Yield and Fertilizer Use Efficiency in a High-Input Soybean/Maize Cropping System in the Brazilian Cerrado.

The use of modern cultivars, no tillage system, and improved agronomic practices resulted in increased soybeans and maize yields in the Brazilian Savanna (Cerrado). However, in order to obtain additional yield increases, farmers often tended to over fertilize their fields even on high soil fertility conditions. This study evaluated NPK rates that resulted in high yields and optimum fertilizer efficiency use in a clayey Oxisol under no tillage. The experiment was conducted during two growing seasons (soybean in 2010/11 followed by maize in 2011/12) in a farm located in the Northwest of Minas Gerais State, Brazil. Treatments consisted of a factorial combination of four level of a fertilizer mix (NPK 10-32-10) at sowing and four levels of either KCl (soybean) or urea (maize) at topdressing. On average, 0,0,0; 16,51,16; 33,103,33 and 49,151,49 kg ha^-1 of N, P₂O₅, and K₂O, respectively was applied at sown.  K₂O levels were 0; 15; 30 and 45 kg ha^-1 at topdressing and urea levels were 0; 79; 158 and 236 kg N ha^-1. The rates chosen represent 0; 50; 100 and 150% of the fertilizer amounts normally applied at the farm. There was no treatment effect on soybean yields (average yield of ~ 3,466 kg ha^-1). Maximum fertilizer efficiency use in maize was obtained when applying 18; 59 and 18 kg ha^-1 of N, P₂O₅, and K₂O, respectively at sowing and 79 kg ha^-1 of N at topdressing. The maize yield ranged from 9,729 to 12,963 kg ha^-1 for treatments receiving none and 54;172 and 54 kg ha^-1 of N, P₂O₅, and K₂O, respectively. Results indicated fertilizer use efficiency in soybean/maize system in Brazilian Cerrado Oxisol can be increased by at least 50%; however economic impact should be considered before making nutrient management decision.