Journal of Taiwan Agricultural Research

Author:En-Tsun Chou, Chong-Ho Wang, Ren Shih Chung, and Chi-Ling Chen*

Abstract:

    Nitrogen (N) and phosphorus (P) are the most common limiting nutrient on the growth and yield of crops. There are many factors that influence the availability and transformation of N and P in soils. The objectives of this study were to evaluate the effects of different fertilization managements and application of different kinds of fertilizers on the different fractions of soil N and P under uplandlowland (corn and rice) rotation for nine years. There were seven treatments, namely, 1. CK (without fertilization), 2. Chem-N (applying chemical N fertilizer only), 3. Comp (applying compost with the same rate as N of Chem-N treatment), 4. Comp + l/3 N (applying compost complemented with 33% of chemical N fertilizer as Chem-N treatment), 5. Comp + 2/3 N (applying compost complemented with 66% of chemical N fertilizer as Chem-N treatment), 6. GM + 1/3 N (applying green manure complemented with 33% of chemical N fertilizer as Chem-N treatment), and 7. Peat + 1/3 N (applying peat complemented with 33% of chemical N fertilizer as Chem-N treatment). The methods proposed by Bremner (1965a, 1965b, 1965c) and Sui et al. (1999) were used to fractionate N and P, respectively, into different fractions. The results indicated that soil total N and organic N were not affected the proportion of hydrolysable N increased by the application of chemical N fertilizer. Application of compost and peat resulted in increased soil total N and organic N. Furthermore, both hydrolysable and nonhydrolyzable N increased. The chemical N fertilizer applied with compost had no effect on the concentrations of soil total N and organic N. Application of green manure gradually increased soil total N and hydrolysable N. The unidentified hydrolysable N and amino sugar-N were less affected by different fertilization managements. Compost increased soil amino acid-N and hydrolysable ammonium N. Different fertilization managements resulted in change of concentration and proportion of different soil P fractions. Residual fertilizer P predominantly became sodium bicarbonate extractable inorganic P (NaHCO₃-IP) and sodium hydroxide extractable inorganic P (NaOH-IP). The greater the P fertilizer applied, the more the increase in these fractions of P. The characteristics of organic fertilizer affected the transformation of residual fertilizer P in the soil. Residual P and hydrochloric acid extractable P were less affected by fertilization management.

Key words:Hydrolyzable nitrogen, Nonhydrolyzable nitrogen, Sodium bicarbonate extractable phosphorus, Hydrochloric acid extractable phosphorus

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