The factors affecting time series fluctuations of pistachio yield

One of the issues in pistachio orchards is the wide range of fluctuations of crop yield in different years. These fluctuations have resulted in different yield of dry crop per hectare in different years. Thus, the two indicators i.e. pistachio yield average and pistachio yield fluctuations are effective in creating a suitable and reliable income for farmers; it is important to identify the factors affecting these two indicators.

In this study, by using 9-year-old data (2010-2018) of 286 pistachio orchards from 4 commercial pistachio cultivars; Ahmad Aghaei, Akbari, Kaleghoochi, and Ohadi in two cities i.e. Anar and Rafsanjan in Kerman province, it was attempted to investigated different factors affecting time series fluctuations of pistachio yield. In this regard, two indices i.e. coefficient of variation and probability of yield loss to less than long-term average, 1000 kg of dry pistachio per hectare, were used.

In terms of crop yield’s coefficient of variation, Ohadi (cultivar) had the least fluctuation, Kaleghoochi showed the highest fluctuation, and Akbari and Ahmad Aghaei were reported to have an average fluctuation. As for probability of crop yields falling to less than a certain level of yield (1000 kg per hectare), Ahmad Aghaei had the lowest risk, Akbari had the highest risk, and the two other cultivars, Ohadi and Kaleghoochi, were reported to have an average level of risk. The management factors affecting the pistachio yield fluctuations include: water quality and quantity, irrigation time and system; type, quantity and time of the fertilizers consumed; number, quality, time, and dose of pesticides; and pruning. Pistachio spring frost damage resulted in increased crop yield fluctuation in all cultivars, and lack of chilling requirement had significant effect on crop loss only in Akbari cultivar i.e. it did not affect other cultivars.

Factors such as pistachio cultivar, soil and water quality, climatic conditions, and pistachio orchard management affect two indices i.e. pistachio yield average and pistachio yield fluctuations over different years. This has made it impossible to estimate a specific order, including biennial bearing cycles, in the time series fluctuations of pistachio yield.