[Blueboard] Thesis Defense of Ms. Marjorie S. Muyrong

Department of Economics [LS] economics.soss at ateneo.edu
Sat May 7 10:37:51 PHT 2016

The Department of Economics

School of Social Sciences

Ateneo de Manila University

Cordially invites you

To a thesis defense

“Diminishing Marginal Returns to Artificial Fertilizer: Evidence from the

by Ms. Marjorie S. Muyrong

on May 12, 2016 (Thursday)

at 2:00 p.m.

Economics Department, Conference Room

Panel of examiners:

Cristina M. Bautista, Ph.D.

Noel P. de Guzman, Ph.D.

Philip Arnold P. Tuaño, Ph.D.


Victor S. Venida, Ph.D.


Productivity slowdown in agriculture arises from either diminishing
marginal returns or from the effects of negative externalities arising from
crop production. Thus, productivity slowdown observed since the 1980s may
be linked back to high-input cultivation brought by Green Revolution
(Byerlee 1992; Gollop and Swinand 1998; Aldy, et al. 1998). Empirical
analyses on the potential negative impacts of artificial fertilizer use are
scarce (Pingali, et al. 1990, Umetsu, et al. 2003; Padilla-Fernandez and
Nuthall 2009). The study therefore implements a regression analysis on the
hypothesis that higher levels of fertilizer application decrease yield
levels in the Philippine rice sector. Employing data on the top four
fertilizers used in the country, evidence supporting the hypothesis is
found for the use of Urea. At higher levels of application, every
additional bag of Urea significantly reduces rice yields by 2 to 3 percent.
The fertilizer Ammosul follows the same trend as Urea but the negative
impacts at higher application were not significant. Ammophos and Complete,
on the other hand, show a different pattern in which lower amounts applied
is related to lower yield levels and higher amounts applies is related to
higher yields. Further studies that integrate land degradation variables
from agricultural and environmental sciences into economic models of
production and productivity are warranted.
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