2018 ASHS Annual Conference

Nitrogen fertilization and irrigation are two essential management practices to achieve adequate plant growth and yield. For many years, the peach industry in the southeastern U.S. has been using fertilizer recommendations for young plants that are believed to be outdated and not well-suited to modern production practices. On the other hand, irrigation recommendations for young plants are non-existent, and irrigation is typically not used until three years after planting. We tested different fertilizer and irrigation rates from field planting, at the University of Georgia, with the objective of improving current recommendations for young plants. To complement that research and to improve our understanding of the seasonal nitrogen dynamics in orchards, we determined how different nitrogen rates and irrigation availability influence the amount of nitrogen being utilized by young peach plans. The amount of nitrogen removed by plant material during major management practices that affect plant growth (pruning, thinning, harvest, and defoliation) was quantified for the 2016 and 2017 seasons. ‘Julyprince’ plants grafted onto ‘Guardian’ rootstock were planted in 2015, at a density of 358 plants/hectare. Two irrigation rates (sensor-based irrigation at volumetric water content of 15-25% versus non-irrigated), two irrigation systems (drip versus micro-sprinkler), 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. Plants growing in the highest fertilizer rate had 230 g of nitrogen removed by the management practices compared with ~205 g with the lowest fertilizer rates. Fall defoliation was where most of the nitrogen was allocated and removed from the system. Irrigated plants had more nitrogen removed through the management practices than non-irrigated plants (248 g vs. 174 g per plant), with most of the nitrogen removed by defoliation and pruning. When comparing the irrigation systems, drip irrigation induced greater nitrogen removal than sprinkler irrigation (231 g vs. 191 g per plant), mainly through defoliation. The results of this research are important indicators that when more nitrogen is applied, plants primarily allocated resources to produce vegetative structures, not affecting fruit yield if plant’s needs are met. Irrigation induces greater nitrogen absorption by the plant, resulting in greater vegetative and reproductive structures. Even with all these variations in nutrient allocations and removal, no nutritional deficiency was found across treatments.