Cold Hardy Citrus

EVALUATING UF950 ON DIFFERENT ROOTSTOCKS:

UF950 is a seedless and easy to peel mandarin cultivar developed by UF/IFAS Citrus Research and Education Center, Lake Alfred. Its fruit size is similar to clementine with dark orange in color both internally and externally. It is very sweet in taste and matures in December. Here at NFREC we have evaluating this cultivar for more than six years. We have evaluated its yield and other fruit quality characteristics. It has shown great cold tolerance in north Florida. In our previous research trials, UF950 was evaluated just on two rootstocks i.e., swingle and US897. In our new research project, we are evaluating UF950 on eight different HLB and cold tolerant rootstocks from citrus breeding programs at UF and USDA. The main objective is to identify the best rootstock for 950 which can produce good quality and high yield while limiting the chances of alternate bearing.

914 PUMMELO GRAPEFRUIT HYBRID EVALUATION FOR FRESH MARKET PRODUCTION IN NORTH FLORIDA:

"914" is a Pummelo Grapefruit hybrid which produces large fruits with Brix about 10 or more while less acidity than grapefruit. Fruit gets ready for harvesting in October. It produces uniform red-fleshed and large fruit (680g approximately). Its skin shows a significant red blush enhancing its attractive appearance. The unique attribute in “914” is its low furanocoumarin compounds (FCs), which is high in grapefruit and cause so called grapefruit juice effect. Due to high FCs peoples on different medications can not consume grapefruit. Since “914” has very low FCs, so peoples on medications will not have juice effect. Some clinical studies demonstrated that ‘914’ juice behaves differently than grapefruit juice in cell culture studies, and clinical trials are underway to confirm this in human subjects. Currently we are evaluating “914” on two rootstocks and going to another trial on 10-12 rootstocks. Based of its growth and fruit characteristics it could be an excellent addition to diversify fresh citrus market in north Florida.

NITROGEN MANAGEMENT IN COLD HARDY CITRUS PRODUCTION IN NORTH FLORIDA:

Cold hardy citrus (CHC) production particularly "Satsuma mandarins" for the fresh market, is a newly emerging industry in north Florida. In north Florida (FL), CHC is grown on about 2,000 acres with acreage increasing each year. There is a lack of proper nitrogen (N) management guidelines for CHC fresh fruit market as current citrus nutrient guidelines are based on research conducted in central and south FL, where soils and climatic conditions differ compared to north FL. Soils in north FL tend to have a higher clay content that often results in greater cation/anion exchange and water retention capacities, thereby translating into potentially lower annual fertilizer requirements compared to the sandier soils of the south FL flatwoods and central ridge. Moreover, most current recommendations are for the juice market, while citrus in north FL is grown primarily for the fresh market. The objective of this project is to identify best N application rate and timing for getting optimum yield and good quality while having minimal environmental impacts.

DEVELOPING SITE-SPECIFIC N AND P RATES FOR YOUNG AND MATURE COLD HARDY CITRUS PRODUCTION IN NORTH FLORIDA:

Current citrus nutrient guidelines are based on studies of healthy citrus trees conducted in the pre-Huanglongbing (HLB) era and may no longer be valid for the present situation where 100% of mature citrus trees in Florida are HLB-affected. We are conducting research on different N and P rates for young/mature citrus cultivars including sweet oranges, grapefruits, and mandarins. Our project will evaluate different N and P rates. These rates will address the objective of evaluating different levels of N and P in identifying the appropriate site-specific rate of N and P for north Florida. Using fertigation and controlled release fertilizer (CRF) fertilization sources, we should be able to develop and provide site specific N and P guidelines for young and mature citrus trees of Satsuma mandarins in north Florida.