Dinitrogen and Nitrous Oxide Flux from Urea Basally Applied to Puddled Rice Soils
- R. J. Buresh ,
- S. K. De Datta,
- M. I. Samson,
- Sakorn Phongpan,
- Patoom Snitwongse,
- A. M. Fagi and
- R. Tejasarwana
International Fertilizer Development Center (IFDC)/International Rice Research Institute (IRRI) Cooperative Project, P.O. Box 933, Manila, Philippines
Agronomy, Physiology, and Agroecology Div., IRRI; P.O. Box 993, Manila
Isotope Lab., Division of Agricultural Chemistry, Dep. of Agriculture, Bangkok 10900, Thailand
Sukamandi Research Inst. for Food Crops, Jln. Raya no. 9, Sukamandi, Subang, West Java, Indonesia
Nitrification-denitrification is often regarded as an important N loss process in puddled rice soils, but few direct field measurements of denitrification loss have been reported. Field studies were conducted on a Typic Tropaquept in Thailand, an Aeric Tropaqualf in Indonesia, and an Andaqueptic Haplaquoll in the Philippines to measure (N2 + N2O)-15N flux, (N2 + N2O)-15N trapped in soil, and total gaseous 15N loss following basal application of 15N-labeled urea (87 kg N ha−1) to irrigated rice (Oryza sativa L.) grown on puddled soils. Urea treatments included broadcast applications with and without incorporation to 0.07-m soil depth. Directly measured (N2 + N2O)-15N flux during the 10 d following urea application by each method was less than 0.1% of the applied N at the Thailand and Indonesia sites. The (N2 + N2O)-15N collected from the soil after 10 d did not exceed 0.02% of the applied N. Total gaseous N loss determined from a 15N balance at 10 d after N application without incorporation was 34% of the applied N in Thailand and 31% in Indonesia. Incorporation reduced total N loss to 22% in Thailand and 10% in Indonesia. In the Philippines, the measured (N2 + N2O)-15N flux during the 15 d immediately following urea application with incorporation was 2.2% of the applied N with chambers placed between rice plants and 3.0% with chambers over the plants. Total N loss at the Philippine site was 40% of the applied N. Ammonia volatilization appeared to be much more important than nitrification-denitrification as a mechanism of urea-N loss at the three irrigated lowland study sites.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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