivity, bulk density and soil porosity.The non-significance effect observed in the study could strongly be attributed to the low quantity of MSW applied and its duration in the soil at the time of study.However, the application of composted municipal solid waste and NPK fertilizer significantly improved maize performance.The result of the experiment showed that the vegetative traits (plant height and leaf area) and the yield of maize performed better with increase in the treatment concentration.The result also show that combined application of MSW with NPK performed better than sole application of either MSW or NPK fertilizer.Combination of 2000 and 300 kg/ha performed better than other treatment combinations and was found satisfactory to improve maize performance in the study.

Table 1 .
Treatment combinations used for the study.

Table 2 .
Effect of municipal solid waste and NPK fertilizer on height and leaf area of maize plant at 4 and 8 WAP in 2012.

Table 3 .
Effect of composted municipal solid waste and NPK fertilizer rates on yield traits.

Table 4 .
Initial physicochemical properties of the soil before amendment.

Table 5 .
Chemical property of municipal solid waste.
on short duration crop like maize.Table4shows the soil physicochemical properties.The soil is sandy loam in texture and moderately acidic.It is low in organic matter content, total nitrogen and exchangeable bases but had relatively moderate cation exchange capacity (CEC) and available phosphorous values.The low fertility status of the soil is common to most tropical soils due to their advance stage of weathering and high leaching tendency.

Table 6 .
The soil physical properties at the end of the experiment.