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ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Water Management Research » Research » Publications at this Location » Publication #305403
Title: Nitrification and acidification from urea application in red soil (Ferralic Cambisol) after different long-term fertilization treatments

Author
item CAI, ZEHIANG - Chinese Academy Of Agricultural Sciences
item WANG, BOREN - Chinese Academy Of Agricultural Sciences
item XU, MINGGANG - Chinese Academy Of Agricultural Sciences
item ZHANG, HUIMIN - Chinese Academy Of Agricultural Sciences
item ZHANG, LU - Chinese Academy Of Agricultural Sciences
item Gao, Suduan

Submitted to: Journal of Soils and Sediments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2014
Publication Date: 9/1/2014
Citation: Cai, Z., Wang, B., Xu, M., Zhang, H., Zhang, L., Gao, S. 2014. Nitrification and acidification from urea application in red soil (Ferralic Cambisol) after different long-term fertilization treatments. Journal of Soils and Sediments. 14:1526-1536.

Interpretive Summary: Organic fertilizer such as manure was found to prevent or even reverse acidification of acid soils but its long-term effect or the resistance to re-acidification from chemical fertilizers is unknown. This study examined the effect of urea application on nitrification and acidification processes in an acid red soil after 19 years of continuous application of manure in comparison with chemical fertilizer treated soils. Following urea addition, manure-treated soils exhibited the highest acidification and nitrification rates due to high soil pH (5.75–6.38). The results indicate that continuous incorporation of manure or other organic materials can help prevent acidification to maintain soil productivity.

Technical Abstract: Purpose. Long-term manure applications can prevent or reverse soil acidification by chemical nitrogen (N) fertilizer. However, the resistance to re-acidification from further chemical fertilization is unknown. The aim of this study was to examine the effect of urea application on nitrification and acidification processes in an acid red soil (Ferralic Cambisol) after long-term different field fertilization treatments. Materials and methods. Soils were collected from six treatments of a 19-year field trial: 1) non-fertilization control, 2) chemical phosphorus and potassium (PK), 3) chemical N only (N), 4) chemical N, P and K (NPK), 5) pig manure only (M), and 6) NPK plus M (NPKM; 70 % N from M). In a 35-d laboratory incubation experiment, the soils were incubated and examined for changes in pH, NH4+, and NO3-, and their correlations from urea application at 80 mg N kg-1(-80) compared to 0 rate (-0). Results and discussion. Manure-treated soils reduced acidification (soil pH 5.75–6.38) and the lowest pH was in the chemical N treated soils (soil pH 3.83–3.90). In untreated soils, the pH was 4.98–5.12. By day 35, soil pH decreased to 5.21 and 5.81 (0.54 and 0.57 unit decrease) in the NPKM-80 and M-80 treatments, respectively, and to 4.69 and 4.53 (0.43 and 0.45 unit decrease) in the Control-80 and PK-80 treatments, respectively, with no changes in the N-80 and NPK-80 treatments. The soil pH decrease was highly correlated with nitrification potential, and the net protons released. The maximum nitrification rates (Kmax) of NPKM and M soils (14.7 and 21.6 mg N kg-1 d-1, respectively) were significantly higher than other treatments (2.86–3.48 mg N kg-1 d-1). The priming effect on mineralization of organic N was high in manure treated soils. Conclusions. Field data have shown clearly that manure amendment can prevent or reverse the acidification of the red soil. When a chemical fertilizer such as urea is applied to the soil again, however, soil acidification will occur at possibly high rates. Thus, the strategy in soil N management is continuous incorporation of manure to prevent acidification to maintain soil productivity. Further studies under field conditions are needed to provide more accurate assessments on acidification rate from chemical N fertilizer applications.