ABSTRACT
Field and pot trials were conducted during the 2012 rainy season at the Research Farm of the Institute for Agricultural Research Samaru and in the Orchard of the Department of Agronomy, Ahmadu Bello University, Zaria to evaluate the effects of levels of NPK fertilizer (0, 50, 100 kg ha-1) and poultry manure (0, 2, 4 t ha-1) on the performance of two okra varieties (Clemson spineless and Ex-Samaru-4). The designs used were Randomized Complete Block Design (RCBD) and Complete Randomized Design for field and pot trials respectively, replicated and repeated three times in all possible factorial combinations. Results showed no significant difference in days to 50% flowering, 100-seeds weight, fruit length, fruit diameter and plant height when NPK fertilizer was varied from 0 to 100 kg ha-1, but at 7 WAS, significantly increased, and gave higher number of leaves per plant (9.0 and 7.0), number of primary branches per plant (5.0), shoot fresh weight (44.9 g), number of fruits per plant (5.0), number of seeds per pod (80) and fruit weight (17 g) from 0 to 50 kg NPK ha-1 in both trials. Other parameters were significantly at par. Application of poultry manure from 0 to 2 t ha-1 significantly increased plant height, number of leaves per plant, shoot fresh weight and days to 50% flowering, a further increase to 4 t ha-1 gave parameters that were at par. But varying poultry manure from 0 to 4 t ha-1 significantly increased number of primary branches per plant and fruit yield in both field and pot trials. Significant interactions were observed on variety and poultry manure on number of fruits per plant, variety and NPK fertilizer on shoot dry weight, NPK fertilizer and poultry manure on number of primary branches per plant and between poultry manure and variety on number of leaves per plant. Okra variety Clemson spineless significantly gave taller plants, longer fruits and fewer days to 50 % flowering than variety Ex-Samaru-4, however both varieties were statistically at par on fruit yield kg ha-1 in both trials. A highly significant and positive correlation were obtained between okra fruit yield and plant height, number of leaves per plant, number of fruits per plant, fruit length and fruit weight. Regression analysis carried out indicated that NPK fertilizer variation resulted to linear response and poultry manure had a quadratic response in both trials. Based on the result obtained in this study, it could be suggested that for good growth and yield of okra at Samaru application of 3.5 t ha-1 poultry manure in variety Clemson spineless should be recommended.
CHAPTER ONE
1 INTRODUCTION
1.1 Origin and Distribution
Common Okra (Abelmoschus esculentus L. Moench) is a popular vegetable in tropical and sub-tropical countries of the world; it is grown for its “pod” (Ogeniyi and Folorunso, 2003). It is a member of the hibiscus family, Malvaceae and has the typical floral characteristics of that family originating from Africa. It is now widely distributed in the tropics including Nigeria (National Research Council, 2006). It is an important vegetable crop occupying a land area of 277,000 hectares with a production of 731,000 metric tons worldwide and productivity of 2.63 t ha-1 in Nigeria (FAO, 2006). Okra is also believed to be found in its wild state on the alluvial banks of the Nile and the Egyptians were the first to cultivate it in the basin of the Nile (12th century BC). The crop is native to West Africa and has become established in the wild in some new world tropical areas. Okra was domesticated in West and Central Africa (Kochhar, 1986) and known as „okro‟ in the Anglophone African countries as a fast growing common annual vegetable widely consumed in Africa (Schippers, 2000).
