Document Type : Original Article
Authors
1
PhD student in Agro-Technology (Crop Ecology), Department of Plant Production and Genetics, University of Kurdistan, Sanandaj, Iran
2
Associate Professor, Department of Plant Production and Genetics, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran
3
Associate Professor, Department of Horticultural Science, University of Kurdistan, Sanandaj, Iran
4
Assistant Professor, Department of Plant Production and Genetics, University of Kurdistan, Sanandaj, Iran
5
Assistant Professor, Department of Horticultural Science, University of Kurdistan, Sanandaj, Iran
Abstract
Introduction
Global climate change, water scarcity, and environmental stresses threaten the sustainability of forage production, particularly in arid and semi-arid regions. Coronilla varia L. (syn. Securigera varia L.), commonly known as crownvetch, is a perennial legume valued for soil conservation, nitrogen fixation, and erosion control. Native to Europe, crownvetch has spread to the Mediterranean region, Russia, the Middle East, and the United States, with growing interest in Iran for forage production, particularly in pastures and field margins. Despite these benefits, crownvetch remains outside commercial crop rotations. With increasing drought frequency, understanding the effects of water deficit on crownvetch growth and nutritional quality is essential. Drought stress can impair germination, plant growth, photosynthesis, nutrient uptake, and biomass production. Utilizing drought-tolerant species such as crownvetch may provide a sustainable approach to forage production under water-limited conditions. Previous research has shown that the effects of drought on forage quality traits, including crude protein, fiber content, digestibility, and mineral content, vary depending on plant genotype, developmental stage, and environmental conditions.
Materials and methods
This study evaluated the morphological and nutritional responses of different crownvetch ecotypes to varying levels of water deficit. The experiment was conducted in the greenhouse of the University of Kurdistan in 2024 using a factorial completely randomized design with three replications. Ten ecotypes collected from different regions of Iran, including Hamadan, Nahavand, and Kermanshah, were subjected to five irrigation intervals (2, 4, 6, 8, and 12 days) to impose different levels of water deficit. The seeds were sterilized, germinated, and grown in pots containing a soil–sand–manure mixture. After transplanting, plants were maintained at field capacity until reaching the four-leaf stage and were then subjected to the respective irrigation treatments for two months. Morphological traits, including plant height and root length, along with biomass, were measured after harvest. Laboratory analyses were conducted to determine crude protein, fiber fractions, including neutral detergent fiber (NDF) and acid detergent fiber (ADF), digestible dry matter (DDM), and ash content according to AOAC methods. Analysis of variance (ANOVA) revealed significant effects of ecotype, irrigation interval, and their interaction on plant traits and forage quality. The results were visualized using graphs and interaction plots.
Results and discussion
The analysis demonstrated that ecotype, irrigation interval, and their interaction significantly affected plant growth and forage quality traits (p < 0.01). Under a 6-day irrigation interval, the Nahavand, Hamadan, and Saghez ecotypes exhibited superior performance, with higher biomass and plant height than the other ecotypes. The Nahavand ecotype produced the highest biomass (~33.5 g.plant⁻¹), whereas the Paveh ecotype subjected to the longest irrigation interval (12 days) produced the lowest biomass (~12.5 g.plant⁻¹), highlighting the potential adverse effects of prolonged water deficit. Root length increased under moderate water deficit, possibly as an adaptive response to enhance water acquisition, whereas longer irrigation intervals resulted in reductions in morphological traits, possibly associated with impaired photosynthesis, stomatal closure, and cellular dehydration. Nutritional analysis revealed that crude protein (CP) content increased under moderate water deficit, reaching approximately 21% in the Hamadan and Saghez ecotypes, but declined under the longest irrigation interval to approximately 13%, possibly due to reduced nitrogen uptake. Fiber fractions, including neutral detergent fiber (NDF) and acid detergent fiber (ADF), increased with increasing irrigation intervals, particularly at the 12-day interval, whereas the Paveh ecotype exhibited the highest fiber concentrations (~60% NDF and ~35% ADF), suggesting increased cell wall deposition and potentially reduced digestibility. Correspondingly, digestible dry matter (DDM) decreased under severe water stress, whereas DDM remained higher (~79%) under moderate water stress, suggesting a potential balance between biomass production and forage quality. Ash content increased with increasing irrigation intervals, possibly reflecting changes in mineral accumulation or a biomass dilution effect. The Hamadan and Saghez ecotypes maintained higher digestibility and lower fiber concentrations under moderate water stress, highlighting their relative tolerance to water limitation. Overall, moderate water stress may induce adaptive responses, such as increased soluble sugar and protein levels, that contribute to the maintenance of forage quality. However, prolonged water deficit markedly reduced plant growth and forage quality, highlighting the importance of appropriate irrigation management and the selection of water-stress-tolerant ecotypes, particularly Hamadan, Saghez, and Ilam, for sustainable forage production under water-limited conditions.
Conclusion
This study highlights the significant effects of water deficit on the growth and forage quality of crownvetch ecotypes. Moderate water deficit improved certain forage quality traits, such as crude protein and digestibility, whereas prolonged water deficit markedly reduced biomass and forage quality. The Hamadan, Saghez, and Ilam ecotypes exhibited greater tolerance to water deficit, suggesting their potential suitability for cultivation under water-limited conditions. Implementing strategic management practices, including the selection of ecotypes tolerant to water deficit and appropriate irrigation management, may help sustain forage production under climate variability and water-limited conditions.
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