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R. M. A. ONYANGO et.al. 3

EVALUATION OF ORGANIC AND INORGANIC FERTILISERS FOR SMALL HOLDER MAIZE PRODUCTION IN NORTH RIFT KENYA

ONYANGO, R. M. A., T. J. MWANGI, W. W. KIIYA, M. K. KAMIDI and M. W. WANYONYI

Kenya Agricultural Research Institute (KARI), National Agricultural Research Centre (NARC) P. O. Box 450, Kitale, Kenya

ABSTRACT The aim of the study was to educate farmers through demonstrations and field visits on the importance of soil fertility in crop production with special emphasis on maize. Farmers were exposed to a range of locally available organic materials for soil fertility improvement. A multidisplinary team of researchers, farmers and extension officers were involved in the trials. Demonstrations were held on methods of making high quality compost and also collection and preservation of farm yard manure (FYM). On-farm trials using organic fertilisers and in combination with inorganic fertiliser were compared to determine their effects on maize yield. Soil samples collected in the farms indicated phosphorus and nitrogen deficiencies. Organic fertilisers were high in pH, available P and organic carbon. The highest rates of compost or FYM (10 tha-1) gave yields that were significantly higher than control (P < 0.05). Where mixtures of organic and inorganic amendments on half/half basis were used, maize yields were not significantly (P > 0.05) different from recommended fertiliser (60 P2O5 and 60 N kg ha-1) plots. This trend was observed in the second and third years. Combining organic and inorganic fertilisers is the best option of realising high yields in the study area.

Key words: Soil fertility, small holder, organic/inorganic fertilisers

INTRODUCTION Low soil fertility, particularly N and P deficiencies, is one of the major biophysical constraints affecting agriculture in Sub-Saharan Africa (Smaling, 1993; Wang`ati and Kebaara, 1993; Mokwunye et al., 1996). According to Sanchez and Palm (1996) soil fertility depletion in smallholder farms is the fundamental biophysical root cause of declining per capita food production in the region, and its replenishment should be considered as an investment in natural resource capital (soil nutrients).

Continuous cropping, removal of field crop residues for feeding ruminants and overgrazing between cropping seasons with little or no external inputs, have reduced the productive capacity of arable lands and threatened the sustainability of food production systems not only in the densely populated humid and subhumid highlands of East Africa (Smaling et al., 1992; Hudgens,1996) but throughout the Sub-

Saharan Africa (Stoorvogel et al 1993; Sanchez et al., 1997. Traditional mechanisms for maintaining soil fertility are no longer feasible (Hudgens, 1996; Sanches et al., 1997). At the same time, high input and transport costs for agrochemicals make the use of inorganic fertilisers on staple food crops uneconomical for most smallholder farmers (Kamasho et al., 1992; Heisey and Mwangi, 1996; Sanches et al., 1997; and Bashir et al., 1997). Traditional approaches for soil fertility management range from recurring fertiliser applications to low external input agriculture based on organic sources of nutrients (Sanchez et al., 1997, Bashir et al., 1997).

Research to date has mainly compared inorganic verses organic sources of N and P with little consideration of nutrient content of the organic sources. N and P are the most deficient nutrients for maize production in the high and medium altitude zones of Kenya (Smaling, 1993; Smaling et al., 1992). The quantitative interaction between organic and inorganic sources of N is essentially a new

Evaluation of organic and inorganic fertilisers for small holder maize production 4 4

subject of research in the tropics (Palm et al., 1997). Sanchez et al., (1997) suggested that soil N should be replenished in the tropics using systems that add N inputs in situ in consistency with the constraints of the farmer. The recommendations coming out were usually too broad to cater for specific sub-agro ecological zones (KARI, 1995), and were based mainly on trials oriented towards the interest of large scale farmers (Kamasho et al., 1992). Long term experiments in Africa provide indirect evidence in support of combined organic and inorganic approach to replenishing N and C reserve. Kapkiyai (1996) reported a 29% loss of total soil N (1.06 t N ha-1 in top 15 cm) when maize and beans were grown in rotation for 18 years without nutrient inputs and with crop residues removal in Kabete, Kenya. The same loss was recorded in plots with the recommended fertiliser applications with no residues returned. However, when fertiliser and manures were added and maize stover retained the decline in total N was reduced by half.

