Plant And Substrate Based Factors Affecting Design And Management Of In-Field Soilless Strawberry Production Systems

The strawberry industry in California has expressed interest in soilless field production as an alternative to soil fumigation, so this research was undertaken to study the response of 'Albion' strawberry plants to plant- and substrate-based factors that affect the design and management of such systems.;Low substrate aeration reduced shoot and root dry weight, as well as leaf area, stomatal conductance, photosynthesis, plant water potential, and leaf nitrogen concentration. Root growth was greatest at air-filled porosity values between 13% and 25%. With proper irrigation management, strawberries grown at average air-filled porosities between 10% and 25% should achieve high productivity.;Root-zone volumes of soilless substrate as low as 2 liters per plant and once-daily irrigation (twice-daily irrigation of mature plants during high-ET conditions) can be used for field production of strawberries without affecting yield, as long as the substrate provides adequate air-filled porosity and available water. Daily plant water uptake peaked in summer at about 0.5 to 0.7 L, and maximum daily nitrogen uptake per plant was 28.5 mg. Nitrogen supplied in a liquid feed at a concentration of 60 ppm is sufficient to support high yields. Large root zone temperature fluctuations negatively affected strawberry plant growth, water relations, fruit yield and quality. We attribute this reduced growth to the very negative stem water potentials that occurred when root zone temperatures were near 5ºC. Root zone temperature had little or no effect on photosynthesis, gas exchange, fluorescence, or foliar nutrient levels. The consequences of diurnal RZT fluctuations during strawberry production appear to be small if the minimum temperature is above 7ºC.;Clonal integration (the capability of reciprocal resource translocation among interconnected plants through their shared stolon) alleviated salinity stress by allowing for resource transfer between interconnected mother and daughter plants. Leaf area, shoot and root dry biomass, gas exchange parameters and instantaneous water use efficiency in salinity-challenged plants were maintained near the values for non-stressed plants. Interclonal resource translocation was mainly driven by the contrast in stress intensity between mother and daughter plants.;The results from these experiments are applicable to specification of appropriate conditions for soilless field production of strawberry. Aeration, water-holding and nitrogen requirements for the system were defined so that the volume needed for field production and resources were minimized. Detrimental effects of high fluctuating temperatures can be anticipated so that the planting date may be changed later in the season to avoid low temperatures. These experiments supported efforts to design and build a cost-efficient soilless field production system for strawberry, providing the industry with a non-chemical alternative to pre-plant soil fumigation with methyl bromide.