African Journal of
Agricultural Research

  • Abbreviation: Afr. J. Agric. Res.
  • Language: English
  • ISSN: 1991-637X
  • DOI: 10.5897/AJAR
  • Start Year: 2006
  • Published Articles: 6854

Full Length Research Paper

Investigating viability of the premium influenced land agro-usage structure for production of African leafy vegetables in Vihiga and Jinja

Munialo S.
  • Munialo S.
  • Department of Plant Science and Crop Protection, Faculty of Agriculture, P. O. Box 30197-00100, University of Nairobi, Kenya.
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Akundabweni L. S. M
  • Akundabweni L. S. M
  • Department of Plant Science and Crop Protection, Faculty of Agriculture, P. O. Box 30197-00100, University of Nairobi, Kenya.
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Mburu J.
  • Mburu J.
  • Department of Agricultural Economics, Faculty of Agriculture, P. O. Box 30197-00100, University of Nairobi, Kenya.
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Namutebi A.
  • Namutebi A.
  • Department of Food Technology and Nutrition, School of Food Technology, Nutrition and Bio-systems Engineering, Makerere University, PO Box 7062, Kampala, Uganda.
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Joshua K.
  • Joshua K.
  • Department of Food Technology and Nutrition, School of Food Technology, Nutrition and Bio-systems Engineering, Makerere University, PO Box 7062, Kampala, Uganda.
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  •  Received: 01 December 2014
  •  Accepted: 01 April 2015
  •  Published: 02 April 2015

 ABSTRACT

Land subdivision has reduced land for agricultural production resulting in its intensive cultivation. This has lowered soil fertility which has contributed to reduction in the diversity of African Leafy Vegetables thus restricting the otherwise traditional dietary diversity that was once beneficial to smallholder farmers. As land continues to decline, there needs to be some impetus in place that can retain the diversity of African Leafy Vegetables. This study therefore recognized the need to niche the African Leafy Vegetables to a none-competing, specially constructed raised cropping bed referred to us the Premium Influenced Land Agro-usage structure (PILA). A study to investigate the viability of the PILA structure for production of vegetable crops was undertaken in Vihiga and Jinja. The objective of the study was to evaluate the benefits of the PILA structures. PILA structures were constructed on 20 smallholder farms in Vihiga and Jinja. Vegetable crops Solanum scabrum, Cleome gynandra, Amaranthus hybridus) and exotic vegetables (Daucas carota) were grown on these structures. The same procedure was done on farmers’ conventional plots (Flat beds). Analysis to compare the performance of vegetable crops between the PILA and Flat beds was done using Genstat. The net present value was used to assess the viability of the structure for long term use. Results indicated high significant differences (p≤0.001) in yield and height of vegetables crops grown on PILA and flat beds, (PILA yield (kg/ha) was 42254 versus 27772 for flat beds, PILA height in (cm) was 14.8 versus 10.8 for flat beds). Comparisons in vegetable performance between seasons showed better performance of vegetable crops in the Long Rains than the Short Rains seasons for both sites with significant difference (p=0.001) in yield (kg/ha) for the Long Rain (LR) was 36064 against 33962 for the Short Rain (SR), mean height (cm) for LR was 13 against 12.5 for SR, mean branching (score out of 3) for LR was 2.5 against 2.4 for SR. Also significant differences in vegetable performance were detected between Vihiga and Jinja in height and yield; mean yield (kg/ha) for Vihiga was 34962 and 36064 for Jinja, mean height (cm) for Vihiga was 12.8 and 16.6 for Jinja. The PILAs had a high net present value (KSH191390) compared to flats beds (KSH122087). Vegetable crops on PILA structure performed better than on Flat beds, the PILA structure can be promoted for production of vegetables in areas with small land sizes like the urban and peri-urban. However, there is need to increase the acceptability and adoption of the structure through awareness.

