ABSTRACT
Weeds are undesirable in agriculture activities since they
compete with food crops for available soil nutrients, air, water, sunlight and
space. Reports indicate that when these herbicides are applied, only about 1%
is effective whereas the remaining 99% exist as residues in the surroundings
thus posing serious threats to human health, the environment, wildlife and
other non-target organisms. The objective of this work was to determine the
level of some herbicide residues in sweetpotato. The sweetpotatoes were
cultivated in a completely randomized block design (CRBD) with four
replications at the Crops Research Institute Agronomy fields, Kwadaso where
different treatments made up of combinations of five (5) pre-emergence
herbicides (butachlor [50g/L-3L/Ha], imazethapyr [240g/L-3L/Ha], metolachlor
[333g/L-4L/Ha], pendimethalin [500g/L-3L/Ha] and terbutryn [167g/L-4L/Ha]) and
one (1) post-emergence herbicide (propaquizafop [100g/L-1.2L/Ha]) were applied
and a control which involved strictly hoeing. After harvest, samples were
randomly selected and extracted using a modified QuEChERS extraction method
followed by Liquid Chromatography-Mass Spectrometry (LC-MS) to determine the
residual levels of the herbicides. The results showed that sweetpotato samples
from the control (field work which was strictly hoeing as the method of weed
management) had no residues detected. Butachlor, imazethapyr, terbutryn and
propaquizafop were also not detected in their respective sweetpotato samples
analysed. However, pendimethalin and metolachlor residues were detected at
concentrations of 0.0023 µg/g and 0.0029 µg/g, respectively. The findings
suggest that herbicide residue levels detected in this study were considerably
lower than the maximum acceptable limit (0.05 mg/kg) and thus the dietary
exposure could be considered safe to humans.
CHAPTER ONE
INTRODUCTION
1.1 Background
Sweetpotato (Ipomoea batatas L.) is
a very vital food and industrial crop, cultivated globally with an annual
production of over 122 million metric tonnes (Ofori et al., 2009). According to
Milind et al. (2015), sweetpotato cultivation dates back to the 750 BC, thus
one of the oldest vegetables known to mankind. Several species have been
commonly used in religious rituals, medicinal and ornamental purposes. It is
known to be a staple starchy and tuberous root vegetable and its production is
increasing rapidly in many countries in the Sub-Saharan Africa (Korada et al.,
2010). According to Amengor et al. (2016), Saharan-Africa has about 13.37
million hectares of land cultivated with sweetpotato, thus making it the third
most important root crop after cassava and yam. Here in Ghana, sweetpotato is a
major non-traditional export crop and in the year 2013, the harvested area was
about 74,000 hectares (FAOSTAT, 2015). Odebode et al. (2008) attributed the
wide spread of sweetpotato in Africa to its ease of cultivation, high ability
to tolerate drought and hence its capacity to withstand the rather harsh
environmental conditions characteristic of this agro-ecological zone. Other
factors that have contributed to the widespread cultivation of this food crop
includes the low requirement for fertilizers and the flexible planting and
harvesting periods. The white or yellow–fleshed sweetpotato are the commonly
grown varieties in most parts of Africa, including Ghana (Kapinga et al. 2001).
The orange-fleshed cultivars in particular have been reported to possess a high
content of naturally bio-available precursors of vitamin A (β-carotene) and its
cultivation is therefore encouraged in the developing countries due to their prominence in combating
vitamin A deficiency (Laurie et al., 2015). Furthermore, properties such as
anti-carcinogenic, cardio-vascular disease-preventing and its high nutrient
content has resulted in its recognition as a health food (Njintang et al.,
2016). A report by Ofori et al. (2009) showed that sweet potato is not usually
integrated into the menu of most food service establishments and even in the
household menu, and this is probably because more importance and uses are
attached to the other roots crops such as cocoyam, cassava and yam
(Adu-Kwarteng et al., 2002; Opare-Obisaw et al., 2000).
Degras (2003) reported that, 57% of
food crops in some parts of Africa are lost due to the presence of weeds, hence
the need to effectively apply herbicides. Weeds influence agricultural
activities by competing with crops for available soil nutrients, air, water,
sunlight and space, and also harbouring other invasive pests (Wyss and
Müller-Schärer, 2001). In modern times, agrochemicals form an integral part of
agricultural production systems globally. Herbicides are described as a subtype
of pesticides which are applied with the intention of killing, controlling or
preventing the excessive growth of weeds or unwanted plants. The control of
weeds with herbicides in modern day agriculture has become indispensable due to
the acute shortage of farm labourers (Ponnusamy et al., 2015). Dinham (2003)
estimated that about 87% of Ghanaian farmers apply pesticides to control pests,
diseases and weeds during the cultivation of fruits and vegetables. Ntow et al.
(2006) reported that out of the pesticides used in Ghana, herbicides make up
44%, 33% for insecticides and 23% are fungicides. Due to the chemical nature of
herbicides, using them excessively and repeatedly may result in serious
problems including phytotoxicity to food crops, residual effects on susceptible
crops, adverse effects on non-target organisms and ultimately severe health
hazards to human and animals due to the accumulation of residues in the crops, soil, surface and
ground water (Ponnusamy et al., 2015). Furthermore, upon the realization of the
effectiveness of these herbicides, farmers tend to increase application
consistently to meet their production targets without taking into consideration
the negative aspects associated with these herbicides. According to Das and
Mondal (2014), the improper use of these chemicals can injure food crops,
severely damage the environment and also pose health threats to the applicator
as well as other people exposed to the chemicals.
For more Food Science & Technology Projects Click here
===================================================================Item Type: Ghanaian Topic | Size: 85 pages | Chapters: 1-5
Format: MS Word | Delivery: Within 30Mins.
===================================================================
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.