HANOI UNIVERSITY OF AGRICULTURE
FACULTY OF AGRONOMY
UNDERGRADUATE THESIS PROPOSAl
TITLE: “Comparison of the paddy rice yield models
responding nitrogen in Vietnam”
Student: Pham Van Chuyen
Class: KHCT52T
Year: 2011
Major: Crop science
Supervisor: Dr. Vu Duy Binh
Department: Faculty of Information Technology
Hanoi - 2011
CHAPTER 1 - GENERAL INTRODUCTION
1.1 Introduction
Paddy rice is the most important crop of 5 main cereals in Vietnam. Not only
ensuring food security in Vietnam, rice production is as source of foreign currency
earnings of country. In 2009, rice production was grown in 7.4 million hectare area
and obtained 38.9 grain million tones. Exporting rice quantity was about 5.6
million tones, responsed 2.8 billion USD. While rice area hasn’t increased and
trends to decrease, increasing the rice productivity is essentially to ensure the food
security and exporting. To do it, rice production technology need to be provided as:
selecting the high yield varieties, irrigation management, fertilizers, pest
management, tillage In there, mostly the applied fertilizer quantities are derived
from field studies in which crop yield and quality responses to a range of fertilizer
rates are measured. Responses are often modeled to determine optimum fertilizer
rate. The lacks of these studies are economic efficiency and environment pollution
of over-fertilization. So, the fertilizer response yield mathematic models applied to
improve these lacks.
Some study shows nitrogen is the most important fertilizer factor that determines
the rice yield and is very interested in rice simulation models. Proportion between
applied nitrogen and yield are positive and depends on rice varieties, time, by soil

Nitrogen is the most important nutrient for rice and affect the yield an quality of
seed (Yoshida S, 1981). Rice cans uptake nitrogen from soil, applied fertilizer,
organic debris. When increasing the nitrogen fertilizer, yield can significantly.
Fertilizer introduction trends to optimize the rice yield. This usually causes the
environment pollution due to over-fertilizer and currently reduces the economic
profit. Application of mathematic model can solve the above problem. Linear (L),
quadratic (Q), and linear with plateau (LP), quadratic with plateau (QP) functions
are introduced to simulate the rice yield response fertilizer (Blackmer, 1990).
Linear model is proposed early. It is simply, easy to use. it describe the linearly
proportion between applied nitrogen and yield. In fact, with high nitrogen,
response yield doesn’t increase. The model is not significance at high nitrogen
To improve the limitation of the linear model, some study use combination of
linear and plateau equations to fit data.
Logistic model expressed the goodness of fit to foliage, vegetable crop response
nitrogen (Overman, A.R. and Scholtz, R.V. III, 2002). For cereal as maize, wheat,
barley, the application of logistic model in yield simulation responding nitrogen
also showed the good fit.
CHAPTER 3 - MATERIALS AND METHODS
3.1. Experimental site and duration
3.1.1 Experimental site
Experiment is conduct in the field at Faculty of Agronomy, Hanoi university of
Agriculture, Hanoi
3.1.2 Duration
Summer-autumn season in 2004
3.2 Methods
3.2.1 Materials
Materials consist of 3 rice varieties including 2 hybrids Vietlai 20, Bac Uu 903, 1
inbreeding CRD
There are 4 applied nitrogen fertilizer rates: 0, 60, 120, 180 kg N/ha. With each
dose of nitrogen were accompanied by an common dose 90 kg P

3.2.2.3 Linear with plateau (LP) model
(LP) model is described following
Y = a + bX if X < C [3]
Y = P if X ≥ C [4]
Where Y = grain yield (tons/ha), X = fertilizer application rate (kg/ha), a =
intercept parameter, b = applied N coefficient for rice yield (tons/kg), C =critical
fertilizer rate (kg/ha), which occurs at the intersection of the linear response and
the plateau lines), and P (plateau yield) is the constant obtained by fitting data to
the model function.
3.2.2.3 Quadratic with plateau (QP) model
The QP model is defined by following equations:
Y = a + bX + cX2 if X < C [5]
Y = P if X ≥ C [6]
Where Y is grain yield (tons/ha), X is fertilizer application rate (kg/ha), and a
(intercept), b (linear coefficient), and c (quadratic coefficient), C (critical fertilizer
rate, which occurs at the intersection of the quadratic response and the plateau
lines), and P (plateau yield) is the constant obtained by fitting data to the model
function
3.2.2.4 Logistic (LO) model
Logistic model was defined by following equation
[7]
Where Y=grain yield, N= applied nitrogen rate (kg/ha), A= maximum grain yield
at high nitrogen, b= intercept parameter, c= nitrogen response coefficient.
3.2.3 Analysis of variances (ANOVA)
For (1), (4), (6) equations, the plateau yield are defined as maximum yield at high
nitrogen and are estimate by virtual inspection.
The analysis of variance of the linear and quadratic equation are performed though
linear and quadratic regression respectively by SPSS v.16 of IPM Corporation
For the logistic model, the [7] equation is linearized to the form:
[8]

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