Articles
METHODS OF FORECASTING WALNUT YIELD
Article number
544_79
Pages
565 – 572
Language
Abstract
All those concerned with the trade in walnuts need to be able to estimate the expected yield in a given year so as to develop an appropriate marketing strategy. To do this effectively a reliable method for forecasting the harvest is essential. Two such methods have been developed at the Creysse Experimental Station. The results obtained from these methods have been compared with the actual production of the growers who operate in association with the French Fruit and Vegetable Committee of the great south-west region (Comité Economique Agricole Fruits et Légumes du Bassin Grand Sud-Ouest). Their production data are the only reliable ones available and cover about half the tonnage produced in south-west France.
Method 1: Forecasting from pollen emission
This method is based on the fact that the female flowering rate and the effect of weather conditions can be estimated from the natural emission of pollen during the phases of flowering and of pollination. Observations over the last 5 years appear to show an inverse correlation between this emission and the subsequent yield. This method does not however take into account conditions which may affect production after the flowering period.
Method 2: Forecasting by counting a sample of nuts
This method is based on the principle of a ratio between the average number of walnuts on 100 bearing shoots of the current year (the fertility coefficient) and the actual yield. A first study begun in 1992 in 6 orchards seems to show a positive correlation between this coefficient and actual production in the 6 orchards concerned. This coefficient takes account not only of the abundance of female flowering but also of the setting rate and of possible parasite damage up to the time of the count in July. The use of this method in 44 representative orchards in the Périgord each year since 1997 has made it possible to estimate the harvest in this area with reasonable accuracy.
Method 1: Forecasting from pollen emission
This method is based on the fact that the female flowering rate and the effect of weather conditions can be estimated from the natural emission of pollen during the phases of flowering and of pollination. Observations over the last 5 years appear to show an inverse correlation between this emission and the subsequent yield. This method does not however take into account conditions which may affect production after the flowering period.
Method 2: Forecasting by counting a sample of nuts
This method is based on the principle of a ratio between the average number of walnuts on 100 bearing shoots of the current year (the fertility coefficient) and the actual yield. A first study begun in 1992 in 6 orchards seems to show a positive correlation between this coefficient and actual production in the 6 orchards concerned. This coefficient takes account not only of the abundance of female flowering but also of the setting rate and of possible parasite damage up to the time of the count in July. The use of this method in 44 representative orchards in the Périgord each year since 1997 has made it possible to estimate the harvest in this area with reasonable accuracy.
Publication
Authors
J.P. Prunet, T. Ginibre
Keywords
walnut, forecast, yield, pollen, counting, fruiting branch
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