The 2012 ASHS Annual Conference

Biodegradable mulches which can be tilled into the soil at season’s end could provide economic and environmental benefits compared to polyethylene plastic mulch film (PEM) if they do not negatively affect yield. A study at Mount Vernon, WA in 2010 and 2011 compared three commercially-available mulches marketed as bio-degradable [BioBag® (BB), BioTelo® (BT), and WeedGuardPlus™ (WG)] and one experimental spun bonded poly(lactic acid) mulch fabric (PLA) to PEM and bare ground (NM) controls on yield of tomato cv. ‘Celebrity’ grown in high tunnels and open field. In 2010, BB (12.5 kg/plot), BT (12.0 kg/plot), and paper WG (10.0 kg/plot) produced yields statistically equivalent (P = 0.0036) to PEM (10.1 kg/plot); BB, BT, and PEM yields were greater than bare ground (8.3 kg/plot); and, BB and BT yields were greater than PLA (9.0 kg/plot). In 2011, BB (15.2 kg/plot), BT (16.5 kg/plot), and NM (15.1 kg/plot) produced similar yields to PEM (15.8 kg/plot; P = 0.0259); and, BB, BT, and PEM yields were greater than PLA (13.9 kg) and WG (12.7 kg/plot). In 2010, using the USDA standard for Grade 1 tomatoes, NM (19.6%) had a greater percentage of marketable fruits (by weight) than BB (7.8%), BT (8.9%), PLA (12.7%), and PEM (7.1%); and, WG (14.1%) had a greater percentage of marketable fruit than BB and PEM (P = 0.0018). In 2011, using a slightly different direct market standard, NM (71.7%) and WG (68.5%) produced a greater percentage of marketable fruits than BB (50.0%), BT (50.4%), PLA (54.2%), and PEM (38.6%); PEM was significantly lower than all other treatments (P ≤ 0.0001). Though NM consistently produced a greater proportion of marketable fruits, BB, BT, and PEM tended to produce higher overall yields. NM tended to have less fruit cracking compared to BB, BT, and PEM (P = 0.0003 in 2010, P= 0.4541 in 2011), and this cracking was likely the reason for increased marketable fruit with NM. Fruit cracking was the primary unmarketability factor both years.