Soil nitrogen amendment effects on nitrogen uptake and grain yield of maize

Efficient use of soil N amendments in maize (Zea mars L.) production is nec essary to maximize producer's economic returns and to maintain soil and wat er quality. A 5-year field experiment was conducted on a Brandon loam soil (fine loamy, mixed, mesic Typic Endoaquoll) (Orthic Humic Gleysol) with the objective of measuring N uptake and grain yield of two maize hybrids under different N amendments [no amendment, NH4NO3 at 100 and 200 kg N ha(-1), a nd stockpiled and rotted dairy manure at 50 and 100 Mg ha(-1) (wet wt.)] to determine differences in N use efficiency (SUE) and its components, N upta ke efficiency and N utilization efficiency. The N amendments increased the grain yield (by an average of 20%) and NUE (by an average of 17.5%) of a mo dern hybrid (Pioneer '3902') more;han that of an old hybrid ('Pride 5'). Th e difference method that was used to estimate N recovery indicated that, ov er the course of the study, Pioneer 3902 took up 48% of inorganic fertilize r N and 20% of the manure N, compared with 42 and 16%, respectively, for Pr ide 5, Manure application resulted in total N uptake comparable to the 200 kg N ha(-1) treatment. Grain yields of manure treatments in 1993 and 1994 w ere generally lower (5-15%) than the 200 kg N ha(-1) treatment. During the latter periods (1995 and 1996) of the study with repeated application under continuous maize, all manure treatments produced grain yields equal to or slightly greater (6-13%) than the fertilizer treatment. Dairy manure applic ation increased N uptake and grain Yield of maize. The NUE, based on added mineral N levels, for all manure treatments was greater than for the 200 kg N ha(-1) treatment.