NEXT FERTILIZERS - NUTRITIOUS FOOD AND HEALTHY SOILS
As mentioned earlier, most of today’s fertilizers were developed several decades ago and for temperate agricultures, with plant-available nutrient contents (mainly NPK) as high as possible (high analyses) with the intent of delivering them at the lowest cost to farmers. These fertilizers dramatically increased the agricultural productivity of temperate-zone countries. These same fertilizers were a part of the package that triggered the “Green Revolution” in Asia in the 1970s. Farmers broadcasted fertilizers according to blanket fertilizer application recommendations. Production increased but not proportionally to the fertilizer application rate, resulting in a progressive decrease in NUE-N, resulting in NOx emissions to air, contributing to GHG (IPCC 2014). The soil characteristics, average soil temperature, and rainfall pattern in the tropics and subtropics are different from the temperate regions for which most of the current suit of fertilizers were developed. Hence there is a need for new fertilizers, new application techniques, and more conducive policies for the tropics and subtropics regions.
Reflecting on (1) the magnitude of the future food supply challenge in the face of increasing land and water scarcity and uncertain climatic conditions, (2) the increasing role that smallholder farmers will have to continue to play in the food supply chains in developing countries, and (3) the inherent flaws in current fertilizers, advanced technologies must be applied to introduce new fertilizers and improve production. But fertilizer alone is not the answer. It must be a part of a package that is anchored in soil fertility management practices, particularly nutrient management, conducive policies, extension, and information and knowledge management. With the vast amount of data that are generated through research and satellite systems, information must be converted into knowledge and packaged for easy access by smallholder farmers through new and emerging communication tools. Nevertheless, manufactured fertilizers will be an essential component for increasing food production.
The Haber-Bosch is a high-temperature (~500°C) and high-pressure process (-200 atm) to produce ammonia that is subsequently reacted with CO, to produce urea. Natural gas is the energy and feedstock of choice. Even though a new plant’s energy consumption is close to theoretical, the energy requirement to produce nitrogen fertilizer is about 87% of the energy requirement for fertilizer production (Figure 13.8). Therefore, the current research focus should be to produce ammonia as close to the room temperature and atmospheric pressure as possible. If successful, lowering the operating temperature and pressure would reduce the energy requirement for nitrogen fertilizers and reduce GHG emissions, mainly CO,.
But the low NUE-N efficiency is a bigger contributor to GHG than that from production and use (Figure 13.9). While product characteristics make them more susceptible to losses, policies and management are also contributing factors. For example, overapplication of nitrogen fertilizer due to heavy product subsidies has reduced NUE-N and increased losses to air and water. Nevertheless, new nitrogen products that are needed to improve efficiency are produced for selected markets. Additionally, there is a drive to produce fertilizers containing micronutrients to match the nutrient requirements of biofortified crops (Roy 2015).
As mentioned earlier, compared with efforts to improve the efficiency of nitrogen, improving the efficiency of phosphate fertilizers has not been a priority. But recently that has changed, and one approach being heavily explored to improve P use efficiency is to limit the physical and temporal association of the nutrient with the reactive component of the soil. The products that are being commercially produced or are under development can be grouped in the following categories: (1) coatings, (2) scaffolds, and (3) organic matrices and minerals of limited solubility. A detailed discussion of these approaches is in Weeks and Hettiarachchi (2019). At a more fundamental level, there is a need to evaluate the effect of phosphate-solubilizing bacteria in making the nutrient available more predictably.
