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Growth, Maturity, and Yield Responses of Silage Maize (Zea mays L.) to Hybrid, Planting Date and Plastic Mulch

ABSTRACT Information on planting date-by-hybrid combinations is needed for the successful production of silage maize (Zea mays L.) in Newfoundland, Canada. In 2001 and 2002, field studies were conducted to determine the effects of plastic mulch and planting dates on emergence, growth and dry matter (DM) yield of maize hybrids of different maturity. The hybrids were ‘Pioneer(r) 39NO3’, ‘Pioneer(r) 39D81’, and ‘Pioneer(r) 37H24’, abbreviated P39NO3, P39D81 and P37H24, with 2100, 2600 and 3000 CHU (corn heat units), respectively. The planting dates were 23 April (PD1), 7 May (PD2), 21 May (PD3), and 4 June (PD4). The plastic mulch consistently increased daytime soil and air temperatures but effects on nighttime soil and air temperatures were inconsistent. Soil and air temperatures 15°C or higher promoted optimal stand establishment and growth. The plastic mulch generally improved percent emergence (EM), accelerated days from planting to emergence (VE), and 50% silking (R1), and also increased whole-plant DM content and DM yield. Percent emergence and days advanced by plastic mulch on VE and R1 were highest at PD2. All hybrids, except P37H24, reached the harvestable stage of 50% kernel milk line (R5.5) before the first autumn killing frost. With plastic mulch, significant increases in DM contents, DM yields, and harvest index (HI) of P39NO3 and P39D81 were consistent at all planting dates, except at PD4. The plastic mulch had less yield advantage at PD1 and PD4 compared to PD2 and PD3 because extremely slow germination reduced the expected yield advantages at PD1. On the other hand, emergence and growth at PD4 happened during the warmest part of the summer and therefore, minimized the beneficial effects of plastic mulch. As planting was delayed between PD2 and PD4, DM yield declined at the rate of 1.5% d−1 on bare ground and 1.7% d−1 with plastic mulch. The growth and yield benefits of using plastic mulch were most apparent at PD2 with P39NO3 and P39D81. The results suggest that it is not possible to stagger maize planting in eastern Newfoundland, and that to assure adequate maturity and DM yield before the first killing frost, seeding of hybrids ≤2600 CHU should begin under plastic mulch on or soon after 7 May provided soil temperature is not too low to limit emergence.