Saffron (Crocus sativus L.) belongs to the lily family (Iridaceae), is a perennial geophyte (Khan, 2004; Behboodi & Samadi, 2004), and mainly thrives in the western regions of Asia characterized by low annual rainfall, cold winters, and hot summers (Sepaskhah & Kamgar-Haghighi, 2009). Its low water requirement and growth season adaptation to the rainfall patterns of saffron-growing areas allow for prolonged utilization, eliminating the need for heavy machinery, and generating income for rural communities, thus promoting saffron as a substitute crop in low-input farming systems (Koocheki et al., 2012; Aghaei & Rezagholizadeh, 2011).
Effective management of agricultural operations, alongside suitable climatic and soil conditions, is crucial for maximizing the potential of the environment and achieving significant yields in saffron cultivation (Naderi Darbaghshahi et al., 2009; Koocheki et al., 2012). Given the perennial life cycle and production period of saffron in Iran (Naderi Darbaghshahi et al., 2009), maintaining a balanced nutrient supply through proper fertilizer management is one of the most effective factors for the sustainability of saffron production, especially in dry and semi-dry regions (Behdani, 2004; Amiri, 2008; Koocheki et al., 2009). Approximately 80% of the formation and variations in saffron flower yield are influenced by soil variables, particularly organic matter content (Nehvi et al., 2010; Shahande, 1990). In this regard, research by Behdani et al. (2006) indicated that in the climatic zones of central and southern Khorasan, up to 67% of the variations in saffron yield are affected by the application of organic and phosphate fertilizers. Conversely, the negative impact of chemical fertilizers on the sustainability of saffron production (Hatami Sardashti et al., 2011) and the low organic matter content in most saffron-producing areas (Southern Khorasan) (Shirani et al., 2011; Sepaskhah & Kamgar-Haghighi, 2009) suggest that using organic fertilizers, such as manure, can significantly enhance saffron yields in these regions. In this context, Rezvani Moghaddam et al. (2010) reported that increasing manure levels improved saffron flower yield and dry stigma weight. Research by Jahan and Jahani (2007) also indicated that organic fertilizer application effectively increased the number of flowers and dry stigma weight per unit area.
In addition to nutrient management from organic sources, determining appropriate planting density is one of the most influential factors for improving saffron yield (Behnia, 2009). Properly determining the planting pattern and density can influence the harvesting period of saffron, thus enabling increased production (Koocheki et al., 2012; Mohammad Abadi et al., 2011; Behdani et al., 2006). Research by Koocheki et al. (2012) showed that during three years of land utilization, increasing the corm density from four to 12 tons per hectare significantly enhanced flower counts per unit area and improved both fresh and dry saffron stigma weights.
Generally, studies conducted in Iran recommend a density of 50 plants per square meter based on row planting to achieve maximum saffron yield (Kafi et al., 2002). On the other hand, low-density saffron cultivation may not be economically viable, particularly in the first year. Therefore, implementing high-density planting patterns of up to 400 corms per square meter may be considered a strategy to compensate for reduced yields (Koocheki et al., 2011). Based on the aforementioned explanations, the aim of this study was to investigate the flower yield and behavior of saffron corms in response to high-density planting levels and the application of organic manure in the second year.
Materials and Methods
This experiment was conducted during the 2009-2010 and 2010-2011 agricultural years as a factorial experiment within a completely randomized block design, comprising 20 treatments and three replications at the research farm of the Faculty of Agriculture, Ferdowsi University of Mashhad, located 10 kilometers east of Mashhad, at a latitude of 36 degrees and 16 minutes north, a longitude of 59 degrees and 36 minutes east, and an altitude of 985 meters above sea level. Prior to planting, soil samples were collected from a depth of 0 to 30 centimeters to determine the physical and chemical properties of the soil.