It ranks above other vegetable crops such as Amaranths, lettuce Cabbage etc (Babatunde et al., 2007), it is one of the home garden vegetables popularly grown and consumed in the tropics (Fayemi, 1999). According to CBN (1996), the average rate at which vegetables crop are grown including okra production in Nigeria between 1989 and 1993 was 14.0 % compared to 6.4 % of cassava and 3.8 % for maize. The plant is tolerant to drought stress (Majanbu et al., 1985); however, supplementary irrigation may be necessary during extended drought periods for a satisfactory yield. In Nigeria, the widely cultivated okra is distributed and consumed either fresh (usually boiled, sliced or fried) or in a dried form (Fatokun and Chedda, 1983). The approximate nutrient content of the edible okra pod is as follows: water, 88%; protein, 2.1%; fat, 0.2%; carbohydrate, 8.0%; fibre, 1.7% and ash, 0.2% (Tindall, 1983). However, the nutritional quality of okra can be influenced by the application of organic fertilisers, such as liquid seaweed, with the following composition, according to Zodape et al., (2008): carbohydrate, 7.39%; protein, 28.04%; and dietary fibre, 35.55%. The oil content in the seeds could be as high as that in poultry eggs and soybeans (Akinfasoye and Nwanguma, 2005).
1.2 Soil and Climatic Requirements
Okra requires a moderate rainfall of 80 – 100 cm well distributed to produce its young edible fruits. An average temperature of 20°C to 30°C is considered optimum for growth, flowering and fruiting (Rice et al.,1987). Seeds will only germinate in relatively warm soils, no germination occurs below 160C. A monthly average temperature range of 200 _ 300C is considered appropriate for growth, flowering and development (Tindall et al., 1986). A wide range of soil types has been found suitable even though it was found that it thrives best in a moist friable, well-drained soil (Eke etal., 2008). In Nigeria, production is mainly during the warm season, although it can be grown all the year round depending on the varieties. The pH of about 6.0 to 6.8 is recommended for okra production (Kochlar, 1981).
1.3 Cultivation
The land on which okra is to be cultivated should be well ploughed and harrowed in order to create a favourable environment for its growth. In the dry season, it is grown on ridges or on beds at a favourable environment for its growth. While in the wet season, it is grown on ridges or on beds at a spacing of 40-45 cm at a rate of three seeds per hole and later thinned to one plant per stand. Okra is predominantly grown in Nigeria during the wet season; it is limited to the irrigation sites during the dry season especially in Fadama (Daniel and Kalko, 1982). The cultivation of okra is mostly done by small scale farmers and the harvests are sold for some extra income which also helps for the cultivation of staples, after the need for subsistence has been adequately met. It is grown mainly as an intercrop with maize, groundnuts, yams, cassava, melon or other vegetables (Nath, 1976). In most cases the crop is intercropped with other field crops at a population lower than the 10,000 plants ha-1 recommended for okra production (Udoh et al., 2005). In some regions, it is grown as sole crop during the late wet season. The late season crop when harvested may be dried and stored for the use in the dry season when fresh pods are not likely to be readily available in the market. In the fresh form, okra fruits are highly perishable except when stored frozen.
1.4 Uses
Okra is mainly cultivated for its “pods” which are cooked and eaten in African countries like Nigeria, Egypt and Sudan. It is also important in other tropical areas including Asia and South America, fresh okra fruits are used as vegetable while the roots and stems are used for preparing brown sugar (Chauhan, 1972). Okra pods are used for oil extraction. The protein found in okra is very important in human diet, it helps to build muscle tissue and make up enzymes which control all the hormones that control the organ. The soluble fibre in okra helps to lower serum cholesterol, reducing the risk of heart disease, the other half is insoluble fibre which helps to keep the intestinal tract healthy decreasing the risk of some form of cancer especially colorectal cancer. Nearly 10% of the recommended level of vitamin B6 and folic acid are present in half a cup of cooked okra, vitamins are required for good vision, help bone growth, proper circulation of blood and aids 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). Although okra fruits are one of the most commonly harvested fruits in Africa, there are places where the leaves are at least as important as the fruits. This is the case in Eastern Nigeria and in the Bongor region in western Chad. People mainly collect small, young leaves, or new sprouts after the fruit have been collected, the leaf yield in this area is 3-6 t/ha (Dupripez et al., 1989). Fresh green fruits of okra considered to be good quality in the Nigerian context, should be smooth, short and highly mucilaginous. Fruits that are over matured are generally not fit for consumption and therefore, are preserved for seeds (Splittstoessor, 1990).Fruits are normally sliced and dried when okra cannot be sold at the market and has become tough or hard and unsuitable for use in raw form, but processing allows these fruits to be preserved for later use
