No abstract

No abstract

Interaction among plant nutrients can yield antagonistic or synergistic outcomes that influence nutrient use efficiency. To provide insight on this phenomenon, peer-reviewed articles were selected that quantified the interaction effects of nutrients on crop yield levels. In total 94 articles were selected that described 117 interactions between all macro-and micronutrients for different agricultural crops. In 43 cases the interaction was synergistic, in 17 cases the interaction was antagonistic, and in 35 cases the interaction was zero-interaction; the other 23 cases were non-significant (16) or showed a negative response (7). Generally: (a) when the availability of two nutrients is characterized as deficient, a large increase in yield can be expected by diminishing these deficiencies: (b) for most macronutrients the mutual interactions on yield levels are synergistic; and (c) antagonistic effects on yield are often found for divalent cations. Knowledge of nutrient interactions can guide fertilizer design and optimization of fertilization strategies for high yields and high nutrient use efficiencies.

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, plantmicroorganism 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.

Micronutrients are essential mineral elements required for both plant and human development. However, micronutrients are often lacking in soils, crop, and food. Micronutrients are therefore used as fertilizer to increase crop productivity, especially when the application of conventional NPK fertilizers is not efficient. Here, we review the application of micronutrients in crop production. Reports show that micronutrients enhance crop nutritional quality, crop yield, biomass production, and resiliency to drought, pest, and diseases. These positive effects range from 10 to 70 %, dependent on the micronutrient, and occur with or without NPK fertilization. We discuss the uptake by plants of micronutrients as nanosize particulate materials, relative to conventional uptake of ionic nutrients. We also show that packaging of micronutrients as nanoparticles could have more profound effects on crop responses and fertilizer use efficiency, compared to conventional salts or bulk oxides.