The experimental treatments were based on a combination of four planting density levels (100, 200, 300, and 400 corms per square meter) and five levels of manure application (zero [no manure application], 40, 60, 80, and 100 tons per hectare). The field had been under barley cultivation the year before the experiment. After land preparation operations, including initial plowing, disking, and leveling the soil with a roller, plots measuring 1 × 2 meters were established. The distance between the plots and blocks was set at 0.5 meters and three meters, respectively. The application of manure was carried out based on the mentioned treatments before planting. Planting operations were conducted on June 5, 2010, at a depth of 20 centimeters, using corms weighing 4-8 grams sourced from the saffron farm of the Faculty of Agriculture at Ferdowsi University of Mashhad. The selection of these corms with relatively low weight was based on the objective of the experiment, which was to investigate the behavior of saffron daughter corms regarding growth in size or weight in response to different density levels and manure application. Manure was applied to the soil simultaneously with planting. Throughout the experiment, no chemical fertilizers, herbicides, or pesticides were used.
In the second year of the experiment, flower harvesting took place in mid-November 2011, and corm harvesting was performed in the first half of June 2012. It should be noted that data regarding flower and corm yield in the first year were examined in another article (Koocheki et al., 2012). The number of flowers, fresh and dry flower yield, stigma yield, and the yield of stigma + style were determined from an area of one square meter in each plot. The dry weight of flowers, stigmas, and styles was also measured after drying the samples in the open air. Additionally, to accurately evaluate the behavior of saffron daughter corms in response to density levels and manure application in the year following planting, the number and yield of daughter corms were separately determined in sizes of 0.1 to 4 grams, 4 to 8 grams, 8 to 12 grams, and over 12 grams in June 2012, from an area of 0.5 square meters (1 meter × 0.5 meters) in each plot.
For data analysis obtained from the experiment, SAS 9.1 and Mstat-C software were used, and for creating related figures, Excel software was utilized. The means were compared using Duncan’s multiple range test at a significance level of five percent.
Results and Discussion
Quantitative Indicators of Saffron: The results of variance analysis indicated that the interaction effects of high-density planting of corms × manure application were significant for all indicators related to the number and yield of saffron flowers (Table 2). According to the results obtained, the planting density levels of corms had a significant role in the meaningful increase of the number and yield of fresh and dry saffron flowers per unit area. It was observed that at all levels of manure application (from zero to 100 tons per hectare), the highest number and yield of fresh and dry flowers were recorded at a planting density of 400 corms per square meter.
In this regard, collaborators stated that in the first and second years of the experiment, increasing high-density planting levels (from eight to 21 tons per hectare) significantly increased the number of saffron flowers per square meter. On the other hand, at all four planting density levels (100, 200, 300, and 400 corms per square meter), manure application also played a significant role in increasing the number and yield of fresh and dry saffron flowers.
The significant effect of manure application in the first year after planting the corms may be due to improved nutritional conditions for effective growth of the corms and also improved physical conditions of the soil to facilitate flowering. Regarding the effective role of organic fertilizers, Behdani et al. (2006) also stated that the gradual release of nutrients from manure, while providing the nutritional needs of the plant, can play a significant role in improving the physical and chemical structure of the soil.
Despite the positive effects of manure application, the results presented in Figures 1 and 2 indicated the varying levels of effective manure application at each high-density planting level. For example, in terms of the number of flowers per unit area, at densities of 100 and 400 corms per square meter, the application of 40 and 60 tons of manure per hectare, respectively, was determined to be the optimal amount of this organic fertilizer. This difference may be due to the direct relationship between manure application and the number of planted corms; as the high-density planting levels increase, the optimal level of manure application also increases. Therefore, it seems that for the successful implementation of saffron fertilization programs, the desired high-density planting level should be specifically considered.
Similar to the fresh and dry saffron flower yields, the yields of saffron stigma and stigma + style were also significantly influenced by the interaction effects of high-density planting × manure application. In each of the manure application levels, as the planting density of corms per unit area increased, the yield of saffron stigma and stigma + style significantly increased.
