Increasing Fertilizer Rates - Impact on Yield in Twin-Row Corn and Soybean Grown in Rotation.

Twin-row planters and twin-row (TR) production have been used since mid- to early-2000's for both soybean and corn. The system has become standard practice in many wide-row (38- or 40-in) production fields as the landscape has shifted to more grain crops and away cotton. Corn and soybean, when planted early with irrigation potential, have gained both in popularity and profitability and are adaptable to many soil types. Field studies were established in 2012 (6-yr study) at the Delta Research and Extension Center to evaluate both crop rotation effects and the impact of increased nitrogen, phosphorus, and potassium (NPK) fertility on differing soils. The soils chosen included sandy loam (favoring corn production) and clay (favoring soybean production). Both areas were bedded on 40-in (102-cm) rows with twin-rows spaced 10 inches (25 cm) apart on the raised bed. Producers are more conscious of soil testing but often choose to apply no fertilizer or apply without soil testing. The fertility component of this research evaluated a standard practice (SP) and a high fertility (HF) system. The SF system included 220 lb N/acre (246 kg N/ha) for corn , and no P or K for either crop. The HF system included increased N (260 lb N/acre, 291 kg N/ha) plus 26 lb P/acre (29 kg P/ha) and 50 lb K/acre (56 kg K/ha). Cultural practices were maintained across each field with planting and harvesting as possible but influenced by weather and wet soil conditions. The two center rows of each 4-row plot were harvested for yield with samples taken to determine harvest moisture, bushel test weight and Seed Index (100-seed weight). Grain yields varied across years with most response associated with N rate. on the clay (soil test P and K were high), added fertilizer had no effect.