The exclusive use of organic inputs as external nutrient sources has been advocated as a logical alternative to expensive fertilisers in Africa (Reinjitjes et al., 1992). One of the main arguments against their use is their low nutrient concentration in comparison with inorganic fertilisers (Sanchez et al., 1997). In particular they have very low P content (Palm et al., 1997). The application of organic materials will therefore be insufficient to overcome soil P deficiency in the Kenyan highlands. The combination of small amounts of inorganic P fertiliser with farmer-available organic materials offers a strategy to meet the P requirements of crops while maximising the use of costly purchased P (Smaling et al., 1992; Murwira et al., 1995). This formulation may lead to realistic recommendations which will take into account the farmers’ cropping systems, management practises and capital constraints (Jonga, et al., 1997, Benson et al., 1997,). Organic fertilisers have one major advantage in that they contain all essential nutrients plus carbon, the source of energy for soil biota that regulates nutrient cycling (Sanchez et al., 1997).

In a survey carried out in Cherangani division, Trans-Nzoia district, Mwania et al., (1989) found that only one third of sample farmers topdressed maize with N. A broader survey throughout Kenya by the Maize Data Base Project (MDBP) conducted in 1992-93 confirmed the same trend in the other districts (Onyango, 1997). The report indicated high to medium basal fertiliser use in Trans-Nzoia, Uasin Gishu and Elgeyo Marakwet districts and low use in West Pokot district. About 87 and 76 % of farmers in Trans-Nzoia and Uasin Gishu top dress maize respectively. There is little or no topdressing in Marakwet and West Pokot districts. Maintenance of soil fertility becomes even more important as pressure on agricultural land increases (Onyango, 1997; Bashir et al., 1997; Sanchez, 1997). The experience of using organic fertilisers may not be very different from the neighbouring Tanzania. Kamasho et al., (1992), reported that 40% of small holder farmers in Southern highlands of Tanzania used organic materials for soil improvement without proper guidelines or recommendations. Manure was either collected and applied daily or heaped in piles and spread in the field when dry. Bulkiness, limited availability, and lack of knowledge among farmers about preparing and using compost and manure were some of the major limitations (ASSP, 1988, 1992).

Towards the end of 1994, the Soil Management Project funded by the Rockefeller Foundation was launched at NARC-Kitale with the sole aim of identifying soil fertility related issues affecting food productivity in resource poor farmers fields, and at the same time initiate research to address the problem. Emphasis was on the use of locally available agricultural organic materials such as FYM and adoption of traditional cropping systems that would replenish soil fertility. Participatory rural appraisal (PRA) tools were used as a tool for problem diagnosis. Soil fertility, though not ranked first in farmer priority list, was a problem throughout the four districts covered by the NARC-Kitale mandate. The broad objectives of the study were to: 1). educate farmers on collection, and storage of FYM, 2). demonstrate to farmers through on farm trials


how to use composts and FYM in maize production by, (i) evaluating the effect of FYM and compost on maize yields, (ii) comparing the effect of organic fertilisers and inorganic fertilisers on maize yields and, (iii) determining the effect of combining FYM or compost with inorganic fertiliser on yield of maize.

MATERIALS AND METHODS Site description of the farming system. Researcher extension farmer managed trials were conducted among five communities in Trans-Nzoia (Matunda and Weonia), Uasin Gishu (Chobosta), West Pokot (Cheptuya) and Keiyo (Anin) districts. The rainfall ranges from 900 - 1200 mm per year and the soils are predominantly Ferralsols. The farms are representative of maize-based cropping systems of the mid to highland areas (1000-1700 m asl) of northern Rift Valley, Kenya. Farm sizes vary between 0.2 to 5 ha. Most households are engaged in crop production and small scale dairying. A variety of crops are grown both as food and cash crop, and most farmers own indigenous animals viz poultry, cows, sheep and goats.

