Thesis Abstract

Abstract
Water deficit is a major environmental stress that affects plant growth and productivity. Okra (Abelmoschus esculentus L. Moench) is a popular vegetable crop grown in many parts of the world and is known to be sensitive to water stress. Understanding the response of okra to water deficit is crucial for developing strategies to improve its tolerance to drought conditions. This research project aimed to investigate the growth response of okra to water deficit conditions. The study involved subjecting okra plants to different levels of water deficit by implementing varying irrigation regimes. The growth parameters measured included plant height, leaf area, biomass accumulation, and root characteristics. Physiological parameters such as leaf relative water content, chlorophyll content, and stomatal conductance were also assessed to determine the plant's response to water stress. The results of the study revealed that okra plants exhibited significant changes in growth and physiological parameters in response to water deficit. Under mild water deficit conditions, okra plants showed a reduction in plant height, leaf area, and biomass accumulation compared to well-watered plants. However, the root characteristics of okra plants were found to be positively influenced by water deficit, with increased root length and root biomass observed in water-stressed plants. Physiological analysis indicated that okra plants subjected to water deficit experienced a decrease in leaf relative water content and chlorophyll content, indicating water stress-induced changes in plant hydration and photosynthetic activity. Stomatal conductance was also significantly reduced in water-stressed plants, reflecting the plant's response to conserve water under drought conditions. Overall, the findings of this study suggest that okra plants exhibit a range of responses to water deficit, with both growth and physiological parameters being affected. The positive impact of water deficit on root development highlights the adaptive responses of okra to drought stress. These results provide valuable insights into the mechanisms underlying okra's response to water deficit and can contribute to the development of drought-tolerant okra varieties through breeding and management practices.

Thesis Overview

1.1     ORIGIN AND DISTRIBUTION OF OKRA

Okra (Abelmoschus esculentus(L.)Moench)originated in Ethopia in the year 120 BC. It is a common vegetable in tropical and sub-tropicalcountries, native to west and central Africa. It is known as a fast growing annual vegetable commonly grown in field and home gardens in Africa (Fayemi, 1999and Schippers, 2000). It belongs to the family,Malvaceae and was domesticated in West and Central Africa (Kochhar, 1986). It is known as ‘Okro’ in the Anglophone African countries. Okra is cultivated throughout the tropical and warm temperate regions of the world for its fibrous fruits (N.R.C., 2006). Okra is mainly cultivated in African countries such as Nigeria, Sudan, Egypt, Niger and Cameroun. It is also important in other tropical areas including Asia and South America.

1.2       SOIL AND CLIMATIC REQUIREMENT

A range of soil types have been found suitable for okra production even though it thrives best in moist, friable, well- drained soils. Sandy loam soils high in organic matter are the most desirable.A pH of about 6.0 - 6.8 is recommended for Okra production.In Nigeria, production is mainly during the rainy season. Okra requires a moderate rainfall of about 800-1000mm. Studies on the optimum weather requirement for high yields ofOkra showed that it performs best (growth, flowering and fruiting) when the minimum and maximum temperatures are between 200 and 300 celsius, respectively.Okra is sensitive to low temperature and develops poorly below 150 Celsius. The seeds germinate in relatively warm soils only(Tindall et al., 1986).

1.3       PRODUCTION AND ECONOMIC IMPORTANCE OF OKRA

Okra ranks third in Nigeria in terms of production area andconsumption, following tomato and pepper in that sequence. India is the major producer of Okra, producing about 5,784, 000 metric tons per year (FAO, 2015). Production statistics of 2016 shows that Nigeria produces an estimated 1,978,286 tons ofOkra per annum,placing the country at second place after India.

In Nigeria, there are two distinct seasons for Okra production, the peak and lean seasons. During the lean season, okra fruit are produced in low quantities, scarce and expensive to get while in the peak season, it is produced in large quantities much more than the local populace can consume (Bamire and Oke, 2003).

