Changes in available nitrogen levels of experimental rice pots irrigated with wastewater effluents

Date

3-1987

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Nieva T. Librojo

Abstract

In a pot experiment using wastewater effluents from Republic Flour Mills (RFM) and UPLB, the available nitrogen levels of the so'-were correlated with nitrogen utilization by rice (var. 1158). The soil pH, organic matter content, total Kjeldahl nitrogen (TKN), and exchangeable nitrogen were determined. Collection of soil samples were done at five stages, namely: initial, first day after transplanting the rice seedlings, title ring, panicle initiation, and harvest. Soil pH was observed to gradually increase with time, specifically up to the panicle initiation stage. The general decrease is soil pH after the panicle initiation through harvest was accounted to increased nitrate-N uptake by rice plants. The organic matter content of the soils were lower at harvest than at initial sampling due to mineralization during the course of cropping. The total nitrogen content at harvest was generally higher than that of the initial. TKN because of incorporation of plants and plant residues with the soil samples. The available nitrogen levels considerably, increased from the initial to the first day after transplanting the rice seedlings. Subsequent samplings revealed decreasing Ni-14-N levels which was attributed to increased plant uptake with increased pH, ammonia volatilization, and nitrification. Nitrate-N levels also decreased because of plant uptake and denitrification. The high NU -N levels in the lower layers of the soil profile and decreased p11 of surface soil during harvest indicated some leaching action. The grain yields of fertilized rice, which were higher than in unfertilized rice, were similar for the three irrigated soils. However, the grain yields of unfertilized rice fell below reported yields of 2 to 4 tons per hectare. General findings show that efficiency of N uptake of native NH -N and NO,-N and that of N fertilizer by rice plants was relatively po3r. The RFA and UPLB wastewater effluents can be recycled through crop irrigation.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 1987 C4 M46

Document Type

Thesis

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