 

Key words: Raised bed planting, land size, premium land agro-usage structure, african leafy vegetables, dietary diversity.


 INTRODUCTION

Land subdivision as a result of population pressure has resulted in reduced land for agricultural production which has had an effect on soil fertility. Traditionally, farmers would restore soil fertility by leaving part of their land uncultivated for many years while new and more fertile land was cultivated for food production. The small land sizes have otherwise destabilized this traditional system of maintaining soil fertility (Amadalo et al., 2003).  For instance, the current land holdings on smallholder farms are approximately 0.4 ha which is usually considered to be below the FAO recommendation for subsistence food purposes of 1.4 ha / household (FAO, 2008). Consequently, long-duration natural fallows are no longer possible. The apparent implication of the low soil fertility status and reduced land holding is the decline in the abundance and distribution of phyto-diversity found on smallholder farms (Tittonell et al., 2005).

 

The declining quantity, distribution and consumption of edible phyto-diversity has led to reduction in the diversity of African leafy vegetables (ALV) grown on the smallholder farms thus restricting the otherwise traditional dietary diversity that was once beneficial to the locals (Vorster et al., 2008; Abukutsa-Onyango, 2008; Mitra and Pathak, 2008). Recent studies have shown that ALV’s such as Curcubita maxima, Amaranth spp., Cleome gynandra and Solanum nigram are mineral micro-nutrient (MiMi) richer than cereal crops such as maize and sorghum (Akundabweni et al., 2010). In fact, almost all the leafy vegetables are good sources of micronutrients including iron and calcium as well as vitamins A, B complex, C and E. For example, Amaranth contains a multiple of these nutrients compared to Brassicca oleracea (IPGRI, 2003; Abukutsa-Onyango, 2007). Some of the African leafy vegetables even contain micro-nutrients content higher than those found in their exotic counterparts (Steyn et al., 2001; Odhav et al., 2007; Nangula et al., 2010). These indicates that the consumption of these leafy vegetables has both nutritional, health and a potential role to play in the mitigation of ‘hidden hunger’ [Hidden hunger is a condition manifested in increased malnourished children and adults because of lack dietary diversity (Hughes, 2008)].

 

Unfortunately, because of intense cultivation of the small land holdings, these ALVs can easily be marginalized in favour of the major agronomic crops. For instance there is increased production of some staple crops like maize at the expense of vegetable crops resulting in low dietary diversity. Diets poor in leafy vegetables may lead to xerophthalmia (a form of blindness) associated with vitamin A deficiency. It is also recognised that a diet rich in energy but lacking other essential    components   can  lead  to  a   heart  disease, diabetes, cancer, and obesity (Frison et al., 2004). These conditions are no longer associated with affluence; they  are on the increase among poor people from urban and

rural areas in developing countries. A diverse diet offers nutritional buffers and there should be a key policy reform to combat this unhealthy trend (Johns and Sthapit, 2004). Since no approaches are possible in expanding the land resource, sustainable utilization of the limited land parcels for increased yield and dietary diversity is paramount (Mutiga et al., 2011).

 

Raised beds have been widely used in the production of commercial crops like rice, wheat and maize than vegetable crops. (Aquino, 1998; Hobbs and Gupta., 2003; Limon-Ortega et al.,2003,2006). Raised beds concentrate a large percentage of crops on a small piece of land thus increasing yield. Raised bed planting has also been shown to offer better weed control, water and fertilizer management, thus leading to the lower inputs of water and fertilizers and higher stress-resistance (Tripathi et al., 2005; Kong et al., 2010).  Additionally, raised beds create a micro-climate (Microclimate- In this context, micro-climate refers to creation of an internal warm climate by plants that makes plant mature fast) in the field of the growing crop that reduces crop lodging and disease incidences (Fahong et al., 2004).

