THE EFFECTS OF REFUSE DUMP COMPOST AND POULTRY MANURE ON THE GROWTH AND YIELD OF AMARANTHUS HYBRIDUS L

ABSTRACT

A  screen  house  experiment  was  conducted  in  the  Botanical  Garden  of  Plant  Science  and Biotechnology Department, University of Nigeria, Nsukka to assess the effects of refuse  dump compost and poultry manure on the growth and yield of Amaranthus hybridus. The accumulation of heavy metals (Hg, Cu, Cd, Zn, Pb and Cr) in the leaves, stems, roots and seeds of A. hybridus at the end of the experiment were also assessed. The treatment comprised Treatment A (garden soil and river sand in the ratio of 3:1 as control); Treatment B (garden soil, refuse dump compost and river sand in the ratio of 3:2:1); and Treatment C (garden soil, poultry manure and river sand in the ratio of 3:2:1). The treatments were replicated nine times in a completely randomized design with five experimental units. A. hybridus was raised in a nursery and transplanted at 3 weeks after planting. The resulting data was subjected to ANOVA and means separated using DNMRT at P ≤ 0.05. The results of the study showed that application of Treatment C produced the highest mean plant height (88.00±5.13 cm), number of leaves (55.80±2.62), leaf area (140.89±6.92 cm2), fresh weight of leaves, stems, roots and seeds (52.47±1.42 g, 41.57±2.10 g, 10.19±0.41 g and 0.24±0.10 g respectively);  and dry weight  of leaves,  stems,  roots and  seeds (5.36±2.21  g, 3.96±1.63  g, 1.78±0.74  g and 0.19±0.08  g respectively).  Treatment  B performed  better  than Treatment  A, indicating some improvements in the soil fertility with the application of refuse dump compost. The concentrations of cadmium (0.263±0.019 mg/kg in the leaves and 0.300±0.010 mg/kg in the stems)  and  lead  (2.833±0.708  mg/kg  in the  leaves  and  0.380±0.111  mg/kg  in the  stems)  in Treatment B were above the FAO/WHO limits for heavy metals in vegetables (0.20 mg/kg for cadmium and 0.30 mg/kg for lead). Therefore, A. hybridus grown with refuse dump compost is unsafe for consumption since they can greatly accumulate toxic heavy metals. This ability of A. hybridus can also be used in the phytoremediation of heavy metals in contaminated sites.

CHAPTER ONE

INTRODUCTION

1.1   BACKGROUND OF THE STUDY

In  Nigeria,  as  in  most  other  tropical  countries  of  Africa  where  the  daily  diet  is predominated by starchy staple foods, vegetables are the cheapest and most readily available sources of important proteins, vitamins, minerals and essential amino acids (Akubugwo et al.,

2007). Since about 1980, Amaranthus spp. have been rediscovered as a promising food crop mainly due to its resistance to heat, drought, diseases and pests, and the high nutritional value of both the seeds and leaves (Wu et al., 2000).

1.1.1   Morphology and taxonomy of Amaranthus hybridus L.

Amaranthus spp., collectively known as amaranths are cosmopolitan annual or short- lived perennial plants, consisting of approximately 60 species. Over 400 varieties within these species are found throughout the world in both temperate and tropical climates, and they fall roughly into one of four categories: grain, vegetable, ornamental or weed. Many fall into more than one (Mlakar et al., 2010).

1.1.1.1   Scientific classification Kingdom: Plantae Phylum: Spermatophyta

Subphylum: Angiospermae

Class: Dicotyledonae Order: Caryophyllales Family: Amaranthaceae Genus: Amaranthus Species: A. hybridus

(Vouch et al., 2000).

1.1.1.2   Plant description

Amaranthus  hybridus  is an annual  herbaceous  plant  of  1-6  feet  high.  The  leaves  are alternate  petioled,  3 – 6 inches long,  dull green,  rough,  hairy,  ovate  or rhombic  with  wavy margins. The flowers are small, with greenish or red terminal panicles borne in dense elongated clusters, usually on the tips of the branches. The taproot is long, fleshy red or pink. The small seeds of A. hybridus are usually shiny black in colour, lenticellular  in  shape with each seed averaging 1.0 – 1.5 mm in diameter and 1000 seeds weighing 0.6 –  1.2 grams. It is rather a

common species in waste places, cultivated fields and barnyards (Akubugwo et al., 2007).

Leaves

Stem

PLATE 1:  Amaranthus hybridus growing in a screen house.

