Magnesium-fortified phosphate fertilizers improve nutrient uptake and plant growth without reducing phosphorus availability

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(MgSO_(4)),magnesium oxide(MgO),anhydrous magnesium chloride(MgCl_(2)),and dolomite(CaMg(CO_(3))_(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(NH_(4))_(2)(SO_(4))_(2)·6H_(2)O),schertelite(Mg(NH_(4))_(2)H_(2)(PO_(4))_(2)·4H_(2)O),magnesium hydrogen phosphate(Mg(H_(2)PO_(4))_(2)),and dolomite(CaMg(CO_(3))_(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.

Efficiency of soil-applied ^(67)Zn-enriched fertiliser across three consecutive crops

A very small amount of applied zinc(Zn) is taken up by crops, resulting in low recovery by plants. Adding elemental sulphur to zinc oxide(ZnO) fertiliser could improve Zn solubilisation and exert a higher residual effect on crops than soluble Zn sources. We produced an isotopically labelled Zn-elemental sulphur fertiliser and evaluated its performance in comparison to traditional Zn sources during sequential crop cultivation. Three ^(67)Zn-labelled fertilisers,ZnO, zinc sulphate(ZnSO_(4)), and ZnO co-granulated with elemental sulphur(ZnOS^(0)), were soil applied, and their contributions to the uptake of Zn by three consecutive crops, wheat, ryegrass, and corn, were assessed in a 294-d pot experiment. The contributions of Zn fertilisers followed the order: ZnSO_(4) > ZnO= ZnOS^(0). The relative contributions of Zn fertilisers were lower in the first crop than in the subsequent crops. The overall recovery of applied Zn by the three crops was higher for ZnSO_(4) than for ZnO and ZnOS^(0), reaching 1.56%, 0.45%, and 0.33% of the applied Zn, respectively. Zinc recovery by plants was very low, regardless of the source of Zn. Adding elemental sulphur to ZnO did not increase its effectiveness up to 294 d after application. Fertiliser contribution was higher for the subsequent crops than for the initial crop, indicating the importance of assessing the residual effects of Zn fertilisers.