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To acquire accurate volumetric water content (VWC) measurements from horticultural substrates using dielectric sensors, a substrate-specific calibration is critical. Calibrations typically are conducted with a substrate without plants, but water in the root system may affect soil moisture sensor readings. We investigated the effect of root growth on the measured VWC. Lettuce seedlings (Lactuca sativa L. ‘Joek Chi Ma’) were grown in 10 cm round containers (440 mL) filled with soilless substrate. Four EC-5 soil moisture sensors (Decagon Devices Inc., Pullman, WA, USA) were used to determine the effect of root system size on sensor calibration over an eight week period. Both calibration coefficients (slope and intercept) decreased (P

Most orchid growers use bark as substrate to avoid too wet conditions, although it requires excessive water use of leaching. We conducted research to investigate the applicability of a soil moisture sensor-based automated irrigation system in Cymbidium production for efficient irrigation management and compared the growth and water use of Cymbidium under various substrate conditions. One-year-old Cymbidium ‘Hoshino Shizuku’ plantlets were grown in bark, coconut husk chips, coir dust, or a commercial growing mix at a similar matric potential within the easily available water range. Irrigation occurred when the substrate dried below the volumetric water content thresholds at 0.25, 0.30, 0.35, and 0.40 m3 m−3 in the bark, coconut husk chips, coir dust, and the commercial growing mix, respectively. Pseudobulb size, net photosynthetic assimilation rate, fresh shoot, and root weight of the Cymbidium showed no differences among the substrates, although Cymbidium grown in the commercial growing mix had better shoot growth than plants in the other substrates. The amount of irrigation was higher (ca. 6 times) in coarse substrates (bark and coconut husk chips) than fine substrates (coir dust and the commercial growing mix), indicating that fine substrates with higher water-holding capacity could use water more efficiently. The amount of irrigation and nutrient availability of the substrate in the coarse substrates were much lower than those in the fine substrates, producing a difference in growth of the Cymbidium among the substrates. Water use efficiency was 8–9.5 times higher in Cymbidium grown in fine substrates than plants grown in coarse substrates. Overall, the soil moisture sensor-based automated irrigation system could provide an appropriate moisture level for Cymbidium grown in fine substrates, avoiding too wet conditions, and produced quality Cymbidium with more efficient water and nutrient use than orchids produced in coarse substrates.

a b s t r a c t Independently controlled irrigation plots were designed to test two container nursery irrigation regimes on oakleaf hydrangea (Hydrangea quercifolia 'Alice') in both nursery and controlled greenhouse environ- ments. The experiments were conducted in both 3.8 and 11.4 L containers. Plants were automatically irrigated by one of two soil moisture sensor-based regimes: (1) a daily water use (DWU) system that delivered the exact amount of water that had been lost in the previous 24 h and (2) an on-demand (OD) irrigation system based on a specific substrate moisture content derived from the relationship between substrate moisture and photosynthetic rate. In this system, irrigation was applied when the substrate

Irrigation technologies that conserve water are necessary to assure the economic and environmental sustainability of commercial agriculture. This study was conducted in the Rio Grande Valley in Texas to evaluate yield and quality of subsurface drip irrigated onions ( Allium cepa L.) using different scheduling strategies and water stress levels. One strategy consisted of initiating irrigation when the reading of a granular matrix sensors (Watermark ® 1 soil moisture sensor, Irrometer, Co., Riverside, CA) installed at 0.2 m depth reached −20 kPa (optimum), −30 kPa and −50 kPa. The second strategy was to replace 100%, 75%, and 50% of crop evapotranspiration (ETc) weekly. Higher total yields, and jumbo onion size yields were obtained when the soil moisture was kept above −30 kPa. Yields were not affected when water applications were reduced from 100% to 75% ETc and from −20 to −30 kPa. The ETc strategies of 100%, and 75% ETc resulted in similar water usage to the soil moisture monitoring strategies of initiating irrigation at −20 and −30 kPa. Total yields dropped significantly when soil water stress increased below −50 kPa. For the ET based strategy yields also dropped with the 50% ETc treatment. Onion bulb pungency and brix were unaffected by water level.

Zucchini squash ( Cucurbita pepo L.) is an economically important vegetable crop in Florida. Typically, it is intensively managed with high inputs of fertiliser and irrigation water. Our objectives were to evaluate the interaction between fertilisation rates and irrigation treatments, and to quantify nitrate leaching in a plastic mulched/drip irrigated zucchini squash production systems. Three studies were carried out. The first study evaluated different depth placement of drip and fertigation lines on plant growth and fruit yield. Treatments included SUR (both irrigation and fertigation drip lines placed on the surface); SS and SDI (irrigation line placed 0.15 m below the fertigation line on the surface). The second and third studies compared three different N-rates and different soil moisture sensor-based irrigation strategies. Nitrate-N leaching was monitored by zero tension drainage lysimeters and soil samples. N leaching increased when irrigation and N-rates increased, with values ranging from 2 to 45 kg ha −1 of N. Use of SDI increased yields by 16% compared to the S&S treatment, and reduced nitrate leaching by 93% while increasing the water use efficiency by 75% compared to a fixed 2-h irrigation event per day treatment. Application of N above the standard recommended rate of 145 kg ha −1 did not increase yield, although yields were reduced at the lowest N-rate. The use of soil moisture sensors for automatic irrigation control reduced irrigation application and minimized nitrogen leaching. In addition, combining the soil moisture controlled SDI system that had surface applied fertigation resulted in similar or higher yields, while reducing both water use and potential N leaching because of improved nutrient retention in the root zone.