Abstract

An incubation study was conducted to quantify the effects of salinity waters (1, 4, 8, 12 and 16 dSm-1) on N mineralization dynamics of two fertilizers : sulfur coated urea (SCU) and urea phosphate (UP) in clay soil after 5, 10, 20, 30 and 40 days of incubation .Results showed that a significant proportional relation (P  0.01) was recorded between water salinity and N mineralization of both fertilizers. Increasing the salinity level for 1 dSm-1 statistically increased the contents of NH4-N and NO2-N by 2.86 and 0.33 mg N kg-1 soil, respectively. Meanwhile, it caused significant decreases of both nitrification and nitrification rate (NR) by 7.20 mg N kg-1 and by 1.01%, respectively. High contents NH4-N (for 5, 10, 20 d) and NO2-N ions (for 5 – 40 d) were accompanied with SCU. However, the highest NO3-N production and NR were recorded with UP fertilizer.Results also confirmed that ammonification rate of both fertilizers drastically decreased, meanwhile, the content of NO2-N , NO3-N, and NR significantly enhanced by increasing the period of incubation. The first order and logarithmic equation can be satisfactorily employed for predicting the N of both test fertilizers. We conclude that urea phosphate (UP) is the most speedily and easily hydrolyzed in Iraqi calcareous soils than sulfur coated urea (SCU).

The article was added to IASJ on 2015-05-27

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