2017 ASHS Annual Conference

Raised-bed system is broadly used for high-value crop production, such as strawberry in California. Typically, the raised-beds are covered with standard polyethylene (PE) film and have two drip tapes installed near soil surface for applying water and nutrients throughout the crop season. The drip tapes are also used for applying soil fumigants before planting to control soilborne disease, named drip fumigation. However, these fumigation practices often result in high fumigant emission loss and poor pest control results, impacting the sustainability of the crop production. Over past years, we carried out a series of trials in growers’ fields in southern coastal region of California, with the objectives of reducing fumigant emission and improving pest control efficacy for strawberry production. In the trials, we covered the raised beds with low permeability film (LPF) and applied fumigants (either with full rate according to growers’ standard or with half rate) through two or four drip tapes in compassion with the conventional fumigation methods (full rate fumigants applied through two drip tapes under PE). A non-fumigated control is also included in the trials. Each treatment was replicated four times in a randomized complete block design. Our results showed that the fumigant emissions were reduced dramatically from LPF covered raised-beds, which was <10% of the PE covered beds. The LPF covering was found to improve fumigant retention significantly and even the beds with half-rate had higher fumigant concentrations than the beds with full rate under PE. The four drip-tape layout further improved fumigant distribution compared to the two drip-tape layout. Corresponding with the improved fumigant distributions, the LPF beds showed better pest control results and higher early-season berry production than the PE beds or the non-fumigation control. Particularly, the beds with four drip tapes were superior. Our findings indicate that LPF covering and increasing drip tape number is the optimized fumigation solution for raised-bed production systems. Further research will be needed for optimizing the irrigation and nutrient management with the adoption of the LPF and multiple-drip tapes.