 

Other studies have shown that raised-bed planting reduces seed mortality rates, increases water- and nitrogen (N)-use efficiency, and improves soil quality. In addition, less labour is required for irrigation and fertilizer is better managed relative to conventional flat planting (Limon-Ortega et al., 2000). This therefore represent the social-economic benefits likely to be derived from using raised beds for production of crops. Can raised beds be improvised to enable production of vegetable crops in areas with land as a scarce resource?

 

This study sought to investigate the viability of the premium influenced land agro-usage structure (PILA), a land use innovation for production of ALV. The PILA is an improvised raised bed to enable production of vegetable crop.


 MATERIALS AND METHODS

The study sites
 
The study sites were Jinja-Uganda and Vihiga-Kenya, as shown in Figure 1.
 
The study period
 
The study was done in the long and short rain of year 2011. The long rain season covered the months of April, May, June  and  July while season 2 was the short rain season covered the months of September, October November and December.
 
 
 
The experimental design
 
The treatment was the PILA structure. PI[1] Structures were established on 10 smallholder farms in Vihiga and the same number in Jinja (Figure 2 diagram 1). Each PILA was designed in three layer stair-case raised bed with each succeeding layer smaller than the preceding one. African Leafy Vegetables (Solanum scabrum, Cleome gynandra, Amaranthus hybridus) and exotic vegetables (Daucas carota) were planted on these beds. Weekly monitoring of the plots was done to determine their performance. The following agronomic appeal attributes were taken; vigour and robustness, plant height, branching and leaf density. Yield was also determined.
 
[1]PILA structure was the treatment factor. This is an improvised raised beds constructed in a special way. See explanation of how the structures were constructed in description 1.2.4.
 
 A similar procedure was done on the flat beds as shown in Figure 2 diagram 2. The Flat beds[1] were the farmers’ conventional way of planting vegetables. The measurements of PILA and flat beds were kept the same (21.3 m2). The plant spacing was also similar. However, the size of the Flat bed could not contain the seed density as had been applied on the PILA structures. The seed density used on PILA structure was 300 gm compared to 250 gm that was appliedo n the flat bed.
 
Construction of premium influenced land agro-usage structures
 
The beds were prepared using old sacks, posts and manure. Each bed measured 21.3 m2. Land preparation by clearing to remove unwanted trash was done on the specific site where the beds were to be situated. The initial procedure involved taking measurements of the bed using a tape measure and a rope. This was done by making a central spot for the bed. A diameter measuring 240 cm from the central spot was then marked. The bed was then divided into three micro-beds measuring 60 cm in diameter. Vertical posts of 40 cm long were put all round the first stair from the ground. Filling materials (a mixture of stones and plant material) were then put up to the 20 cm mark from the ground. The purpose of putting stones was to help in strengthening and prevent sinking of the soil in case of rain. The remaining 20 cm up was filled with a mixture of soil and manure. The second stair case was constructed by erecting posts up to the 60cm length from the ground. Filling materials were put to 40 cm mark, a mixture of soil and manure was then put in the remaining 20cm length. The same procedure was repeated for the third and fourth stair cases. Posts were used to provide support. Sheeting of harvesting sacks was then put round to help in retaining the soil and control soil erosion in the case of rainfall.
 
Determination of costs and benefits of the PILA structures and flat bed
 
The costs for production and the corresponding revenue of vegetable crops contained in the PILA structures and flat beds were determined. The annual crop net benefits were computed by taking the total revenue less total variable costs as in the formula:
 
GMy=TRy-TCy
 
Where GM was the gross margin, TRy was the total revenue, TC total costs and y a selected vegetable crop. The net present values of vegetable crops were then calculated for a period of 30 years at the rate of 12%. The 12% was the average rate of inflation for the past 10 year according to the World Bank Data (Appendix 3). Assumption made included; the rate of inflation of 12% would remain constant for the next 30 years, the 30 years period was the time that a person could be actively involved in farming, the cost of constructing the premium influenced land agro-usage structures would be incurred in the first year and after every five years, the costs of the flat beds would be the same throughout the farming period.
 