In this regard, Behnia (2009) reported a significant increase in the dry flower yield and stigma + style yield of saffron due to increased planting density in row and cluster planting methods. Naderi Darbaghshahi et al. (2009) also stated that increasing planting density from two to eight corms per cluster (from 4.44 to 6.177 corms per square meter) led to a significant increase in stigma yield and saffron harvest index. The positive effects of planting density on the improvement of saffron flower and stigma yields can be attributed to the plant’s ability to absorb environmental resources. Koocheki et al. (2011) also reported a significant increase in the dry weight of petals and stigma of saffron as a result of increased planting density, noting that higher planting densities could accelerate flowering and earlier utilization of resources, thus enhancing economic efficiency.
Furthermore, in terms of saffron stigma yield, the greatest impact of manure application was observed at a density of 400 corms per square meter. At this specified density, the application of 100 tons of manure per hectare (1216 mg per square meter) compared to its absence (893 mg per square meter) resulted in a 36% increase in stigma yield. Rezvani Moghaddam et al. (2010) also observed an increase in fresh flower and dry stigma yields of saffron due to higher manure application levels.
Saffron Corm Indicators: The results of variance analysis indicated that the interaction effects of manure application × corm planting density were significant for all indicators related to the daughter corms of saffron in the first year after planting (Table 3). The lowest and highest numbers of saffron daughter corms were obtained at densities of 100 and 400 corms per square meter, respectively (Table 4). Among the experimental treatments, the lowest number of daughter corms per unit area was observed due to the absence of manure application at a density of 100 corms per square meter (123 corms per square meter).
This relationship was also noted by Naderi Darbaghshahi et al. (2009), who reported an increase in the number of produced corms per square meter under the influence of a fourfold increase in planting density from two to eight corms per cluster (4.44 to 6.177 corms per square meter).
Based on the results presented in Table 4, the highest significant increase in the number of corms weighing more than 12 grams was observed with the planting of 300 corms per square meter; with the increase in density from 100 to 300 corms per square meter, the number of daughter corms weighing more than 12 grams increased nearly threefold. On the other hand, at a density of 300 corms per square meter, the number of daughter corms weighing more than 12 grams due to the application of 100 tons of manure per hectare (48.7 corms per square meter) was four times higher than in conditions without manure application (11.3 corms per square meter). As previously mentioned, balanced availability and gradual release of nutrients from manure, along with the improvement of the physical and chemical structure of the soil (Behdani et al., 2006), can have a significant role in enhancing the growth of saffron corms.
On the other hand, increasing the density from 300 to 400 corms per unit area led to a sharp decrease in the number of corms weighing more than 12 grams. At a density of 400 corms per square meter, the number of corms weighing more than 12 grams (5.7 corms on average across manure application levels) decreased by about sevenfold compared to a density of 300 corms (35.8 corms per square meter).
Conclusion
Overall, the results of the experiment indicate the significant role of manure application in improving the flower and corm yields of saffron. Additionally, the results showed that, based on the level of manure application, increasing the planting density of saffron corms can effectively enhance the behavior and performance of saffron corms while improving flower yields. Therefore, it seems that planning for proper fertilization management of saffron should be based on high-density planting levels. On the other hand, the results indicated that considering high-density planting and fertilization management, it is possible to produce suitable corms for planting over the long term and across more than two agricultural years.
**References**
Journal of Saffron Research, 2 (1392), 155-144.
Alireza Koocheki¹
Parviz Rezvani Moghaddam¹
Abdolhamid Faalabi²
Mohammad Seyedi³
¹ Professor, Department of Agronomy, Faculty of Agriculture, Ferdowsi University of Mashhad
² Faculty Member, Department of Food Biotechnology, Research Institute of Food Science and Industries
³ Ph.D. Student, Ecology of Agricultural Plants, Faculty of Agriculture, Ferdowsi University of Mashhad
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