Problem identification and formulation of treatments. At least 200 small holder resource poor farmers with less than 2 hectares of land, were identified under the guidance of local extension officers as having severe soil fertility problems. This was also confirmed through PRA exercises conducted by a multidisciplinary team of officers from KARI, Ministry of Agriculture and Rural Development, NGO’s, farmers and their key informants. Through meetings and workshops, the entire team interracted with farmers to list and prioritise their problems. During these discussions, causes of low crop yields and potential solutions for increasing yields were identified. Maize was given special emphasis among the crops grown due to its importance as a staple food crop. A basket of choices was discussed for soil fertility improvement. Use of compost manures, FYM and inorganic fertilisers alone or in combination and applied at different rates was selected for the trials. Prior to the experimentation, extension

officers and farmers were trained on how to prepare compost manures. Officers were then able to carry out demonstrations on farmers fields in their respective areas. The FYM was collected and stored for on-farm investigations. Follow up visits were made to assist the farmers with the composting process and to assess their appreciation of the practice. After demarcating the area for the trials, composite soil samples (at 0-15 cm and 15-30 cm) were taken at each farm and analysed for pH, N, P, K, Mg, Ca and organic carbon to determine the initial soil nutrient status. The analytical procedure used for determination of pH, organic carbon and all the elements are as described by Page (1982).

Experimental layout. The on farm trials were started in 1995 at 3 sites (Matunda, Chobosta and Anin). Two additional sites were initiated at Cheptuya and Weonia in 1996 and 1997, respectively. Each community was responsible for identifying those farmers who would participate in the trial. Their interest and involvement from problem identification, implementation, monitoring and evaluation helped in determining their perceptions and overal adoption potential during the trial period. The trials were collaborative in nature and the role of each stakeholder discussed during the meetings.

The trial was laid out as a RCBD with each farmer in a village or location as a replicate. During the first season, the fields were prepared by oxen or tractor, but in the subsequent seasons plots were prepared by hand to avoid mixing soils from different plots. H614D was planted 3 seeds/hill at a spacing of 75 cm between rows and 60 cm in between hills followed by thinning 3 to 4 weeks after emergence to 2 plants/hill. The plots varied in size according to community choices, from 6 x 6 m at Cheptuya and Anin to 9 x 6 m in Chobosta and Matunda. Pests, mainly stalk borers, were controlled by use of Dipterex at 4 -5 kg ha-1. Non-treatment variables e.g. time of planting, weeding and pest control were managed to near optional levels as possible. The manure, compost and inorganic fertilisers were weighed and placed into the planting hole according to the

Evaluation of organic and inorganic fertilisers for small holder maize production 6

particular treatment. The data were subjected to analysis of variance using the general linear model procedure (GLM) of the SAS program (SAS Institute, 1995) to determine the effects of different treatments on maize yields. Farmers opinions were sought during evaluations at individual farm level, field days and intergroup visits using check lists prepared by the stake holders. Apart from yield, other criteria recorded included, plant vigour, sustainability, time and costs of production.

The complete set of treatments were: (1) Recommended fertiliser rate - 60 kg P2O5 + 60 kg N ha-1, (2) 10 t ha-1 FYM, (3) 10 t ha-1 compost, (4) 5 t ha-1 FYM, (5) 30 kg P2O5 + 30 kg N + 5 t FYM ha-1, (6) 30 kg P2O5 + 30 kg N + 5 t compost ha-1, (7) 30 kg P2O5 + 30 kg N ha-1, (8) Farmers practice and (9) Control. Not all the treatments were represented at each site, the maximum number being limited to Anin and Cheptuya with seven treatments each, followed by Matunda and Chobosta with six and five, respectively.

RESULTS Soil Analysis. Soil tests were interpreted and communicated to all farmers during workshops, field days and normal field visits. Generally the soils were moderately acidic with very low organic matter. Nitrogen and phosphorus deficiencies were observed in all farms (Table 1). In all sites, major deficiencies were observed in soil phosphorus, carbon and to some extent, calcium in Matunda and Cheptuya. These soils had nutrient levels below critical values and are the fundamental causes of low maize yields.

Farmyard manure collection, management, storage and compost making. The demonstrations/workshops held in 1994 through March 1995 were well attended. A total of 75, 72 and 41 farmers attended the initial workshops in Anin, Matunda and Cheptuya respectively. More than 30 heaps of composts were made and during the monitoring period, farmers were instructed on the best ways of storage to avoid losses of valuable nutrients through volatilization and leaching. Farmers were generally excited with the new idea of using organic manures for maize production to alleviate the high costs of inorganic fertilisers. However, some farmers were concerned with the high labour demand of composting in addition to non-availability of water and green materials during the dry season. They opted for farm yard manures which were readily available from the number of livestock they owned. They were therefore encouraged to undertake bomas composting which would provide larger quantities of manure. Analysis of composts and manures indicated that in comparison to the farm soils, both these organic fertilisers were high in pH, P and organic carbon compared with the soils (Table 2).

