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Traditional soil fertility management strategies: Do they conform to recommendations in organic farming? A case study of the smallholder farmers of the Central Rift Valley Province of Kenya

Richard N. Onwonga1, Bernhard Freyer2 and Joyce J. Lelei3

1Department of Land Resource Management and Agricultural Technology, University of Nairobi, P.O. Box 30197 – 00100 Nairobi, Kenya, Email: ronwonga@yahoo.com
2
Division of Organic Farming, University of Natural Resources and Applied Life Sciences (BOKU), Gregor MendelStra 33, A-1180 Wien, Austria,
3Department of Crop, Horticulture and Soils, Egerton University, P.O. Box 536, Njoro, Kenya.

Abstract

The low input nature of organic farming (OF) is often likened to the traditional soil fertility management practices (TSFMP) of smallholder farming systems in developing countries. There are however no concrete studies to support this assertion. The present study aims at comparing the TSFM practices with recommendations in OF specifically recycling of organic wastes of crop and animal origin and maintenance of long-term fertility of the soil. These were monitored through resource flow mapping and calculation of nitrogen balances, at crop production level, using NUTMON toolbox. The study was conducted in Gilgil, Lare and Molo divisions of the Rift Valley Province of Kenya.

Crop residues and manure were the principal organic resources recycled within the smallholder farming systems. The calculated N balances were negative; -70.9, -80.2 and -99.8 kg/ha/year for Gilgil, Lare and Molo, respectively. The organic resources recycled within the farm were therefore insufficient to sustain soil fertility. This is contrary to recommendations in OF, in which the long-term soil fertility should be maintained and/or enhanced. There were however opportunities; composting, biomass transfer and improved use of external and internal farm boundaries, enhanced livestock manure handling and integration of agroforestry trees, for improving the TSFMP to expectations of OF.

Key words

IFOAM; low input agriculture; nutrient monitoring; organic wastes; resource flow mapping

Introduction

The low input nature of organic farming (OF) is often likened to the traditional soil fertility management practices (TSFMP) of developing countries. OF, as defined by the International Federation of Organic Agriculture Movements (IFOAM), includes all agricultural systems that promote environmentally, socially and economically sound production of food and fibres. These systems take soil fertility as key to successful production. Soil fertility, the ability of a soil to supply nutrients to crops, is fundamental in determining the productivity of all farming systems (Swift and Palm 2000).

Some of the technologies for soil fertility management acceptable to organic farmers are deeply rooted in the TSFMP in developing countries. OF is however regulated and has a strict set of basic standards against which it is practised (IFOAM 2002).

This study compared recycling of organic wastes, of crop and animal origin, and maintenance of long-term fertility of soil in the TSFMP with OF systems. The findings will be valuable in informing policy, research and extension with a view of enhancing and/or maintaining the standards of TSFM to those of OF.

Materials and Methods

Study site

The study was conducted in three administrative divisions; Gilgil, Molo and Lare, of Nakuru District situated in the central Rift Valley highlands of Kenya, 170 km North West of Nairobi.

Research approach and Methods

Introduction to community and selection of farmers In the first meeting with the respective communities, the researcher introduced himself, explained the objectives of the study and proposed ways of working with the community. Twelve representative farmers were selected for detailed analysis of the TSFMP. The study was carried out during the long and short rain seasons of 2006 and 2007.

Analysis of the farmers’ TSFMP Two sets of individual interviews were conducted for the selected farmers. The questionnaires served both to get more quantitative and qualitative data for a better understanding of the TSFMP. Resource flow mapping (Defoer and Place 2000) and calculation of nutrient balances, at crop production level, using farm NUTMON (De Jager et al. 2001) were the tools used in this study. The NUTMON toolbox is based on the description and quantitative estimation of the main inputs and outputs of nutrients in land use systems. The crop production system was preferred, as the unit of analysis, because of its high nutrient turnover. N, a nutrient with highest dynamic changes, lost through several pathways (De Jager et al. 2001) and most frequently limiting in tropical land use systems, was determined.

Concluding village meetings The results on the organic resource flows and nutrient balances were summarized on charts and shared with farmers. The implications of the research findings and subsequent joint formulation of better soil management strategies, taking into account the research objective, were discussed with the respective communities.

Statistical Analysis

The data output from NUTMON was exported to SPSS for further statistical analysis. The Student’s t-tests were used to evaluate significant differences between variable means.

