EFFECT OF WATER  SALINITY ON N MINERALIZATION OF SULFUR COATED UREA AND UREA PHOSPHATE

K. Al-Uqaili, J.; A. Al-Joburi, B.; H. Al-Ameri, B.

	EFFECT OF WATER SALINITY ON N MINERALIZATION OF SULFUR COATED UREA AND UREA PHOSPHATE
IRAQ JOURNAL OF AGRICULTURE
Article 1, Volume 11, Issue 1, 2006, Pages 0-0
Authors
J. K. Al-Uqaili; B. A. Al-Joburi; B. H. Al-Ameri
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).

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