Maize yields. In the first year of experimentation recommended fertiliser rate (RF) gave high yields of 8.73, 7.22 and 8.75 t ha-1 in Anin Sublocation, Matunda and Chobosta village, respectively.

Yields using full rates of fertiliser were not significantly different (P>0.05) from yields where mixtures of RF and FYM (30 kg P2O5 +

TABLE 1. Soil chemical properties at the beginning of the trial in 1995

Deficiencies are underlined.

Location

Depth (cms) pH H2O Na (me) K (me) Ca (me) Mg (me) Mn (me) P (ppm) C

Matunda 0-15 5.55 0.18 0.35 2.82 1.30 0.34 7.90 1.29

Cheptuya 0-15 5.60 0.21 0.23 1.20 1.60 0.15 15.70 0.70

Chobosta 0-15 5.58 0.18 1.13 6.00 2.17 0.75 17.08 1.87

Keiyo 0-30 5.59 0.23 1.00 7.08 3.68 0.75 40.62 1.52

Chemical properties


30 kg N + 5 t FYM ha-1) were used, at Matunda (7.19 t ha-1) and Chobosta (9.44 t ha-

1) (Tables 3). However in Anin the two treatments were significantly different (P<0.05). Yields from the mixed treatment RF + compost (30 kg P2O5 + 30 kg N + 5t compost ha-1), did not significantly differ (P>0.05) from those of RF treatment (Table 3). At Matunda, Chobosta and Cheptuya, farmers used some fertilisers on their normal maize fields resulting in yield differences with the control treatments. In the second year (Table 4) similar trends were observed. In Matunda, RF treatment had the highest yield which was significantly different from the other treatments. At Anin however the RF gave yields that were not significantly different from the other treatments except the control and farmers practise.

At Cheptuya where very low soil fertility was observed, all the treatments showed significant yield differences from each other. In year three, combining organic and inorganic fertilisers gave yields which were not significantly different from the RF (Table 5). This was more so at Anin sub location where the organic amendments contained high amounts of phosphorus and organic carbon. Similar trends were observed at various sites in 1998 (Table 6).

Farmers' Assessment. Farmers were impressed by the yield gains. During field days and intergroup visits, most farmers

preferred treatments that gave higher maize yields compared to the control treatment. They believed this would cut down their production costs. They did not attach monetary value to composting and farmyard manure collection but mainly worried about the labour requirements, occasional poor availability of water, and the time taken for preparation, collection, storage and application of these organic fertilisers. Farmers agreed that these alternatives gave increased yields and crop vigour (data not included). Since most of them also kept various forms of livestock (goats, indigenous cattle, sheep and poultry) the sustainability of the production of high boma manure was assured. Generally farmers from different clusters came up with their own criteria for ranking the treatments. The assessments were made at individual farm visits, farmer workshops (“barazas”), intergroup visits or field days. Some of the criteria used when deciding the best treatments are listed in Table 7.

For most farmers the most important criteria was the cob size. This visual observation was indicative of the grain weight. Based on the above mentioned criteria, farmers from Weonia cluster ranked the full inorganic fertiliser treatment (60 kg P2O5 + 60 kg N ha-1) as their best treatment, followed by the combined half rates of organic and inorganic fertilisers (30 kg P2O5 + 30 kg N + 5 t FYM ha-1 and 30 kg P2O5 + 30 kg N + 5 t compost ha-1) (Table 8).

Due to the poor soil fertility status of these farms, there was need to make frequent follow up to encourage farmers to prepare and incorporate organic manures in their farms.

Location

Chemical properties

pH (H2O) Na K Ca Mg ( Mn P C

Cheptuya FYM 8.75 0.68 16.69 135.94 5.52 0.33 301.25 4.34

Chobosta FYM 7.60 0.73 19.78 62.33 6.23 4.10 274.8 6.91

Matunda FYM 8.30 0.24 0.60 3.00 1.75 0.28 21.00 5.40

Anin FYM 8.50 0.55 15.55 64.58 7.60 0.51 247.9 8.77

Compost 8.80 0.53 12.16 40.00 8.00 1.21 190.0 3.70

Sample

TABLE 2. Chemical properties of organic amendments used in 1995


Based on the criteria used above, Matunda farmers could not see any differences from using full rates of inorganic fertilisers and half rates of organic and inorganic fertilisers (Table 9).

