COMPARATIVE EFFECTS OF LIME, POULTRY MANURE AND NPK COMPOUND FERTILIZER ON SOIL PHYSICOCHEMICAL PROPERTIES AND YIELD OF MAIZE IN AN ULTISOL OF SOUTHEASTERN NIGERIA

ABSTRACT

Field and greenhouse experiments were conducted at the University of Nigeria, Nsukka, in 2011, to examine the effects of lime, poultry manure and NPK 15-15-15 on the soil nutrient content and yield of maize.  The experiment was first carried out in the greenhouse and later evaluated in the field. The experimental  designs used were 6 x 4  factorial in completely randomized   design   (CRD)   and  randomized   complete   block   design   (RCBD)   for  the greenhouse   and  field  experiments   respectively.   Two   factors  were  considered   in  the experiments.  Factor A: different fertilizer rates and their combinations viz: T1 (200  kgha- 1NPK + 6 tha-1  PM), T2 (300 kgha-1NPK + 4 tha-1  PM), T3 (400 kgha-1NPK + 2 tha-1  PM), T4 (400 kgha-1NPK  only),  T5 (8 tha-1  PM only),  T6 (Control;  no fertilizer  application). Factor B: liming levels:   pH 6.0, pH 6.5, pH 7.0 and pH 5.5 (control). Maize plant was used as a test crop. In the greenhouse trial, among the six treatments applied, T5 (8 tha-1 PM only) had significant (P < 0.05) effect on soil available P, soil pH, cation exchange capacity and exchangeable  magnesium  but not on other  parameters  measured.  For the field evaluation, treatment T1 had significant (P < 0.05) effect only on soil aggregate stability but not on mean weight diameter (MWD), aggregate stability (AS), bulk density, total porosity and hydraulic conductivity. Also this treatment had significant (P < 0.05) effect on the soil nutrient contents than other treatments applied. This was similar to that obtained from the  greenhouse trial. Soil limed to pH 7.0 significantly (P < 0.05) decreased the soil  acidity and increased the exchangeable calcium. A combination of NPK and poultry manure at various rates had better effects than either sole application of NPK or poultry manure on maize parameters measured namely:  plant height,  leaf number,  leaf area  index,  tasselling  number,  cob weight,  chaff weight, and dry matter. Similarly, liming the soil to different pH levels had significant (P < 0.05) effect on maize plant performance.  The highest plant physiological  parameters  were obtained  from the soil limed to pH 7.0 while soil limed to pH 6.0 gave the  least plant parameters.    The  order  of performance  was  as follows:  soil limed  to pH  7.0 > pH  5.5 (control) > pH 6.5 > pH6.0 in plant parameters namely plant height, cob weight, tasseling number, and seed weight. From the study, soil of pH 5.5 with the application of 200 kgha-1

NPK + 6 tha-1 or 8 tha-1 PM only is recommended for maize production.

CHAPTER ONE INTRODUCTION

Soil fertility decline is one of the acute problems facing farmers in the world and Nigeria in particular.   The  constraints   to  food  security  and  widespread   poverty,   as  they   affect development and livelihoods, are well known even in Sub-Saharan region of Africa (SSA), where population  growth at 3% supersedes agricultural  production rate  of  2% per annum (Bationo et. al, 2006). Although the causes of food insecurity and poverty are numerous, the decline  in soil fertility with resultant  decreasing  crop  yields  is severally  highlighted  and stressed (Sanchez et. al, 1997; Smaling et. al, 1997; Bationo et. al, 2006).

In Nigeria, the practice of shifting cultivation which was one of the effective methods  of overcoming  the problem  of poor  crop  yield  due  to decline  in soil  fertility  has  virtually disappeared.  This  could  be  linked  to  the  increasing  population  explosion  and  the  stiff competition for land space by other land uses (Hati et. al, 2005). According to Ayoub (1994), population  explosion added to the increased  continuous  farming on  the available  land by farmers  who often do not add adequate  soil nutrient  supplements  (organic  and inorganic fertilizers) to beef up soil fertility and increase yield.

Makinde et. al, (2001) reviewed that decline in soil fertility is a fundamental impediment to agricultural  growth and food production.  According  to them, crop  production  in the past relied on shifting cultivation  to maintain the fertility and  productivity  of the soil through organic matter build up during a long fallow period. This practice enabled farmers to produce substantial  crop yield over a period even without  adding external  inputs.  Okalebo  et. al, (2009) observed that decreases in available  nitrogen and phosphorous are among the most severe nutrient problems in the tropics.