Results and Discussion

Recycling of organic resources of crop and animal origin within the smallholder farming systems

Sources of organic resources

Crop residues, weeds, agroforestry tree prunnings, household waste and livestock manure were the principal sources of organic resources used on farm. Maize and common beans grown singly or as intercrops with common beans were the main sources of crop residues in addition to napier grass.

Manure production There were seven different types of livestock kept on the smallholder farms with cattle, sheep, goats, and chicken being important in terms of manure production. At all sites, the predominant livestock kept were cattle and local chicken. Donkeys, ducks and rabbits were least dominant across study sites. The number of livestock expressed in tropical livestock units (TLUs)1, was significantly higher in Gilgil (8.02) than Molo (4.98) which was not significantly different from Lare (4.63).

Organic resource flows within the farming system

The most important components of the farming systems in terms of organic resource flows were; crops, livestock and the household production systems (Figure 1).

Figure 1. Sample organic resource flow diagram

There were marked similarities in the pattern of organic resource flows (Figure 1) and uses across sites. Notable differences were the import of manure through external livestock grazing in Gilgil by all farmers, tree prunings and leaf litter use by 25% of the farmers in Molo and acquisition of external crop residues in Lare by 50% of the farmers.

The organic resource flows from crop fields to livestock included crop residues (maize and beans stover), weeds and napier grass. Flows from livestock to crops and household were manure and milk, respectively. The flows to household were mainly the crop edible parts (e.g. irish potato tubers, maize and bean grain, vegetables and fruits) and livestock products (e.g. milk and eggs). Food crops were either consumed once harvested or were temporarily stored for later consumption by the household or for limited sale.

The use of on farm organic resources ensured closed flows of materials and organic matter within the farm (Palm et al. 1997). Since most nutrients flowed from food crops to livestock in the form of crop residues and weeds and back to the crop as manure, the integration of livestock was key to maintaining this flow (Huxley 1999). Some of the nitrogen ingested by ruminants appears in faeces and urine. Much of this nitrogen, apart from volatile losses, could therefore be available for return to soil (Lekasi et al. 2001).

The observed differences in organic resource flows are attributable to variations in biophysical and socio-economic characteristics of the study sites, which influenced the farmers’ decision-making on organic resources use. Each soil fertility management strategy fits, but also needs, specific conditions and farmers adopt those practices that best fit their conditions (Defoer and Budelman 2000).

N balances at crop production level

The annual N balances, at crop production level, were calculated for the common crops in addition to fallow for each site (Table 1, 2 and 3). Ranking of N balances showed that napier grass and banana production units had highly negative N balances compared to the other crops. The cropping activities were thus nutrient mining to the detriment of long-term fertility of the soil.

The highly negative N balances are attributable to crop harvests of grain, removal of crop residues and sale without adequate replenishment of the mined nutrients. The contribution of N through biological fixation (IN4), across study sites, was low (Tables 1, 2 and 3) because the legume involved, common bean, is a poor nitrogen fixer. Furthermore legume stover was removed at harvest which results in a significant removal of N from the system (Esilaba et al. 2005).

Table 1 Mean annual N flows and balances at crop production level for Gilgil (kg/ha)

Crop activities

IN2a

IN2b

IN3

IN4

OUT1

OUT2a

OUT2b

OUT3

OUT4

OUT5

Balance

Beans

7

0

1.9

18

-8

-13.7

0

-15.8

-3.8

-1.9

-16.4

Fallow

2.2

17.7

1.7

2.4

0

0

-38.8

-20.5

-5.6

-1.5

-42.4

Maize

7

0

2.6

3.1

-16.1

-4

0

-29.8

-8

-11.8

-57.1

Maize/beans

11

0

2

21.8

-30.4

-28

0

-25.7

-5.8

-9.8

-64.9

Cabbages

9.1

0

2.1

21.8

-69.9

-13.6

0

-22.3

-5.5

-16.1

-94.3

Maize/potatoes

9.7

0

2.5

3.3

-40.4

-5.3

0

-21.5

-5.1

-8.3

-65

Napier grass

18.9

0

3.3

2.7

0

-169.4

0

-38.6

-8.2

-2.4

-193.7

Bananas

9.1

0

2.1

21.8

-69.9

-13.6

0

-22.3

-5.5

-16.1

-94.3

Potatoes

10

0

2.3

2.9

-48.6

-3.6

0

-23.4

-5.4

-4.7

-70.5

Tomatoes

14

0

2.1

3

-18.5

-0.4

0

-23.3

-6

-7.5

-36.6

Kales

7.6

9.8

3.5

3.3

-2.1

-0.5

-22.7

-30.8

-8.3

-4.5

-44.7

Total

9.6

2.5

2.4

9.5

-27.6

-22.9

-5.6

-24.9

-6.1

-7.7

-70.9

Legend; IN2a - imported organic fertilizer and feeds, IN2b - Manure imported from external grazing, IN3 - Wet and dry deposition, IN4 - Biological N fixation, OUT1 - crop products, OUT2a - Exported crop residues and manure, OUT2b –Excretion of manure outside the farm, OUT3 – Leaching, OUT4 - Gaseous losses and OUT5 - Soil erosion.