DISCUSSION In order to increase yields, the limiting nutrients must be added to soils in the form of organic and/or inorganic fertilisers. Farmers were made to realise that soil problems in their

farms could not be addressed by just adding phosphorus and nitrogen alone. In future, treatments that have proved superior will be verified outside the current communities on larger plots to make conclusive recommendation and obtain realistic economic data. The number of farmers varied from site to site and within subsequent years. Mistakes arose even though the farmers’ roles were explained during the beginning of the trials. Some farmers still ploughed using tractors or

TABLE 3. Maize yields (t ha-1) in plots applied with inorganic, organic fertilisers and their combinations in 1995

Figures in the same column followed by the same letter are not significantly different (P<0.05) Fig-ures in brackets denote number of farmers using that particular treatment (replicate)

Figures in the same column followed by the same letter are not significantly different (P<0.05) Figures in brackets denote number of farmers who used the treatment (replicate)

TABLE 4. Maize yield (t ha-1) in plots applied with inorganic, organic fertilisers and their combinations in 1996

Location Matunda Chobosta Anin

60 kg P2O5 + 60 kg N 7.22 (6) a 8.75 (6) ab 8.73 (6) a 30 kg P2O5 + 30 kg N + 5t FYM 7.19 (6) a 9.44 (6) a 7.69 (6) bc

30 kg P2O5 + 30 kg N + 5t compost - - 8.53 (6) ab 10 t FYM 5.11 (6) bc 7.67 (6) bc 7.06 (6) bc

10 t Compost - - 6.70 (6) c Farmers’ practice 6.24 (6) ab 9.34 (6) a 4.12 (4)

Control 4.16 (6) b 6.63 (6) c 4.47 (7) c Site mean 5.98 8.37 6.85

C.V 14.76 11.91 19.61

Treatments

Treatments Matunda Cheptuya Chobosta Anin 60 kg P2O5 + 60 kg N 6.56 (5) a 6.04 (8) a 6.69 (6) ab 9.34 (6) a 30 kg P2O5 + 30 kg N 4.69 (5) b 3.75 (6) c 6.74 (3) ab 6.76 (2) ac 30 kg P2O5 + 30 kg N + 4.49 (5) ab 4.82 (8) b 7.74 (3) a 8.68 (6) a

30kg P2O5 + 30 kg N + 5 - - - 7.43 (4) a

10 t FYM 3.02 (5) c 2.15 (8) de 5.53 (3) bc 7.45 (6) a 5 t FYM - 1.16 (8) e - - 10 t Compost - - - 8.20 (5) a Farmers’ practice 2.79 (5) c 2.70 (2) de 3.49 (3) c 1.97 (2) c Control 2.97 (5) c 0.97 (2) e 4.71 (3) bc 4.34 (5) bc Site mean 4.25 3.20 5.81 7.29 C.V 23.10 30.64 22.54 25.88

Location


Figures in the column followed by the same letter are not significantly different (P<0.05) Figures in brackets denote number of farmers who used that particular treatment (replicate)


Location

Matunda Cheptuya Chobosta Anin Weonia

60 kg P2O5 + 60kg N 6.00 (6) ab 4.35 (6) ab 8.60 (5) a 4.63 (5) b 6.25 (11) a

30 kg P2O5 + 30kg N 5.03 (6) b 3.63 (6) bc 7.62 (5) a 2.95 (3) a 4.48 (8) a

30 kg P2O5 + 30 kg N 6.04 (6) a 5.07 (6) a 7.48 (5) a 5.03 (4) b

30 kg P2O5 + 30 kg N - - - 5.87 (5) b 4.81 (10) b

10 t FYM 4.07 (6) c 2.92 (6) cd 5.89 (5) b 4.80 (5) b 6.09 (11) a

5 t FYM - 0.93 (5) e - - 6.30 (7) a

10 t Compost - - - 4.75 (4) b _

Farmers’ practice 2.37 (6) d 1.91 (4) de - - _

Control 2.62 (6) d 0.63 (4) e 3.51 (8) c 2.19 (5) a _

Site mean 4.75 2.98 6.62 4.34 5.62

C.V 15.77 34.94 17.39 22.14 22.73

Treatments

Figures in the same column followed by same letter are not significantly different (P<0.05) Figures in brackets denote number of farmers using that particular treatment (replicate)

