ABSTRACT
Low soil fertility, especially deficiencies in nitrogen and phosphorous, is one of the key constraints to snap bean production in Kenya. An on farm trial was carried out in Karungua village in Kawanjara Sub-location, Runyenjes division, Embu East District. The first season trial was planted on 26th July 2014 and the second trial on 15th August 2014, respectively. The objectives of the study were: (1) to determine the effect of combining inorganic and organic fertilizers on growth, yield and quality of snap bean; and (2) to determine the cost effectiveness of various nutrient management options for snap bean production. The treatments comprised the following: (i) control (no fertilizers applied); (ii) farmyard manure (5 t/ha) and di-ammonium phosphate (50 kg N/ha) at planting and top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting; (iii) di-ammonium phosphate (50 kg N/ha) at planting and top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting; (iv) NPK (23:23:0) (50 kg N/ha) fertilizer at planting and top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting (main farmer practice); (v) di-ammonium phosphate (50 kg N/ha) at planting, calcium ammonium nitrate (50 kg N/ha) at 21 days after planting and foliar feed spraying at pre- flowering stage; (vi) farmyard manure (5 t/ha), NPK (23:23:0) (50 kg N/ha) fertilizer at planting and top dressing with NPK (17:17:0) (50 kg N/ha) fertilizer at 21 days after planting; (vii) farmyard manure (5 t/ha) at planting and foliar feed spraying at pre- flowering stage; (viii) farmyard manure (5 t/ha) at planting; (ix) farmyard manure (5 t/ha), di-ammonium phosphate (50 kg N/ha), NPK (23:23:0) (50 kg N/ha) fertilizer at planting, top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting and top dressing with NPK (17:17:0) (50 kg N/ha) fertilizer at 35 days after planting; (x) farmyard manure (5 t/ha) and calcium ammonium nitrate (50 kg N/ha) at planting and top dressing with calcium ammonium nitrate (60 kg N/ha) at 21 days after planting; (xi) farmyard manure (5 t/ha) at planting and top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting. The trial was laid out in a randomized complete block design and replicated three times. The agronomic data collected included: 50% emergence, plant stand, days to 50% flowering, days to 50% podding, number of nodules per plant, shoot dry weight, pod yield and yield components, pest and disease infestation. Data for estimating cost effectiveness included the costs of inputs and revenue from the operations during the planting trial. Data were subjected to analysis of variance and mean separation was done using the least significant difference test at p=0.05.
The results of the study showed that nutrient management options did not significantly affect the number of days to 50% emergence and plant stand of snap bean. Application of farmyard manure (5 t/ha) alone and application of farmyard manure (5 t/ha) at planting plus foliar feed spraying at pre- flowering stage significantly took the shortest time to attain 50% flowering. Fertilizer application significantly depressed nodule number. Treatments with inorganic fertilizers alone had significantly fewer nodules than treatments with farmyard manure. Nutrient management options had no effect on 50% podding, extra-fine pod length, pest and disease infestation. Significantly higher extra-fine, fine and marketable pod yields were recorded in di-ammonium phosphate (50 kg N/ha) plus calcium ammonium nitrate (50 kg N/ha) treated plots than in plots with other nutrient management options. Economic analysis showed that application of di-ammonium phosphate (50 kg N/ha) at planting plus top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting had the highest net benefit and marginal rate of return in both plantings compared to other nutrient management options. The control plots (no-fertilizer) had a higher net befit first planting compared to the fertilized treatments. The study has demonstrated that application of di- ammonium phosphate (50 kg N/ha) at planting plus top dressing with calcium ammonium nitrate (50 kg N/ha) at 21 days after planting can enhance yield and profitability of snap bean in Embu County.
