Can localized fertilization become a key strategy for green agricultural development?

In agricultural ecosystems, there exists a remarkable heterogeneity in the spatial and temporal distribution of soil nutrients. This heterogeneity can cause the nutrient concentrations that different roots of the same plant are exposed to vary by several orders of magnitude, which undoubtedly poses a great challenge to plant growth. In the face of such a complex soil environment, plants have gradually developed a series of coping strategies during the long evolutionary process. Their roots can keenly sense the nutrient-rich hotspots and make corresponding responses. However, traditional fertilization methods are difficult to precisely meet the needs of plants. They not only result in nutrient waste but also cause environmental pollution. Therefore, localized fertilization, as a new strategy, has attracted widespread attention.

Since plants have their unique nutrient acquisition mechanisms in the natural environment, how will the roots of plants behave in the context of artificially intervened localized fertilization? In fact, the response of plant roots to heterogeneous nutrients is quite unique. Morphologically, in nutrient-rich areas, the roots will exhibit a proliferation phenomenon, specifically manifested as an accelerated root elongation rate, an increase in total root length, and an increase in lateral root branching. Physiologically, in nutrient-rich patches, the physiological activities of plant roots will be significantly enhanced, and the nutrient absorption rate will also increase accordingly. In addition, rhizosphere microorganisms also play an important role in the nutrient acquisition of plants. Mycorrhizal fungi form symbiotic associations with plant roots, facilitating nutrient absorption.

A review study (DOI: 10.15302/J-FASE-2024575) conducted by the research team led by Professor Jianbo Shen from China Agricultural University and published in Frontiers of Agricultural Science and Engineering shows that as an important rhizosphere management strategy, localized fertilization has obvious advantages. It can reduce the fixation of insoluble nutrients in the soil, adjust the morphological structure of the roots, and promote the roots' capture of nutrients. Taking the intensive agricultural system in the North China Plain as an example, localized fertilization has increased the yield of maize by 5% to 15%, while significantly reducing the amount of fertilizer applied. Its incremental amplification effect is achieved through changing the root morphology to increase the absorption area, enhancing the root physiological processes to improve nutrient activation ability, and stimulating specific microbial communities to strengthen the underground interactions. For example, the local application of phosphorus and ammonium nitrogen can stimulate root proliferation, and the root exudates in nutrient-rich patches will accelerate. There are also studies indicating that localized fertilization can activate the soil microbial community, regulate the ethylene signal of plants, and promote root growth and nutrient absorption.

Currently, localized fertilization has been applied in actual production. The base fertilizer commonly used in maize production in the United States is a typical example. In China, it is also being gradually promoted and has been listed as one of the main agricultural promotion technologies by the Ministry of Agriculture and Rural Affairs. Overall, localized fertilization has demonstrated many advantages. It has significantly improved the nutrient utilization efficiency, reduced fertilizer waste, and achieved an increase in crop yield with less fertilizer input, which has been effectively verified in the intensive agricultural system of the North China Plain. At the same time, it is more environmentally friendly, reducing the risk of environmental pollution caused by excessive fertilization. By stimulating the activities of beneficial rhizosphere microorganisms, it can also improve the soil microecological environment and promote soil health. With these advantages, localized fertilization shows great potential in promoting the process of green agricultural development. However, to truly become a key strategy for green agricultural development, further in-depth research is needed to overcome the existing challenges such as salt damage, ammonium toxicity, and the influence of inherent soil fertility, so as to provide more solid and powerful support for the sustainable development of agriculture.