NAIROBI, KENYA: Low crop productivity is a perennial problem among smallholder farms. Some factors that contribute to this reality is exponential decline in soil fertility and high fertiliser costs.
In addition, chemical fertilisers do not directly improve soil physical structure or enhance soil biological activity and are often insufficient to maintain soil health.
Research on soil fertility, crop nutrition and socioeconomics in smallholder farming systems has been done in Sub-Saharan Africa and shown that combined interventions on fertiliser and organic inputs coupled by use of improved crop varieties are prerequisite for achieving high and sustainable yields.
This is where Integrated Soil Fertility Management (ISFM) comes in. ISFM is defined as a set of soil fertility management practices that include use of fertiliser, organic inputs, and improved germplasm combined with the knowledge to adapt these practices to local conditions.
The use of improved germplasm enhances yield potentials as well as combat pests and diseases. Mineral fertiliser use in ISFM targets the formulation, placement, rate and timing of inorganic nutrient inputs.
Integration of different fertiliser placement and/or rate practices such as micro-dosing, deep placement, banding, and harmonising of inputs with rainfall and nutrient demands enhance nutrient uptake and productivity of crops. Interventions on organic resource management targets the return of crop residues and use of manure, compost and other types of organic wastes.
Organic wastes
Additionally, crop rotation or inter cropping with legumes and use of plant growth promoting micro-organisms make an integral part of ISFM. The last entry point of ISFM deals with any other amendments that may be needed to reduce the limitations to productivity such as soil acidity, micronutrient deficiency, erosion, soil compaction or pests and diseases. On the other hand, local adaptation of nutrient management refers to specific decision-making processes in relation to the allocation of agro-inputs and management practices at the farm level, thus recognising production objectives, resource endowments, and farm-specific soil fertility conditions.
The combined application of mineral fertiliser and organic inputs is practical to smallholder farmers because; (i) both fertiliser and organic inputs are often in short supply in smallholder farming systems due to limited affordability and/or accessibility; (ii) both inputs contain varying combinations of nutrients and/or carbon, thus addressing different soil fertility-related constraints; and (iii) extra crop produce can often be observed due to positive interactions between fertiliser and organic inputs. ISFM fits well with small scale farmers due to its wide applicability across different soil types, cropping systems and resources endowment.
Research has reported an increase in maize grain from 1 to 2.4 tonne per hectare under ISFM systems compared to the sole use of mineral fertilisers.
The higher productivity and yield stability achieved in the ISFM system prove that the practices significantly strengthen the resilience of crops to climate change impacts.
Additionally, soil organic carbon content (an indicator of soil fertility) increases when fertilisers and organic inputs are combined as compared to when either is used solely. Despite the significant benefits of ISFM in food security, the adoption of practices in African smallholder systems is usually low and incomplete.
This is due to; high costs of input and poor produce trading, shortage of credit facilities for making initial investments, high cost and availability of labour, small land sizes, lack of information about the soil status among others. Regardless of these challenges, ISFM remains the most sustainable solution to food and nutritional security among smallholder farmers.
[Martin Koinange, works at Faculty Agribusiness Programs Strathmore Business School, agribusiness@strathmore.edu ]
