1 Introduction

Inland Valley Swamp (Flood Plains/Valley swamps/Fadama) are low lying areas including streams, channels and streamlets depressions which are waterlogged or flooded in wet season (Turner, 1977). IVS soil can potentially produce short duration crops like rice, maize and vegetables, at least, twice in a season. This is as a result of adequate water supply and relatively moist soil which are basic to the attainment of high crop yield. The shallow water table depths contribute to soil moisture storage via capillary rise, and in addition to high soil fertility, resulting from organic matter accumulation offers opportunity for dry season farming in inland flood plains. The agricultural potentials of tropical inland valley swamps or flood plains (Fadama ecosystem) can be harnessed via the effective management of its fertility.

Sound environmental and economic manure management is important in determining the availability of soil nutrients for crop utilization, especially in inland valley swamp (IVS) areas. However, there is difficulty in predicting the amount of nutrients available for plant growth because mineral elements in manure are in both organic and inorganic forms (Beauchamp and Paul, 1989). It is also important to know that N applied in excess of that required can contribute to nitrate contamination of ground water (Zebarth et al., 1996) in inland valley swamp with shallow water table.

Proper manure management is particularly important in Inland Valley Swamp (IVS) of Owo, a humid tropical rainforest because of the increase in swine farm establishment and poor waste disposal which can lead to high N-loading rates to agricultural land. A large proportion of manure is advocated for and used in agricultural land to improve soil fertility and prevent acidity (Awanlemhen and Ojeniyi, 2012) resulting from the use of inorganic fertilizer, especially in rain forest humid ecosystem, during arable and perennial crop production (Kwari and Bibinu, 2002; Adeniyan and Ojeniyi, 2003, 2005; Wapa et al., 2013). It is therefore important to have a system for making nitrogen management recommendations for maize that take manure into account.

Series of research have estimated N availability for maize production in different climate region or ecosystem. Beauchamp (1983) and Safley et al. (1986) estimated N availability based on crop yield response. Xie and Mackenzie (1986) estimated N availability relative to inorganic fertilizer with respect to residual soil nitrate at harvest. Also, Khan (1986) determined the nitrogen (N) availability in liquid pig manure for silage-corn production under south coastal condition.

Large areas of inland valley swamp (IVS), including those in rainforest humid zone are characterized seasonal by flooding with a high degree of irregular and high variability of N availability due to erosion and leaching, making most of these soils to be acidic and low in available phosphorous, CEC and nutrient base, but are rich in iron and alumina, resulting in a high iron toxicity potential for maize plants (Sanchez and Logan, 1992). Soil surface drainage, as well as liming may also favour the successive maize production by suppressing the toxicity from the excessively reduced conditions and by increasing the available nutrients such as phosphorus, to maize plants (Yasuhiro et al, 2010). However, the influence of ash for liming has been found to improve the availability of nutrients, increase crop yields and activities of soil micro-organisms due to amelioration of soil physichochemical properties (Ojeniyi et al., 1999; Ano and Agwu, 2005; Kekong et al., 2010). This has direct implication for nutrient, and particularly nitrogen (N) management. Nitrogen management is of particular concern, as it is the most limiting nutrient in inland valley swamp (IVS) (Linquist et al., 1998). Nitrogen is also required by maize in higher quantities, and is more susceptible to losses than other nutrients (Sanchez and Logan, 1992). There is need to improve the nitrogen status of inland valley swamp in order to make judicious use of its agricultural potential. The objective of this study is to determine the influence of pig dung manure and spent bleaching earth combination on maize yield and nitrogen uptake of maize at harvest.

2 Results

2.1 Physiochemical properties of the experimental site

The pre-soil and post-soil physicochemical analysis is presented in Table 1. The soil is sandy loam in texture and acidic in nature (pH 5.07). The percentage Organic carbon was 1.14, available phosphorous was 8.92 mg/kg and total nitrogen was 0.2 g/kg.

2.2 Effect of spent bleaching earth and pig manure on physical and chemical properties of soil in the experimental site

The result from the post soil analysis conducted after maize harvest in 2014 and 2015 showed that the physicochemical properties of the soil improved with the application of SBE and PM (Table 2). There was no significant difference in clay content of the soil at maize harvest. The percentage sand in the soil reduced significantly in both seasons with application of SBE and PM. Also, the alteration of the levels of PM and SBE further improved the characteristics of the soil at significant level in 2015, as compared to the control plots.

