The Influence of Foliar Application of Humic Acid, Amino Acid and Extract of Otostegia persica, Artemisia abrotanum and Teucrium polium Medicinal Plants on Yield and Yield Components of Tomato (Solanum lycopersicum)

The rapid growth of the world's population and food demand have made the use of agricultural inputs such as pesticides and chemical fertilizers inevitable to achieve the highest yield per unit area. The result of these activities during recent years has been the crisis of environmental pollution, especially the pollution of water and soil resources, which has entered the human food chain and threatened the health of human society. In order to overcome these issues and increase soil productivity rate and improve plant growth, fertilizers and biological compounds could be considered as efficient solution. Foliar application of organic compounds and bio-fertilizers is a suitable method for optimal nutrition of plants and is considered as one of the effective solutions to quickly improve the yield and quality of various crops. Therefore, this research was conducted with the aim of investigating the effect of foliar application of humic acid, amino acid, and extract of Otostegia persica, Artemisia abrotanum and Teucrium polium medicinal plants on the yield of tomato plant cv. “Sunseed 6189” under field condition.

In order to investigate the effect of foliar application of humic acid, amino acid and extract of Otostegia persica, Artemisia abrotanum and Teucrium polium medicinal plants on the yield and yield components of tomato (Solanum lycopersicum) cv. “Sunseed 6189”, an experiment was conducted based on randomized complete blocks design with 15 treatments including humic acid (2, 4 and 6 g L-1), amino acid (2, 4 and 6 g L-1), extract of Otostegia persica, Artemisia abrotanum and Teucrium polium medicinal plants (2 and 4 g L-1), mixed extracts (2 g L-1), humic acid + amino acid (4 g L-1) and control (water), and 3 replications in Kohnuj, Kerman province during 2018-2019. In this research, “Sunseed 6189” cultivar was cultivated. The seeds were purchased from Nanhenz Company (Netherland). At the end of December, tomato seeds were sown in seedling trays contained peat moss substrate, and after 30 d, the seedlings were ready to be transferred to the field. After the establishment of seedlings (4-leaf stage), which took about 20 d, the foliar treatments were applied. Drip Irrigation was done according to the rainfall and climate conditions, so that all experimental units were watered twice per day, one time in the morning and the other in the evening for 20 min. Duration of daily watering was gradually increased to 1 h as the seedling grew. At the end of the experiment, plant fresh and dry weight, carotenoid, chlorophyll a, chlorophyll b and total chlorophyll content, fruit number, length and diameter, yield per plant, marketable yield and total yield, tissue firmness, total soluble solid content, vitamin C, fruit carotenoid, fruit anthocyanin, potassium and phosphorus content were measured.

The results showed that the highest fresh and dry weight of plant was observed in control (water-treated plants) (1150 and 200 g). Also, the highest number of fruits per plant (30.3) and yield (2.51 kg plant-1 and 50.3 ton h-1) was related to humic acid + amino acid (4 g L-1) treatment. The results of previous researches demonstrated that humic acid increases the amino acids and proteins content of plant tissues leading to enhancing the plant growth and yield performance. Also, the results of this study showed that using combined treatment of humic acid and amino acid can amplify this positive effect, so that the fruit diameter and length, and total yield of treated plant with humic acid + amino acid was significantly higher than those of control. The lowest anthocyanin content of fruit (3.212 μmol g-1) was for combined treatment of humic acid + amino acid. The highest tissue firmness was recorded in fruits treated with mixed extracts. Based on studies, using medicinal plants extract can lead to lower activity of cell wall degrading enzymes resulting in more tissue firmness. According to obtained results, amino acid treatment improved qualitative characteristics of tomato fruit and increased its nutrients content. Increasing the absorption rate of N, P, K and some micro-nutrients induced by amino acids foliar application was reported in different studies. Amino acids improve the efficiency of root absorption rate resulting in higher macro and micro-nutrients content of plant cells.

Based on the obtained results, humic acid + amino acid (4 g L-1) and the mixed extract of Otostegia persica, Artemisia abrotanum and Teucrium polium medicinal plants (2 g L-1) were the best treatments to increase yield and yield components, and enhancing the fruit quality. Therefore, using these treatments during the cultivation of tomato plant cv. “Sunseed 6189” is recommendable.