EFFECTS ORGANIC FERTILIZERS ON GROWTH PERFORMANCE, NUTRIENTS AND TOXICOLOGICAL COMPOSITION OF AMARANTHUS CAUDATUS AND AMARANTHUS CRUENTUS

Abstract

The objective of this study is to evaluate the effect of different types organic fertilizers on growth performance, nutrient and toxicological composition of two varieties of amaranth (Amaranthus caudatus (Samaru local variety) and Amaranthus cruentus (NH84/452)).The study consists of seven treatments which includes control (no fertilizer), poultry manure of 5 tons/ha and 10 tons/ha, sewage sludge of 5 tons/ha and 10 tons/ha, NPK compound fertilizer of 35 kg/ha and 70 kg/ha; with two varieties of amaranth (Amaranthus caudatus (Samaru local variety) and Amaranthus cruentus (NH84/452)) in factorial arrangement fitted into a randomized complete block design (RCBD) and replicated three times. Growth performance data were collected on plant height, number of leaves, leaf length, leaf width, leaf area and leaf area index from 2 weeks after transplanting (WAT) to 6 weeks after transplanting (WAT) using measuring tape and ruler. At 6WAT, poultry manure of 10 tons/ha recorded the highest value for all the growth parameters for both varieties except for leaf length, leaf width and leaf area of Amaranthus caudatus (Samaru local variety), where 10 tons/ha sewage sludge and 70kg/ha NPK compound fertilizer were highest. All the treatments showed increased effect on proximate composition (ash, moisture, fat, crude protein, crude fibre, available carbohydrate and energy) for the two varieties but there was no significant (p<0.05) difference except for protein which was significantly (p<0.05) highest at 9.67 ± 0.16% for the 70kg/ha NPK compound fertilizer in Amaranthus caudatus (Samaru local variety), proximate composition was determined according to A.O.A.C. (1999). Water soluble vitamins were analyzed using High Performance Liquid Chromatography (HPLC) while the metals were analyzed using Atomic Absorption Spectroscopy (AAS) For Amaranthus caudatus (Samaru local variety). β-carotene, zinc, riboflavin, iron, niacin and vitamin C levels were highest for 10 tons/ha sewage sludge, poultry manure of 10 tons/ha, NPK compound fertilizer of 70 kg/ha, poultry manure of 10 tons/ha, NPK compound fertilizer of 70 kg/ha, and 10 tons poultry manure respectively while for Amaranthus cruentus (NH84/452), β-carotene, zinc, niacin, iron, vitamin C and riboflavin were highest for 10 tons/ha sewage sludge, poultry manure of 10 tons/ha, 70kg/ha NPK compound fertilizer, sewage sludge of 10 tons/ha, NPK compound fertilizer of 70kg/ha and 10 tons/ha sewage sludge respectively. The 10 tons/ha poultry manure gave the highest value of tannins for both varieties but there was no significant (p<0.05) difference among the treatments. The 70 kg/ha NPK compound fertilizer recorded the highest level of phytate while the 10 tons/ha sewage sludge had the highest level of saponins, oxalate, and lead for both varieties of amaranth. Total aflatoxins and cadmium were not detected in any of the treatments including the control. The experimental results of this study have shown that poultry manure had higher growth performance and nutrients on the two varieties of Amaranth when compared with sewage sludge and NPK compound fertilizer, while sewage sludge resulted in the plants having higher anti-nutrients and heavy metals. The application of poultry manures at 10 tons/ha is therefore recommended for farmers to use to obtain higher yields of Amaranth.

CHAPTER ONE

INTRODUCTION

1.1         Background

Increasing population of the world has doubled the food demands and inundated the available land resources. Alongside other food alternatives, vegetables are considered cheap source of energy (Hussain et al., 2009). Vegetables are rich sources of essential biochemicals and nutrients such as carbohydrates, carotene, protein, vitamins, calcium, iron, ascorbic acid and palpable concentration of trace minerals (Salunkhe and Kadam, 1998). Plants also contain compounds which can potentially compromise health. These are termed ‗anti-nutritive‘ compounds such as oxalates, tannins, nitrates which are present in spinach. Amaranth is one of important vegetables of Amaranthaceae family. Amaranth has been naturalized in central parts of Asia and possibly Iran (Kawazu et al., 2003) and has cultivation history of more than 2000 years (Daneshvar, 2000), but it is also widely grown in Nigeria and many part of the North including Kaduna state. Amaranth is eaten as a vegetable across various states in Nigeria.

Organic and inorganic fertilizers are essential for plant growth. Both fertilizers supply plants with the nutrients needed for optimum performance (Erisman et al., 2008). Organic fertilizers have been used for many centuries whereas chemically synthesized inorganic fertilizers were only widely developed during the industrial revolution. Inorganic fertilizer has significantly supported global population growth, it has been estimated that almost half the people on the earth are currently fed as a result of artificial nitrogen fertilizer use (Erisman et al., 2008). Commercial and subsistence farming has been and is still relying on the use of inorganic fertilizers for growing crops (Masarirambi et al., 2010). This is because they are easy to use, quickly absorbed and utilized by crops. The continued dependence of developing countries on inorganic fertilizers has made prices of man agricultural commodities to skyrock (Makinde et al., 2010). Most vegetable farmers in tropical Africa are small holders who cannot afford cost of inorganic fertilizers, although soil fertility limits yield of vegetables especially in urban centres (Makinde et al., 2010). In Nigeria, fertilizer being costly and sometimes scare can make farmers not apply enough for good growth (Alonge et al., 2007). Fertilizer application rates in intensive agricultural systems have increased drastically during recent years in Nigeria. Farmers depend largely on locally sourced organic fertilizers (Makinde et al., 2010). In Nigeria, huge amount of organic wastes such as poultry waste, animal excreta, sewage sludge, refuse soil and palm oil mill effluent are generated and heaped on damp sites, posing potential environmental hazard (Agboola and Omueti, 1982). Incorporating these wastes materials into the soil for crop production is expected to be beneficial to the buildup of organic matter layer that is needed for a steady supply of nutrients by tropical soils (Agboola and Omueti, 1982). However, due to high quantity needed, adequate quantity of an organic and inorganic waste may be obtained, hence the farmers often apply organic and inorganic fertilizer combined. Also, getting the appropriate application protocol or rates is important in obtaining good yield (Agboola and Omueti, 1982).

