Integrated soil fertility managment

Soil fertility depletion and soil quality decline have been threatening the ecological and economic sustainability of crop production. In order to improve soil fertility and nutrient management approaches, on-farm integrated soil fertility management (ISFM) trials were conducted to evaluate the effects of organic and inorganic fertilizers on wheat (Triticum estivum L.) and tef (Eragrostis tef) yield and soil fertility in the highland Nitisol area of Ethiopia during 2010 and 2011 cropping seasons. The treatments were five selected combinations of N and P, manure and compost. These included control, farmers' practice (23/10 kg NP ha-1), recommended NP rate (60/20 kg NP ha-1), 50% of recommended NP rate (30/10 NP kg ha-1) + 50% manure and compost as inorganic N equivalence (3.25 tons ha-1). and 50% manure + 50% compost as N equivalence. Results revealed that yields of wheat and tef, and some soil chemical properties significantly responded to the different soil fertility management treatments. The application of 60/20 kg NP ha-1 and 30/10 kg NP ha-1 with 50% manure and compost as N equivalence increased mean grain yield of wheat by 151 and 129% respectively compared to the control, and by 85 and 68% respectively compared to the farmers' treatment (23/10 kg NP ha-1). Similarly, the same treatments increased tef grain yield by 141 and 122% compared to the control, and by 44 and 33% compared to the farmers' treatment.The application of compost or manure with half the recommended NP fertilizer rate resulted in a comparable yield as that of full NP dose, which could beconsidered as an alternative option for sustainable soil health and crop productivity. In conclusion, the two year result showed that the application of ISFM may optimize yield of wheat and tef as well as improve the fertility status of the soil.

Abstract:

Fertilizer use in Ethiopia is low, and crop yields and malnutrition rates reflect this low usage rate.  Urea is too expensive for most farmers, and compost supplies are inadequate.  A locally-produced bio-fertilizer produced by harnessing cyanobacteria could help bridge this gap.  The objective of these experiments was to optimize a cyanobacterial bio-fertilizer production system and, specifically, to identify the most productive cyanobacterial culture, water source, plastic liner type, and aeration schedule to optimize bio-fertilizer production on a village-level.  Factorial combinations of four cyanobacteria strains cultured from Ethiopian soils and three water sources (Hawassa groundwater, Lake Hawassa, and Wesha River water) were laid out in a complete randomized design with three replications in a laboratory study.  The river water provided the highest cyanobacterial growth rates for each of the strains.  Cyanobacteria strain E3 (Anabaena sp.) consistently had the highest optical density, growth rate, heterocyst frequency, and total N concentration.  Therefore, strain E3 and river water were selected for the next experiment to optimize parameters for mass production of cyanobacterial bio-fertilizer.  A factorial combination of two pond lining materials (transparent and black plastic sheeting) and two aeration schedules (30 min on followed by 30 min off and 60 min on followed by 60 min off) were laid out in a randomized complete block design with three replications in 1 x 2  x 0.2 m ponds (~400 L each). The transparent plastic lined pond with 60 min on/off aeration performed significantly better than other combinations with higher biomass, optical density and growth rate.  However, there was no significant different in total N fixed under the two aeration schedules.  In conclusion, the E3 strain grown in Wesha river water in transparent plastic lined ponds fixed the most N.  Additional research is needed to optimize aeration schedules and approaches.

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The increasing attention paid to local soil knowledge results from a greater recognition that farmer knowledge can offer many insights into the sustainable management of tropical soils and that the integration of local and technical knowledge systems helps extension workers and scientists work more closely with farmers. A participatory approach and a methodological guide were developed to identify and classify local indicators of soil quality and relate them to technical soil parameters, and thus develop a common language between farmers, extension workers and scientists. This methodological guide was initially developed and used in Latin America and the Caribbean-LAC (Honduras, Nicaragua, Colombia, Peru, Venezuela, Dominican Republic), and was later improved during adaptation and use in eastern African (Uganda, Tanzania, Kenya, Ethiopia) through a South–South exchange of expertise and experiences. The aim of the methodological guide is to constitute an initial step in the empowerment of local communities to develop a local soil quality monitoring and decision-making system for better management of soil resources. This approach uses consensus building to develop practical solutions to soil management constraints identified, as well as to monitor the impact of management strategies implemented to address these constraints. The particular focus on local and technical indicators of agroecosystem change is useful for providing farmers with early warnings about unobservable changes in soil properties before they lead to more serious and visible forms of soil degradation. The methodological approach presented here constitutes one tool to incorporate local demands and perceptions of soil management constraints as an essential input to relevant research for development activities. The participatory process followed was effective in facilitating farmer consensus; for example, about which soil related constraints were most important and what potential soil management options could be used. Development of local capacities for consensus building constitute a critical step prior to collective action by farming communities resulting in the adoption of integrated soil fertility management strategies at the farm and landscape scale.

