The effect of broadcast P applications and small amounts of fertilizer placed with the seed on continuously cropped corn (Zea mays L.)

The response of corn (Zea mays L.) to broadcast P applications and to small amounts of fertilizer placed with the seed (fws) was measured in three field trials conducted for 10 years. Five rates of P (0, 11, 22, 45, and 90 kg ha^–1 yr^–1) were applied with and without 4.0-6.4-3.2 kg N, P, K ha^–1 placed with the seed (fws) in a factorial arrangement of treatments. The fws treatment delayed emergence at all sites, reduced final emergence at two of the three sites, increased seedling dry weights at the 4 to 6 leaf stage and reduced the time to 50% silking at two of the three sites. Ear moisture content at harvest was reduced by fws at all sites which indicated that fws advanced maturity. The fws treatment increased grain yield at two of the sites by 1.3 and 2.3%, respectively. Broadcast P applications increased seedling dry weight at all sites but decreased the time to 50% silking only at one site. Broadcast P decreased ear moisture content and increased grain yield at two sites. There was a significant fws by broadcast P interaction in the most P deficient soil such that response to broadcast P was lessened by fws. The interaction was strongest during the early stages of growth and decreased with maturity resulting in no fws by broadcast P interaction for grain yield.