2.3 Interactive effect of SBE and PM on the vegetative growth of maize (Zea mays L.) at 2WAP

The two sources of organic materials applied to the plots have significant effect on the vegetative growth of maize during the two dry season farming. In 2013/2014 dry season, applications of different levels of PM at zero level of SBE have variable effects on the vegetative growth of maize. There was no significant difference in number of leaves at 2WAP. A significant increase were recorded in plant growth parameters when 5 tons of SBE was added to various levels of PM. Plots that received 5 tons SBE combined with 5 or 10 t/ha^-1 PM are not significantly different in terms of leaf area, plant height, stem diameter, number of roots and total root length (Table 3a).

Mean followed by the same letter(s) within a treatment group are not significantly different at 5% probability level using Duncan Multiple Range Test (DMRT).

In 2014/2015 dry season experiment, at 2 WAP, progressive significant increases were recorded with increase in the levels of SBE at zero level of PDM. An instant of increase in the level of PM from zero to 10 t/ha^-1, at various levels of SBE brought about a significant linear increase in growth parameters of maize plant. However, application of 7.5 or 10 t/ha^-1of SBE combined with 10 t/ha^-1 of PM do not show significant difference on leaf area, plant height, stem girth, number of roots and total root length (Table 3b).

Mean followed by the same letter(s) within a treatment group are not significantly different at 5% probability level using Duncan Multiple Range Test (DMRT).

2.4 Interactive effect of SBE and PM on the vegetative growth of maize (Zea mays L.) at 8 WAP

The trend of response of vegetative growth of maize to the combined application of SBE and PM at various levels at 8 WAP (2013/2014) is relatively similar in performance to results obtained in 2 WAP (2013/2014), except for increase in sizes of vegetative plant parts. There was significant difference in number of leaves, leaf area, plant height, stem diameter, number of roots and total root length when 5 t/ha^-1SBE was added to various levels of PM. Plots that were treated with 5 t/ha^-1SBE combined with 5 or 10 t/ha^-1PM are not significantly different in number of leaves, plant height, stem diameter, number of roots and total root length, but is significantly different in leaf area (Table 4a). There was a positive interaction between 5 t/ha^-1SBE and 10 t/ha^-1 PM as compared to 0 level of SBE and 0-10 t/ha^-1 of PM.

Mean followed by the same letter(s) within a treatment group are not significantly different at 5% probability level using Duncan Multiple Range Test (DMRT).

In 2014/2015 planting, at 8 WAP, a significant increase was recorded with increase in the levels of SBE at 0 level PM. Increase in the level of PM from 0 to 10 t/ha^-1, at various SBE level; brought about a significant linear increase in growth parameters of maize plant. Also, application of 7.5-10 t/ha^-1 SBE combined with 10 t/ha^-1 PM showed a significant difference in number of leaves, plant height and number of roots while leaf area, stem girth and total root length are not significantly different (Table 4b).

Mean followed by the same letter(s) within a treatment group are not significantly different at 5% probability level using Duncan Multiple Range Test (DMRT).

2.5 Interactive effect of SBE and PM on the yield and nitrogen utilization of maize (Zea mays L.) at harvest 12WAP

Application of PM significantly affected yield and yield components of maize in 2013/2014. Plots that received combination of t/ha^-1SBE and 10 t/ha^-1 PM recorded the highest DMY, Cob yield, Grain yield, Harvest index and Leaf nitrogen which were significantly higher than their controls (Table 5a).

Mean followed by the same letter(s) within a treatment group are not significantly different at 5% probability level using Duncan Multiple Range Test (DMRT).

Also in 2014/2015, combine application of 10 t/ha^-1 of PM and 10 tons/hectare of SBE recorded the highest values of DMY (3.64), Cob yield (3.80), Grain yield (3.00), Harvest index (0.87) and leaf nitrogen (0.44). These values are significantly higher than the values obtained from the control plots. However, there was no significant difference in yield values obtained from plots treated with 10 t/ha^-1 PM and 7.5 – 10 t/ha^-1 SBE (Table 5b). From all results obtained from this investigation, all plots treated with the combination of SBE and PM gave significantly higher value than control plot. The best performed level of PM (10 t/ha^-1) in 2013/2014 combined with the best level of SBE (7.5 – 10 t/ha^-1) in 2014/1015 to give the highest values in both vegetative growth and yield of maize.