Table 2 Mean annual N flows and balances at crop production level for Lare (kg/ha)

Crop activities

IN2a

IN2b

IN3

IN4

OUT1

OUT2a

OUT2b

OUT3

OUT4

OUT5

Balance

Beans

5.8

0

2.2

18.9

-9

-7

0

-23.2

-6.9

-6.4

-25.5

Fallow

0

18.4

1.1

4

0

0

-34.7

-15

-4.4

-0.8

-31.3

Maize

10.4

0

2.1

2

-19.1

-13.4

0

-20.5

-6.1

-4.3

-48.7

Maize/beans

8.8

0

2.8

22.7

-30.4

-14.7

0

-22.5

-6.7

-11.4

-51.4

Cabbages

13.6

0

3.6

24.1

-63.2

-17.2

0

-34.9

-10.3

-4.9

-89.1

Maize/potatoes

8.8

0

2.8

4

-41.7

-6.1

0

-24.4

-7.2

-7.7

-71.5

Napier grass

19.4

0

4.1

4

0

-283.1

0

-49.9

-14.7

-2.6

-322.8

Bananas

13.6

0

3.6

24.1

-63.2

-17.2

0

-34.9

-10.3

-4.9

-89.1

Potatoes

12.8

0

2.2

3.3

-50.2

0

0

-20.8

-6.2

-4.7

-63.6

Tomatoes

9

0

2.6

5

-18.5

-7

0

-34.1

-10.1

-4.1

-57.1

Kales

7.1

16.8

3.8

3.3

-2.1

-2.3

-6

-37.1

-11

-4.2

-31.7

Total

9.9

3.2

2.8

10.5

-27.0

-33.5

-3.7

-28.8

-8.5

-5.1

-80.2

For legend see under Table 1

Table 3 Mean annual N flows and balances at crop production level for Molo (kg/ha)

Crop activities

IN2a

IN2b

IN3

IN4

OUT1

OUT2a

OUT2b

OUT3

OUT4

OUT5

Balance

Beans

11.2

0

2

17.1

-10.8

-11.3

0

-25.9

-11.2

-26.4

-55.3

Fallow

0

33.7

1.3

4.3

0

0

-29.1

-18.5

-8.1

-2.2

-18.5

Maize

0.3

0

3

3.3

-23.5

-2.6

0

-29.9

-12.8

-10.9

-73

Maize/beans

4.2

0

3.7

18.9

-33.3

-20.9

0

-36.3

-17.2

-8.3

-89.1

Cabbages

16.1

0

3.6

19.7

-77.8

-4.6

0

-28.7

-12.3

-6.2

-90.2

Maize/potatoes

5.5

0

4

3

-45.4

-6.7

0

-30

-13.1

-10.3

-93

Napier grass

18.2

0

4.6

3.3

0

-275.4

0

-59.2

-25.7

-3.2

-337.3

Bananas

16.1

0

3.6

19.7

-77.8

-4.6

0

-28.7

-12.3

-6.2

-90.2

Potatoes

16.5

0

3.4

2.3

-71.4

0

0

-38.9

-19.9

-6.4

-114.5

Tomatoes

7.7

0

2.9

4.9

-22.8

-0.3

0

-35.9

-15.6

-11.3

-70.5

Kales

4.6

6.3

4

3.3

-4.5

0

-4.9

-44.7

-19.5

-11.2

-66.4

Total

9.1

3.6

3.3

9.1

-33.4

-29.7

-3.1

-34.2

-15.2

-9.3

-99.8

For legend see under Table 1

In spite of the high amount of manure added (IN 2b) to napier grass at all sites, the intensity of cutting offsets the additions. According to De Jager et al. (1998), a large addition of nutrients often stimulates an improved biomass production, but this in turn extracts considerable quantities of nutrients from the soil. The high N depletion in banana production units was mainly due to banana harvests for home consumption and stems for livestock feeding without adequate replenishment of the nutrients removed.

