Effects of water regimes, silicate rock powder, and nitrogen rates on yield, water productivity, and GHG emissions of lowland rice (Oryza sativa L.) in the Philippines.

Date

12-2025

Abstract

This study evaluated the effects of water regimes, silicate rock powder (SRP), and nitrogen N) rates on crop performance, water productivity, GHG emissions, and soil inorganic carbon (SIC) in irrigated lowland rice. AWD, although constrained by frequent rainfall, sustained grain yields comparable to CF (AWD = 6 t ha-1 compared with CF = 5.70 t ha-1) while improving water productivity and reducing CHa emissions by 20-41% across treatments. Consequently, AWD consistently produced lower total GWP than CF. SRP application (5 t ha-1) enhanced grain weight and consistently increased SIC across growth stages, indicating active carbonate formation through SRP mineral release. SRP also contributed to early-stage CH suppression (11%). Nitrogen exerted the strongest influence on plant height, and gran yield components (GYC), with increasing N improving both parameters. While N2O emissions increase slightly with higher N inputs, they contributed only 1-2% of total GWP, highlighting the dominance of CH4 emissions in net GWP. Total GWP ranged from 6.56 to 11.31 t CO2-eq ha-1, with CF producing higher GWP than AWD. Overall, the combined implementation of AWD, SRP amendment, and optimized nitrogen management improved grain yield, enhanced SIC accumulation, and decreased GHG emissions, demonstrating their potential as complementary climate-smart strategies for sustainable rice production.

Document Type

Master Thesis

Degree

Master of Science in in Agricultural Engineering

College

Graduate School (GS)

Adviser/Committee Chair

Rubenito M. Lampayan

Committee Member

Rosa B. De Los Reyes, Ronaldo B. Saludes

Language

English

En – AGROVOC descriptors

ORYZA SATIVA; IRRIGATED RICE; GRAIN CROPS; LOWLAND; SILICATE MINERALS; NITROGEN CONTENT; WATER PRODUCTIVITY; GREENHOUSE GAS EMISSIONS

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