Mean followed by the same letter(s) within a treatment group are not significantly different at 5% probability level using Duncan Multiple Range Test (DMRT).

4 Discussion

The climatic data favourable to maize production is typical of the tropics. In spite of the climate change scenarios in seasonal precipitation (Hulme et al., 1992) rainfall distribution pattern is still bimodal in the study area. This therefore contributed to higher volume of water deposited in inland valley swamp (lowland depression) ecology, thus facilitating dry season farming.

The inland valley swamp (IVS) of the study area was low in plant nutrients, slightly acidic, resulting from flooding and heavy leaching of highly drained sandy soil with low pH markedly by forcing variables like soil temperatures, parent materials and hydrology. The sand proportion of soil in the study site was high. This implies that basic cations such as Calcium, Potassium, Sodium, Magnessium and Silicate would be leached more easily. Brammer and Brinkman (1990) linked the low fertility of soils in level land or depressional sites to temporary flooding or water saturation that results in leaching and hence low organic matter decomposition.

To achieve a greater productivity of IVS in crop production, activities that will improve the soil fertility and increase pH value must be put in place. Application of either SBE or PM at rates different from 0 (zero) had increased the pH and organic matter content of the soil in the study area. An increase soil pH with the application of ash was reported by different researcher (Ojeniyi, 2007; Aderibigbe and Eleduma, 2016). Favoured microbial populations have been reported by the application of organic manures (Senjobi et al., 2013). However a single recipe would not be generally applicable in different conditions. For instance, application of PM and SBE, which is a form of ash, had significantly improved the physical and chemical properties of soils as evidenced by this experiment. Fernandez et al. (2013) and Christo et al. (2011) reported an increase in the pH and fertility of soil with combine application of ash and organic manure.

Increased in vegetative growth of maize at 2WAP and 8WAP in this present study could be attributed to the combined application of SBE and PM at their highest rates, which supplied the nutrients required and provided suitable ecology for microbial build-up. This agrees with the work of Christo et al. (2011); Soretire and Olayinka (2013); Ogunrewo and Olayinka (2013); and Fernandez et al. (2013).

There were significant (P<0.05) difference in yield and leaf nitrogen content of maize at harvest. These depended on the level of SBE and PM applied. Plots which had been fertilized with higher rate of SBE and PM exhibited higher yield than those that received lower rates, this could be attributed to large quantities of available phosphorous and potassium in the PM. Also, SBE contains large quantities of silicon which mobilizes the availability of cations to the plant roots. Rao (1991) reported that soil could be enriched by application of higher quantities of organic materials which tends to decompose and release large amounts of nutrients, mainly nitrogen, phosphorous and potassium into the soil. Another study by Xu et al. (2005) showed that higher levels of organic manure produced better vegetative growth and resulted in a final higher total yield than those grown on lower amount of manure. In this study productivity of maize increased with increase in the quantities of SBE and PM combined. The trend of increase in maize yield was linear in the direction of additional input of SBE and PDM combination. However, there was no significant difference in the vegetative growth, yield and leaf nitrogen of maize between 7.5 and 10 t/ha^-1SBE in combination with 10 t/ha^-1 PM (P<0.05). This could be as a result of increased soil pH which does not always bring the expected result in the immobilization of some trace metal like zinc that is needed by maize for good growth and yield. Pendias and Henryk (1985) pointed out that the metals that are most likely to occur in soil as organic chelates in larger particulates may become soluble quite easily after heavy liming, as has been reported mainly for Cu, Zn and Cr. This emphasis is similar to the observation of this experiment.

Separate application of PM and SBE increased growth and leaf nitrogen of maize in inland valley swamp. It was the combined use of the materials (PM and SBE) that most enhanced growth and yield parameters. This can be adduced to the release of nutrients to synchronize with the growth of the maize plant. The PM and SBE releases nutrients and reduced the acidic nature of the inland valley swamp soil of the study area.

There is synergistic relationship between PM and SBE since the silicon in SBE will stimulate the build-up of higher pH value which influences microbial activity and mineralization of nutrients from the PM. This reaction is expected to improve uptake of nutrient by maize plant. It can be seen that application of 10 tons PDM and 7.5-10 tons of SBE is suitable for ameliorating acidic nature of Inland Valley Swamp and increasing plant productivity for sustainability.

