Magnesium (Mg) deficiency can significantly limit crop yield and quality. Separate application of straight Mg fertilizer is unattractive because of additional labor costs. Meanwhile, bulk blending Mg with other macronutrient fertilizers is also a suboptimal solution because bulk blended fertilizers often yield poor nutrient distributions. One rapid and economical alternative to alleviating Mg deficiency is to co-granulate macronutrient fertilizers with Mg. However, few commercial products have implemented this approach. One of the barriers hindering the production of Mg-fortified phosphorus (P) fertilizers is the assumption that precipitation of P with Mg will reduce P solubility. In this study, four Mg compounds, anhydrous magnesium sulfate (MgSO4), magnesium oxide (MgO), anhydrous magnesium chloride (MgCl2), and dolomite (CaMg(CO3)2), were co-granulated with mono-ammonium phosphate (MAP), and their granule strength, Mg and P availabilities, and agronomic effectiveness were evaluated. Results showed that there were no significant differences in P solubility between Mg-fortified MAP and MAP treatments. X-ray diffraction (XRD) indicated that the Mg species after co-granulation were boussingaultite (Mg(NH4)2(SO4)2·6H2O), schertelite (Mg(NH4)2H2(PO4)2·4H2O), magnesium hydrogen phosphate (Mg(H2PO4)2), and dolomite (CaMg(CO3)2). A pot experiment using an acidic soil demonstrated an average 9.6-fold increase in shoot Mg uptake, 3.0-fold increase in shoot P uptake, and 3.2-fold increase in soybean shoot dry matter in Mg-fortified MAP treatments, compared to those in MAP treatment. The current study provides a simple, effective, and low-cost approach for the addition of Mg to macronutrient fertilizers, to minimize Mg deficiency.

Zhenya LU;Yanyan WANG;Fien DEGRYSE;Chengdong HUANG;Cuihong HOU;Liangquan WU;Rongfeng JIANG;Michael J.MCLAUGHLIN;Fusuo ZHANG

College of Resources and Environmental Sciences,National Academy of Agriculture Green Development,Key Laboratory of Plant-Soil Interactions,Ministry of Education,China Agricultural University,Beijing 100193 China;Department of Pomology,College of Horticulture,China Agricultural University,Beijing 100193 China;Fertilizer Technology Research Centre,School of Agriculture,Food and Wine,University of Adelaide,PMB 1,Glen Osmond SA 5064 Australia;School of Chemical Engineering,Zhengzhou University,Zhengzhou 450001 China;International Magnesium Institute,Fujian Agriculture and Forestry University,Fuzhou 350002 China

土壤圈（英文版）

[1]Zhenya LU;Yanyan WANG;Fien DEGRYSE;Chengdong HUANG;Cuihong HOU;Liangquan WU;Rongfeng JIANG;Michael J.MCLAUGHLIN;Fusuo ZHANG-.Magnesium-fortified phosphate fertilizers improve nutrient uptake and plant growth without reducing phosphorus availability)[J].土壤圈（英文版）,2022(05):744-751

unattractive,granulate,boussingaultite,schertelite

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