Thesis Abstract

Low soil fertility and low level of fertilizer application have caused low productivity of tomatoes in Jega LGA. Therefore, this experiment was conducted to determine the effects of sole and combined application of rice straw and inorganic fertilizers on growth and yield of two tomato varieties (Gelilea and Roma VF), and on soil properties. The inorganic fertilizers encompassed recommended Nitrogen and Phosphorous (NP) and blended fertilizer (BF) formulated for the study area (NPSZnB). Hence, a factorial combination of six levels of fertilizers and two types of tomato variety were laid out in RCBD with three replications. The studied soil was loam in texture and moderately acidic (pH 6.0). It had low total N (0.11%), organic carbon (1.64%), available P (10.2 ppm) and moderate in cation exchange capacity (20.2 cmol(+) kg-1). All phenological parameters of tomato were significantly affected by the main effects of fertilizer and variety. The effect of fertilizer had significant influence on all growth parameters. Furthermore, the main effect of fertilizer and variety had significant influence on all yield and yield parameters except the main effect of variety on marketable and total fruit number of tomato. Fertilizer and variety interacted to significantly influence days to flowering, number of primary and secondary branches, cluster per plant and average fruit weight. High total fruit yield (35.8 t ha-1) and marketable fruit yield (32.4 t ha-1) were recorded when NP combined with Rice straw, and BF combined with Rice straw. Total N and OC increased in soil after harvest as compared to their concentration in soil before sowing for all treatments. The correlation analysis showed that total and marketable fruit yield exhibited positive association with all parameters studied, except with days to flowering, fruiting, maturity, and fruits per cluster. In conclusion, the results showed that the highest marketable fruit yields were obtained at the applications of NP+Rice straw and BF+Rice straw. Furthermore, economic analysis indicated that application of NP+Rice straw and BF+Rice straw resulted in the highest net benefit with acceptable marginal rate of return (above 100%). Generally, the organic and inorganic nutrient sources applied in sole and in combination have improved most of the tomato growth and yield components as well as some soil chemical properties. However, the result of this study was from one season. Hence, similar studies have to be conducted in a number of seasons and locations of similar agro-ecology, soil type and crop in order to draw firm conclusions and make final recommendation.

Thesis Overview

INTRODUCTION

Agriculture contributes more than 40 % to GDP, 80 % of foreign exchange earnings, 70 % of raw material for domestic industries, and 85 % of employment for the population in Nigerian economy. The country still has a sizeable number of households that are food insecure due to lack of balance between food production and the feeding population. The situation is also further aggravated by a number of environmental challenges (like soil fertility degradation, deforestation, rainfall variability, etc), resulting directly or indirectly from human activities due to unsustainable agricultural practices, rapid population growth, and consequently increase in the exploitation of natural resources (Getachew, 2011).

Decreasing soil productivity has become a global concern as soil fertility is diminishing gradually for many reasons including soil erosion, nutrient mining, accumulation of salts and other toxic elements. Intensification of agriculture emphasizes heavy use of inorganic fertilizers, which leads to adverse environmental effects. Many efforts are being exercised to combat these, the unfavorable consequences of chemical farming (Faheed et al., 2008). As a solution, organic fertilizers have emerged as a promising component of integrating nutrient supply system in agriculture.

Fertilizers specifically, DAP and Urea was used for crop production as major inorganic fertilizers in Nigeria. However, blended fertilizers have been introduced recently. With the increasing population and decreasing land availability for agricultural production, fertilizer has become the leading resource for increased productivity per unit area. However, smallholder farmers do not afford full levels of recommended inorganic fertilizer application. Although, balanced use of both macro and micro nutrients in crops plays significant role in increasing the yield, it may not be available from inorganic fertilizers. Besides, the world agriculture focuses on Integrated Soil Fertility Management

(ISFM) which has enhanced the need of eco-friendly organic farming in agriculture sector (Amrit, 2006).

Biogas dregs and slurry are by-products of biogas generated during gas production. These residues, especially biogas slurry, are a good source of plant nutrients and can improve soil properties (Garg et al., 2005). In Nigeria, few crop residues are often retained on farmers’ field due to their competitive use in livestock feed, energy, cash source and construction material. Given the poor economic capacity of smallholder farmers, the inorganic fertilizers used for crop production are still at inadequate rates (Girma, 2016).

The farmer needs to use optimum inorganic fertilizer to increase their crop production. However, if only mineral fertilizers are continuously applied to the soil without adding organic manure, productivity of land will decline due to depletion of soil microbial biomass and activity.

