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

New N management and conservation tillage systems are needed to improve agr icultural sustainability on the Blackland Prairie of Texas. In 1994, an exp eriment was established to determine plant response to N fertilizer rate an d timing within three different tillage systems. A split plot experiment wi th four replications was established on a Houston Black clay (fine, smectit ic, thermic Udic Haplusterts) soil. The main plots were chisel tillage syst em without beds (conventional for the area), chisel tillage system with rai sed wide beds, and no-tillage system with raised wide beds. The subplots we re 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 th e fall, at planting, and split between at planting and 30 d later). The cro p rotation was wheat (Triticum aestivum L.), corn (Zea mays L.), and sorghu m [Sorghum bicolor (L.) Moench]. The experimental treatments were imposed o n corn each year for 4 yr. Plant samples were collected for grain yield, bi omass 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 w ith fertilizer application at planting. The highest yields were observed wi th the no-tillage. Results from this study indicate that application of fer tilizer in the fall may result in lost yield potential and that conservatio n tillage systems may be the most reliable in the Texas Blackland Prairie.