Twin-Row Soybean/Corn Rotation Response to Increased NPK Fertility.

Twin-row planting has gained in popularity and is now an established practice in the Mississippi Delta for both corn and soybean production. Over the last 20-25 years, crop rotations have regained their popularity among producers as grain crops replace cotton. Field studies were established to evaluate grain production in 1:1 or 2:1 (soybean:corn) systems planted in a twin-row configuration. Twin rows were spaced 25 cm apart on 102-cm (on center) bedded rows. Studies were designed and implemented on both sandy loam soil (favoring corn production) and clay soil (favoring soybean production). The fertility component was included to evaluate 1) a standard (SP) practice (soil test based) and 2) high (HF) fertility (increased nitrogen [N], phosphorus [P], and potassium [K]). The SF practice included 246 kg N ha-1, 0 kg P ha-1, and 0 kg K ha-1 while the HF practice included 290 kg N ha-1, 29 kg P ha-1, and 56 kg K ha-1. Plots received uniform N at planting (134 kg N ha-1) with the other nutrients applied after the stand was established. All cultural practices were maintain across each location (managed independently) with the same cultivars. At maturity, the center two rows of each plot were harvested with subsamples taken to determine harvest moisture, test weight, and Seed Index (100-seed weight). Grain yields for both and soybean were adjusted to a uniform moisture content. Results have varied from year to year with some response N response on the wetter years. On the clay site, where soil test P and K are high, the addition of extra fertilizer has not led to increased yields. Following soil test recommendations, especially under high yield environments is essential for economic yields.