A silicon–potash fertilizer prepared from magnesium slag and how it can improve soil fertility and agronomic performance

Abstract

ABSTRACT A silicon–potash (Si–K) fertilizer was synthesized from magnesium slag (Ms), which is an industrial residue generated from the refining process of magnesium and magnesium alloy. Nutrient release characteristic and the effect of Si–K fertilizer on soil fertility and agronomic performance were evaluated so that an alternative, effective, and sustainable method of utilizing Ms in Chinese agriculture could be developed. The results showed that unevenly shaped aggregates were formed, and Ca, K, Si, and Mg coexisted in a mixed heterogeneous mass of amorphous and crystalline materials when Ms reacted with K2CO3 at high temperature. The solubility of K+ in synthetic Si–K fertilizer was decreased, and that of Si was improved due to K+ entering in the Si–O network resulting in the depolymerization of Si–O tetrahedrons. Application of Si–K fertilizer improved the accumulation of K and Si in soil and two plant tissues. Maize plants exhibited larger K demand to maintain growth compared to pakchoi plants. And as a monocotyledon of gramineae, maize could accumulate more Si concentration than pakchoi, which is a dicotyledon of non-gramineae. Compared to K2SO4, Si–K fertilizer prepared from Ms had an equivalent and superior impact on the growth of pakchoi and maize plants, respectively. In conclusion, Si–K fertilizer synthesized from Ms has a potentially beneficial application in the calcareous cinnamon soil of Northern China. Abbreviation: Ms: Magnesium slag; Si–K fertilizer: silicon–potash fertilizer; NUE: nutrient use efficiency; K: potassium; Si: silicon; NER: nutrient efficiency ratio; PE: physiological efficiency; AE: agronomic efficiency; APE: agrophysiological efficiency; ANR: apparent nutrient recovery efficiency