The approximate nutrient content of edible Okra pod is as follows: water, 88%; protein, 2.1%; fat, 0.2%, carbohydrate, 8.0%; fiber, 1.7% and ash, 0.2% (Tindall, 1983).The green pods are rich sources of vitamins, calcium, potassium, and other minerals. In Nigeria, Okra is distributed and consumed either fresh (usually boiled, sliced or fried) or in a dried form

(Fatokun and Chedda, 1983). Young leaves may also be used in cooked or processed forms. Fresh Okra fruits are used as vegetable while the roots and stems are used for preparing brown sugar (Chauhan, 1972). The protein found in Okra helps to build muscle tissue and constituent of enzymes which control all the hormone`s activities. The soluble fiber in Okra helps to lower serum cholesterol, reducing the risk of heart disease. The insoluble fiber helps to keep the intestinal tract healthy, reducing the risk of cancer especially colorectal cancer. Okra has also found medical application as a plasma replacement for the body.Nearly 10% of the recommended level of vitamin B6 and folic acid are present in half a cup of cooked Okra. The vitamin is required for good vision, proper circulation of blood, bone growth and normal digestion (Wolford and Banks, 2006). Okra is a good source of calcium which helps to keep bone strong and lessen the chance of fractures (Grubben and Denton, 2004). The seeds however can be roasted and used as substitute for coffee (Farinde and Owolarafe, 2007). Okra mucilage is used industrially for glace paper production and is also used in making confectionaries. (Akinyele and Temikotan, 2007).

Interestingly, Okra’s potential as an oilseed crop and its ability to tolerate drought in a world facing global climate change underscores its growing importance (Ibeawuchi, 2007). Oil content of Okra seed can be as high as that in poultry eggs and soybeans (Robert et al., 2011) Okra fruits are considered to be of good quality in the Nigerian context when they are smooth, small, narrow and highly mucilaginous. Fruits that have exceeded physiological maturity rarely give these characteristics and are generally not commonly consumed. They are frequently left on the plants to dry and then preserved for seeds (Splittstoessor, 1990). Fruits are often sliced and dried to ease preservation when it cannot be sold in the market and has become hard or tough and unsuitable for use in fresh form.

1.4       JUSTIFICATION AND OBJECTIVES OF THE STUDY

The limiting factors in Okra production include the use of low yielding varieties, poor soil fertility and the use of sub-optimal stand density. Overtime, the cultivation of improved varieties of Okra by farmers have beennarrowed to only a few popular ones such as Yar`balla especially in the Northern Guinea savannah zone based on fruit size, fresh yield of fruit, taste and viscosity when processed. There is need to find out whether other available varieties could be cultivated efficiently with higher output.

Despite the high nutritive value of Okra, optimum yields have not been attained as a result of continuous decline in soil fertility and decreased use of organic amendments (Akanbi et al., 2010). There are concerns about the use ofinorganic fertilizers under intensive agriculture due to increased soil acidity, pollution of water bodies and nutrientimbalance. The extent to which farmers depend on inorganic fertilizer, is constrained by unavailability of the right type of fertilizer, high cost, lack of technical know-how and inadequate access to credit for purchase (Chude, 1999). Hence, animal manure which is readily available is proving to be an alternative option for improvingOkra yield especially in the Guinea savannah of Northern Nigeria.Among organic manures, poultry manure has been found to have higher nutrient composition (Iken and Amusa, 2004). Poultry manure contains more nutrients relative to goat, sheep and cow dung, in addition, it is less bulky compared to other organic fertilizers. This makes transportation and handling easier and the needed amount smaller thanmany other types of organic manure. In addition, poultry manure is relatively cheap, readily available and helps in the improvement of soil physical and biological properties and also a source for most of the essential plant nutrients. On the other hand, the use of organic fertilizer as source of nutrient for vegetable crops assumed an increasing importance as there is an increasing demand for organic farm produce because of health benefits and long term positive effects on the environment.

Based on several research works and surveys, the World Bank has stated that enriching the soils with micronutrients by using organic fertilizers reducesoil nutrient deficiencies and enhances the nutritional condition of humans and animals through the food chain. The hazardous environmental consequences and high cost of inorganic fertilizers make them less desirable and out of reach to the poor farmers dominating the Nigerian agricultural sector (Shiyam and Binang, 2011). This has led to the increased use of organic manure, a readily available alternative which proves more environmentally friendly.

Under conditions of sufficient soil moisture and nutrients, higher population is necessary to utilize all growth factors efficiently and to subsequently produce high yieldsbecause land is a limiting factor in agricultural production.The yield of Okra could be as high as 30tha-1 but in most of the developing countries, it is as low as 1.8 tha-1(Whitehead and Singh, 2000). Higher stand density and proper fertilization are critical elements in increasing the productivity of

Okra. Siemonsma (1998) also stated that with increasing stand density, yield per unit area increases up to certain limit, beyond which resources for plant growth and development becomes limited and yield decreases.Therefore, proper stand density is required to attain optimum growth and development of the crop that will result in higher yield.It is in view of this, that the study was designed to achieve the following objectives;

1.     To study the performance of Okra varieties under varied poultry manure rates and stand density.

2.     To determine the most suitable variety, poultry manure rate and the stand density that will result in higher yield of Okra.