To cope with these problems, there has been an increase in the use of inorganic  fertilizer mostly  ammonium  sulphate  ((NH4)2SO4)  fertilizer.  The  continuous  use  of  the  mineral fertilizers  resulted  to increase  in acidity  of such  soils.  Researchers  have  shown  that  pH decline occurs more rapidly in continuously cropped lands and soils tend to acidify over time particularly when large application of ammonium-based fertilizers and urea-based fertilizers, [Co(NH2)2] are used.

Soil acidity is a major problem in crop production in the tropics. This is especially so in more than  90%  of  soils  in  the  agroecological  zones  in  Nigeria  (Enwezor  et.  al,  1990).  The problems of soil acidity are very prevalent in southeastern Nigeria where coarse sedimentary parent  materials  had  undergone  earlier  cycles  of  weathering  before  deposition  (FDALR, 1990).

According to Ohiri and Ano (1989) the acidic nature of the soils in Southeast Nigeria are due to their parent materials, leaching and degradation in soil physical properties. In acid soils, there  are  problems  of  both  plant  nutrient  deficiencies  and  toxicity  of  three  elements (Aluminum, Manganese, and Hydrogen). Plant growth, especially root growth, in acid soils is retarded by toxicity of Al, Mn, and H. The degree of toxicity depends upon how high the concentration of soluble or exchangeable Al3+  is and how low the pH is (Crawford et.  al, 2008).

Soil acidity can also reduce the availability of phosphorous by forming insoluble compounds when combined with Fe and Al oxide at pH < 5.0. Thus, due to the increased acidity of the soil, inorganic phosphorous applied to the soil becomes fixed  or  immobilized (Tinker and Nye, 2000).  Chude et. al, (2004) reported that soil acidity is one of the major constraints to crop production  in humid tropical region.  This  according  to them, it is due to the usual accompanying  effects of aluminum  and  manganese  toxicity and nutrient deficiencies  and their  consequential  effects  on  crop  growth  and  yield.  Soils  with  pH  <5.5  have  high exchangeable  aluminium  and  outright  toxicity  to most crops (Carver  and Ownby,  1995). According  to Atiwag  (1992),  the way of improving  crop output  from such soils include application of nitrogenous and phosphatic fertilizers, liming and addition of organic manure.

Soil acidity can affect plant growth directly and indirectly by affecting the plant-availability of nutrients, levels of phytotoxic elements, microbial activity, and other soil properties. Soils may become acidic in the long term as a result of several natural processes. In the short term, however,  soil acidity develops  mainly due to application  of  N fertilizers,  primarily those having high concentrations of ammonium or urea because nitrification releases hydrogen (H) ions. To make  soils less acid, it is a  common practice  to apply a material  that contains calcium and/or magnesium oxides or carbonates.

Liming has long been recognized as an important way of ameliorating soil acidity. Soils are limed to reduce the harmful effects of low pH, aluminium and manganese toxicity by adding calcium  and  magnesium  to the  soil.  The  amount  of  lime  needed  to achieve  certain  pH

depends on the pH of the soil and its buffering capacity which is related to the C.E.C of the soil. Lime applied to acid soils raises the pH of soils, resulting in enhanced availability of nutrients, such as P, Ca, Mg, Mo etc. and improved crop yields (Nekesa, 2007; Kisinyo et. al, 2009).

According to Osodeke (2000), women used lime as a source of soil amendment to improve the fertility of their farms and also as liming material to reduce the acidity of the soil. Lime is an additional purchase for farmers; who seek good return for their  investment by using a product that is fast-acting and which has benefits for both crop  yield and soil properties. Farmers appreciate the important value of lime and manure application but they seldom apply them at the recommended rates and at the appropriate time because of the high cost, lack of credit facilities, inefficient distribution and poor delivery system (Ayoub, 1994).

Most of the results of the field trials across the ecological zones of the country have clearly brought out the fact that neither organic fertilizer nor the mineral NPK fertilizer alone can achieve the desired soil fertility level needed for optimum crop production. The use of both inorganic and organic fertilizers often results in improving efficiency of nutrients and water use (Onwueme and Sinha, 1991). Onwuka (2008) reported better performance of organic – inorganic fertilizer combination than either farmyard or inorganic fertilizers.

The main objective of this work was to evaluate the effect of lime and different combining levels of organic and inorganic fertilizer on soil physicochemical properties and maize yield.

The specific objectives were to determine:

i. the effect of different levels of poultry manure combined with NPK fertilizer and lime on some physicochemical properties of the soil

ii. the lime rate(s) required for optimum maize performance in an Ultisol, Southeastern

Nigeria.

iii. the  effect  of  poultry  manure,  NPK  fertilizer  and  their  combination  on   maize performance.

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