Row spacing effects at different levels of nitrogen availability in maize

No-tillage maize (Zea mays L.) grown without adequate N intercepts less tha n 95% of the incident radiation at flowering. Reducing the distance between rows could increase radiation interception and grain yield. A 2-yr experim ent was conducted at INTA Research Station, Balcarce, Argentina (37 degrees 45' S; 58 degrees 18' W), to study the effect of row spacing and N availab ility on intercepted radiation, kernel number, and grain yield of no-till m aize. Treatments consisted of a factorial combination of row width (0.35 an d 0.70 m) and N (0 and 120 or 140 kg ha(-1) each year) at a constant plant density. Low N decreased kernel number and grain yield. Narrow rows signifi cantly increased kernel number per unit area and grain yield. Average incre ases in response to narrow rows were 14.5 and 20.5% fbr kernel number and g rain yield, respectively. However, relative increases in response to narrow rows were greater at low N. A close association between kernel number and intercepted radiation during the bracketing-silking period was observed. Wi th conventional row spacing, relative grain yield responses to narrower row s decreased as crop radiation intercepted at flowering increased. A decreas e in row distance when N was limiting partially offset the negative effects of N deficiency on grain yield. Our results indicate that 27 to 46% increa ses in grain yield were obtained in response to narrow rows in N-deficient maize crops.