TABLE OF CONTENTS
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
TABLE OF CONTENTS v
LIST OF TABLES vii
GENERAL ABSTRACT ix
CHAPTER ONE: INTRODUCTION 1
1.1 Background information 1
1.2 Problem statement and justification 3
1.3 Objectives of the study 5
1.4 Hypotheses 5
CHAPTER TWO: LITERATURE REVIEW 6
1.1Ecology and importance of snap bean 6
2.2 Constraints to snap bean production 8
2.3 Effect of nitrogen fertilizer application on growth, yield and quality of snap bean 10
2.4 Effect of phosphorus fertilizers on growth, yield and quality of snap bean 12
2.5 Effect of integrated nutrient management on growth, yield quality of snap bean 13
2.6 Effect of foliar feed application on growth, yield and quality of snap bean 14
CHAPTER THREE: MATERIALS AND METHODS 18
3.1 Description of the experiment site 18
3.2 Experimental layout and design 18
3.3 Crop husbandry practices 19
3.4 Data collection 20
3.4.1 Agronomic data collection 20
3.4.2 Economic data collection 22
3.4.3 Agronomic data analysis 23
3.4.4 Economic data analysis 23
CHAPTER FOUR: RESULTS 25
4.1 Effect of nutrient management options on the number of days to 50% emergence of snap bean 25
4.2 Effect of nutrient management options on the plant stand of snap beans at 50 days after emergence 26
4.3 Effect of nutrient management options on the number of days to 50% flowering of snap bean 27
4.4 Effect of nutrient management options on the number of days to 50% podding of snap bean 28
4.5 Effect of nutrient management options on the number of snap bean nodules per plant 29
4.6 Effect of nutrient management options on shoot dry weight of snap bean per plant 30
4.7 Effect of nutrient management options on snap bean extra-fine pod yield 31
4.8 Effect of nutrient management options on snap bean fine pod yield 32
4.9 Effect of nutrient management options on snap bean marketable pod yield 33
4.10 Effect of nutrient management options on length of extra-fine snap bean pods 34
4.11 Effect of nutrient management options on length of fine snap bean pods 35
4.12 Effect of nutrient management options on pest (scores) infestation in snap bean 36
4.13 Effect of nutrient management options on diseases (scores) infestation in snap bean 37
4.14 Total variable costs of various nutrient management options for snap bean 38
4.15 Net benefits of various nutrient management options for snap bean 40
4.16 Dominance analysis of various nutrient management options for snap bean 43
4.17 Marginal rate of return of various nutrient management options for snap bean 45
CHAPTER FIVE: DISCUSSION 47
5.1 Discussion 47
6.1 Conclusions 53
6. 2 Recommendations 53
REFERENCES 55
APPENDICES 76
LIST OF TABLES
Table 4. 1: Effect of nutrient management options on the number of days to 50% emergence of snap bean 25
Table 4. 2: Effect of nutrient management options on the plant stand (number of plants/plot) of snap beans at 50 days after emergence 26
Table 4.3: Effect of nutrient management options on the number of days to 50% flowering of snap bean 27
Table 4.4: Effect of nutrient management options on the number of days to 50% podding of snap bean 28
Table 4. 5: Effect of nutrient management options on the number of snap bean nodules per plant 29
Table 4. 6: Effect of nutrient management options on snap bean shoot dry weight per plant.30
Table 4. 7: Effect of nutrient management options on snap bean extra-fine pod yield (kg/ha) ...........................31
Table 4. 8: Effect of nutrient management options on fine pod yield (kg/ha) in snap bean 32
Table 4. 9: Effect of nutrient management options on marketable pod yield (kg/ha) 33
Table 4. 10: Effect of nutrient management options on length (cm) of extra fine snap bean pods 34
Table 4. 11: Effect of nutrient management options on length (cm) of fine snap bean pods .35 Table 4. 12: Effect of nutrient management options on pest (scores) infestation in snap bean............................36
Table 4. 13: Effect of nutrient management options on disease (scores) infestation in snap bean 37
Table 4. 14: Total variable costs (Kenyan shillings) of various nutrient management options for snap bean (per ha) 39
Table 4. 15: Net benefits of various nutrient management options for marketable snap bean (per ha) in the first planting 41
Table 4. 16: Net benefits of various nutrient management options for marketable snap bean (per ha) in the second planting 42
Table 4.17: Dominance analysis for various nutrient management options for snap bean (per ha) in the first planting 43
Table 4. 18: Dominance analysis for various nutrient management options for snap bean (per ha) in the second planting 44
Table 4. 19: Marginal rate of return (per ha) of various nutrient management options for snap bean in the first planting 46
Table 4. 20: Marginal rate of return (per ha) of various nutrient management options for snap bean in the second planting 46
LIST OF APPENDICES
