- J H Oosthuizen
- lnstituut vir Tropiese en Subtropiese Gewasse, Privaatsak X11208, Nelspruit 1200
- 1994
Op hierdie stadium, vyf seisoene na aanvang van die projek, kan die gevolgtrekking gemaak word dat boomvolume effektief beheer kan word en dat groei gemanipuleer kan word met snoei of die chemiese groeireguleerder paklobutrasool, asook ‘n kombinasie van beide. Die behandelings het egter tot op hierdie stadium meer variasie in vrugproduksie getoon as die onbehandelde (kontrole) borne. Alhoewel die behandelings meer arbeidsintensief is en hoer insetkostes vereis, is geen negatiewe invloed waargeneem op vruggehalte tussen enige van die behandelings nie. Finale gevolgtrekkings kan eers gemaak word nadat die langtermyneffek van die behandelings en residue van paklobutrasool in vrugte bepaal is.
Die projek kan in die 1993/94 verslagjaar afgesluit word, nadat die komende seisoen se oes ingesamel is en boomgrootte bepaal is.
Summary:
- The study evaluated the control and manipulation of mature litchi tree volume and growth using pruning, the chemical growth regulator paclobutrazol (PP 333), and combinations of both.
- Five years into the project, it was concluded that tree volume can be effectively managed with these treatments, although they caused more variation in yield compared to untreated control trees.
- These treatments are labor-intensive and have higher input costs but did not negatively affect fruit quality over the study period.
- Final conclusions will await long-term effects of treatments including potential paclobutrazol residues in fruit after the 1993/94 season.
- Litchi trees naturally respond to pruning with vigorous vegetative growth, which can reduce fruitfulness, depending on timing and amount of wood removed.
- Managing tree size can offer advantages such as higher planting density and ease of harvesting.
- Paclobutrazol registered in South Africa is effective as a soil drench in reducing vegetative growth and promoting flowering, more so than foliar sprays.
- Various treatment regimes were tested, including foliar sprays and soil drenches of paclobutrazol, pruning methods targeting fruiting shoots, and combinations.
- Soil application of paclobutrazol combined with pruning provided the best control of tree volume.
- Spraying treatments alone did not effectively control tree volume due to limited uptake and rapid breakdown of the chemical in plant tissues.
- Yield varied considerably among treatments, with some treated trees showing improved cumulative yields despite size control.
- Fruit quality, size, and ripening times showed no significant differences among treatments, though soil treatments led to slightly larger and later ripening fruit.
- Treatments using chlormequat chloride (CCC) were discontinued due to poor responses and negative effects on yield.
- The study emphasized the need for balancing tree size control with sustainable yields and cost-effectiveness.
- The project was planned to conclude in the 1993/94 season after collection of final yield and tree size data for decision-making on practical recommendations.