Volume 19, Issue 2 (7-2025)
مرتع 2025, 19(2): 179-194 |
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Effects of Nitrogen and Phosphorus Fertilizers on the Production of Vegetative Forms of Rangeland Plants in the Semi-Steppe Region of Kurdistan Province. مرتع 2025; 19 (2) :179-194
URL: http://rangelandsrm.ir/article-1-1284-en.html
URL: http://rangelandsrm.ir/article-1-1284-en.html
Abstract: (490 Views)
Background and objectives: Fertilization of rangelands is a common management practice that can exert short-term and substantial effects on plant production and species composition by enhancing soil nutrient availability under suitable conditions. Indeed, fertilization is considered one of the most practical and effective methods to increase dry matter yield in rangeland ecosystems. This study aimed to investigate the effects of nitrogen and phosphorus fertilizers on the annual biomass production of various plant functional groups in the Saral and Majidabad rangelands of Kurdistan province.
Methodology: Representative areas within the rangelands at the two study sites were selected based on soil properties and homogeneity. Experimental plots measuring 5 × 5 meters were established with 5–10 meter spacing, with three replications per year, over the period of 2013 to 2016. A simple (single-factor) experimental design was implemented during the first two years, followed by a factorial design in the third year. Nitrogen fertilizer was applied at four levels (0, 50, 100, and 150 kg ha⁻¹) each spring of 2014, 2015, and 2016. Phosphorus fertilizer was applied at two levels (50 and 100 kg ha⁻¹) in the fall of 2013, 2014, and 2015, with at least three control plots maintained annually. Soil concentrations of nitrogen and phosphorus were measured each year. Vegetation canopy cover and biomass production were assessed separately for each species, categorizing plants into grasses, forbs, shrubs, and annuals. Statistical analysis was performed using combined analysis of variance for an unbalanced completely randomized design, and mean comparisons were made using Duncan’s multiple range test.
Results: Analysis showed that nitrogen concentrations did not cause significant variation among treatments. However, phosphorus showed significant effects related to year, year × replication, and year × treatment interactions. In the factorial experiment, soil phosphorus concentration did not significantly influence measured variables, whereas soil nitrogen concentration was significant at the 5% level. At the Majidabad site, combined analysis over three years revealed that in the simple fertilization trials, soil nitrogen concentration varied significantly only with year, and phosphorus concentration did not show significant differences except in the year × frequency interaction. Factorial fertilization treatments did not produce significant changes in soil nitrogen or phosphorus concentrations. Regarding vegetation production, simple fertilization significantly influenced only the biomass of annual species, with other plant functional groups unaffected. Factorial fertilization treatments significantly affected the production of grasses and a combined group of broadleaf + grass species. At Majidabad, simple fertilization significantly increased production of annual and grass species (p < 0.05), with year also having a significant effect. Other functional groups did not show significant responses to fertilization. Similarly, in factorial treatments, production of annuals and grasses was significantly affected, while other vegetative forms remained unchanged.
Conclusion: Nitrogen fertilization often led to an undesirable increase in annual species production, while phosphorus application sometimes resulted in a reduction of grass family biomass. Based on these findings, routine fertilization practices may not be advisable in the rangelands of Kurdistan province and similar bioclimatic zones. It is recommended that fertilization be integrated with reclamation efforts involving seeding or seedling planting to ensure fertilizer availability at the root zone and improve establishment success.
Methodology: Representative areas within the rangelands at the two study sites were selected based on soil properties and homogeneity. Experimental plots measuring 5 × 5 meters were established with 5–10 meter spacing, with three replications per year, over the period of 2013 to 2016. A simple (single-factor) experimental design was implemented during the first two years, followed by a factorial design in the third year. Nitrogen fertilizer was applied at four levels (0, 50, 100, and 150 kg ha⁻¹) each spring of 2014, 2015, and 2016. Phosphorus fertilizer was applied at two levels (50 and 100 kg ha⁻¹) in the fall of 2013, 2014, and 2015, with at least three control plots maintained annually. Soil concentrations of nitrogen and phosphorus were measured each year. Vegetation canopy cover and biomass production were assessed separately for each species, categorizing plants into grasses, forbs, shrubs, and annuals. Statistical analysis was performed using combined analysis of variance for an unbalanced completely randomized design, and mean comparisons were made using Duncan’s multiple range test.
Results: Analysis showed that nitrogen concentrations did not cause significant variation among treatments. However, phosphorus showed significant effects related to year, year × replication, and year × treatment interactions. In the factorial experiment, soil phosphorus concentration did not significantly influence measured variables, whereas soil nitrogen concentration was significant at the 5% level. At the Majidabad site, combined analysis over three years revealed that in the simple fertilization trials, soil nitrogen concentration varied significantly only with year, and phosphorus concentration did not show significant differences except in the year × frequency interaction. Factorial fertilization treatments did not produce significant changes in soil nitrogen or phosphorus concentrations. Regarding vegetation production, simple fertilization significantly influenced only the biomass of annual species, with other plant functional groups unaffected. Factorial fertilization treatments significantly affected the production of grasses and a combined group of broadleaf + grass species. At Majidabad, simple fertilization significantly increased production of annual and grass species (p < 0.05), with year also having a significant effect. Other functional groups did not show significant responses to fertilization. Similarly, in factorial treatments, production of annuals and grasses was significantly affected, while other vegetative forms remained unchanged.
Conclusion: Nitrogen fertilization often led to an undesirable increase in annual species production, while phosphorus application sometimes resulted in a reduction of grass family biomass. Based on these findings, routine fertilization practices may not be advisable in the rangelands of Kurdistan province and similar bioclimatic zones. It is recommended that fertilization be integrated with reclamation efforts involving seeding or seedling planting to ensure fertilizer availability at the root zone and improve establishment success.
Type of Study: Applicable |
Subject:
Special
Received: 2024/08/29 | Accepted: 2025/06/28 | Published: 2025/07/1
Received: 2024/08/29 | Accepted: 2025/06/28 | Published: 2025/07/1
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