Location Matunda Weonia Cheptuya Chobosta Anin

60 kg P2O5 + 60 kg N 7.83 ab 6.52 a 7.40 a 11.78 a 7.75 a 30 kg P2O5 + 30 kg N 6.51 ab - 6.09 ab 8.83 bc 4.31 ab 30 kg P2O5 + 30 kg N 8.81 a 6.67 a - 10.90 a 9.33 a

30 kg P2O5 + 30kg N - 6.91 a 5.80 ab - 7.59 ab

10 t compost 5.80 b 6.32 a - 9.03 b 6.91 ab 10 t FYM - 7.00 a 3.82 bc - 6.85 ab 5 t FYM - - 2.89 cd - - Farmers practice 6.53 ab 5.28 b 3.81 bc - - Zero rate` 3.55 c - 1.35 d 7.62 c 2.65 b Site Mean 6.5 6.45 4.45 9.63 6.48 CV (%) 25.7 19.7 33.9 12.6 40.3 Maximum number of farmers 5 20 6 4 4

Treatments



TABLE 7. Criteria for ranking maize treatments

Cluster Criteria

Weonia 1. Leaf colour (green = best) 2. Stem size 3. Stand count 4. Plant height

Matunda 1. Foliage colour 2. Stem thickness 3. Height 4. Plant Population 5. Grain density (1000 grain weight) 6. Yield

TABLE 8. Matrix ranking of maize treatments at Weonia, 1997

Key: Bad = 0 Moderate = + Good = ++ Better = +++ Best = ++++

Treatment t ha-1 Emergence Grain Cob Pests Stem Leaf Points Rank

60 kg P2O5 + 60 kg N + ++++ ++++ ++++ +++ ++++ 20 1

10 t FYM +++ ++ + ++++ + _ 11 5

10 t comp ++++ + +++ ++++ _ + 13 4

30 kg P2O5 + 30 kg N ++ +++ ++ ++++ ++++ +++ 18 2

30 kg P2O5 + 30 kg N ++ +++ ++ ++++ ++ ++ 15 3

TABLE 9. Farmers evaluation of fertility treatments at Matunda cluster, 1997

Treatments (t ha-1)

Foliage colour

Stem thickness

Plant height

Plant population

Yield Yields (t ha-1)

Beans Maize 60 kg N + 60 10 8 8 6 10 9 2.83 6.00

Control 1 4 3 8 2 1 2.62 2.62

30 kg N + 30 5 7 7 7 6 7 2.40 5.03

30 kg N + 30 kg P2O5 + 5 ton

7 9 10 9 9 8 3.39 6.04

10 ton compost 8 8 9 10 8 9 2.47 4.07

Grain weight

Key: 10 - very good 1 - very poor

oxen, which resulted in the mixing up of the soils while other farmers simply lost interest.

CONCLUSION The results have so far indicated that proper manipulation of compost and FYM with reduced amounts of inorganic fertilisers can increase farmers' maize yields. Although the organic fertilisers do not generally contain sufficient nutrients to meet crop demand, and are sometimes of poor quality in terms of nutrients supplying capacity, their nutrient

composition is high in pH, P and organic carbon compared to the soil in the study area. Although farmers have expressed a number of negative points on preparation of composts, collection, storage and application of FYM, they have also seen their positive attributes in terms of increased maize yields and less expenditure on inputs.

ACKNOWLEDGEMENT The authors wish to convey their sincere thanks to Rockefeller Foundation for funding


the project and the Director KARI for providing facilities to carry out these activities. We would like to express our gratitude to the entire NARC-Kitale (SMP) team members incharge of the various clusters for their tireless efforts in planning, implementation and monitoring of project activities. Thanks also to all cooperating farmers, collaborators departmental heads of MoALD & M in our regions and NGO’s (Vi, KWAP, Environmental Action Team and Manor House Agricultural Centre). Appreciation is expressed to the Director of NARC-Kitale for providing administrative support services.

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