A Comparative Study on the Impact of Compost, Humate, and Silicate on the Nutritional Characteristics of Calcareous Soil Cultivated by Soybean

Two field experiments have been carried under the calcareous soil conditions during the summer seasons of 2018 and 2019. Their aim was to compare the effects of compost, K-humate, and K-silicate applied at 50% and 100% of the recommended dose (compost: 7.81 t ha^-1, potassium silicate: 16.67 L ha^-1, potassium humate: 15.63 kg ha^-1) on soil nutritional status regarding macro-nutrients (N, P, and K) and soybean yield and quality. Treatments were distributed in a randomized complete block design with three replicates. The study showed that soil applied K-H at 100% of the recommended dose has increased the available N (mg kg^-1) in soil significantly at a significance level of P = .05 by 77.78 % compared to the control. The 100 % application rate of compost showed the most significant increase in seed yield (kg ha^-1, 84.88%) followed by K-H (69.07%) then K-Si (67.39%) compared to the control. Also, compost at rate 100 % showed the most significant increase of protein and total N (~77.07%) followed by K-Si (~60.67%) then K-H (~ 17.69%). However, compost and K-Si have almost decreased the concentration (mg kg-1) of Cu, Fe, Mn, Zn, and Si in soybean seeds significantly by increasing the application rate from 50 to 100 %. Potassium silicate was the most effective Si-source in this study due to its content of readily soluble Si in soil solution. Silicon uptake can partially control the availability and uptake of some nutrients from soil. Soil may be enriched by versatile advantages upon application of K-H and K-Si but the compost is still the most effective.