A better use of fertilizers is needed for global food security and environmental sustainability

Abstract

The massive use of fertilizers during the last decades allowed a great increase in the global capacity of food production. However, in the last years, several studies highlight the inefficiency and country asymmetries in the use of these fertilizers that generated environmental problems, soil nutritional imbalances and not optimal food production. We have aimed to summarize this information and identify and disentangle the key caveats that should be solved. Inadequate global management of fertilization produces areas with serious nutrient deficits in croplands linked with insufficient access to fertilizers that clearly limit food production, and areas that are overfertilized with the consequent problems of environmental pollution affecting human health. A more efficient use of nitrogen (N), phosphorus (P) and potassium (K) fertilizers for food security while preserving the environment is thus needed. Nutrient imbalances, particularly the disequilibrium of the N:P ratio due to the unbalanced release of N and P from anthropogenic activities, mainly by crop fertilization and expanding N-fixing crops that have continuously increased the soil N:P ratio, is another issue to resolve. This imbalance has already affected several terrestrial and aquatic ecosystems, altering their species composition and functionality and threatening global biodiversity. The different economic and geopolitical traits of these three main macronutrient fertilizers must be considered. P has the fewest reserves, depending mostly on mineable efforts, with most of the reserves concentrated in very few countries (85% in Morocco). This problem is a great concern for the current and near-future access to P for low-income countries. N is instead readily available due to the well-established and relatively low-cost Haber–Bosch synthesis of ammonium from atmospheric N2, which is increasingly used, even in some low-income countries producing an increasing imbalance in nutrient ratios with the application of P and K fertilizers. The anthropogenic inputs of these three macronutrients to the environment have reached the levels of the natural fluxes, thereby substantially altering their global cycles. The case of the excess of N fertilization is especially paradigmatic in several areas of the world, where continental water sources have become useless due to the higher nitrate concentrations. The management of N, P and K fertilizers is thus in the center of the main dichotomy between food security and environmentally driven problems, such as climate change or eutrophication/pollution. Such a key role demands new legislation for adopting the well-known and common-sense 4R principle (right nutrient source at the right rate, right time and right place) that would help to ensure the appropriate use of nutrient resources and the optimization of productivity.

The input reduction principle of agroecology is wrong when it comes to mineral fertilizer use in sub-Saharan Africa

“…In SSA, the scope to improve N-use efficiency is also large, as the current average agronomic efficiency of N is estimated at 14 kg maize grain per kg N applied, compared with the global average of 30 kg kg −1 (Vanlauwe et al, 2023). In general, improvement of nutrient-use efficiency can be achieved by widely adopting the 4R principles (the right nutrient source at the right rate, right time and right place) (Penuelas et al, 2023). In the context of SSA, site-specific nutrient management tailored to the high spatial heterogeneity of smallholder farming systems will be key (Chivenge et al, 2021).…”

Bangladesh's food security under input problems: An analysis of constrains and policy response

“…Fertilizer is one of the most critical inputs in agriculture; as Penuelas et al (2023) suggest, fertilizer is a vital factor in increasing yield production and closing the gap between actual and attainable yields, which has been at the center of the green revolution debate over the past decades. There is no alternative to fertilizer in achieving self-sufficiency.…”

Elucidation of the Mechanism of Greenhouse Gas Generation by Abiotic Transformation of Nutrient Ions Flowing into Closed Water Areas with Little Phytoplankton

“…Among the greenhouse gases, the formation mechanism of N 2 O is not well understood. − A clear point is that nitrogen fertilizers consisting of ammonia produced by the Haber–Bosch process are one of the main sources of N 2 O . However, as the population is expected to grow in the future, it will be difficult to reduce the amount of nitrogen fertilizer used. − Processing of nitrogen by microorganisms in rivers requires substrates, reactant inputs, suitable redox conditions, and intermediate residence times and is therefore thought to occur primarily in hyporheic zones rather than in surface waters. , Therefore, in order to establish a way to reduce N 2 O, we need to know how N 2 O is produced from nitrogen fertilizer. − For example, the dissimilatory reduction of nitrate to ammonium (DNRA) in soil does not produce N 2 O. , Additionally, denitrification and nitrification, which is used as a purification method for septic tanks, is thought to be less likely to generate N 2 O . However, much of the nitrogen fertilizer that remains in the soil without being absorbed by plants is broken down by nitrifying and denitrifying bacteria.…”