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Effect Of Agriculture Waste And Inorganic Fertilizer On Polluted Soil


In Sub-Saharan Africa, acidic soils occupy 29% of the total area, while about 13% of the Nigerian total land area has acidic soils, widely distributed in croplands of the central regions. The high soil pollution coupled with soil nutrient depletion negatively affect performance and yields of maize in the region. This study was therefore carried out at Itu in Akwa Ibom State for two cropping seasons; short rains (SR) in 2016 and long rains (LR) in 2017 to determine the effects of manure, lime and inorganic fertilizer on (i) soil pollution (ii) maize yield and (iii) profitability. The treatments included manure (0, 5 and 10 t ha-1), lime (0 and 2 t ha-1), and P fertilizer (0, 30 and 60 kg P2O5 ha-1). Maize (H516) was used as the test crop. The experiment was laid out in a randomized complete block design with eight treatments replicated ten times in farmer’s fields. Key variables measured were soil pollution, plant growth parameters; height, chlorophyll content, grain yield and economic data. Data generated was subjected to analysis of variance and means using least significant differences of means (LSD at p≤0.05). The results showed that sole lime (2 t ha-1) significantly (p=0.0001) increased soil pH by 17.7%. Reduction in soil exchangeable pollution was clearly seen in treatments lime and manure; Lime and fertilizer had the highest change of 27.8% and 30.6% in 2016 short rains and 2017 long rains respectively. Application of combined agriculture waste and P fertilizer had the highest increase in soil available P (+22.5) and plant height (296.13 cm). The study observed high maize yield of 5 t ha-1 with application of combined agriculture waste and P fertilizer obtained at the end of the second season. Lime and fertilizer had the highest net benefit of 128.75 USD/ha in the 2017LR followed by sole fertilizer with 105.94 USD/ha. Treatments that had high grain yields did not have high net benefit. There is need to consider economic returns when selecting agricultural production technologies. Use of lime plus fertilizer could therefore, be recommended to smallholder farmers of Akwa Ibom State, Nigeria.




1.1 Background Information

Globally, soil pollution is a key problem contributing towards reduced agricultural productivity (Van, 2007) hence threatening food security in Africa. About 4 billion hectares face the effects of pollution, representing a total area of approximately 30% of the land worldwide (Sumner and Noble, 2003). Most of these soils with high pollution are mainly found in Asia, North and South America, and Africa, attributed to extensive leaching and weathering (Kisinyo et al., 2014). In Sub-Saharan Africa (SSA), acidic soils occupy 29% of the total area, which is associated with reduced fertility levels (Muindi et al., 2016). Acidic soils in Nigeria occupy approximately 13% of the agricultural area which is estimated to be 7.5 million hectares of land (Kanyanjua et al., 2002). Over 5 million small-scale farmers in the central and western part of Nigeria grow maize, legumes, tea, and coffee in over million ha covered by acidic soils (Gudu et al., 2007).

Soil pollution is the most significant cause of low yield for many of crops (Mugai, 2004). It limits soil productivity, crop development and growth, as well as yield in highly weathered soils due to deficiency of essential crop nutrient elements (Akinrinade et al., 2006). The most important being loss of essential crop nutrients through leaching (Ca Mg and K) with replacement by Al, H and Mn ions that

contribute to acidification of soils (Okalebo et al., 2009).

There is minimal and reduced crop productivity on such acidic soils, mostly where the application of acid-forming fertilizers like di-ammonium phosphate (DAP) are used continuously over the years (Nekesa, 2007). Low crop production as a result of multinutrient deficiencies has made it mandatory to use mineral fertilizer in order to increase crop yield. Nevertheless, mineral fertilizers are costly, inadequate and their continued use without liming may result to soil pollution problems (Oguike et al., 2006).

The soil pollution problem can be resolved by application of lime (Kanyanjua et al., 2002) an important practice because of reducing exchangeable pollution and increasing pH. However, lime use by farmers in Nigeria is minimal. Only 10% of the farmers in

Embu and Siaya; and 5% of farmers in Nyeri and Eldoret use lime (Muindi et al., 2016). Low use of lime is perhaps due to lack of awareness on the benefits of liming, unavailability in the market and high liming materials costs (Kanyanjua et al., 2002; Okalebo et al., 2009).

