Hydromulches offer yield protection comparable to plastic mulch in organic strawberry production

Abstract Organic strawberry production using the annual hill system relies predominantly on polyethylene (PE) mulch for weed control. However, although nonbiodegradable PE mulches are allowed to be used in organic production, albeit with restrictions, they pose environmental risks, and disposal can be a problem. We assessed cellulose-based hydromulches (HMs) as a PE mulch substitute in organic strawberry production. HMs made from shredded newsprint, water, guar gum (6% of HM dry mass), and with or without a biochar-based colorant were applied to raised beds, then day-neutral strawberry plants were transplanted. Four HM treatments combining dark (D) or light (L) colored and low (L) 5,800 or high (H) 8,700 kg DW ha −1 rates, were tested against paper mulch (PAP), white-on-black PE mulch, and weedy and weed-free checks at two sites in North Dakota: Absaraka (with a sandy soil, common purslane-dominated) and Fargo (with a clay soil, Venice mallow-dominated). At Fargo, high-rate HMs suppressed weed density as effectively as PE mulch. At Absaraka, HMs reduced weed density less effectively than PE and PAP mulches; low-rate HMs performed poorly compared with high rates (35 and 40 weeds m −2 vs. 4 and 17 weeds m −2 ), likely because of rainfall after HM application and location-specific differences in the weed communities and soil types. At Absaraka, strawberry yield from the use of HM-DH was greater than PE (272 vs. 144 g plant −1 ), whereas yield from HM-LH, HM-DL and HM-LL mulches (215, 168 and 141 g plant −1 , respectively) were similar to yield with PE mulch. At Fargo, yield for all HMs (287, 223, 211, and 162 g plant −1 ) did not differ from that of PE (253 g plant −1 ). Although only high-rate HMs at Fargo suppressed weeds similarly to PE, fruit yield and quality were similar to that of PE with all HMs. Therefore, HMs could be promising sustainable alternatives to PE mulch for use in organic strawberry systems.