The total nutrient balances at the crop production level were more highly negative in Molo and Lare than Gilgil. This is attributable to access to a nearby canning factory and main highway road terminus (external components) for Lare and Molo respectively. These acted as the gateway through which farm products (mainly potatoes, tomatoes and kales) were sold and consequently loss of nutrients. A study on nutrient flows and stocks in smallholder-diversified farms in Kenya indicated that a high market orientation was correlated with more negative N and K balances (Esilaba et al. 2005).

Do the TSFMP conform to recommendations in organic farming?

It is evident that the recycling of organic wastes of crop and animal origin per se, within the smallholder farming systems, conformed to recommendations in OF. On the maintenance and increasing long-term fertility of the soil, as determined from the N balances at the crop production level, the TSFMP practices were not in conformity with recommendations in OF. OF practices aim to minimize loss of nutrients from the system, and maximize the efficiency of nutrient recycling within the farm. The large negative N balances suggest that the organic residues being recycled and/or their management were insufficient in counterbalancing nutrient removal from the cropping system. The crop production system was therefore relying on utilising soil nutrient reserves that, in the long-term, would not be sustainable.

Opportunities for improvement There were nonetheless opportunities; composting, biomass transfer and use of improved external and internal farm boundaries, livestock manure handling and management, integration of agroforestry trees and shrubs and a well-designed crop rotation system, for improving the efficiency of nutrient recycling within the smallholder farming systems and accordingly increase short-term productivity as well as long-term sustainability. This would raise the standards of the TSFMP to levels comparable to those of OF.

Policy, research and extension The research had implications on (i) policy, in which a policy on improving TSFMP among the smallholder farmers to the standards of OF should be put in place, (ii) research, the most important research implication arising from the study was the issue of sustainable soil fertility management in the smallholder farming systems which should be addressed and (iii) extension, the priority for extension is to work with farmers to address the poor manure handling and identify the locally available unexploited organic resources. This is in addition to promotion of a diversity of legume crop cultivation tailored to an appropriate crop rotation system.

Acknowledgement

This study was made possible through funding from the sterreichischer Austauschdienst (AD). Gratitude to all the farmers who participated in the research and the Ministry of Agriculture extension staff; Jane Bisera, Mary Kiiru, Joseph Gathuruku and Charles Kiarie for organizing community meetings and assiduously assisting in data collection.

References

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Defoer T and Place F (2000). Mixed farming in western Kenya. In Managing Soil Fertility in the Tropics. A Resource Guide for participatory learning and action research. Eds T Defoer and A Budelman. Royal Tropical Institute, Amsterdam, The Netherlands

De Jager A, Nandwa SM and Okoth PF (1998). Monitoring nutrient flows and economic performance in African farming systems (NUTMON). I. Concepts and methods. Agriculture, Ecosystems and Environment 71 (1-3), 37-48.

De Jager A, Onduru D, Van Wijk MS, Vlaming J and Gachini, GN (2001). Assessing sustainability of low-external-input farm management systems with the nutrient monitoring approach: a case study in Kenya. Agricultural Systems 69, 99-118.

Esilaba AO Nyende P, Nalukenge G, Byalebeka JB, Delve RJ and Ssali H (2005). Resource flows and nutrient balances for crop and animal production in smallholder farming systems in eastern Uganda. Agriculture, Ecosystems and Environment 109, 192–201.

Huxley P (1999). Tropical agroforestry. Blackwell Science, Oxford, United Kingdom.

IFOAM (2002). IFOAM training manual for organic agriculture in the tropics. Tholey-Theley, German.

Lekasi JK, Tanner JC, Kimani SK and Harris PJC (2001). Managing manure to sustain smallholder livelihoods in East African Highlands. HYDRA Publications, Kenilworth, UK

Palm CA, Myers RJK and Nandwa SM (1997). Combined use of organic and inorganic nutrient sources for soil fertility maintenance and replenishment. p. 193-217. In Replenishing Soil fertility in Africa. Eds RJ Buresh, PA Sanchez and F Calhoon. SSSA Special Publication 51, Madison, Wisonsin.

Swift MJ and Palm CA (2000). Soil fertility as an ecosystem concept: A paradigm lost or regained? In Accomplishments and changing paradigm towards the 21st Century.

1 A standard animal with live weight of 250 kg is called TLU (Defoer et al. 2000).

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