Oyedeji et al. (2014) reported that NPK and poultry manure improve the growth and yield of three different species of amaranth (Amaranthus hybridus, Amaranthus deflexus and Amaranthus cruentus) but influenced proximate composition differently where NPK had the highest crude fibre, protein and fat while poultry manure showed the highest fat content. Emede et al. (2012) reported that poultry manure influenced the plant growth and yield of Amaranthus cruentus L. positively. Makinde et al. (2010) reported that organic material alone or in combination with NPK significantly increased protein and ash while fibre was reduced; NPK gave least values of protein, fibre and ash compared with organic material. Funda et al. (2011) studied the effect of organic and inorganic fertilizers on yield and mineral content of onion and reported that the treatments influenced K content, but did not influence N, P, Ca, Na, Mg, Fe, Zn, Cu and Mn contents of the onion bulb. In the second year, the treatments influenced Na content, but did not influence the others. Coolong et al. (2005) reported that N, P, Mn, Fe and Zn content of bulb were increased by N treatments but the content of N was decreased by N doses but K, Cu and Mo contents were not affected by the treatments. Abdelrazzag (2002) found that increasing the rate of sheep and chicken manure increased N content of onion significantly, while P and K contents had low level. Mixture of chicken manure and biofertilizer increases the yield of onion and enriched nutrient content in tuber (Fatma et al., 2007). Application of organic manures significantly increased levels of organic C and N and the formation of water stable aggregates, as compared with application of chemical fertilizers (N’Dayegamiye, 2006). Several studies have centered on the effect of organic, inorganic fertilizer or used in combination on soil properties, nutrients uptake, growth, yield and some minerals contents. However, there is scarce research information on the effect of organic and inorganic fertilizer on nutritional and toxicological composition of Amaranthus caudatus and Amaranthus cruentus.

1.2         Statement of Research Problem

According to the Food and Agricultural Organization (FAO), there are about 795 million undernourished people in 2015 (FAO, 2015). To apprehend the situation, interests have been centralized on the exploitation, quantification and utilization of food plants, especially vegetables (Dini et al., 2005). In spite of the integrated use of various soil fertility amendment input aimed at alleviating nutrient deficiency and improving their availability in soil reserves, crop and nutrient yield still fall short of their potential because of inadequate nutrient and chemical inputs, inappropriate quality of the organic materials and insufficient combination (Palmer et al., 1997). Various studies has been done on how fertilizer use affect the yield on different plants but fewer research is carried on their effects on growth performance, nutrient and toxicological composition in leafy vegetables especially spinach which is commonly consumed in this part of world.

Furthermore, there are various fertilizers that have been shown to have effect on the yield of spinach in terms of growth. Therefore, it is necessary to investigate the exact effect different sources of organic fertilizers will have on the growth performance, nutrients and toxicological composition Amaranthus caudatus (Samaru local variety) and Amaranthus cruentus (NH84/452).

1.3         Justification

Vegetables are cheaper sources of many nutrients, biochemicals and phytochemicals which are responsible for normal physiological functions and also help in reducing the risk of chronic diseases. To enhance the optimal production of this nutrients and phytochemicals, appropriate use of fertilizers has to be employed. Many organic materials are produced around the home, or can be obtained at little or no cost from livestock operations, municipal green waste collection centers, and local landfills. Virtually any organic material can be used as a fertilizer; however, materials vary considerably in the concentration of plant nutrients they contain and the rate at which these nutrients are released for plant use. Therefore, some organic fertilizers are better for certain situations than others, and different materials need to be applied at different rates to supply the correct amount of plant nutrients (Koenig and Johnson, 1999).

A common misconception is that organic fertilizers are safer for plants and the environment than inorganic (chemical) products. Improper organic fertilizer application can also contribute to surface and ground water pollution, may induce a plant nutrient deficiency or toxicity. If properly used, both organic and inorganic fertilizers are safe for plants and the environment (Koenig and Johnson, 1999). Hence, it is necessary to evaluate the effect organic fertilizers will have on growth performance, nutrients and toxicological composition of Amaranthus caudatus (Samaru local variety) and Amaranthus cruentus (NH84/452).

1.4         Null Hypotheses

Application of different organic fertilizers does not have any effect on growth performance, nutrients and toxicological composition of Amaranthus caudatus (Samaru local variety) and Amaranthus cruentus (NH84/452).

1.5         General Aim

The general aim and objective of this study is to evaluate the effect of different types of organic fertilizers on growth performance, nutrients and toxicological composition of Amaranthus caudatus (Samaru local variety) and Amaranthus cruentus (NH84/452).

1.6         Specific Objectives

The specific objectives of this study are to determine:

1. The effect of different types of organic fertilizer application on growth performance of Amaranth varieties leaves.
2. The effect of different types of organic fertilizer application on nutrient composition of Amaranth varieties leaves.
3. The effect of different types of organic fertilizer application on toxicological composition of Amaranth varieties leaves

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