Effect of Different Sources of Potassium on the Nutrient Status of Saline Calcareous Soil and Carrot (Daucus carota L.) Yield and Quality

Aims: A field experiment was performed in a saline calcareous soil. Its aim was to evaluate the fertilization effects of potassium (K) from different sources in the form of a liquid solution sprayed on both plant and soil on some soil properties and on the carrot (Daucus carota L.) yield and quality. The purpose of the study is to try replacing the traditional soil application of some K fertilizers by spraying application using the liquid solution form.

Study Design: A split plot design with four replicates.

Place and Duration of Study: The experiment was carried out during two successive winter seasons (2016/2017 and 2017/2018) at the El-Road village, Sahl El-Hussinia, El-Sharkia Governorate (32°15' 00" N 30°50' 00" E), Egypt.

Methodology: The K sources used were K-humate (K-H), K-nitrate (KNO3), and K-sulphate (K2SO4) in individual treatments with and without the compost in addition to the control. They were applied in a solution form sprayed on plant and soil at two rates: 600 and 1200 g K2O/ha. Sowing of seeds was performed and K application doses were applied three times at 21, 45, and 65 days after sowing.

Results: The lyotropic order of K mitigates salinity stress on the plant. The compost along with the applied K significantly intensified the soil available nitrogen and K, but no significant effect was observed for available phosphorous. Spraying K from different sources with the compost caused a significant increment in the soil available K in a descending order K-H > K2SO4 > KNO3. Soil available Zinc was significantly affected by K sources with a more pronounced effect by K-H. The carrot root length (cm), fresh weight (g), and yield, as well as the plant K use efficiency (KUE), were significantly increased by applying the K-H with the compost compared to the control alone. Minimum values were obtained for the KNO3 treatment without the compost.

Conclusion: The complex composition of compost may limit the fertilization effect of sprayed K in the humate form but improves that of sulphate and nitrate.