Abstract
Meeting human needs within the ecological limits of our planet calls for continuous reflection on, and redesigning of, agricultural technologies and practices. Such technologies include fertilisers, the discovery and use of which have been one of the key factors for increasing crop yield, agricultural productivity and food security. Fertiliser use comes, however, at an environmental cost, and fertilisers have also not been a very economically effective production factor to lift many poor farmers out of poverty, especially in African countries where application on poor soils of unbalanced compositions of nutrients in fertilisers has shown limited impact on yield increase. Agronomic practices to apply existing mineral fertilisers, primarily containing N, P and K, at the right time, the right place, in the right amount, and of the right composition can improve the use efficiency of fertilisers. However, the overall progress to reduce the negative side effects is inadequate for the desired transformation toward sustainable agriculture in poor countries. Globally, there have been no fundamental reflections about the role and functioning of mineral fertilisers over the past 5 decades or more, and compared to other sectors, dismal investments have been made in mineral fertiliser research and development (R&D). In this paper, we reflect on current fertilisers and propose a more deliberate adoption of knowledge of plant physiological processes—including the diversity of mineral nutrient uptake mechanisms, their translocation and metabolism—as an entry point in identifying the physicochemical “packaging” of nutrients, their composition, amount and timing of application to meet plant physiological needs for improved instantaneous uptake. In addition to delivery through the root, we suggest that efforts be redoubled with several other uptake avenues, which as of now are at best haphazard, for the delivery of nutrients to the plant, including above ground parts and seed coating. Furthermore, ecological processes, including nutrient-specific interactions in plant and soil, plant-microorganism symbiosis, and nanotechnology, have to be exploited to enhance nutrient uptake. It is hoped that concerted R&D efforts will be pursued to achieve these strategies.
Highlights
The use of mineral fertilisers is among key factors driving the increased global agricultural production required to feed the rising human population
It has been estimated that the over-fertilisation with N in China, occurring in the order of 11.8 Mt, could potentially double yields if used on the 174 million ha of cropland in sub-Saharan Africa (Ju et al 2009; Twomlow et al 2010)
With secondary and micro-nutrients, use in crop production is virtually lacking in Africa
Summary
The use of mineral fertilisers is among key factors driving the increased global agricultural production required to feed the rising human population. In Africa, N and P consumption is estimated at 2.8 Mt and 96 Kt, signifying increases of 150 and 16 %, respectively, between 1975 and 2005 (Peñuelas et al 2012, 2013). This contrasts from the industrialised countries where both N and P supplies are balanced, or where soil P capital has been built up over time to offset any under supply (van der Velde et al 2014; Withers et al 2014). Nutrients in fertilisers do not all end up in the plant; up to 20– 80 % of nutrients in fertilisers may be lost to the environment or temporarily accumulate in the soil due to several complex soil chemistries that preclude their immediate availability to the plant. We discuss a number of considerations that could guide the production of novel fertilisers and alternative—and even complimentary—mechanisms to more efficiently deliver the nutrients into plants, thereby increasing fertiliser use efficiency
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