Investigating the effects of different levels of triple superphosphate fertilizer on some quantitative and qualitative characteristics of Sefid variety of pistachio



Introduction

Pistachio (Pistacia vera L) is one of the Iran’s most important horticultural products and ranks as the third most significant export of the country. Considering the increase in the cultivated area through the construction of new pistachio orchards in the provinces of the country and its low domestic consumption compared to the amount of production, the need to pay attention to the issue of pistachio exports is of particular importance. Like other agricultural products, increasing pistachio yield per unit area is possible if production factors are at optimal and desirable levels. One of the weak aspects of management in the pistachio growing areas of the country is the management of nutrition and fertilization of orchards or, in general, soil management and plant nutrition. Today, fertilizers play a fundamental role in nourishing fruit trees, and chemical fertilizers play the most important role in increasing yields per unit area. Phosphorus (P) is the second essential element and plays a key role in plant growth. Considering the importance of phosphorus in the growth and yield of pistachio trees, this study was conducted to investigate the effects of different levels of triple superphosphate (TSP) fertilizer on some quantitative and qualitative characteristics of Sefid variety pistachio.

Materials and Methods

In order to investigate the effect of different levels of triple superphosphate fertilizer on some quantitative and qualitative characteristics of Sefid pistachio cultivar, an experiment was conducted in a randomized complete block design with three replications during two consecutive years (2023 and 2024) in pistachio orchards in Ferdows County, South Khorasan Province, Iran. The experimental treatment included triple superphosphate (TSP) at four levels (0, 150, 300, and 600 grams per tree). Triple superphosphate fertilizer (21% phosphorus) was applied in March 1401 (the ON year before the OFF year) as a slurry in a section 30 to 40 cm deep and 20 cm wide in the shaded area along the water path (one-way stream), under canopy area. Sampling was conducted over two consecutive years (1402 and 1403).

Results and Discussion

The results of variance analysis showed that soil phosphorus application had a significant effect on branch length, number of buds abscised per branch in the first year, number of panicles per branch, number of nuts per panicle, percentage of indehiscence pistachios in the first year, percentage of blank nuts in the first year, percentage of closed pistachios in the first, yield of two years, chlorophyll index (based on SPAD evaluation) in the second year, chlorophyll a and b, and branch phosphorus content. The results of mean comparison showed that the highest branch length in both years of the experiment was obtained by supplying 600 g of TSP fertilizer. The least number of abscised buds per branch in the first year was obtained from the use of 300 g of TSP fertilizer. Application of 300 g of TSP fertilizer in the first year resulted in the highest number of clusters on the branch. In the second year, the use of 600 g of TSP fertilizer had the highest cluster number. The highest number of nuts per cluster was observed in 300 g treatment and control, during the first and second years of study. In the first year of the experiment, the highest percentage of indehiscence and the lowest percentage of closed nuts were related to the control treatment. The lowest percentage of blankness obtained in 600 g of TSP in the first year. In the first year of the experiment, the maximum yield was obtained from the consumption of 300 g and in the second year from the consumption of 600 g of TSP fertilizer. In both years of the experiment, the highest chlorophyll a and b were obtained from the use of 600 g of TSP. The highest amount of branch phosphorus concentration was observed from the supplying 300 g of TSP during the two years of the experiment.

Conclusion

Finally, the results of this study showed that the supplying TSP at amounts higher than 300 grams might be helpful to increase some vegetative and reproductive characteristics of pistachio trees.

Keywords: Chemical Fertilizer, Phosphorus, Plant nutrition, Yield.