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Mangifera indica L. cv. Kent trees were subjected to five irrigation treatments during the 2000/2001 growing season with the aim of assessing the effects of irrigation on tree productivity and fruit quality. Two progressively reduced irrigation treatments (75 and 50% of the amount of irrigation water applied to the control), a control (100% field capacity), a regulated deficit irrigation (RDI) treatment and a farm control were compared with each other. Fruit yield, number and mean fruit weight were not significantly influenced by the different irrigation treatments. Peel colour and storage potential were improved in the reduced irrigation treatments. The RDI treatment improved the total soluble solids concentration (TSS) of fruits but increased the occurrence of split pit. Fruit firmness was not significantly influenced by the different irrigation treatments. In the second experiment, 'Kent' trees were covered with white shade netting of four mesh densities (50, 75, 100 and 125 g m-2) on a long¬term basis, while control trees remained uncovered. During the 2000/2001 growing season, light shading (50 g m-2) increased the yield and fruit numbers above that of control trees, while, heavier shading decreased the yield and fruit number below that of the control with the most dense net (125 g m-2) having the greatest affect. Peel colour, firmness and total soluble solids (TSS) at harvest were not affected by shading while the heaviest shade (125 g m-2) reduced storage potential of the fruit. Shading improved the appearance of fruits through the reduction of split pit, sunburn and wind damage. No fruit damage caused by bacterial black spot was observed in any of the shade treatments or the control. / Dissertation (M Inst Agrar (Horticultural Science))--University of Pretoria, 2006. / Plant Production and Soil Science / unrestricted

The success of a breeding program depends upon the ability of the plant breeder to not only develop new lines, but also to determine which lines or varieties are superior. For this purpose, yield trials are an important yardstick for determining the value of the trial in assessing the merits of the different lines. Variation encountered is due to several factors; with true genetic differences, environment, and human error being of major importance. In order for yield trials to give meaningful information on a line or variety, it is essential that variation due to human error and environment be reduced to a minimum. Uniform space planting, careful cultivation, and irrigation can help reduce the human error. However, the effect of environment, mainly soil heterogeneity, is not so easily handled. Randomization, replication, and planting experimental plots of the proper shape with sufficient size to give the desired information are techniques devised to minimize the effect of soil heterogeneity. In general, it has been found that the larger the experimental plots, the smaller the variation (1, 23). Also, plots with a large length to width ratio lying in the direction of greatest soil variability have been found to decrease the variability of the yield trial (2, 8, 32, 35). However, both expense and convenience will modify the size and shape of plot that is desired. The optimum size and shape of a plot would be one that gives a maximum amount of information at a minimum cost and be of convenient handling dimensions. Such information must be determined for each individual crop.

Call number: LD2668 .T4 1930 S41

Call number: LD2668 .T4 1933 G51

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