TILLAGE AND NITROGEN-SOURCE EFFECTS ON GROWTH, YIELD, AND QUALITY OF FORAGE MAIZE

Manure has not been evaluated as an N source for maize (Zea mays L.) p roduction under ridge tillage (RT). A 2-yr field study was conducted o n a Kendaia-Lima silt loam (fine-loamy, mixed, nonacid, mesic Aeric Ha plaquept) to evaluate growth, yield, and quality of forage maize under moldboard plow (MP) and RT with fertilizer N (MPF and RTF) or with ma nure and supplemental fertilizer N (MPM and RTM, respectively). Soil w ater pressure and leaf carbon exchange rates (CER) were measured frequ ently; and plant N concentration, leaf area index (W), and dry matter (DM) accumulation were measured at the six-leaf stage (V6), silking (R 1), and hat-vest. The MPM treatment generally had lower CER from V5 to vs, lower whole-plant N concentrations at V6 in 1989 (24.7 g kg(-1)) and 1990 (28.2 g kg(-1)), and lower W and DM accumulation at V6 (0.39 and 37 g m(-2)) and R1 (3.27 and 844 g m(-2), respectively) in 1989. I n contrast, RTM compared to MPF and RTF had similar CER, whole plant N concentrations, W and DM accumulation on most measurement dates. The MPM treatment compared to MPF, RTF, and RTM had lower DM yields (13.6, 16.3, 15.7, and 14.9 Mg ha(-1)) and whole-plant N concentrations (7.8 , 8.5, 8.5, and 8.4 g kg(-1)) in 1989, and lower DM yields (13.7, 15.3 , 15.0, and 15.9 Mg ha(-1), respectively) in 1990. Surface application of manure before planting with supplemental fertilizer N at V5 was a viable N management system for forage maize under RT.