Page 72 - SA Fruit Journal VOLUME 14

water is applied, and at longer intervals. Therefore, irrigation is continued but at a re- duced level. Trees should be irrigated lightly two weeks prior to harvest. No water stress should be imposed during the initial growth phase of the fruit, i.e., during and after flow- ering, but only during the final maturation phase, i.e., the last two months prior to har- vest (January for Satsuma). Any water stress earlier than the end of January could lead to reduced fruit size and loss of rind integrity. In high rainfall areas, regulated deficit ir- rigation may not be successful. The deficit should be imposed slowly, so that the trees can adjust without symptoms of drought. Se- vere water stress can have adverse effects on tree health, fruit size and fruit quality. High nitrogen is antagonistic to the effect of deficit irrigation. Management of this technique is much easier when trees are planted on ridges and when the right scheduling equipment is used. Additionally, regulated deficit irriga- tion imposed the last two months prior to harvest also enhances the rate of colour de- velopment. Selective harvest of outside fruit and delaying harvest of inside fruit will result in a higher proportion of fruit with higher TSS and better colour.Maturity indexing on early cultivars like Satsuma should commence. Maturity index- ing is done to predict the rate of change in fruit maturity in order to harvest fruit at optimal maturity, to maintain acceptable commercial shelf life. The aim is to define changes or rate of change in acids and sugars and to build up a data base over a number of years for com- parison. Random sampling of fruit every week from each of ten representative trees should start 4 to 6 weeks before the expected harvest date. Titratable acidity is determined by titra- tion with sodium hydroxide, sugar content (Brix) is determined using a refractometer, the sugar:acid ratio calculated and fruit colour should be read from a colour chart. All the parameters mentioned above should be plot-ted on a graph over time. Once plotted, trends will become apparent, harvest dates can be estimated and problem areas in internal and external quality parameters can be identified and manipulated.Fruit growth and sizeFruit growth during this time is important to achieve optimum size at harvest. Ensure op- timal irrigation and try to avoid stress con- ditions, as this might have an adverse effect on fruit size. Fruit thinning plays a critical role in fruit size. Correct pruning practices are the most effective way to manipulate the number of fruit per canopy volume and the eventual fruit size.Regrowth control should be done, espe- cially after heavy pruning earlier in the season. A lot of regrowth adversely affects fruit size and is antagonistic to fruit colour develop- ment, especially for early maturing cultivars.Oleocellosis: Late summer vegetative growth of bearing trees should be kept to a minimum as excessive vegetative vigour dur- ing this period is associated with high inci- dence of oleo at harvest.Rind colour development: Late nitrogen application and the use of heavy summer oil sprays should be avoided as these treatments are antagonistic to rind colour development.GEÏNTEGREERDE BEMESTINGT. VAHRMEIJERBlaar- en grondontledingsBy sitrus word blaar- en grondmonsters ge- durende Februarie tot Mei geneem maar die periode kan tot Julie verleng word. Die enigste probleem met monsters wat in Julie geneem word, is die beperkte tyd om die re- sultate betyds te verskaf sodat met bemesting in Julie/Augustus begin kan word.Geen ontleding, hoe gesofistikeerd ookal, kan die kwaliteit van die monster verbeter nie. Bestee dus tyd, energie en aandag aan die monsternemingsproses. Op grond van dieresultate van dié monsters word baie geld aan kunsmis bestee, terwyl die oes ook benadeel kan word. Monster elke jaar dieselfde groep bome (Indeksbome) en hou by dieselfde pro- sedure en tyd. Soos by enige monster moet dit die eenheid wat gemonster word, in alle opsigte verteenwoordig.Leaf analysesLeaf analyses are an indicator of the nutri- tional status of the trees. During the research into this method a relationship was estab- lished between the concentration of the nu- trient elements in the leaves and production. This relationship was developed for almost every nutrient element. For some like chlo- ride and sodium only the maximum toler- able concentration was determined.Let ook op die volgende spesifieke ver- eistes:• Verdeel die boorde in monster-eenhede, verkieslik nie groter as 5 ha nie.• Kies twee of vier INDEKS-RYE wat die monster-eenheid in alle opsigte verteen- woordig en merk die rye.• Gebruik elke jaar dieselfde indeksrye om blaar- en grondmonsters te neem.• Pluk sowat 50 tot 75 blare per monster deur aan die linker- en regterkant (son- en skadu- kant) tussen heup- en kophoogte, blare te pluk.• Pluk blare van agter ʼn vrug, wat op dieselfde takkie as die vrug, en in die lente gevorm is (Figuur 1).• Pluk die blaarmonsters gedurende Febru- arie tot Mei.• Plaas die blare in ʼn skoon plastiek sakkie, druk die lug uit en knoop toe.• Merk die monsters deur ʼn etiket op die sak- kie te plak of aan die sakkie te bind.Ensure that the correct leaf is picked from the trees in the index rows or blocks. The correct leaf is one that was formed during the pre- vious spring and situated behind a fruit onTECHNOLOGY 69 FEB | MARCH 2015