Researchers say the nitrogen needs of crops cannot be adequately met solely through biological nitrogen fixation by legumes and recycling of animal manure.Credit: Jake Lyell & Associates / Alamy Stock Photo
Reducing mineral fertilizer in crop farming reduced production yields and may aggravate nutrient depletion in croplands in Sub-Saharan Africa, an analysis in Outlook on Agriculture shows.
The researchers argue that the use of practices such as intercropping of legumes and use of manure to help boost crop productivity without the need for more mineral fertilizer is unreliable.
They say that the “nitrogen needs of crops cannot be adequately met solely through biological nitrogen fixation by legumes and recycling of animal manure.” They call for increased use of mineral fertilizers in combination with agroecological practices to boost crop production and food security in the continent.
The team reviewed 150 scientific articles that collate 50 years of knowledge on nutrient balances, natural nitrogen fixation of tropical legumes, manure production and use in smallholder farming systems, and the environmental impact of mineral fertilizer in Sub-Saharan Africa.
They found that very low mineral fertilizer use coupled with mixed crop-livestock systems and crop diversification could lead to reduced soil fertility.
“More fertilizer is required in sub-Saharan Africa in order to sustain crop productivity and ensure good soil fertility,” says Gatien Falconnier, the study’s lead author and an agronomist based at French Agricultural Research Centre for International Development in Zimbabwe.
“Efficient fertilizer use is key, otherwise the nutrients are lost, reducing profit for the farmers, and with detrimental impact to the environment in the form of leaching and greenhouse gas emissions,” says Pauline Chivenge, the study’s co-author, and a principal scientist at the African Plant Nutrition Institute.