Appendix 1a: Soil test result (first planting) 76
Appendix 1b: Soil test result (Second planting) 76
Appendix 2: Table showing variable cost Ksh/ha (Non- fertilizer production cost) 77
Appendix 3: Table showing Cost of fertilizer and fertilizer application per regime Ksh/ha……………………..77
Appendix 4: Table showing Total variable cost (KES) 78
Appendix 5a: Table showing Net Benefit Cost (KES) (first planting) 79
Appendix 5b: Table showing Net Benefit Cost (KES) (second planting) 80
Appendix 6a: Table showing Dominance analysis (first planting) 81
Appendix 6b: Table showing Dominance analysis (second planting) 82
Appendix 7a: Table showing marginal analysis (first planting) 83
Appendix 7b: Table showing marginal analysis (second planting) 83
CHAPTER ONE: INTRODUCTION
1.1 Background information
Snap bean, commonly known as French bean or green bean, is a strain of common bean (Phaseolus vulgaris L.) commonly grown in Kenya for export mainly to the European market (CIAT, 2006). Over the years, the crop has gained popularity in the domestic market, especially in the supermarkets. Nevertheless, the consumption of French beans locally has increased hence a rise in demand at the domestic markets (HCDA, 2016). Its green pods are harvested for fresh, frozen and for canning purposes. Snap bean varieties vary in pod shape (flat, cylindrical or oval shape), color (green, light green, yellow, or purple) and length (Musaana et al., 2011). The crop is grown by both large scale farmers and small scale farmers. Even so, its production is mainly dominated by rural small-scale farmers. Snap bean pod yield varies from 2 to 8 tonnes ha-1 among the smallholder’s farms compared to 14 t ha-1 for large-scale producers (Ndegwa, 2003). Depending on the total size of the farm, snap bean growers can be categorized as follows: small producers with less than 2.2 ha; medium scale producers with 2.2 to 4.4 ha; large scale producers with 4.4 to 44.0 ha; and plantations are those with more than 44.0 hectares (Mauch et al., 2006).
In the year 2009, snap bean was ranked first among horticultural export crops contributing to 20% of the total horticultural crop exports by Kenya. The total production was 30,000 metric tonnes valued at 4 billion shillings (HCDA, 2010). In contrast, in the year 2013 the total production of snap bean was 38,398 metric tonnes valued at Kshs 1.8 billion, consequently dropping to sixth place in value among the main vegetables, due mainly to challenges in meeting maximum residue limits. Despite the interceptions and rejections by the market of snap bean because of maximum residue levels (MRLs), the exports recovered from 22,553 MT in 2012 to 31,973 MT in 2013 (HCDA, 2013). This has been attributed to the integration of the traceability system in supply chains enabling exporters to monitor chemical use by farmers directly. Even though the French bean production has increased from 34,779 tons to 41,789 tons while the value has increased from Ksh 1.38 billion to Ksh 1.81billion representing 20 per cent and 31 per cent increase from 2015, the crop has also dropped to the eighth place in value among the main vegetables (HCDA, 2015). The leading counties were Kirinyaga, Machakos and Murang’a that accounted for 32, 20.7 and 13.5 per cent respectively of the countries value in 2016 (HCDA, 2016).
Snap bean has a potential to stimulate higher private sector investment in agro-processing and export, thus creating employment for young women and men (Lenne et al., 2005). It requires less energy to cook and is a rich source of micronutrients (iron and zinc) thus is important where there is high prevalence of iron and zinc deficiencies (Broughton et al., 2003).
Despite its importance, snap bean production in small holders’ farms is constrained by many biotic and abiotic stresses. In the tropics, pests and diseases present a major constraint to agricultural productivity of snap bean (Graham and Vance, 2003). In the whole world, yield losses caused by insect pests alone are estimated to vary from 35% to 100% annually (Sing et al., 2011). Key pests include aphids, thrips, whiteflies, caterpillars, nematodes and leafhoppers while diseases include bean rust, anthracnose, powdery mildew, angular leaf spot, common bacterial blight and common mosaic viruses (Kimani et al., 2004; Musaana et al., 2011). Therefore, farmers rely on costly pesticides to control pests and diseases thereby increasing the cost of production of snap bean (Nderitu et al., 2001: Musaana, 2002; Mwangi, 2008).
Low soil fertility is one of the major key challenges to the snap bean productivity in Kenya. Low nitrogen, potassium and calcium in the soils can cause bean yield loss equivalent to 744,900 metric tonnes in East Africa, because smallholder farms are usually cultivated continually without adequate replenishment of plant nutrients (Wortman et al.,1988).
