Soil Organic Matter Influences Citrus Growth, Nutrient Uptake, and Root System Architecture

Abstract

Florida citrus production faces multiple challenges, including low nutrient retention, low soil organic matter (SOM) and, more importantly, the devastating impacts of citrus greening, which is a bacterial disease that impacts root growth and nutrient uptake. Growers are exploring management practices to improve SOM and hoping to enhance tree health, nutrient uptake, and yield. Despite these efforts, research of the effects of SOM on citrus root systems and nutrient absorption remains limited, particularly that defining a target SOM range for optimal production. This study investigated the influence of varying SOM levels on citrus tree root system architecture, biomass, and nutrient uptake. This experiment was conducted in a greenhouse where 1-year-old ‘US-942’ rootstocks were assigned to a completely randomized experimental design and exposed to one of six experimental treatments with differing levels of SOM as the growing media [0% (control), 1%, 2%, 3%, 5%, or >10% (100% compost)]. Each pot was considered an experimental unit and replicated six times (n = 6), for a total of 36 seedlings. The results indicated that although root biomass did not change significantly, lower SOM levels resulted in longer roots with greater surface area and volume, likely because of increased soil exploration for nitrogen. Higher SOM treatments, however, showed improved leaf nutrient content, with increased nitrogen, phosphorus, and potassium uptake. In conclusion, the results of this study indicate that 3% SOM may be ideal for citrus because it positively impacted both root system architecture and nutrient uptake, which are both of primary concern because of citrus greening. Further research is necessary to establish critical SOM thresholds and evaluate the effects under field conditions and in combination with different irrigation and fertilizer regimes.

Keywords

• citrus
• florida
• us-942
• rootstock
• soil amendment