Delayed Soybean Emergence: Competition or Compensation?.

The effects of delayed emergence of soybean have not been well studied. Our objectives were to quantify the response of individual plants and yield components as various emergence rates and plant populations. The study focuses on row-to-row delay of soybean planted in 0.19 m rows. The delays were created by planting initial 0.38 m rows and interplanting between rows at succeeding growth stages of the initial stand of soybean. Row-to-row delay is studied across three factors:  2 initial plant populations (247,105 plants ha^-1; 123,552 plants ha^-1), 3 interplant populations (33%, 67%, and 100% of both initial populations), and 4 successive delays of interplanted rows (when initial rows were:  planted, VC, V2, and V4). Treatments were arranged in a randomized complete block design with four replications at West Lafayette Indiana. Five flagged plants per row in initial and interplanted rows were measured for plant height, growth stage, and nodes per plant. Post-harvest measurements were taken on 2 m of harvested row and included branches per plant, pods and seeds per main stem, pods and seeds per branch, total seed weight per main stem, and total seed weight per branch. Preliminary results indicate that the percentage of the stand which is delayed is less important than the amount of delay itself. However, at these populations total yield does not appear to be affected by either the number of delayed soybeans or the length of delay for these soybeans.