Introduction
Since groundbreaking efforts in plant nutrition within the late 19th and 20th centuries. Complicated nutritional disorders and biological functions of most mineral nutrients are being systematically investigated. Research efforts have remained largely focused on crop yield and quality-related. Most frequently occurring limiting macro-elements such as nitrogen, phosphorus, and potassium. Nevertheless, the essentiality of other mineral nutrients such as magnesium (Mg) has long been disregarded in terms of soil and plant tests and fertilization programs. And its deficiency is not regarded as a substantial concern in agriculture productivity. Indeed, Mg mediates a wide array of central physiological and biochemical processes in plants. While Mg deficiency undoubtedly weakens the performance and productivity of different agricultural systems (Figure 1).
Problem
The multifaceted result of the introduction of high-yielding fertilizer-responsive cultivars, intensive cropping without replenishment of Mg, soil acidification, and exchangeable Mg (Ex-Mg) leaching continuously depleting indigenous exchangeable Mg reserves. Therefore, the incidences of Mg deficiency or approaching deficient levels are expanding in most production systems. Efficient Mg deficiency remedy roadmaps for optimum crop production depend on a clear understanding of the distribution pattern. As well as magnitude of Mg deficiency in different cultivated regions of the world.
Main Findings
To gain a better understanding of the spatial patterning of Mg, we first time critically evaluated the geographical distribution and magnitude of Mg deficiency in the cultivated regions of China. Which has diverse soil, crop, and ecological zones.
Figure 1: Scheme depicting distinct responses of plants to magnesium availability.
Compiling the soil database (n = 2,544) of five distinct regions covering 24 provinces in China. It is revealed that ∼55% of arable lands in China are Mg-deficient (<120 mg kg-1 soil Ex-Mg), with an obvious spatially declining trend of soil Ex-Mg from northern (331 mg kg-1 on average) toward southern (65 mg kg-1 on average) China (Figure 2). The rising Mg deficiency is primarily traced back to higher depletion of soil Ex-Mg by fruits, vegetables, sugarcane, tubers, tea, and tobacco cultivated in tropical and subtropical climate zones. Further, each unit decline in soil pH from neutral reduced ∼2-fold soil Ex-Mg.
Figure 2: Spatial distribution and magnitude of Mg deficiency in China’s farming system.
Way Forward
To efficiently combat rising Mg deficiency in our agricultural systems. It is proposed to match soil providing capacities of Mg with crop demand by precise plant and soil testing, proper fertilizer formulation, and optimal fertilization rates and timing to minimize net soil mining.
Figure 3: A proposed model to combat rising Mg deficiency in different agroecosystems.
Given spatial variations of soil Ex-Mg, a considerable amount of research work is suggested to study responses of different crops to Mg supplementation and develop site-specific Mg benchmarks in distinct agroecosystems. Further, creating awareness and eliminating misconceptions among local growers, together with subsidizing Mg fertilizers, especially in Mg-deficient regions is recommended to be beneficial to close yield and quality gaps among different cultivated regions. Together, this comprehensive work provides a useful quantitative framework for a wide range of plant scientists and growers to understand Mg dynamics in the soil-plant system, and accordingly, to optimize fertilization strategies to sustain agricultural productivity and food security.
Reference: Ishfaq M, Wang Y, Yan M, Wang Z, Wu L, Li C and Li X. 2022. Physiological essence of magnesium in plants and its widespread deficiency in the farming system of China. Front. Plant Sci. 13:802274. doi: 10.3389/fpls.2022.802274
