Maize Grain Yield Response to Tillage and Fertilizer Nitrogen Rates on a Tara Silt Loam

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AbstractEffects of tillage on the appropriate fertilizer N applications needed to achieve maximal grain yield are poorly denned. The study objective was determination of relative corn grain yield response to N application rate for four tillage practices: no‐tillage (NT), ridge tillage (RT), fall chisel plowing (CP) and fall moldboard plowing (MP). Maize (Zea mays L.) grain yield and N accumulation were monitored over a 6 year period with the same tillage treatment and the same fertilizer N rate applied each year to each plot. Two hybrids, differing in relative maturity rating, were planted each year. Fertilizer N rates ranged from 10 to 190 kg ha−1 and consisted of 10 kg ha−1 of liquid starter N applied at planting with varying amounts of fall applied anhydrous ammonia. With only starter fertilizer, grain yields increased with tillage intensity in the order NT ≤ RT ≤ CP ≤ MP. With ≥ 55 kg total applied Nha−1, 6 year average grain yields were unaffected by tillage. Total N removed in grain annually with only starter fertilizer ranged from 25–85 kg ha−1 Maximal amounts of N removed, about 145 kg N ha−1, occurred with 100–145 kg applied N ha−1 for all tillage treatments under the more favorable climatic conditions. Several interactions affecting grain yield appear climatically sensitive with exception of tillage by fertilizer N interactions. Because of variability in climate, planting dates varied by almost 4 weeks. Relative yield loss due to planting delay were Fertilizer N (mean change ≅−124 –−275 kg ha−1 day−1) > Starter N only and MP (mean ≅− 259 kg ha−1 day−1) > other tillages in general. Yield loss due to delayed planting ranged from 0.0–275 kg ha−1 day−1. Grain yield gains due to early spring soil temperatures were 16.0–21.8 kg ha−1 index‐degree−1 with MP tillage and averaged 2.7– 16.7 kg ha−1 index‐degree−1 more than those of other tillage‐hybrid combinations.