A. hybridus is one of the neglected leafy vegetables, which form part of the diet of many indigenous people of Africa and other parts of the world (Shackleton  et al.,  2009).  Almost

universally, the plants have been scorned as a poor people’s resource. Mnzava et al. (1999) and Van  der  Walt  et  al.  (2009)  actually  labeled  them  as  ‘neglected  crops’.  The  increasing popularity is due to the tolerance  to drought,  its preference  for high  temperatures  and the ability to grow on marginal lands.

1.1.2   Cultivation of Amaranthus hybridus

Agronomically, Amaranths require a well-drained soil rich in nitrogen, phosphorus and potassium  and will perform better in non-acidic  conditions (Mbonu  and Arifalo,  2006). A. hybridus is one of the few dicotyledonous plants that exhibit C4  metabolism,  a much more efficient form of photosynthesis than the more common C3 (Grubben, 2004). The C4 amaranth metabolism  therefore  predisposes  it to high productivity and is thus  an essential  vegetable candidate  to ensure food and nutritional  security in developing  countries  of Africa.  It can survive with much less water than other food crops in the region such as maize and beans. In good growing conditions, each amaranth plant will produce 40,000 to 60,000 seeds seasonally. They also  can tolerate  a variety of  unfavorable  abiotic conditions,  including  high salinity, acidity, or alkalinity, making them uniquely suited for subsistence agriculture. By implication, amaranth has the potential for significant impact on malnutrition (Maughan et al. 2011).

1.1.3   Some uses of Amaranthus hybridus

Amaranthus  hybridus  is  a  common  and  widely  grown  vegetable  among  farmers  in southwestern  Nigeria.  They are referred  to  as “tete”  in Yoruba,  “alaiyaho”  in  Hausa  and “inine”  in  Igbo  (Akubugwo  et  al.,  2007).  In  Nigeria,  vegetable  amaranths  are  planted throughout the year and harvested for food. It also serves as a source of income for small-scale farmers during the dry season. The consumption of  vegetables in diet has been reported to protect  the  human  body  from  degenerative  diseases  and  the  main  protective  action  of vegetables had been attributed to the antioxidants present in them (Ogunlesi et al., 2010).

Amaranths have received considerable attention in many countries because of the high nutritional  value of some species that are important sources of food, either as  vegetable or grain. The leaves, shoots, tender stems and grains are either eaten as  potherb in sauces or soups, or cooked with other vegetables as a main dish. In Nigeria, A. hybridus leaves combined with condiments are used to prepare soup (Mepha et al.,  2007). The leaves and the softest portions of the shoots are usually boiled in water and then cooked with onions, tomatoes, oil and or other additives of modern culinary delights. It is recommended that the leaves should not be boiled for more than fifteen minutes, in order to prevent significant losses of the vitamin C in them (Adekayode and Ogunkoya, 2011). Vorster et al. (2008) reported that the flavor of raw and cooked vegetable amaranth was equal to or better than that of spinach or other similar greens.  It  can also be dried for subsequent  use during the dry season (Masarirambi  et al.,

2010). They can also be used as forage for livestock.

In Africa, Amaranths are among the most important leafy vegetables, a fact attributed to their ease of cultivation, wide occurrence, low pests and diseases incidence, low labour input, ease in cooking and high nutritional value (Maundu et al., 2009). In traditional medicine, the boiled  leaves  and  roots  are used  as laxative,  diuretic,  anti-diabetic,  antipyretic,  anti-snake venom, anti-gonorrheal, expectorant, and can also be used to relieve breathing in patients with acute bronchitis.  It also has anti-inflammatory properties,  immunomodulatory  activity, anti- androgenic activity and anthelmintic properties (Alegbajo, 2013).

1.2   PROBLEM STATEMENT

One of the greatest  problems  facing most  African countries  is the  inability to  grow enough food for her ever-increasing population and this can be attributed to the inherent low fertility of the soils. Research also indicates that a considerable part of the required nitrogen and potassium for intensive cropping could be met by including legumes in crop rotation and by recycling nutrients through the application of good quality compost (Agboola, 1974). Some

of the problems encountered by amaranth growers in Nigeria are low soil fertility and lack of capital to buy chemical fertilizers for optimum crop productivity (Adeyemi et al., 1987).