Nitrogen is an important element in plant growth and in achieving high harvests. Nitrogen and phosphorus are identified as the major limiting nutrients for many cropping systems in Kenya (Kwambiah et al., 2003) and their application in form of inorganic and organic sources is essential to maximize and sustain snap bean yields (Hartemink et al., 2000). Inorganic sources of N and P are however not readily available to small-scale farmers (Smestad et al., 2002). It is therefore important for small holder farmers to use the available options to manage nitrogen and phosphorus in their fields. Therefore, chemical fertilizers are often considered a solution to the current nutrient deficiencies in the soils (Chemining’wa et al., 2004; Gentili et al., 2006). The high cost of inorganic fertilizers coupled with low returns and unreliable markets for agricultural produce have limited the use of fertilizers by the majority of smallholders in Kenya (Hassan et al., 1998). The common method of maintaining soil fertility is the application of farmyard manure, but its quality is usually low because of poor handling and poor quality feeds for livestock (Lekasi et al., 2003). In order to increase snap bean production, there is a need to consider an integrated approach to nutrient management which includes the use of affordable, easily accessible and environmentally friendly soil fertility management options.
1.2 Problem statement and justification
Low levels of nitrogen, potassium, organic carbon and micro-nutrients are a major constraint to rural small scale farmers in Embu County. Most of the soils in Embu County are deficient in nitrogen and phosphorous which are the key elements for crop growth and yield, therefore resulting in poor and low quality yield of snap bean (Wortman et al., 1998, Wangechi, 2009; Kamanu et al., 2012). Deterioration in soil fertility is as a result of smallholder farmers continually cultivating their lands without appropriate protection and amendments, hence leading to massive surface soil erosion and land degradation over time (Smaling, 1993).
Symbiotic nitrogen fixation by legumes plays an important role in sustaining crop production and maintaining the soil fertility. However, symbiotic nitrogen fixation is particularly sensitive to environmental stresses such as low levels of nitrogen, phosphorous and other nutrients in the soil therefore further constraining snap bean productivity (Serraj et al., 2004). Hence rural small scale farmers have to depend on the use of inorganic and organic fertilizers to be able to manage and supply the major nutrient deficiencies in their farms. Even though the use of inorganic fertilizers is recognized as the suitable way for rapid correction of nutrient deficiencies in the soils, its high cost limits its wide application by smallholder farmers in Embu County (Ibijben et al., 1996). As a result, small scale farmers use farmyard manure in their farms. The importance of farmyard manure is currently being recognized because of the high cost of commercial fertilizers and their associated long term adverse effects on soil chemical properties. Besides supplying macronutrients and micronutrients to the soil, (Negassa et al., 2001; Tirol-Padre et al., 2007), farmyard manure also improves the physico-chemical properties of the soil (Tirol-Padre et al., 2007). However, unless it is integrated with inorganic fertilizers, the use of farmyard manure alone may not fully satisfy crop nutrient demand, especially in the year of application (Patel et al., 2009). Animal manures are also useful in improving the efficiency of fertilizer recovery thereby resulting in higher crop yield (Gedam et al., 2008). Farmers in Embu County pay little attention to soil fertility management. They rarely apply organic fertilizers to their farms; however, they may use inorganic fertilizer but these are often not economically rationalized nor based on soil analysis (Wangechi et al., 2009; Kamanu et al., 2012). Since most of the small scale farmers do not carry out soil analysis, it is difficult for them to apply the appropriate rates and types of inorganic and organic fertilizers. Some studies have demonstrated that integrated nutrient management increases yield in snap bean as well as lowering the cost of production. This therefore calls for the need to identify fertilizer application regimes which enhance snap bean productivity and profitability.
1.3 Objectives of the study
The main objective of this study was to establish the appropriate nutrient management options for improving growth, yield and quality of snap bean in Embu County. The specific objectives of the study were:
1. To determine the effect of combining inorganic and organic fertilizers on the growth, yield and quality of snap bean.
2. To determine the cost effectiveness of various nutrient management options for snap bean production.
1.4 Hypotheses
1. A combination of inorganic and organic fertilizers improves growth, yield and quality of snap bean.
2. A combination of inorganic and organic fertilizers is more cost effective than application of inorganic or organic fertilizers alone.
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