Nutrient use Efficiency in Calcareous Soil Amended by the Silicate, Humate and Compost

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.