Leaching losses from blueberries grown in sandy soils amended with pine bark

Leaching of irrigation water from blueberry (Vaccinium spp.) plants intensifies when sandy soils are amended with pine (Pinus spp.) bark. In a greenhouse study, leaching fractions of water (LFW) and nutrients (LFN) were determined from two blueberry (V. corymbosum L.) cultivars, 'Emerald' and 'Jewel', grown in biochar-treated and nontreated sandy subsoil and irrigated with drip emitters using one of three pulse frequencies in a factorial design. The LFW was >50% under Emerald and <20% under Jewel, which has a more extensive root system. When the frequency of same volume of irrigation was increased from 2 (F2) to 10 (F10) pulses per day, the average LFW decreased from 46 to 30%. The LFN from a single fertigation was much lower than the total LFN after 6 d of irrigations applied between two fertigation events. The LFN increased linearly with LFW. Amending subsoil with 2% biochar increased soil pH, limited root growth, and did not reduce nutrient leaching. Eighteen months after plant establishment, 1.9% of applied NO₃ ^--N and 2.5% of applied PO₄ ^3--P from Emerald and 0.8 and 1.0%, respectively, from Jewel leached below the root zone during a fertigation event. During irrigations following a fertigation event, 10.5% of both NO₃ ^--N and PO₄ ^3--P from Emerald and 3.0 and 2.5% from Jewel leached below the root zone. All growth parameters including root/shoot ratio were higher in Jewel than Emerald. This study indicated that leaching rates could be reduced by selecting blueberry cultivars with a dense root system and using a drip irrigation system with >5 pulses d^-1 to supply the daily water requirements in pine bark-amended sandy soil.