Studying the Effects of Manure and Zeolite on Nitrogen Uptake and Utilization Efficiency of Saffron (Crocus sativus L.) Under Deficit Irrigation Conditions

Introduction: Saffron, scientifically known as Crocus sativus L., has a dark red, cream yellow, and orange color and a strong odor. Saffron also has stigmas of various shapes and is used in the food, pharmaceutical and raw dyeing industries. This plant is cultivated in an area of about 123,000 hectares of land in the world, and 85,000 hectares are under cultivation in Iran. According to statistics, 94% of the world's saffron is attributed to Iran. The saffron plant has been introduced into regional cultivation patterns due to its high drought tolerance. The use of animal manure in saffron fields, in addition to improving nutrients and preventing soil compaction, also increases corm growth. Zeolites are alkaline porous honeycomb structures of various shapes that reduce the toxicity of heavy metals in the soil such as cadmium, lead and nitrogen and manage irrigation efficiency. The application of cow manure ameliorates salt stress-induced inhibition of flowering by conserving soil moisture, strengthening the root system, increasing weight and improving cation exchange performance, which increases the photosynthesis of saffron plants and reduces flowering performance. Zeolites are natural aluminosilicates with tetrahedral structures of AlO₂⁻ and SiO₄⁴⁻, which are enlarged by the atoms of the equipment. They are economical, selective for nitrogen and have cation exchange. Nitrogen, as a rich source, plays a very positive role in photosynthesis, increasing cell division, producing large corms with a high number and, as a result, flowering in the field. The amount of nitrogen absorbed by a plant per unit of nitrogen applied to the soil is a key component of Nitrogen Use Efficiency (NUE).. An increase in nitrogen absorbed by the plant is directly related to an increase in nitrogen uptake efficiency in saffron. In general, smaller corms also have less total nitrogen. The main objective of this research is to investigate the water absorption efficiency and water consumption of saffron, which was carried out based on the different effects of zeolite and animal manure on water conditions.
 
Materials and Methods: In order to investigate the efficiency of nitrogen absorption and utilization and stigma yield of saffron at different levels of manure and zeolite under deficit irrigation conditions, a study was conducted in the 1401-1402 crop year at the research farm of the Faculty of Agriculture, Ferdowsi University of Mashhad. The annual growth rate is about 150 million meters and this region has a cold and dry climate. This study was conducted in split plots based on a three-block basic design. Experiments were conducted with irrigation treatment at three levels (50, 75 and 100 percent of water requirement) as the main factor, manure consumption at three levels (9, 18 and 27 tons per ha) as a secondary factor, and zeolite consumption at three levels (0, 3 and 6 tons per ha) as a secondary factor. Before starting the study, the chemical and physical characteristics of the soil of the region, the characteristics of the cow manure used and specific comments were examined. The water requirement of saffron was calculated using CropWat software. Saffron corm cultivation was carried out in plots of 6 meters in September at a depth of about 15 cm of soil. Cultivable corms weighed about 8-12 grams and were planted manually. To measure leaf area, a leaf area measuring device (Lincoln, USALICOR, model LI-3100C) was used. In order to evaluate the performance of daughter corms, corms from each plot were removed from the soil in an area equivalent to 0.2 m × 0.2 m. The initial corm diameters were measured using a caliper. In this study, Irrigation was performed at specific timings: before flowering, after flowering, mid-March, and early April. Additionally, weed control was conducted manually on two occasions. In order to study the characteristics of saffron stigma, flowers were collected from each plot for about a month and the weight of the stigma was determined.
Results and Discussion: This study was conducted to investigate the effect of different levels of manure and zeolite on leaf area index, leaf dry weight, stigma dry weight, corm number (5-7, 7-9 grams) and nitrogen uptake and utilization efficiency of saffron under drought conditions. The results showed that under full irrigation, complete manure and complete zeolite conditions, we witnessed an increase in leaf area index and leaf dry weight. Also, in terms of stigma dry weight and saffron corm number under full irrigation, complete manure and complete zeolite conditions, the highest stigma dry weight and corm number (5-7, 7-9 grams) were obtained. Under full irrigation, complete manure and complete zeolite conditions, the percentage of saffron nitrogen uptake and utilization efficiency increased significantly. Simultaneous application of manure and zeolite reduced the negative effects of drought stress on saffron agronomic characteristics. From the perspective of nitrogen uptake and utilization efficiency, it was found that treatments with full irrigation, along with the highest levels of manure and zeolite, provided the highest nitrogen uptake and utilization. In general, the results of this study indicate that although under-irrigation has a very high negative impact on nitrogen uptake and utilization efficiency, simultaneous application of manure and zeolite largely balances the negative effects and at the end of the crop year leads to an increase in the final yield of the field and an increase in the quality of the product from an economic perspective.
Conclusion: The targeted co-application of manure and zeolite effectively mitigates drought stress, thereby enhancing nitrogen use efficiency and increasing saffron stigma yield.