Tillage system, fertilizer nitrogen rate, and timing effect on corn yields in the Texas Blackland Prairie

New N management and conservation tillage systems are needed to improve agricultural sustainability on the Blackland Prairie of Texas. In 1994, an experiment was established to determine plant response to N fertilizer rate and timing within three different tillage systems. A split plot experiment with four replications was established on a Houston Black clay (fine, smectitic, thermic Udic Haplusterts) soil. The main plots were chisel tillage system without beds (conventional for the area), chisel tillage system with raised wide beds, and no-tillage system with raised wide beds. The subplots were seven fertility treatments: four fertility rates (0, 56, 112, and 168 kg N ha(-1) applied at planting) and three timing treatments (N applied in the fall, at planting, and split between at planting and 30 d later). The crop rotation was wheat (Triticum aestivum L.), corn (Zea mays L.), and sorghum [Sorghum bicolor (L.) Moench]. The experimental treatments were imposed on corn each year for 4 yr. Plant samples were collected for grain yield, biomass production, and N uptake. Grain yield ranged from 150 to 8435 kg ha (1). In wet years, grain yields and N uptake increased with N fertilizer up to 168 kg N ha(-1), and fall application reduced yields 30% when compared with fertilizer application at planting. The highest yields were observed with the no-tillage. Results from this study indicate that application of fertilizer in the fall may result in lost yield potential and that conservation tillage systems may be the most reliable in the Texas Blackland Prairie.