Soil and plant samples taken from 90 sweet corn fields in the Willamette Valley during 1978 showed low Cu and B levels but responses to applied Cu and B in commercial fields have been inconsistent. Yields and maturity dates of sweet corn in the Willamette Valley are known to respond to banding P fertilizer at planting. The yield response to various rates of banded P in the presence of high P soil test is unknown. High rates of P and Cu may be antagonistic. In addition, soil pH may affect uptake of Cu, B, and P and soil temperature is also known to affect availability of these nutrients. The following experiments were designed to evaluate the effects of lime, Cu, B, banded P, and broadcast P on sweet corn yield at both an early and a late planting date.
Methods
For the early planting (May 7, 1980), the entire plot area was limed at 3.5 tons/acre. The main plot treatments were 10 pounds/acre of Cu x three pounds/acre of B x 200 pounds/acre of broadcast P205 in randomized block design with four replications. The main plots were split by banded P application of zero, 60, and 150 pounds/acre of P205 and these subplots were split for two harvest dates.
For the late planting (June 5), the main plot variable was zero, two, four, and six tons/acre of lime in randomized block design with four replications. Main plots were split into four randomized subplots for the Cu x B variable described above. These subplots were again split by the above banded P variable and these sub/subplots were split for harvest date. All plots received 180 pounds/acre of total N, 50 pounds banded at planting, and the remainder broadcast when the corn was about one foot tall. Atrazine and alachlor at 1.0 pound and 2.5 pounds/acre, respectively, were used for weed control. The early planting was harvested on September 4 and September 9, the late planting on September 22 and September 25.
Results
For the early planting, there was no significant response to Cu or B. Broadcast P alone, in the absence of banded P, increased yield of mature ears by 34 percent at the first harvest and 11 percent at the second harvest. Thus, the increased yield was primarily because of accelerated maturity. Broadcast P, in the presence of 60 pounds/acre of banded P205, increased mature ear yield by 58 percent at the first harvest and five percent at the second harvest. Broadcast P had no effect in the presence of 150 pounds/acre of banded P205.
For the second planting, P again had the major effect on yield. Yields were higher at 150 than at 60 pounds/acre of banded P205. Liming increased yield in the presence of banded P. At low pH, there was a slight increase in mature ear yield with addition of Cu at the first harvest.