Pecan (Carya illinoinensis) orchards in Georgia and throughout the southeastern United States are commonly established from land that had previously been used for row cropping systems. Soil quality is characteristically low in the loamy-sand, low pH soils of the southeastern Coastal Plain. Changes in land use are known to exhibit different effects on soil quality; however, no studies specifically address soil enhancement from converting row crop land to pecan orchards in this region. Sampling was conducted in eight counties throughout the coastal plain of South Georgia in 2020 and 2021. The objectives of this study were to analyze and compare soil quality indicators of pecan orchards of varying ages and adjacent row crop fields. Soil quality indicators analyzed include soil organic matter (SOM), active carbon or permanganate oxidizable carbon (POXC), aggregate stability, cation exchange capacity (CEC), bulk density, porosity, Solvita CO2-Burst, SLAN (Solvita labile-amino nitrogen), pH, and total N. Results from this study demonstrate that pecan orchards under commercial management had higher soil quality compared with row crop fields based on the indicators measured. Active carbon and Solvita CO2-Burst measurements suggest that pecan orchards exhibited significantly higher rates of microbial activity and soil respiration. Indicators of soil microbial activity such as active carbon and Solvita CO2-Burst were strongly correlated with SOM, which explained much of the variation observed in these measurements of soil microbial activity. Selected soil quality indicators also provide evidence that the soil quality of commercial pecan orchards in this region improves with orchard age.
Current economic conditions demonstrate the need for disease-resistant, highly productive pecan (Carya illinoinensis) cultivars for the southeastern United States that can generate high yield potential and can be produced at a reduced cost to enhance grower profit margins. The objectives of this study were to evaluate the performance of the pecan cultivars Lakota, McMillan, and Excel in the humid growing region of the Coastal Plain of Georgia, USA, in the absence of fungicides. In addition, recognizing the excessive nut production of ‘Lakota’, we evaluated the response of ‘Lakota’ to mechanical fruit thinning. Four trees each of ‘Lakota’, ‘McMillan’, and ‘Excel’ were selected randomly for sampling. Trees within this orchard block receive no fungicide applications. Pecan scab (Venturia effusa) was not observed on any cultivar evaluated throughout the study. Powdery mildew (Microsphaera alni) was observed on all cultivars, but was significantly greater on ‘McMillan’ in 2020 and 2022 as a result of drier conditions in those years. Based on current data, all three pecan cultivars evaluated during this study are suitable for commercial production; however, ‘Lakota’ and ‘Excel’ performed best under these conditions in terms of nut yield. There was no consistent difference in nut weight among cultivars. ‘Lakota’ has the greatest potential in terms of percent kernel, averaging 58% kernel compared with 49% and 52%, respectively, for ‘Excel’ and ‘McMillan’. However, in years of excessive cropping, percent kernel of ‘Lakota’ is reduced significantly. Mechanical fruit thinning increased the following year’s production of ‘Lakota’ by 82% over nonthinned trees.