Journal of Crop Production and Processing

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Tofighiyan N, Rastegar S, Bagheri A. The role of Phosphorus-Containing Fertilizers on the Quantitative and Qualitative Characteristics of Tomato Fruit in Greenhouse Cultivation. Journal of Crop Production and Processing 2024; 14 (4) :75-87
URL: http://jcpp.iut.ac.ir/article-1-3302-en.html

Phosphorus-containing fertilisers play a crucial role in improving both the quantity and quality of greenhouse-grown tomatoes. Greenhouses make it possible to produce fresh tomatoes all year round, and these tomatoes are among the most important and valuable horticultural crops globally. Phosphorus (P) is an essential nutrient contributing mainly to ATP production, root growth, and vigorous vegetative and reproductive growth. Being an immobile ion, P doesn’t move easily in the soil, its deficiency becoming prevalent throughout the plant growth, necessitating P fertilizers application to guarantee an acceptable fruit yield. Research has shown that adding P fertilizer increases fruit yield, fruits/plant, and plant height. It also improves the quality of the fruit, enhancing traits like size, firmness, and nutritional content, particularly vitamins A and C. When P is combined with the right amounts of nitrogen and potassium, the benefits to the crop growth and productivity are even greater, leading to higher fruit yield and quality. To meet market demands and ensure consistent, high-quality tomatoes production, optimising P use in greenhouse farming is crucial.
Materials and Methods
This research was conducted in December 2022 in a greenhouse located at the Aliabad-Hajiabad greenhouse site in Hormozgan province, south of Iran (longitude of 55° 95', latitude of 28°31', an elevation of 1200 meters above sea level, and temperatures ranging from -1 °C to 47 °C). The study followed a factorial design within a completely randomized design (CRD) with four replications.  Seeds of the *Dafnis* tomato cultivar (indeterminate type) were sown on 15 November 2022 in 105-cell trays filled with a mixture of peat moss and cocopeat (1:3 peat moss to 2:3 cocopeat). At the two-leaf stage, seedlings were fertilized with 10-52-10 (N-P-K) fertilizer. Irrigation conducted every two days based on tray moisture levels. Seedlings were transplanted into 10 kg plastic pots on 30th of December 2022. Humic acid was applied twice (55 g for 550 seedlings, equivalent to 2.5 kg/ha). Treatments began on 3rd of February 2023, with 30 plants per treatment group. Fertilization levels included: 0 (no fertilizer), 20-20-20 (N-P-K), 10-52-10 (N-P-K), Phosphoric Acid (75%), Triple Superphosphate which were carried out three times at 15-day intervals. Tomatoe fruits were harvested on 29th April 2023 and transported to the laboratory for further analysis. Fruit length and diameter were measured using a calliper. To determine fruit volume, the fresh weight was recorded using a precise balance, and the volume was calculated based on water displacement after submerging the fruit in a known volume of water. Fruits/cluster was determined and the total weight of each cluster was measured with a balance. Mean fruit weight was determined by weighing individual fruits after harvest. For quality assessment, total soluble solids (TSS) were measured using a refractometer. Titratable acidity (TA) was determined by titration with a standard sodium hydroxide solution. Phenolic and flavonoid contents were quantified using spectrophotometric methods. These measurements provided a comprehensive evaluation of both the physical and biochemical properties of the harvested tomatoes.
Results and Discussion
This study revealed that the maximum fruit weight (141 g), length (4.98 cm), diameter (6.95 cm), and volume (164 cm³) were recorded when 20-20-20 fertilizer was combined with triple superphosphate. Similarly, the highest total cluster weight (637 g) and fruits/cluster (6.8) were observed under this treatment. The synergistic effects of different fertilizers on fruit quality were also investigated. The application of 75% phosphoric acid resulted in the highest soluble solids content in the fruit, indicating enhanced sweetness. Moreover, phosphorus fertilizers significantly increased the titratable acidity of the fruit, contributing to its flavor profile. The highest phenolic content (0.74 mg gallic acid equivalent/g fresh weight) was found in fruits treated with a combination of 20-20-20 fertilizer and phosphoric acid. Both phosphorus fertilizers alone and in combination with the complete fertilizer significantly enhanced the flavonoid content of the fruit. The availability of nitrogen and particularly phosphorus, has a positive impact on flower initiation and development. By supplying essential nutrients such as nitrogen and phosphorus, fruit set was significantly improved. Another possible reason is that increasing the supply of essential nutrients to the tomato plant enhanced nutrient availability, uptake, and mobility within plant tissues, resulting in an increased fruits/cluster..
Conclusions
The research demonstrated that a combination of 20-20-20 fertilizer with triple superphosphate and phosphoric acid can significantly enhance both the quantity and quality of tomato fruit. This fertilizer regime not only increased fruit size and fruits/cluster but also improved other fruit characteristics such as soluble solids content, acidity, and phenol compound. These findings highlight the importance of optimizing fertilizer application to maximize tomato fruit yield and quality.