Smart fertilizers: What should we mean and where should we go?

Abstract

Highlights- A smart fertilizer allows to control the rate, timing and duration of nutrients release.- Nanofertilizers are powder or liquid formulations which involve the synthesis, design and use of materials at the nanoscale level.- Composite fertilizers are formulations containing nutrients mixed or coated with one or more materials that exploit synergy among materials.- Bioformulations are fertilizers containing active or dormant microorganisms capable to trigger physiological growth responses in plants.- Limited information is available for smart fertilizers on herbaceous crops in open field conditions.
 
 Abstract
 The current agricultural system faces several challenges, the most important being the ability to feed the increasing world population and mitigate climate change. In this context, the improvement of fertilizers’ agronomic efficiency while reducing their cost and environmental impact is one of the biggest tasks. Available literature shows that many efforts have been made to develop innovative fertilizers defined as "smart fertilizers", for which, different interpretations and definitions have been used. This paper aims to define, classify, and describe the new frontier of the so-called smart fertilizers with a particular focus on field-scale studies on herbaceous species. Most of the analyzed papers associate the "smart" concept to the controlled and/or slow release of nutrients, using both terms as synonymous. Some others broadened the concept, including the controlled release of nutrients to reduce the environmental impact. Based on our critical analysis of the available literature, we conclude that a fertilizer can be considered "smart" whenapplied to the soil, it allows control over the rate, timing, and duration of nutrients release. Our new definition is: ‘Smart fertilizer is any single or composed (sub)nanomaterial, multi-component, and/or bioformulation containing one or more nutrients that, through physical, chemical, and/or biological processes, can adapt the timing of nutrient release to the plant nutrient demand, enhancing the agronomic yields and reducing the environmental impact at sustainable costs when compared to conventional fertilizers’.

Silicon as a Smart Fertilizer for Sustainability and Crop Improvement

“…In general, smart fertilizers are fertilizers applied in soil that allow for managing the rate, timing, nutrient release duration, and active absorption by the plant roots [ 23 ]. Recently, Raimodi et al (2021) [ 24 ] defined a smart fertilizer as “any single or composed nanomaterial, multicomponent, and/or bioformulation containing one or more nutrients that can adapt the timing of nutrient release to the plant nutrient demand via physical, chemical, and/or biological processes, thereby improving crop growth and development and reducing environmental impact when compared to conventional fertilizers.” Smart fertilizers are classified as (i) nano fertilizers, (ii) composite fertilizers, and (iii) bioformulations [ 24 ].…”

“…Nano fertilizers, which are based on nanoparticles, as their name suggests, are available as powder or liquid formulations, including manufacturing, design, and application [ 24 ]. These fertilizers can help improve nutrient release kinetics and plant uptake efficiency [ 25 ], resulting in benefits including increased crop productivity [ 26 , 27 , 28 , 29 ], decreased nutrient loss to the environment [ 30 ] and enhanced nutritional quality and shelf life [ 31 ].…”

“…Composite fertilizers are composed of various materials containing one or more nutrients that have been developed to take advantage of material synergy and improve essential plant nutrition [ 24 , 32 ]. Based on material properties, organic and inorganic coating materials (including granules and hydrophobic or hydrophilic materials [matrix or gel]) and inorganic compounds with low solubility are commonly used for coating or mixing fertilizers [ 24 , 33 , 34 , 35 , 36 , 37 ].…”

Preparation of an Attapulgite-Modified Composite Hydrogel and Application in an Environmentally Responsive Green Fertilizer

“…Slow-release fertilizers can release nutrients gradually but are unable to release nutrients in accordance with plant requirements and environmental factors such as the temperature and pH. The nutrient release rate is not synchronized with crop requirements, and improvement of the fertilizer utilization rate is still limited. − Environmentally responsive fertilizers have gradually grown in popularity as a research topic in recent years due to their potential to address the dual issues of food security and environmental preservation. , These fertilizers can control the release of nutrients in response to changes in the soil environment, allowing fertilizer release to be coordinated with the soil environment and crop nutrient uptake …”

Mechanical Activation of Smectite-Based Nanocomposites for Creation of Smart Fertilizers

“…Controlled-release fertilizers (CRF), or smart fertilizers [1], are essential for future, environment-friendly agronomic activities [2][3][4][5][6][7][8][9]. The agricultural productivity needs to increase to match the growing demand for food, as food requirement is expected to increase by 50% by 2050 [4,10,11].…”