Improving the fertilizer and irrigation recommendations for peach production in Georgia and the southeastern U.S.

Summary

Georgia and the Southeastern U.S. possess a unique environment that challenges the irrigation management in peach orchards. In the southeast United States, peach trees are not irrigated until their first three or four years after planting. Trees rely only on natural precipitation as their water source. Our previous research has shown that trees with supplemental irrigation since establishment yielded larger canopies (especially in years with limited rainfall) and higher yields in comparison with trees with no supplemental irrigation. For fertilization, recommendations have not been updated in several decades and it is believed that they were based on studies from Mediterranean regions. In our previous research, we tested four different rates of fertilizer to be applied during the first years of orchard establishment. The rates used for this experiment were doubled, half, and a quarter of the recommended rates. These were compared to the standard application. We found that the use of half and a quarter of the recommended rates yielded plants that had a similar growth and yield than plants grown with the recommended rates. The modified rates of half and a quarter of the recommended rates reduced production costs without resulting in nutritional deficiencies and reduction in yield. Currently we are starting year five of this project. Our study is continuing to understand the effects of our different irrigation and fertilization management in a mature peach orchard. No long-term fertilization and irrigation studies have been previously done in Georgia.

Situation

In 2019, U.S. peach production accounted for 74,400 acres with a total of 681,600 metric tons of production and a value of $519M. Georgia (8,500 acres, 39,100 metric tons, $37.8M) ranked third in the U.S. for peach production (USDA-NASS, 2020). During the first years of establishment, trees rely only on natural precipitation as their water source. After irrigation is installed, no recommendations are present and irrigation is based on the grower’s experience. Dr. Chavez identified this as an important area of research as orchard establishment and care can affect fruit production and orchard longevity. Similarly, fertilizer recommendations are believed to be based on studies performed in California under environmental conditions not representative of Georgia’s environment. The current recommendations for irrigation and fertilization used in Georgia need to be updated.

Response

Dr. Chavez established a field experiment at the Dempsey Farm with a total of 240 plants of ‘Julyprince’ peach variety planted in July-August 2015. The experimental area was divided into two areas: One area had the treatment combinations of drip irrigated vs. non-irrigated trees, with fertilization rates of 25%, 50%, 100%, and 200%, totaling eight combinations. The other area had the treatment combinations of micro-sprinkler irrigated vs. non-irrigated trees, with fertilization rates of 25%, 50%, 100%, and 200%, totaling eight combinations as well. These combinations within each area were randomized and replicated in 4 blocks. Irrigation conditions were maintained using a soil moisture sensor to maintain adequate moisture for the plants. The current recommended rates for one-, two-, and three-year-old trees are 65, 95, and 98 kg of N/ha, respectively (referred as 100% in this experiment). Fertilization levels were later simplified in 2019 to 49 and 98kg of N/ha (50% and 100% of the recommended rates). Data was collected in 2016-2020 for plant growth and yield.

Impact

Dr. Chavez identified that irrigated plants had a better development than non-irrigated plants in the three years of establishment. Plants had 55.6%, 18.3%, and 11.2% more canopy volume in years with limited rainfall (2016) and average rainfall (2017 and 2018) in comparison with trees with no supplemental irrigation. There were no differences in canopy volume for 2019 for irrigated vs. non-irrigated plants. Differences in cumulative yield (2017-2019) were observed when comparing irrigated and non-irrigated trees, with irrigated trees yielding 88.2kg per tree in comparison with 68.0kg per tree for non-irrigated plants. This yield increase can bring an additional $9,945.02 per hectare with a cost estimate of installing irrigation per hectare of $232.03. In Georgia, approximately 200 hectares are being replanted every year. If we calculate only the gain produced by using irrigation from year one, the peach growers in Georgia would be making an additional $2,012,306 when the trees become productive. For fertilization, in our study we tested four different rates of fertilizer to be applied during the first years of orchard establishment. The rates used for this experiment were doubled, half, and a quarter of the recommended rates. These were compared to the standard application. We found that the use of half and a quarter of the recommended rates yielded plants that had a similar growth and yield than plants grown with the recommended rates. If we calculate the impact in Georgia peach production of 4,168 ha and savings of 50% of the fertilizer, this will result in gains of about half of the cost of fertilizer per acre with a total estimate of $247,200 in savings for peach growers in Georgia per year. Currently we are finishing year five of this project. Demonstrations plots will be set-up in grower farms to test these new rates and recommendations.

State Issue

Plant Production

Details

• Year: 2020
• Geographic Scope: Multi-State/Regional
• County: Spalding
• Location: Georgia Station, Griffin
• Program Areas:
  • Agriculture & Natural Resources