Fertiliser: Farmers should consider organic route

As the 2022/2023 farming season is almost on its periphery in numerous regions of Africa, and farmers are currently busy with harvesting and marketing their hard-earned produce, one ingredient of primary significance in farming remains a headache to reach the potential harvesting yield in Africa. Fertiliser costs have increased swiftly to an unaffordable and inaccessible extent for smallholder households, writes Motsi Hamond, who holds qualifications in agronomy, crop and soil science.

Even though access to fertiliser has been a traditional challenge, the current rise in prices has catapulted with global factors like the Covid-19 pandemic, increased fuel prices and the ongoing Russian-Ukraine war, which have further destabilised the fertiliser supply chains, thus their price upsurge.

Nevertheless, this rising cost of fertiliser has also affected commercial farmers, even in other developed global regions. Yet it becomes a key concern to smallholder farmers due to their vulnerability in such hard-hitting circumstances.

Lower yields in Africa

Lower fertiliser application rate in smallholder farming is generally among the predominant concerns for lower yields in Africa. For instance, about 10-20 kg/ha of fertiliser is normally applied for maize production (major crop) in Africa, which is relatively inferior to the global target of at least 100 kg/ha, and normally leads to lower yields averaging between 0.8-1.5 t/ha.

Soils in smallholder systems are largely constrained by inherent soil infertility which requires nutrient supplementation to ensure sustained crop productivity. The situation is additionally deepened by poor agronomic practices exercised by farmers such as monocropping, overgrazing, continuous tillage and removal/burning of crop residues after harvesting.

With the high rainfall received from this season, specifically in Southern Africa, soil erosion, leaching, acidity, and salinity become common foes in deteriorating soil fertility because of soil organic matter depletion. Even though the significance of fertiliser in supplementing plant nutrients has been widely acknowledged, fertilisers are also associated with certain detrimental environmental challenges such as eutrophication and gaseous emissions if applied improperly and these environmental risks are exaggerated with heavy rains.

Hence, looking at organic amendments to supplement plant nutrients can be a once-off resolution for poorly resourced farmers.

Not a new concept

The use of organic amendments – also called organic materials or organic fertilisers in managing soil nutrition – is not a new concept but has previously been applied for centuries. They are made of plant or animal materials and mostly include animal manure, crop residues, household waste and compost, and currently, there has been an increased interest in exploring other processed organic materials such as biochar and vermicompost, though their adoption magnitude in smallholder African farming is moving at a tortoise pace.

Additionally, practices such as conservation agriculture, intercropping, and green manuring can be included as indirect pathways for adding organic amendments in the form of crop residues.

Organic amendments may not only serve as soil nutrition management but also as a waste management solution that reduces environmental pollution as these materials are often regarded as agricultural waste.

Organic amendments comprise vital nutrients like nitrogen, phosphorus, and potassium, like inorganic fertilisers, but also consist of abundant secondary and trace elements that lack in inorganic fertilisers. Unlike fertilisers, organic amendments go beyond supplying nutrients, by improving various chemical, physical, and biological soil characteristics attributed to their richness in organic matter which is pivotal in maintaining overall soil quality.

A long list of benefits

Thus, organic amendments can balance the soil pH suitable for optimising the soil-plant ecosystem, improve soil infiltration, water retention and holding capacity, increase cation exchange capacity and nutrient retention, release nutrients gradually and consistently, enhance soil microbial activity and improve aggregate stability and soil strength. In all, these modifications reduce probabilities of soil acidity, erosion, and leaching which are unfavourable for both soil and plant health.

Optimising the yield benefits of organic amendments further requires farmers to consider certain handling and application management practices that will effectively conserve their quality and quantity. The handling of organic amendments constitutes their collection and storage, which is particularly critical to animal manure because of its susceptibility to environmental losses. This is also determined by the type of animal farmers may have.

Animals such as cattle, sheep, and goats are kept in open kraals which are subjected to environmental losses contrary to poultry and pigs which are kept under-housed roofs. Therefore, some of the measures which can be taken for storage consist of composting with or without blending by other amendments, normally crop residues, or in pits, heaps, or roofed stalls.

On the other hand, application management is implemented in the field and follows the 4R stewardships framework (right source, right rate, right time, and right place) likewise inorganic fertilisers. Proper 4R stewardship application of organic amendments provisions optimum nutrient uptake by plants and reduction in environmental losses simultaneously, which enhances crop production and profitability in a sustainable fashion. This may also vary with the availability of amendments, crop type, land size, soil type, and climate.

Combining organic and inorganic

Combining organic and inorganic fertilisers can also be a sustainable strategy in complementing integrated soil fertility management. This strategy can be more applicable in cases where farmers have limited organic amendments, for instance, some farmers use both manure and crop residues for fuel in household cooking which will leave them with few to apply in their fields.

This synchrony is also significant in enhancing inorganic fertiliser efficiency by limiting nutrient loss since the organic matter from organic amendments shields nutrients in their exchange sites leading to sustainable nutrient availability.

Lastly, agriculture extension services’ role in facilitating management practices for smallholder farmers has been the epicentre for the successful adoption of various agriculture technologies. Thus, extension services are required for demonstrations and training of farmers’ knowledge and perceptions on the adoption and handling and application management practices of organic amendments.

Considering the adoption of organic materials in smallholder farming can embrace sustainable productivity to achieve better crop yields and maintenance of soil fertility at lower costs in the current soaring fertiliser prices.

Motsi Hamond is a scholar interested in sustainable agricultural management practices. He holds an MSc in agronomy (cum laude) from Stellenbosch University and BSc Hons in crop science and BSc in crop and soil science (cum laude) both from the University of Fort Hare. You can contact him at onehammond2@gmail.com. The views and opinions expressed in this article are those of the author and do not necessarily reflect the views or positions of Food For Mzansi.

Sign up for Mzansi Today: Your daily take on the news and happenings from the agriculture value chain.