Abstract
Potassium (K) availability in calcareous soils of Iran has been decreased due to intensive crop production and little K application. We hypothesized that different organic materials may affect K release from these soils. For this purpose, release of K from two clayey calcareous soils treated with different organic materials including alfalfa, broad bean, barley, and pea residues; camel, cow, pigeon, poultry, quail, and sheep manures; and household vermicompost was studied. The experiment was a completely randomized factorial arrangement, and factors were organic material treatment, moisture regime, and soil type. Soil samples were treated with 2% of each organic amendment and incubated for 60 days at 22 ± 3 °C under two moisture conditions (field capacity and saturation). Then, kinetics of K release from soil samples during 180 min was determined. Results indicated that all organic amendments (except camel manure) increased K release from soil samples. The highest and lowest contents of K release were found in samples treated with sheep and camel manures, respectively (1280 and 403 mg kg−1, respectively). Cambisol with palygorskitic mineralogy released more K than Vertisol with smectitic mineralogy. Generally, the moisture condition had no significant effect on soil K release. The parabolic diffusion equation was the best model to describe K release from all soil samples. The mean value of equation slope (b) for Cambisol was significantly higher than that for Vertisol (65 vs. 61 mg kg−1 min−0.5). Generally, the highest content of K release was observed in palygorskitic Cambisols treated with sheep manure under field capacity moisture condition. These results indicated that organic material application could be a promising strategy on K fertility management of clayey soils.
Published Version
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