Selected rock powders as sources of nutrients for soil fertilization and maize-wheat grain production in southern Brazil

The current study evaluated alternative sources of nutrients to improve the soil fertility status and yield of maize-wheat succession in Southern Brazil. The treatments were: T1: no fertilization; T2: liming with dolomitic marble; T3: alternative liming (AL) with limestone interbedded with shale; T4: AL + 50% P - with Arad natural phosphate (P-ANP) + 50% P – triple superphosphate (P-TSP); T5: AL + 100% P-ANP; T6: AL + 100% P-ANP + 100% K-rich monzogranite; T7: AL + 100% P-ANP + 100% N (50% N from tung pressed cake (N-TPC) + 50% N-urea); T8: AL + 100% P-ANP + 100% K-rich monzogranite + 100% N (50% N-TPC + 50% N-Urea) + 100% S; T9: AL + regional average rate of NPK (5-20-20) formulation. Except for T7 and T8, all treatments received the full recommended rate of N through Urea. Immediate and residual effects were evaluated over 2.5 years (90, 360 and 900 days) on soil fertility and maize - wheat yield. The limestone interbedded with shale released Ca, Mg and corrected soil acidity similarly to dolomitic marble. The fertilization strategies used in T4, T7 and T8 presented the highest cumulative productivities while T3 (U$ = 1223), T9 (U$ = 1174) and T4 (U$ = 1122) resulted in higher profits than the other evaluated fertilization strategies. The limestone interbedded with shale (T3), alone or combined with 50% of P-ANP + 50% of P – TSP (T4) provided the best economical and technical results, highlighting the potential of selected alternative regional sources for soil fertility improvement and plant-nutrients supply.