Asian Journal of Soil Science and Plant Nutrition

Aims: A study was carried out in the field aims to study the response of a calcareous soil cultivated by soybean to the application of K-silicate (K-Si), K-humate (K-H), and compost at application rates 50% and 100% of the recommended dose.

Study Design: Complete randomized block design with three replicates.

Place and Duration of Study: At El-Nubaryia Agricultural Research Station (latitude of 30° 30°N longitude of 30° 20°E) Agricultural Research Center (ARC), Nubaryia, Egypt (Summer seasons of 2018 and 2019).

Methodology: Compost was mixed with surface soil a week before cultivation at application rates 3.75 and 7.5 kg plot^-1 (3.91 and 7.81 t ha^-1, respectively). Powder K-H was spread on soil at application rates 7.5 and 15 g plot^-1 while aqueous solutions of K-Si; 8 and 16 mL L^-1 for plot was sprayed on soil 30, 60, and 90 days after cultivation.

Results: Results showed that soil moisture(SM, %) was increased by the 100% application rate in the order compost (20.6%) > K-Si (19.3%) > K-H (19.1%). A significant increase was found in the seed yield (kg ha^-1) by 129.5%, 84.8% and 70.6% by compost, K-H and K-Si, respectively. Compost at 100% application rate showed the most significant increase in the available nitrogen N (mg kg^-1) in soil by 104.4% followed by K-H (by 81.8%) then K-Si by 23.4%. Compost also showed the most significant increase in the N uptake from soil (kg ha^-1 soil) by seeds and straw followed by K-H then K-Si. The nutrient use efficiency (NUE, %) and agronomic efficiency (AE) values decreased in the order K-H > K-Si > compost at 50% and 100% application rates.

Conclusion: The quite smaller dose and ease of field application by spraying may make the K-H more agronomically efficient than K-Si and compost.