Document Type : Applicable
Authors
1
Assistant Professor, Soil and Water Research Institute, Agricultural Research, Education and Extension Organization, Karaj, Iran
2
Ph.D Graduate of soil science, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran
3
Associate Professor, Fars Province Agricultural and Natural Resources Research Center; Agricultural Research, Education and Extension Organization, Shiraz, Iran
4
Assistant Professor, Dezful Agricultural and Natural Resources Research Center; Agricultural Research, Education and Extension Organization, Dezful, Iran
5
Assistant Professor, Kerman Province Agricultural and Natural Resources Research Center; Agricultural Research, Education and Extension Organization, Kerman, Iran
6
Assistant Professor, Isfahan Province Agricultural and Natural Resources Research Center; Agricultural Research, Education and Extension Organization, Isfahan, Iran
Abstract
Introduction: Phosphorus (P) is an essential nutrient for plant growth that affects all biochemical and growth reactions. Compared to other essential elements, this element has low bioavailability for plants, which is due to the precipitation of phosphorus in the form of calcium phosphate in calcareous soils. The amount of phosphorus available in 2.5 million hectares of Iranian arable land (70.2% of irrigated land) is less than 15 mg/kg. Due to the lack of phosphorus (P) in a large area of Iran's agricultural soils and the increasing price of phosphorus fertilizers, it is necessary to recommend phosphorus fertilizers more precisely. Identifying phosphorus-efficient safflower cultivars can help reduce the amount of phosphorus fertilizer consumption. Therefore, this study was conducted to investigate the growth, seed and oil yield and phosphorus efficiency indices in different safflower cultivars. Oilseeds after cereals, provide the most energy in the human diet, and are an important source of protein and vitamins. Safflower (Carthamus tinctorius) ranks eighth in the world in terms of oilseed production after soybean (Glycine max L.), peanut (Arachis hypogaea L.), rapeseed (Brassica napus L.), sunflower (Helianthus annus L.), sesame (Sesamum indicum L.), flax (Linium usitatissimum L.), and castor (Ricinus communis L.).
Materials and Methods: A factorial experiment was carried out in Darab, Isfahan, Dezful, and Kerman regions of Iran in a randomized complete block design with three replications (in 2018 and 2019). The factors included P rates of 0, 10, 20, 30, and 40 kg P ha-1 from Triple superphosphate and safflower cultivars Padideh and Goldasht for Isfahan and Darab and Goldasht and Soffeh for Kerman and Dezful regions. The available P in Isfahan, Darab, Kerman and Dezful soil was 10.2, 11, 7, and 7.18 mg kg-1, respectively. After the end of the rosette period and before flowering (before the two-digit growth code 62), five whole plant samples were randomly prepared from each plot and the plant dry weight (DW), phosphorus concentration and plant phosphorus uptake (product of dry weight multiplied by plant phosphorus concentration) were determined at this stage of growth. Shoot dry weight (DW) and P concentration, grain yield and phosphorus efficiency (PE) of DW and grain, P acquisition efficiency (PACE) and P use efficiency (PUTE) of DW was measured too. Statistical analysis of the results, including analysis of variance and Duncan's multiple range test model (p<0.05), was performed using SAS 9.4 software.
Results and Discussion: Based on the results, the soil texture in Isfahan, Darab and Dezful regions was heavier than Kerman region. Organic carbon in all soils was low and calcium carbonate equivalent was high. The soils were non-saline (slightly saline in Isfahan region), with insufficient potassium in Isfahan, Kerman and Dezful regions, and phosphorus content was moderate in all regions. The experiment revealed significant differences in the response of safflower cultivars to soil and fertilizer phosphorus, particularly in biomass yield and phosphorus efficiency indices. Application of 10 kg P ha-1 in Darab, 20 kg in Dezful, 10 kg in Isfahan, and 30 kg in Kerman increased grain yield by 20%, 78%, 28%, and 237% compared to the control treatment, respectively. The results showed that the main effect of P rate was significant on PUTE of DW (p<0.01), PACE (p<0.05), PE of grain (p<0.05), PE of DW (p<0.01) in Darab, Dezful, Dezful, Isfahan regions, respectively. The main effect of cultivar was also significant on PE of DW (p<0.01) in Darab and PUTE of DW (p<0.01, p<0.05) in Isfahan and Kerman regions, respectively. The P efficiency of DW had a higher correlation with the PACE of DW (R2=0.45**, 0.19*, 0.43**, 0.57**, respectively in Isfahan, Darab, Kerman and Dezful regions) compared to the correlation of PE with PUTE (in all four regions non-significant).
Conclusion: The results of the present study showed that the studied cultivars have different responses to phosphorus application. For safflower crops in warm regions with 10 mg P kg-1 soil, application of 10 kg P ha-1 is recommended, while for soils with 7 mg P kg-1, application of 30 kg P ha-1 is suggested. It seems that safflower can uptake further amounts of P if we use further amounts of fertilizer but can still produce optimum yields with lower phosphorus percentages in aerial parts. A phosphorus concentration of 0.18% is deficient, while 0.23% is sufficient in safflower aerial parts during the stem elongation growth stage.
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