To compute the NPVs of the PILA structures, the NPVs of vegetable crops growing on the premium influenced land agro-usage structures were summed as in the following formula;
 
NVPpl=NPVi+NPVj+…….NPVz
 
Where NPVpl was the net present value of the PILA Structures, while NPVi, NPVj and NPVz were the net present values of various vegetable crops grown on the PPILA structures. The same procedure was repeated with the Flat cropping beds.  A comparison of the NPVs of the PILA structures and flat cropping beds was done to determine the most viable cropping bed.
 
The NPV or discounted cash flow method was used as it is a preferred method for evaluating the economic worth of an investment, because it considers the time value of the entire stream of net cash flows over the life of the investment (Casler et al., 1993).
 
Data analysis
 
Data   analysis  was  done  using  Genstat  version 14  and  excel. Results were presented in table and graphs.
 
[1]The Flat beds were the control plots. These were the farmers conventional planting beds where farmers ploughed long rows and planted crops.


 RESULTS

Seasonal variations in the means of the agronomic appeal attributes of selected vegetable crops produced on the PILA Structures
 
There was a high significant difference (P≤0.001) in vegetable performance between the long rain and short rain seasons in the means of the following agronomic appeal attributes; Yield and  height, as shown in Tables 1 and 2. A significant difference of (P=0.001) was observed in the following agronomic indicators; branching and disease incidences in both Vihiga and Jinja. In Jinja, vegetable crops had higher yields, longer height, better leaf density, low disease prevalence than in Vihiga. Generally vegetable crops performed better in the long rain season as compared to the short rain season in both Vihiga and Jinja (Appendix 2).
 
 
 
Differences in the means of the agronomic indicators of selected vegetables grown on PILA structures and flat beds. There was a high significant difference (P≤0.001) in vegetable crops grown on PILA structures and flat beds in the following agronomic appeal attributes; yield and height. A low significant differene was oberved for leaf density, branching and disease prevalence as shown in Tables 3 and 4. 
 
 
 
Generally vegetable crops grown on PILA structures performed better than the ones that were grown on flat beds (Figure 3). Notice the effective use of space in the PILA structure compared to flat beds. 
 
 
Variations in agronomic appeal attributes of selected vegetable crops grown on PILA Structures in Jinja and Vihiga
 
There was a high significant difference in yield and height (P≤0.001) of vegetables crops grown in Jinja compared to the ones that were grown in Vihiga as shown in Table 2. The difference in the following crop indicators was however significantly lower; leaf density (P=0.004), branching (P=0.004) and disease prevalence (P=0.070) as shown in Table 5. Generally, vegetable crops grown in Jinja showed a better performance compared to ones that were grown in Vihiga. More analysis is as shown in Appendix 2.
 
 
The germination percent of vegetable crops on PILA and flat beds
 
The germination percent  of vegetable crops growing on PILA was higher than on Flats beds except for S. Scabru (Figure 4).
 
 
Analysis of the viability of PILA Structures versus flat beds using NPV method
 
There was a high significant difference (P≤0.001) in the mean Net NPV of the PILA structures and flat beds as shown in Table 6. More analysis is given on Appendix 3 and 4.
 


 DISCUSSION

Seasonal effect on vegetable crop performance grown on PILA structures
 
There was a difference in crop performance between the short and long rain seasons  across  all  the  two  sites  of studies (Vihiga and Jinja). The long rain season indicated better crop performance compared to the short rain season mostly in the yield. The difference in yield were likely caused by a variation in the amount of rainfall. The long rain season normally receive high amounts of rainfall compared to the short rain season (Okoola et al., 2008). High amount of rainfall positively interacts with soil nutrients to give a high crop yield. Differences in seasonal vegetable production have also been reported in cowpea (V. unguiculata) as in a study by Chesney et al. (2010) and Kimithi et al. (2009) also found that the yield of chick pea was high in the long rain period as compared to the short rain period.
 
