Nitrogen use efficiency in maize as affected by nitrogen availability and row spacing

Efficient use of N in plant production is an essential goal in crop management. An experiment was performed at INTA Balcarce, Argentina during 3-yr to evaluate the effect of row spacing and N level on nitrogen use efficiency (NUE) in no-till (NT) irrigated maize (Zea mays L.). Treatments consisted of a factorial combination of row width (70, 52 and 35 cm) and N rates (0 to 180 kg N ha(-1)). Nitrogen rate and narrow rows increased total dry matter (DM), grain yield, and N accumulation. Relative responses to narrow rows decreased as N availability increased. The NUE decreased with N rate and increased with narrow row spacing. Narrow rows increased NUE by 12 and 15% expressed as DM or grain yield per unit of available N, respectively. Physiological efficiency decreased with N rate and was not affected by row spacing. Recovery efficiency (RE) decreased with increasing N rate, and increased for the narrow row spacings. The effect of narrow rows on RE decreased as N availability increased. Narrow rows increased NUE largely as a result of increased RE. These increments in RE could contribute to increase the profitability of maize production and to diminish the risk of environmental pollution.