1.5 Justification and Objectives of the study
The use of inorganic fertilizer has not been helpful under intensive agriculture; because it is often associated with reduce crop yield, soil acidity and nutrient imbalance (Ojoniyi, 2000). The extent, to which farmers can depend on this, is constrained by unavailability of the right type of inorganic fertilizer at the right time, high cost, lack of technical know-how and lack of access to credit (Chude, 1999). Hence animal wastes that result to animal manure is better alternative and a necessary option for improved okra production especially in the Guinea savannah of Northern Nigeria. Poultry manure is relatively cheap, readily available and tend to be higher than inorganic fertilizer in terms of yield and improvement of soil physical properties. The use of inorganic and organic fertilizers as source of nutrient for vegetable crops assumed an increasing importance. Use of inorganic fertilizer is still desirable since the land under cultivation is limited, high land use intensity as a result of high population, so the demand for higher production is pressing. This is particularly more so in vegetable production because it is usually in small land scale holdings among many farming families between 0.2 to 2 t ha-1in either sole, but mostly mixed cultivation. The increasing demand for organic farm produce for its attendant health benefits and risk- free characteristic is another dimension to the use of organic manure in Agriculture especially in vegetables and fruits production. Investigations have indicated that Nigerian Savannah soils are largely deficient in major essential nutrients like N, P and K, making it is necessary to supply or enrich the soil with other source of nutrients like poultry, cow and goat manures but among all these, poultry manure has been found to have higher nutrient concentration (Iken and Amusa, 2004). Nutrient elements have specific function in crop growth, development and yield but no single nutrient can produce any meaningful plant growth on its own. The addition of organic fertilizers is necessary due to its readily available nutrient concentration and relative ease of handling and application. However, in terms of quantity, the amount of poultry manure required for cultivation is less, compared to that of cow, goat and sheep manure. This made transportation and handling of the poultry manure easier than the rest of the organic manures, the nutrient concentration is also higher than that in cow manure. This helps our small scale farmers who are the majority to obtain high yield with less production cost because the poultry manure is cheaper than the NPK fertilizer.
In Nigeria the limiting factors in okra production and other vegetables among others include weed management, fertilize soil, tillage practice, low yielding varieties and Sub-optimal planting density (Iyagba et al., 2012). Fertilizer application among the various agronomic practices also influenced the growth and green pod yield in okra. Tropical soils are adversely affected by sub-optimal soil fertility and erosion, causing deterioration of the nutrient status and changes in soil organic population (Economic Commission for Africa, 2001). Use of NPK fertilizer can improve crop yields, total nutrient content, and nutrient availability. Babatola (2006) recorded an increased yield in okra due to NPK fertilizer application. Recommended rates of NPK fertilization vary greatly depending on the variety and environment. Windham (1966) recommended between 27 and 54 kg ha-1 N for Clemson spineless okra variety depending on the soil type. Majanbu et al. (1985) recommended either 35 or 70 kg ha-1 of N depending on the variety. Several authors have also reported the importance and different response of okra varieties to different rates of NPK fertilizer (Blenner Hassett and El-zaftawi 1986, Khan et al., 2002). Dademel et al. (2004) also reported that higher NPK fertilizer dose of about 150 kg ha-1 will cause an increase in the nutrient uptake and hence tends to increase crop yield. Based on these
The objectives of this study therefore are:
- To determine the effect of NPK fertilizer and poultry manure on growth, yield and yield components of okra.
- To assess the performance of two okra varieties under the climatic conditions of Samaru.
