The effect of organic matter, potassium fertilizer levels, and irrigation water salinity on some thermodynamic parameters during the growth stages of yellow corn

الملخص

A field experiment was conducted in a sandy loam soil at one of the fields of the College of 
Agriculture, Wasit University, in Al-Kut District, Wasit Governorate, during the autumn season of 
2023. The experiment was a factorial experiment using a split-plot arrangement and a randomized 
complete block design (RCBD) with three replications. The experiment included three factors: the 
first factor was two levels of irrigation water salinity (1.26 and 4 dS/m⁻¹), designated S1 and S2 
respectively; the second factor was the application of potassium fertilizer (potassium sulfate) at three 
application levels (0, 50, and 100 kg ha⁻¹), designated K0, K1, and K2 respectively; and the third 
factor was the application of organic fertilizer (sheep manure) at three application levels (0, 10, and 
20 tons ha⁻¹), designated M0, M1, and M2 respectively. Yellow corn seeds of the Baghdad-3 variety 
were planted on 1/8/2023. Plant samples were taken during the crop growth stages at three planting 
dates, i.e., after 40, 80 and 120 days from planting. The results showed that the S1M2K2 combination 
achieved the highest values for all thermodynamic parameters of potassium, ionic strength, ionic 
activity, activity coefficient and free energy, compared to the S2M0K0 combination, which gave the 
lowest values for all thermodynamic parameters. By estimating the thermodynamic parameters, the 
availability of potassium to the soil was determined, as it was moderately available for potassium 
during the 40 and 80 days from planting dates to soils suffering from a deficiency in potassium 
availability during the crop maturation stages, i.e., after 120 days from planting. Thus, the 
thermodynamic criteria were distinguished by very high accuracy and efficiency in their results 
compared to the results of the traditional chemical criterion, and were more accurate in describing the 
availability of potassium in the study samples in the short and long term.