Tomato (Lycopersicon esculentum Mill.) is the most widely grown vegetable in the world (Tesfaye, 2008). It is a profitable cash crop and providing a higher income to small scale farmers that widely cultivated both under irrigation and rain fed throughout the year in Nigeria (Lemma, 2002). The national average of tomato fruit yield in Nigeria is often low (198 q ha-1) compared even to the neighboring African countries like Kenya (232 q ha1) (FAO, 2013). Current productivity under farmers condition at Jega LGA is 110 q

ha-1, (personal communication) whereas yield up to 400 q ha-1 can be recorded on research plots (Tesfaye, 2008).

However, its yield and production in Nigeria is highly constrained by several factors. Among these, poor soil fertility, lack of well adapted improved varieties, lack of adequate nutrient supply and poor agronomic management practices (spacing, planting time, irrigation, etc) are the main constraints to agricultural production systems in low-input agriculture in the country and particularly to the study area (Dandena et al., 2011). Furthermore, in the major tomato production belt of central rift valley of Nigeria high temperature, diseases, poor irrigation practices and fertilization are some of the constraints to reduce normal vegetative and reproductive organs development for proper fruit settings and maturation (Dandena et al., 2011).

Inorganic fertilizers are not the most appropriate solution to overcome these constraints, especially for vegetables that have increasingly short time and are consumed fresh. Use of inorganic fertilizers are also expensive and a threat to human health (Weltzein, 1990). So, it is suggested that there should be an emphasis on finding alternatives to inorganic fertilizers such as compost and rice straw, which are cheaper than other sources of nutrients and relatively safe (Rindle, 1997). The use of these organic sources has a role in the management of plant diseases and soil fertility in field and greenhouse (Muhammad, 2011).

It is important to note that in Jega LGA huge number of biogas structure were constructed for household fuel consumption. Therefore, putting emphasis on locally available low cost organic manure becomes an attractive option. Proper use of rice straw can reduce the dependency of many farmers on increasingly expensive inorganic fertilizer.

Moreover, its benefits need to be substantiated with scientific evidence to demonstrate to the agricultural experts and farmers, amongst others, on its impact to increased yield

(Getachew, 2011).

Research efforts on how to use these resources and use of rice straw together with low rates of mineral fertilizers could be an alternative solution for sustainable fertility management and promote food self-sufficiency especially for resource poor farmers. In general, the role of rice straw as organic fertilizer and effects on tomato growth and yield as well as on soil properties has not been studied under contrasting with inorganic fertilizers (blended versus non-blended) in the semi-arid lowland areas around Arba Minch. Hence, this study was proposed with the following objectives:  

1.3       General objective

ï‚· To investigate the potential use of organic fertilizer (rice straw) in combination with soil applied inorganic fertilizers for improved tomato crop production and soil properties

1.3.1   Specific objectives

1. To evaluate the effect of sole and combined application of rice straw and inorganic fertilizers on growth performance, yield and yield components of tomato
2. To determine the residual effects of sole and combined application of rice straw and inorganic fertilizers on physical and chemical properties of soil

• To determine appropriate combinations of rice straw and inorganic fertilizers use for economic yield production of tomato

1.4       Study Questions

1. What are the effects of sole and combined application of rice straw and inorganic fertilizers on growth performance, yield and yield components of tomato?
2. What are the residual effects of sole and combined application of rice straw and inorganic fertilizers on physical and chemical properties of soil?

• How are the combinations of rice straw and inorganic fertilizers use for economic yield production of tomato?

1.5 Significance of Study

Statistical figures (SRID MoFA, 2008) indicate a decline in the production of food, especially fruits and vegetables in Ghana. This is evident in the volume of fresh tomatoes that is imported into the country from neighbouring countries like Burkina

Faso (over 40% of fresh tomato demand) and tinned tomato puree from Europe (Anum, 2009). Findings obtained from this study would provide information to farmers, agriculture extension officers and other stakeholders on the effects of organic and inorganic fertilizer on the growth, yield and quality of tomatoes. Also, the level at which organic and inorganic fertilizer should be applied to tomato plant so as to reduce the level of pollution these fertilizers leached to water bodies creating environmental imbalance This would equip them with the requisite knowledge to help increase their production levels to meet the food demand of the nation hence ensuring food security to meet the Millennium Development Goal 1(i.e. to eradicate extreme poverty and hunger).