Corn response to within row plant spacing variation

Recent interest in establishing uniform spacing of corn (Zea mays L.) plants in the field has prompted many seed companies to offer planter-tuning services. Experiments were conducted in Wisconsin environments between 1999 and 2001 to investigate the response of corn to plant spacing variation (PSV). During 1999, adapted hybrids were grown in the field by overseeding and thinning to 37 000 and 74 000 plants ha -1 in a two-plant pattern with target PSV treatments of 0, 10.2, 20.3, and 30.5 cm and 0, 2.5, 5.1, 7.6, 10.2, and 12.7 cm, respectively. During 2000 and 2001, two-, four-, and eight-plant hill patterns were established with target PSV treatments of 5.1 and 10.2 cm; 5.1, 10.2, and 20.3 cm; 5.1 10.2, 20.3, and 30.5 cm standard deviation. The control treatment was a target PSV of 0 cm. In this study, PSV never affected plant lodging or grain test weight. In one of 24 environments grain moisture was significantly affected, but no relationship was observed with PSV. Grain yield was rarely affected by PSV in two-plant patterns. Relative grain yield was reduced up to 18% as plant spacing became more hill-like in two-, four-, and eight-plant patterns. Relative grain yield was reduced 1.06% cm -1 standard deviation as PSV increased above 12.0 cm. However, for most farmer field situations at current plant density recommendations, corn grain yield would not be affected by PSV, except when obvious hills are planted.