Performance of silage corn (Zea mays L.) in a cool climate ecosystem: effects of photodegradable plastic mulch

Yield of silage corn (Zea mays L.) in Newfoundland (NL), Canada, is limited by low corn heat units (CHU). This is a reflection of generally moderate temperature throughout the growing season in addition to having a late spring and early fall. Clear photo-degradable plastic film, applied to the soil after sowing, may boost soil and air temperatures and hence advance growth and development. Research was conducted at three on -farm sites near St. John’s in 2000 and 2001 to determine the effects of plastic mulch on time from planting to emergence (VE), 50% silking (R1), 50% kernel milk line (R5.5) and dry matter (DM) yield. Three early hybrids with CHU ratings of 2100, 2200 and 2300 were planted in late May of each year when the soil temperature was above 10°C. At planting, half of each plot was covered (PC) with a clear photo-degradable plastic film (X-Tend Plastic System®), 1.32 m in width and 6 m thick, and the other half was not covered (NC). During the first 30-35 d after planting, the crops grew under the thin plastic mulch before breaking through as it started to degrade. During this time, air (10 cm above soil surface) and soil (5 cm depth) temperatures underneath the plastic film were recorded. These were compared to the soil (5 cm depth) and air (100 cm high) temperatures of the NC plots. Soil and air temperatures for PC plots were consistently higher than for NC plots in both years. The plastic continued to degrade during the rest of the season and was completely degraded by the time of harvest in late `September. In 2000, the plastic advanced VE by 9 to 13 d, R1 by 10 to 15 d and R5.5 by 9 to 15 d relative to the NC treatment. In 2001, advancement of VE due to the plastic mulch ranged from 8 and 12 d, 6 to 9 d for R1 and 6 to 11 d for R5.5. Relative to the NC treatment, the plastic improved CHU by 9% and total DM yield by 22% in 2000 and improved CHU by 7% and total DM yield by 14% in 2001. A small increase in CHU due to plastic mulch resulted in a proportionately larger increase in total DM yield. Plastic mulches have the potential to accelerate maturity thereby insuring silage corn crops achieve acceptable DM yields in cool climate regions such as Newfoundland.