<div>Background: The study was carried out to determine the amount of the dolomite phosphate rock (DPR) on the growth and seed yield of black sesame in a paddy field. 
 
Methods: A randomized complete block design was used for the field experiment, which included four treatments, each with four replications. Treatments were applied without the DPR and with 0.25, 0.5 and 1.0 t ha-1 DPR. 
 
Result: Experimental results showed that sesame plants were fertilized with the following formula: 60 N x 60 P2O5 x 30 K2O kg ha-1. Moreover, the addition of 0.5 t ha-1 DPR increased plant height (129.7 cm), the number of leaves and pods per plant (47.4 pods), total chlorophyll content in leaves (12.4 &micro;g/cm2), the number of seeds per pod and seed yield (1.61 t ha-1). The phosphate content increased in the stem but not in the leaves and seeds. The pH of the soil (0-20 cm) and the amount of NH4+, NO3- and PAvailable were also increased.</div>

The Effectiveness of Dolomite Phosphate Rock on Growth and Yield of Black Sesame (Sesamum indicum L.) in Paddy Field

Background: Calcareous soils derived from limestone and related parent materials are widespread in southern T&uuml;rkiye, including the eastern Mediterranean region. These soils typically contain high levels of exchangeable calcium and, in many cases, substantial amounts of magnesium. In calcareous environments, nutrient behavior is strongly linked to cation proportions. Where calcium (Ca) is abundant, it may influence the relative availability of magnesium (Mg) and potassium (K) through exchange-related interactions. Therefore, concentration values alone may not fully represent plant-accessible nutrient status. For this reason, evaluating soil fertility solely on the basis of individual nutrient concentrations may overlook imbalances that affect plant nutrition. To address this issue under practical field conditions, we examined selected soil cation ratios and their relationships with Ca, Mg and K concentrations in peanut grown in the Osmaniye region, where calcareous soils are dominant. 
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Methods: Field sampling was carried out in peanut-growing areas of Osmaniye province. A total of 45 surface soil samples were collected, together with the youngest fully expanded peanut leaves at the full flowering stage. Soil samples were air-dried, sieved and characterized in terms of pH, electrical conductivity (EC), calcium carbonate content, organic matter and exchangeable Ca, Mg and K concentrations. Leaf samples were oven-dried, ground and subjected to wet digestion prior to determination of Ca, Mg and K using atomic absorption spectrophotometry (AAS). Base cation saturation ratios were derived from exchangeable cation data. The associations between soil properties and leaf nutrient concentrations were examined using correlation analysis and principal component analysis (PCA). Spatial variability of selected parameters was mapped by kriging interpolation within a GIS environment. 
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Result: The study area is dominated by soils formed from the weathering of limestone and dolomite and this geological background is reflected in their chemical composition. Exchangeable Ca and Mg levels were consistently high, resulting in elevated Ca/K and Mg/K ratios across most of the sampling area and likely restricting K uptake, thereby causing K deficiency in peanut leaves. Both correlation analysis and principal component analysis (PCA) revealed clear antagonistic relationships between K and the divalent cations, whereas Ca and Mg tended to vary in the same direction. Spatial evaluation further showed that locations with higher soil Ca/K and Mg/K ratios frequently coincided with reduced foliar K levels. This pattern suggests that the dominance of Ca and Mg, largely controlled by parent material, may influence K nutrition in the region. Overall, the results support the consideration of cation balance, in addition to individual nutrient concentrations, when developing fertilization strategies for peanut production. 
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The Effectiveness of Dolomite Phosphate Rock on Growth and Yield of Black Sesame (Sesamum indicum L.) in Paddy Field

Calcium, Magnesium and Potassium Nutrition of Peanut as Influenced by Soil Cation Ratios