Difference in the performance of selected vegetables crops grown on premium influenced land agro-usage structures between Jinja and Vihiga
 
There was a high significant difference in the performance of vegetables grown on PILA structures in both Vihiga and Jinja in yield and height (Table 5). There were however small significant differences in the leaf density, branching and disease prevalence in the two study sites. This would have been as a result of differences in soil properties and climatic conditions across the two study sites. Even though the two study sites are found in the Lake Victoria  Basin,  differences  in climatic and soil properties are noticeable. Similar results on differences in crop performance as a result of variations in soil conditions in the Lake Victoria Basin, have been documented by Fungo et al. (2011).
 
 
Performance of vegetable crops grown on PILA structures compared to flat bed
 
There was a high significant difference in vegetable crop performance between the PILA structures and flat beds. Vegetable crops grown on PILA Structures performed better in the following agronomic appeal attributes; yield, height, leaf density, branching and disease prevalence compared to the ones that were grown on flat beds. The performance of vegetable crops on PILA Structures could have been attributed to better utilization of space, solar energy, water and nutrients.
 
Vegetable crops grown on PILA Structures had a higher germination percentage, were densely packed compared to the ones on Flat beds. Although the plot sizes and spacing was kept the same for PILA and flat beds, the seed densities varied. The design of the PILA structures permitted a special arrangement of the rows resulting in a higher seed density than on the flat bed. This arrangement could not be replicated on the Flat beds. This would have caused the vegetable crops grown on the PILA structures to have more yield than on the flat beds. Notice the effective utilization of space on the PILA beds as shown in Figure 3. The vegetable crops on PILA grew taller than on the Flat beds. But whether this was as a result of competition or sunlight need be investigated.  
 
 
 
Creation of an internal micro-climate also helped in reducing disease incidences and promoting growth as well as ensuring better nutrient use. Similar findings on better performance of crops grown on raised beds have been recorded by Wang et al. (2011) in a study on morphological and yield responses of winter wheat (Triticum aestivum) to raised bed planting. Other studies by Singh et al. (2010) and Fahong’ et al. (2004) have recorded similar findings.
 
Comparison of the cost and benefits of the PILA Structures and flat beds
 
The NPV of the PILA structures were more than for the flats bed. This could be attributed to better crop performance. The total revenue that was obtained from vegetable crops contained on PILA Structures was higher than on flat beds in year 1 as shown in Appendix 1. This is because costs used for production of vegetable crops grown on flat beds were low compared to PILA Structures. Costs of production for vegetable crops contained on PILA structures included costs of construction (purchase of sheeting materials and rope). These costs were not incurred in making flat beds. As the years progressed as shown in Appendix 1, the revenue obtained from vegetable crops grown on PILA structures became higher and continuously increased than the revenue that was obtained from vegetable crops that were grown on flat beds. This made the net present value that was obtained from vegetables crops grown on PILAStructures to be higher compared to flat beds.  


 CONCLUSION

Vegetable crops grown on the PILA structures performed better compared to the ones that were grown on the flat beds. This was shown in the high yield, reduced disease incidences and the high net present value of the vegetables crops that were produced on PILA Structures in comparison to the Flat beds. PILA structures as an innovation or technology could be suitable for home vegetable growing preferably under high family land population pressure and/or less tillable land. Because of its micro-climate, a PILA Structure planting is known for uniform special plant arrangement and therefore good seedling growth and plant produce of an attractive marketable appearance, that is, (premium sale value). Its relevance is thus as follows: (a) Convenient to fit the Premium PILA structures into a main household compound setting; (b) None-competitive in space to an already overcrowded arable piece of land; (c) Within reach for constant care and protection of a high premium value crop.


 CONFLICT OF INTEREST

The authors have not declared any conflict of interest.



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 APPENDIX

 
 
 




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