Row Spacing, Plant Population, and Water Management Effects on Corn in the Atlantic Coastal Plain 1

Lack of water because of erratic rainfall frequently limits corn ( Zea mays L.) production on Typic Paleudults in the Atlantic Coastal Plain. Traditionally, wide (96 cm) row spacing and low plant population have been used to prevent water stress, but recently landowners have begun to invest in irrigation systems. Changes in row spacing, plant population, or fertilization practices may be required to achieve maximum water‐and nutrient‐use efficiency with those systems. We evaluated plant population treatments averaging 7.0 and 10.1 plants m −2 in single and twin rows on a Norfolk (fineloamy, siliceous, thermic Typic Paleudult) loamy sand during 1980, 1981, and 1982. Three water management [nonirrigated, irrigated using tensiometers (TENS) to measure soil‐water potential for scheduling, and irrigated using a computer‐based water balance (CBWB) for scheduling], and two fertilization programs were also evaluated in a four‐factor split‐plot design. Water management and plant population interacted significantly. Planting in twin rows increased grain yield an average of 0.64 Mg ha −1 (10 bu/A), but planting more than 7.1 plants m −2 significantly increased grain yield only in 1980. Irrigation increased grain yield 150, 161, and 8% in 1980, 1981, and 1982, respectively, as a result of increased kernel weight and number of kernels per ear. Increasing total N, P, and K application beyond 200, 30, and 167 kg ha −1 , respectively, did not significantly influence grain yield or yield components. Yield advantages of narrow rows can be obtained on Coastal Plain soils which require subsoiling by using a twin‐row planting configuration. Irrigation can be scheduled using either tensiometers (soil‐water potential) or a computerized water balance without significantly changing corn grain yield, nutrient accumulation, or yield components.