In Nigeria,  Amaranthus  spp.,  including  other common  vegetables,  though  frequently grown by the urban populace in a bid to augment personal incomes and offset food insecurity occasioned by rural-urban drift are often consumed by a greater part of the entire population (Shagal et al., 2012). Under this system, all forms of available lands including contaminated sites such as derelict waste dumps, banks of polluted rivers and streams, high way shoulders and industrial areas are indiscriminately cultivated owing to land tenure problems, inadequate regulation and enforcement system. Adefemi et al. (2012) reported that the contaminated sites as well as the soil amendments (fertilizers,  manures, sludge, compost), irrigation water and pesticides frequently applied to enhance  soil fertility and boost the yield may inadvertently bear chemical stressors including the toxic heavy metals – lead (Pb), chromium (Cr), arsenic (As), zinc (Zn), cadmium (Cd), copper (Cu), mercury (Hg) and nickel (Ni). Evidence keeps mounting that vegetables and other food crops grown under such unwholesome conditions may bioaccumulate the toxic heavy metals at levels exceeding statutory or advisory limits whether measured as metal concentrations in produce or expressed as projected daily intakes (Nabulo et al., 2010).

Before the technological  age, environmental  pollution was due to naturally  occurring phenomena  such as bush burning,  volcanic  eruption and very little from  human activities. Owing  to the increase  in technological  innovations,  lots of chemicals  are emitted  into  the environment both in urban and rural areas (Shagal et al., 2012). These chemicals cause hazards to man and his environment,  causing pollution. The hazardous environmental  consequences and high cost of inorganic fertilizers make them not only undesirable but also uneconomical and  out  of  reach  of  the  poor  farmers  who  still  dominate  the  Nigerian  agricultural  sector

(Shiyam  and Binang, 2011). These have led to increased  use of organic manure, a  readily available alternative, which proves to be more environmentally friendly.

1.3   JUSTIFICATIONS FOR THE STUDY

Large volumes  of organic  wastes produced  all over the world are creating a  serious disposal problem and a major source of environmental pollution. These wastes require large volumes of land for disposal. They release odor and ammonia into the air, could contaminate groundwater  with pollutants,  and might  present  a health risk (Inbar  et al., 1993).  Organic wastes form the major component of refuse solid waste. If properly treated and utilized, it has the potential of being an important resource for food production. Use of urban organic wastes can also reduce the burden upon municipalities of waste disposal, as well as ameliorating the environmental  problems  associated  with  untreated  organic  wastes.  In  search  of  a  better destination  for  residues  produced  by  domestic  activities,  composting  stands  as  a  feasible alternative.

In Nigeria, indiscriminate dumping of waste has become a common practice. Most of these  waste  dumps  are  located  close  to  residential  areas,  markets,  farms  and  roadsides. Olorunfemi and Odita (1998) reported that the composition of waste dumps varies widely with many  human  activities  located  close  to  dumpsites.  The  general  belief  that  wastes  are sometimes hazardous to health cannot be over emphasized. The environmental problems posed by solid wastes range from health hazard, soil and water pollution, repulsive sight to offensive odour. These are worst experienced where wastes are not properly disposed off or managed. Currently where sustainable  agricultural  development  has become  such an integral  part of sound farming practices, it is important to emphasize that what was previously thought of as “a waste” can be used in  many varied, environmentally  friendly ways to minimize  waste and environmental impact.

The  need  for  an  increased  production  of  vegetables  to  meet  the  dietary  vitamin requirements of the people had necessitated a research in the use of manure in improving the soil fertility for an improved yield and quality of amaranth (Adekayode and Ogunkoya, 2011). To increase the availability of high quality amaranth throughout the year and reduction in its price, there is a need to use organic manure such as farmyard  manure, poultry manure and compost, which are available in large quantity.

In recent  decades,  the application  of organic  wastes  from different  origins  (manure, sewage sludge and municipal organic wastes) to degraded soils is a practice globally accepted to recover, replenish and preserve organic matter, fertility and vegetation. Civeira and Lavado (2006) reported that organic manures contain high nitrogen, phosphorus, potassium and other essential  nutrients.  In contrast  to  chemical  fertilizer,  it adds organic  matter  to  soil,  which improves soil structures, nutrient retention, aeration, soil moisture holding capacity and water infiltration. Added to that, Nigerian farmers now use agrochemicals to the barest minimum due to non-availability, unequal distribution or high cost of procurement.

1.4      AIM AND OBJECTIVES OF THE STUDY

–           To  determine  the  nutrient  compositions  and  heavy metals  content  of  refuse  dump compost and poultry manure.

–           To assess the impact of refuse dump compost and poultry manure on the growth and yield of A. hybridus.

–           To assess the concentrations of heavy metals and their deposition in various parts of A. hybridus (leaves, stems, roots and seeds).

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