It is necessary to adopt integrated soil fertility management (ISFM), that involves combined use of organic and inorganic fertilizers, with the use of lime that can be beneficial to improve soil fertility, soil organic matter maintenance and high crop yield by farmers as reported in field trials (Okalebo et al., 2009). Farmers mostly compare costs and returns associated with an appropriate integrated soil fertility management (ISFM), and if the returns outweigh the costs, they will opt to use it. Thus, profitability is the key factor that most smallholder farmers have to consider when making production decisions (Mucheru-Muna et al., 2014) on use of lime, organic and inorganic fertilizers.


1.2 Problem Statement and Justification

Soil pollution results in low crop yield (Muindi et al., 2016) because of poor soil fertility. The smallholder farmers in Akwa Ibom State rely on maize as their staple food. The farmers have small holdings with an average of 1.2 ha, which is subjected to intensive continuous cultivation hence lack of adequate soil nutrients replenishment (Mugwe et al., 2009). The productivity is declining and is estimated at 0.5-1.5 t ha-1 annually (Mugwe et al., 2009). Lime use has been recommended as a way of addressing soil pollution problems. However, in the Nigerian Central highlands, there is limited use of lime and awareness on its effectiveness among smallholder farmers (Muindi et al., 2016). Moreover, organic and inorganic fertilizer use has been recommended to address soil pollution and nutrient depletion (Mucheru-Muna et al., 2014). However, inorganic fertilizer use in the area is constrained by high costs that the smallholder farmer cannot afford and there is limited use of locally available manure. These technologies that combine lime, organic and inorganic fertilizers are better options in increasing fertilizer use efficiency, balance the supply of nutrients and other agro-ecological benefits (Mucheru-Muna et al., 2014). On the other hand, adoption of any technology depends on financial benefits, particularly when additional labour is applied as farmers take up certain technology when assured of benefits in investments. It is therefore, important to account for economic gains to the introduction of new soil techniques. There is need to understand the effect of applying agriculture waste, solely or combined with inorganic fertilizer on polluted soil, maize yields, and profitability on-farm conditions.

1.3 Research Questions

The study sought to address the following questions:

  1. How does agriculture waste, and inorganic fertilizer affect soil pollution in Akwa Ibom State?
  2. How does agriculture waste and inorganic fertilizer influence maize yield in Akwa Ibom State?
  • How does the use of agriculture waste, and inorganic fertilizer influence maize profitability in smallholder farmers in Akwa Ibom State?

1.4 Research Objectives

The general purpose of the study was to promote soil productivity in acidic soils thus improving food security. The study sought to address the following specific


  1. To determine the effect of agriculture waste, and inorganic fertilizer on polluted soil in Akwa Ibom State.
  2. To evaluate the effect of agriculture waste and inorganic fertilizer on maize growth and yield in Akwa Ibom State.

iii. To assess the profitability of agriculture waste and inorganic fertilizer in production of maize in Akwa Ibom State.

1.5 Research Hypotheses

The study was guided by the following hypotheses:

  1. Integrated use of agriculture waste, and inorganic fertilizers significantly improve soil pollution.
  2. Application of agriculture waste, and inorganic fertilizers significantly improve maize yield.
  • Integrated use of agriculture waste, and inorganic fertilizers significantly increase the profits in maize production among smallholder farmers.

1.6 Significance of the Study

The findings from this study will contribute to scientific knowledge on how agriculture waste and fertilizer affect soil properties, maize yield and profitability in the central highlands of Nigeria. This would be helpful to smallholder farmers who have small sizes of land and have difficulties in managing acidic soils. Such information will also enable the extension service providers to advise farmers on the most appropriate integrated soil fertility management to increase yield.

1.7 Definition of terms

Integrated soil fertility management (ISFM): is an approach that have viable

agricultural practices options that are sufficient for sustainable production in agriculture that is adapted to local conditions to utilize efficiency water use and supply of nutrients as well as improved agricultural productivity.

Lime:              refers to calcium or calcium-magnesium containing compounds

capable of reducing harmful effects of an acid soil by neutralizing soil pollution and raising the soil pH

Smallholder farmers:    Farmer with small land parcels of 3 acres or less whose

primary occupation is farming as a source of livelihood.

Soil pollution:  refers to concentration of hydrogen cations in a solution

Soil Amendment:   These are soil additives meant to improve soil quality during the

trials period. They include agriculture waste and P fertilizer.

Soil pH:   refers to the negative logarithm (base 10) of the activity of hydrogen

ions in a solution.

Soil quality: The soil capacity to function within natural or managed ecosystem

boundaries with capacity to sustain plant and animal life; while enhancing water and air quality to support both human and animal health and habitation.


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