ISHS Acta Horticulturae 275: International Symposium on the Culture of Subtropical and Tropical Fruits and Crops
THE CURRENT STATUS OF SOUTH AFRICAN AVOCADO NURSERIES AND SOME FACTORS AFFECTING CLONAL AVOCADO NURSERY TREE GROWTH |
| Authors: | C.B. Mc Kenzie, B.N. Wolstenholme, P. Allan, C.J. Petzer, I.E. Smith |
| Abstract:
The history and present status of South African avocado nurseries producing clonal rootstocks are outlined. Composted milled pine bark has recently become the major or only component of avocado growing media. Various experiments were conducted on nursery avocado nutrient requirements, responses to different controlled temperature regimes, and optimal air-filled porosities (AFP) of the growing medium. These include: (i) The influence of three different day/night temperature regimes, and three nutrition levels on 'Duke 7' growth and total nonstructural carbohydrate (TNC) levels. Aerial growth was best at the highest temperature (30/20 °C) and highest nutrient regime. Root growth was better at the intermediate temperature (26/16 °C). TNC was not always related to temperature and increased with nutritional levels. (ii) A dilute liquid feed experiment with three nitrogen levels and two fixed phosphate : potassium levels compared to a total nutrient solution in pre-enriched pine bark. Plant growth at 160 mg l-1 N and 54:266 mg l-1 P:K was significantly better than at 220 and 280 mg l-1 N, and 27:133 mg l-1 P:K. (iii) An AFP experiment with a wide range of AFPs (4 to 63%) obtained by the addition of medium types and particle sizes to pine bark. Growth was best at an AFP of 19%, but was influenced more by medium type than AFP. | |
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