Wheat and maize yields in response to straw management and nitrogen under a bed planting system

In the Yaqui Valley, northwest Mexico, the crop sequence that is becoming m ore common consists of planting wheat (Triticum aestivum L.) as a winter cr op on a raised bed followed by maize (Zea mays L.) as a summer crop. In thi s area, straw of both winter and summer crops is commonly burned. The conse quences of burning crop residues on crop yields in the Yaqui Valley have no t previously been documented, and alternative practices have not been propo sed.. A 5-yr study was conducted at the CIANO (Centro de Investigaciones Ag ricolas del Noroeste) experiment station in Sonora, Mexico, to compare the effects of burning with other straw management strategies on wheat and maiz e yields. We tested two tillage systems (conventional-tilled bed, CTB, and permanent bed, PB), five straw management treatments (incorporated with CTB and straw as stubble, partly removed, removed, or burned with PB), and sev en N treatments, five applied preplant (0, 75, 150, 225, and 300 kg N ha(-1 )) and two at the Ist node stage (150 and 300 kg N ha(-1)) of wheat. Maize following wheat received a uniform application of 150 kg N ha(-1). The comb ination of PB and straw as stubble produced superior maize and wheat grain yields in high-yielding environments; in low-yielding environments, PB-stra w burned produced greater wheat grain yields. Nitrogen fertilizer applicati on of 150 and 300 kg N ha(-1) at the Ist node stage of wheat increased grai n yields compared with preplant N fertilizer applications. Permanent beds c ombined with retaining all crop residues in the soil as stubble have the po tential to increase both wheat and maize yields in the Yaqui Valley.