5 Materials and Methods

5.1 Study location

The study was conducted at the Teaching and Research Farm, Rufus Giwa Polytechnic, Owo, a humid rainforest zone, south-western Nigeria (Lat. 7^o 14^ʹN and Long. 5^o 08^ʹE) and 35 meters above sea level. The mean annual rainfall is between 1300-1600 mm, bimodal in distribution, usually March to July and September to October, with characteristics August break. There are two distinct season- the wet season, which extends from March to October, and the dry season which is usually from November to February. The average temperature is 30^°C. Relative humidity ranges between 85% during the rainy season and less than 60% during the dry season. The soil at the site of study is a tropical rainforest sandy loam Alfisol, classified as Clayey Skeletal Oxic-Paleustalf (USDA Soil Taxonomy, Soil Survey Staff, 1999).

5.2 Experimental design/ Procedure

Two experiments were carried out in two dry seasons of 2013/2014 and 2014/2015 to determine the effects of soil nutrient management strategies using pig manure and spent bleaching earth combinations at different levels in inland valley swamp, using residual soil moisture to produce late season maize. TOCOB early maturing white maize variety was obtained from Agricultural Development Programme (ADP), Akure, Ondo-State, pig manure was obtained from Livestock section, Teaching and Research Farms, Rufus Giwa Polytechnic, Owo, while spent bleaching earth was obtained from Jof Ideal Family Vegetable Oil Plant, Owo, Ondo State.

In 2013/2014 experiment, the treatments were two levels of spent bleaching earth (0 and 10 ton/ha) as main plots and four levels of pig dung manure (0, 2.5, 5 and 10 ton/ha) as sub plots. Each treatment was replicated 4 times. This gives a total of 32 plots. In 2014/2015 experiment, on different plots, two levels of pig dung manure (0 and 10 ton/ha) as main plot was combined with four levels of spent bleaching earth (0, 2.5, 5 and 7.5 ton/ha), sub plots, in 4 replicates. In both experiments treatments were applied at land preparation. Before planting, the plots were manually tilled, pulverized and laid out at 4 x 6 m (24 m²) and treatments were randomized to plots by balloting. Two seeds were planted at 3 cm deep with a spacing of 60 x 60 cm. Weeds were manually controlled with hand hoe at 2, 4, 6 and 8 weeks after planting. Soil moisture was supplemented with drip irrigation system to complement crop water demand at 50% tasselling.

Ten (10) soil samples were randomly collected across the farm with soil auger at a depth of 0 – 30 cm. Samples were mixed together and a representative composite sample was analyzed for the necessary physicochemical properties before the commencement of the experiments. Particle size (Bouyoucos hydrometer method), soil texture (USDA textural triangle), bulk density (core method), hydraulic conductivity (constant head method), soil pH in water and KCl (1:1) (electrometric method), organic carbon (oxidation method), total nitrogen (Macro-Kjeldahl digestion), CEC (1 N Ammonium acetate), extractible phosphorous (Bray-1 method), calcium and magnesium (EDTA titration), and Na and K (flame photometer). Base saturation was calculated by dividing the sum of exchangeable bases by CEC and multiplying by 100.

Ten (10) representative maize plants from each plot were chopped, and a 500 g sub-sample was used to determine dry matter and total N content by a standard Kjeldahl digestion.

5.3 Data collection and statistical analysis

Observations on growth parameters were taken at 2, 4, 6, 8 and 12 weeks after planting (WAP) on plant height, stem girth, leaf area, leaf area index, number of leaves, root / shoot ratio and days to flowering. The yield components measured include weight of cob, number of seed per cob, weight of 100 seeds and yield per hectare. The data collected were subjected to analysis of variance (ANOVA) using SPSS statistical package 15.0 version. The differences between means were separated with Duncan Multiple Range System at 5% level of probability.

Acknowledgements

Funding for this project was provided by the Tertiary Education Trust Fund (TETFund) and supervised by Center for Research and Development (CRD), Rufus Giwa Polytechnic, Owo. The Director of CRD, Rufus Giwa Polytechnic, Owo, Dr. (Mrs) Ajala Lola is gratefully acknowledged.

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