2018 ASHS Annual Conference

Drought has been common in the southeastern U.S. in the past years, affecting peach production. Traditionally, young peach trees (one to three-year-old) are not irrigated until the third year and rely on rain as water source. There is growing interest in irrigating young plants; however, no scientific guidelines are available for the region. Similarly, current fertilizer recommendations for young peach plants are outdated and/or based on studies performed in Mediterranean regions or California and may not be applicable to the southeastern U.S. Improvement of the irrigation and fertilization recommendations is paramount and the objective of this research. ‘Julyprince’ plants grafted onto ‘Guardian’ rootstock were planted in 2015, at a density of 358 plants per hectare. Two irrigation systems (drip and micro-sprinkler), two irrigation rates (irrigated and non-irrigated), and four fertilizer rates (16, 33, 65, and 129 kg of N per hectare for one-year-old plants; and 23, 48, 95, and 191 kg of N per hectare for two-year-old plants) were tested. A network of sensors and nodes controlled the irrigation and maintained the soil volumetric water content (VWC) above an established threshold (varied from 15 to 25% of VWC). Granular fertilizer was hand-applied following current recommendations: one application of 10.0N-4.4P-8.3K in March and 2 applications of 15.5N-0P-0K, in May and July. Irrigated plants grew more than non-irrigated plants, with trunk cross-sectional area (TCSA) and canopy volume ~1.5X and ~1.7X greater, respectively, for both years. Fertilizer rates did not affect TCSA and canopy volume if plants were drip irrigated; however, higher fertilizer rates induced greater TCSA and canopy volume when micro-sprinkler irrigated, in general. Irrigation alleviated drought stress in 2016, increasing water potential and photosynthesis by ~0.6X and ~1.8X, respectively, for both years. However, no significant physiological responses were found in 2017, likely because it rained more than in 2016. The negative effects of the lack of precipitation and irrigation in 2016 carried over to 2017: the commercial yield of non-irrigated plants was ~20% lower when compared to irrigated plants. The fertilizer rates did not induce major differences for water potential, photosynthesis, and commercial yield. Compared to micro-sprinklers, drip irrigation increased stem water potential and photosynthesis in 2016, and commercial yield in 2017, while applying ~36% less water. In conclusion, drip irrigation was beneficial to young peach trees’ growth and fruit production; and fertilization can be adjusted/cutback by ~50% to reduce the environmental impacts and increase growers’ profit.