Submitted to: Biology and Fertility of Soils
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/10/2001
Publication Date: 5/30/2002
Citation: PHONGPAN, S., MOSIER, A.R. EFFECT OF RICE STRAW MANAGEMENT ON NITROGEN BALANCE AND RESIDUAL EFFECT OF UREA-N IN AN ANNUAL LOWLAND RICE CROPPING SEQUENCE. BIOLOGY AND FERTILITY OF SOILS. 2002. 37:102-107. Interpretive Summary: Rice is the most economically important crop of Thailand, one of the world's leading rice exporters. Lowlands in the Central Plain represent a major rice-growing area where approximately 7 million tonnes per year or more than 30% of the total rice production in Thailand is produced. The need for increased rice production in the Central Plain is now widely recognized under intensified cropping systems (i.e. two or three crops per year) with high inputs especially increased tillage, irrigation, and N fertilizer use. High cropping intensity, improper use of crop residue and input use, particularly N fertilizer, has contributed to decreases in soil organic matter (SOM) and soil quality in general. Improved management systems are needed to provide sustainable rice production in Thailand's Central Plain.
Technical Abstract: Two field experiments were conducted in 1999 (wet season) and 2000 (dry season) on a Ustic Endoaquerts in Central Thailand to examine the impact of rice straw management practices on rice yield, N uptake and fertilizer N use efficiency. Treatments included a combination of urea broadcast at a rate of 70 kg N ha-1 with either straw or compost which were incorporated at a rate of 5 Mg ha-1. At maturity of the wet season rice, 15N recovery by the grain was low (11-14%) as well as the percentage of straw N derived from labeled N (5 to 7%). After harvest, 25 to 29% of applied N still remained in the soil, mainly in the 0-5 cm layer. Large amounts of fertilizer N (53-55%) were lost (unaccounted for) from the soil ' plant system during the first crop. Residual fertilizer N recovery in the second rice crop was less than 3% from the original application. During both fallow seasons NO3-N remained the dominant form of mineral-N (NO3 + NH4) in the soil. In the wet season grain yield response to N application was significant (P = 0.05). Organic material sources did not significantly change grain yield and N accumulation in rice. In terms of grain yield and N uptake at maturity, there was no significant residual effect of fertilizer N on the subsequent rice crop. These results indicated that combined use of organic residues with urea did not decrease total N losses or increase crop yield, uptake of N compared to urea alone.