Cryst. MgNH4PO4 center dot 6H(2)O (struvite) was synthesized by reaction of NH2H2PO4 with MgO in aq. suspension at 40 degrees C and granulated (grain size 3-6 mm). Both struvite forms were used for fertilizing maize culture. The maize crop increase was 67% for the cryst form and 30% for the granulated one when compared with the control exp. without any fertilizer. The uptake of N was 48% and 24%, of P 8.5% and 1.1% and of Mg 10% and 2.9% for the crystand granulated forms, resp.