با همکاری انجمن علمی منظر ایران
نوع مقاله : مقالات پژوهشی
نویسندگان
گروه مهندسی علوم باغبانی و فضای سبز، دانشکده کشاورزی، دانشگاه فردوسی مشهد، مشهد، ایران
کلیدواژهها
عنوان مقاله English
نویسندگان English
Introduction
Water scarcity is a fundamental challenge to global food security, necessitating the optimization of water use in agriculture. Deficit irrigation (DI) has emerged as a key strategy to enhance water productivity, involving the controlled reduction of water application to minimize yield impact while significantly saving water. However, DI can induce physiological stress, disrupting vital processes like photosynthesis, nutrient uptake, and hormonal balance, ultimately compromising crop yield and quality. Greenhouse cultivation provides a controlled environment ideal for implementing DI strategies. To mitigate the adverse effects of water stress, the application of natural bio-stimulants like humic acid (HA) and amino acids (AA) has gained considerable attention. Humic acid improves soil structure, enhances water retention, and stimulates the absorption of macro and micronutrients. Amino acids play crucial roles as protein building blocks,
osmo-regulators, and precursors to hormones, aiding in stress tolerance. This study aimed to evaluate the individual and comparative effects of humic acid and amino acid fertigation on the growth, yield, fruit quality, and nutrient uptake of greenhouse tomato (Solanum lycopersicum L. cv. Termeh) under deficit irrigation conditions.
Materials and Methods
The research was conducted in a commercial greenhouse in Mashhad, Iran. Two independent factorial experiments were laid out in a randomized complete block design (RCBD) with four replications. The experimental factors were: 1) Irrigation regime at two levels: full irrigation (100% of crop water requirement) and deficit irrigation (70% of crop water requirement); 2) Humic acid at two levels (0 and 3 g.L⁻¹) in the first experiment; and 3) Amino acid at two levels (0 and 1 g.L⁻¹) in the second experiment. The commercial HA product (70% humic acid, 15% fulvic acid, 12% K₂O) and AA product (80% free amino acids, 12.8% total nitrogen) were applied via fertigation at three growth stages: two weeks after transplanting, flowering initiation, and fruit set. A wide range of morphological traits, leaf nutrient content, quantitative qualitative fruit traits were measured at the fruit ripening stage. Data were analyzed using SPSS software (v.21), and means were compared using Duncan's multiple range test at a 5% probability level.
Results and Discussion
Morphological Traits: Deficit irrigation significantly reduced all morphological parameters. Main stem length decreased by 7%, internode number dropped from 34.75 to 29.75, internode length from 4.17 cm to 3.53 cm, and leaf area by 13.58%. Shoot fresh and dry weight and root volume were also significantly reduced. Application of both HA and AA significantly improved all growth traits under both irrigation regimes. Humic acid not only compensated for the negative effects of drought stress but also enhanced growth beyond the full irrigation control level in many cases. Comparative analysis revealed the superior efficacy of HA over AA. This superiority was consistent under stress conditions, attributed to HA's multifaceted role in improving the rhizosphere environment and enhancing simultaneous water and nutrient availability.
Leaf Nutrient Content: Deficit irrigation caused a significant decrease in the concentration of all measured macro and micronutrients. Both bio-stimulants significantly enhanced nutrient uptake. Humic acid was more effective than AA in improving the uptake of nutrients especially P, Ca, and Fe under stress. This is likely due to HA's ability to stimulate root development, increase membrane permeability, and enhance microbial activity, thereby improving nutrient solubility and absorption.
Quantitative and Qualitative Fruit Traits: DI led to a 29% reduction in fruit number per cluster, a 6% reduction in single fruit weight, and a consequent 19% reduction in total yield (from 9.45 to 7.69 kg plant⁻¹). Both HA and AA application increased yield under DI, HA increased yield by 31% and AA by 29%. Regarding quality, DI reduced TSS and vitamin C content but increased carotenoids and lycopene. HA was particularly effective in increasing TSS by 59%, vitamin C by 18%, carotenoids by 17%, and lycopene by 10% under DI. AA showed positive but generally lesser effects on quality parameters. On average, HA demonstrated a 17.1% greater improvement in quantitative traits and a significant 42.5% greater improvement in qualitative traits compared to AA.
Conclusion
This study demonstrates that deficit irrigation at 70% of field capacity significantly impairs the growth, yield, and quality of greenhouse tomatoes. The application of both humic acid (3 g.L⁻¹) and amino acids (1 g.L⁻¹) effectively mitigated these negative impacts, often enhancing traits beyond the well-watered control. However, humic acid proved to be a superior bio-stimulant than amino acids in improving morphological development, enhancing nutrient uptake (particularly N, P, K, and Ca), and boosting both quantitative yield and qualitative fruit characteristics. Therefore, humic acid fertigation is recommended as a highly effective management strategy for sustaining greenhouse tomato production under water-limited conditions, ensuring higher yield and premium fruit quality while optimizing water use efficiency.
کلیدواژهها English
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