Technical annual report 2000-01
Dept. of Regional Development, Primary Industry, Fisheries and Resources technical annual report; Department of Regional Development, Primary Industry, Fisheries and Resources technical and annual report; Reports; PublicationNT; Technical bulletin (Northern Territory. Dept. of Primary Industry and Fisheries) ; no. 295
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Dept. of Primary Industry and Fisheries
Technical bulletin (Northern Territory. Dept. of Primary Industry and Fisheries) ; no. 295
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Technical Annual Report 2000/01 133 Although there were no significant differences between treatment groups on quantity (weight and number) of fruit produced, during the five years (1996-2000), the control group (no nitrogen) produced significantly fewer fruit than some of the groups that received nitrogen. Overall the application of nitrogen at golf ball and post harvest stage resulted in significantly more fruit than in the control group. Also, the rate of 140 g appears to be more productive than the control, with no detrimental post harvest blemishes. Again using Bonferronis inequalities, we conclude: Control versus nitrogen treatments: Nitrogen applied groups produced significantly higher cumulative marketable weights and numbers of fruit than controls (p<0.05). Timing of nitrogen: Post harvest and at golf ball size applications gave significantly higher marketable weight and numbers of fruit than controls (p=0.05). Nitrogen rates: Trees that received 140 g nitrogen gave significantly higher marketable weight and number of fruit (p=0.05) than controls. There is suggestion here of a linear relationship; that is as the rate of nitrogen application increases, the cumulative marketable weight of fruit also increases. Interaction between timing and nitrogen rates: The application of 140 g nitrogen post harvest, 140 g at golf ball size and 90 g golf ball size gave significantly higher marketable fruit weights and numbers (p=0.05) than did the control. Leaf analysis revealed no excess or deficient nitrogen levels for any of the treatments for the years 19962000. Discussion: As mentioned last year data for individual years (from a statistical point of view) gives no indication of a significant difference between the rates of nitrogen applied and the timing of nitrogen application. The enormous variability produced in individual years is marginally overcome when we look at cumulative values for each of the treatments. It was thought last year that various strong trends that were not backed by statistical significance were worth noting. Some of the treatment means differ by more than 100% and yet the probability values were too high to be considered significant. I commented that 140 g nitrogen at golf ball size appeared to give a better yield in marketable weight and number than the other treatments. In 2000 the individual year analysis provided no significant differences in yield between timing and rates of nitrogen application. However, cumulative analysis support these previously identified trends using Bonferronis inequalities. Perhaps in future trials with Kensington Pride, it would be necessary to consider cumulative values as well as individual yearly values in order to deal with the high variability of the crop. The application of nitrogen has significantly increased fruit numbers and weights when compared with no nitrogen over the five-year period (cumulative years). Some applications of nitrogen (pre flowering) have caused excessive flush and had a detrimental effect on production. The nitrogen application at golf ball size appears to have given a good yield (fruit number and weight) when compared with other treatments. Over the five years the higher rate of nitrogen has produced higher marketable fruit weight and numbers. This was especially obvious (although not significant) in the higher yielding years 1997 and 1999. The other two treatments that were of significantly greater benefit (cumulatively) were 90 g at golf ball size and 140 g post harvest. The post harvest analysis has shown us that these high rates of nitrogen (which we increased in 1998 to purposely induce disorders in post harvest) are by no means enough to cause significant post harvest disorders. Perhaps current recommendations of rates of nitrogen should be reassessed. It is interesting to note that the plants that were not given nitrogen (control) over the five-year period did not appear to be severely deficient as would be expected. Leaf analysis indicated that all trees were within the DPIF recommended optimum range. Perhaps we may also need to review leaf analysis. From this trial we can suggest that leaf analysis is not a very reliable source for determining yield potential. We can also assume from the leaf analysis that the control crops (0 nitrogen) are able to obtain nitrogen from other sources. This does not imply that no nitrogen be applied, because yield from these trees was well below that from the trees that received nitrogen.