Contemporary African agricultural policy embodies the African Green Revolution’s
drive towards modernisation and commercialisation. Agroecologists have criticised this
movement on ecological, social and political grounds. Northern Ghanaian fertiliser credit
schemes provide a good example through which these critiques can be examined in a
context where agricultural policy reflects the African Green Revolution’s ideals. This
study aimed to determine the relationship of such credit schemes to farmers’ use of
organic amendments, elucidate other factors related to organic amendment use, and
comment on the relevance of this modernisation policy and its relationship to
agroecology. A first research phase employed semi-structured key informant interviews.
Qualitative data from these informed construction of a semi-structured questionnaire that
was used in a survey of 205 farmers. Multistage sampling purposively identified five
villages and selected farmers within who had joined government and donor-funded
fertiliser credit schemes. The use of organic and inorganic amendments was compared to
that of peers who had not taken part in such schemes. Quantitative data were used in
binomial logistic regression, inferential and descriptive statistics. Qualitative data were
content analysed. Credit group membership was associated with higher fertiliser
application and yield, but had little influence on the extent of commercialisation. Farmers
who applied organic amendments were 40% less likely to belong to a fertiliser credit
scheme than not, indicating substitution between organic and inorganic fertilisers.
Organic amendments were 40% more likely to be applied to compound farms than
outfields and six times more likely to be applied by household heads than other household
members. However, household heads also preferentially joined credit groups. This was
part of an agroecological soil fertility management strategy. Household heads
appreciated the soil moisture retention properties of organic amendments, and applied
them to compound farms to reduce risk to their household food supply in a semi-arid
environment. They simultaneously accessed fertiliser to enhance this household
provisioning strategy. They appreciated the increased yields this achieved, yet
complained that the repayment terms of credit schemes were unfair, fertiliser did not
enhance yields in dry conditions and fertilisers were supplied late. Farmers’ use of
credited fertiliser alongside their existing agroecological strategy is helpful to the extent
that it raises yields, yet is problematic in that it conflicts with risk-reduction strategies
based on organics. There is some potential for modernised and agroecological
management paradigms to coexist. For fertiliser credit to play a role in this, schemes
must use fairer repayment terms and involve a focus on simultaneous use of organic
amendments.

Although chemical fertilizers have long been used to meet the high demand of nitrogen (N), the most common limiting nutrient to plant growth, the frequent use of this fertilizer gradually deteriorates soil fertility in addition to its high cost, lower supply and agronomic use efficiency in Ethiopia. Nevertheless, N-fixing cyanobacterial biofertilizers are eco-friendly, and currently considered important to support the developing organic agriculture. Therefore, this study was conducted to evaluate the potential of cyanobacterial biofertilizer for the growth and yield of three commonly growing crops in Ethiopia: maize, kale, and pepper under Alfisol and Andosol, and to investigate the potential contribution of cyanobacteria biofertilizer in selected soil fertility parameters. Three independent factorial experiments were conducted simultaneously in the greenhouse. Each experiment included a factorial combination of four nitrogen fertilizer sources applied at recommendation rate for each crop (control, urea, dried cyanobacteria, and liquid cyanobacteria,) and two soil types with acidic and alkaline pH (Alfisols and Andosols, respectively) arranged in a complete randomized design (CRD) with three replications. Application of dried and liquid cyanobacterial biofertilizer treatments significantly improves the soil N, soil organic carbon (SOC) and available P, Fe and Zn. Cyanobacteria treatments were also found to reduce or maintain the mean soil pH. Accordingly, maximum values of all the vegetative growth attributes of kale, and maize were obtained from the application of two comparable-fertilizer treatments: air-dried cyanobacteria and urea while for pepper crops only dried cyanobacteria. Concentrations of N, P, Zn, and Fe in leaves of kale, pepper, and maize were also significantly increased by air-dried cyanobacterial biofertilizer. Overall, dried cyanobacteria improved the growth and yield of the three crops, and the fertility of the soils. Therefore, the use of dry cyanobacterial biofertilizer could be recommended as a supplementary N source to inorganic fertilizer for kale, pepper and maize production in both study sites.