Rural Development Policies and Sustainable Land Use in the ...

ECONOMETRIC RESULTS 69
Table 5.6—Continued
Inorganic fertilizer Herbicides Insecticides
Standard Standard Standard
Explanatory variable Coefficient error Coefficient error Coefficient error
Prior investments
Stone wall 0.27007 0.23714 0.00710 0.25687 –0.23022 0.26912
Live barrier or fence 0.21597 0.26706 0.03059 0.24456 –0.06302 0.22287
Trees planted –0.69943** 0.35332 –0.21190 0.37590 –0.19980 0.29206
Land use—perennials –1.20583*** 0.20985 –1.56304*** 0.20343 –0.07245 0.31670
Season (cf. 2000 1st season)
2001 primary season (primera) –0.14172 0.11307 0.05500 0.10067 0.14097 0.10686
2000 secondary season (postrera) –1.11640*** 0.27255 0.14039 0.13267 0.48980** 0.19836
2000 tertiary season (apante) –0.38285 0.37800 –0.40316 0.35660 0.33461 0.35060
Intercept 0.25613 0.70615 –0.38856 0.81986 –1.66106** 0.82324
Number of observations 1,728 1,728 1,728
Proportion of positive observations 0.4161 0.4166 0.1028
Mean predicted probability 0.4174 0.4183 0.1029
Hausman test of exogeneity of livelihood p = 1.0000 NE NE
strategies and participation in programs/
organizations (OLS vs. IV linear version
of models)
Hansen’s J test of overidentifying restrictions p = 0.6042 p = 0.1296 p = 0.1014
in IV linear model
Note: NE means the Hausman test could not be computed due to a negative value of the test statistic. *, **, *** mean statistically significant at
10%, 5%, and 1% level, respectively.
a
Coefficients and standard errors adjusted for sampling weights and stratification, and are robust to heteroskedasticity and non-independence
of observations from different plots from the same household (clustering).
Fertilizer
Coffee producing households are less likely
to use fertilizer than those whose livelihood
is focused on basic grains production. Consistent
with this, fertilizer use is also less
likely on perennial than annual plots, and
on plots where trees are planted. On the one
hand, these results are surprising, since we
find also that perennial crop production responds
very well to fertilizer use (results
reported later in this chapter). On the other
hand, coffee prices were at an all-time low
during the survey period and many coffee
farmers had cut back on input use.
Fertilizer is more likely to be used at
higher elevation and less likely to be used in
areas with higher summer rainfall and areas
with greater moisture deficit. The negative
effect of moisture deficit on fertilizer use is
as expected, since moisture constraints can
limit the uptake of plant nutrients. Consistent
with this, we also find that fertilizer use
is less likely during the drier second season
than in the summer season. During the summer
season, rainfall is generally adequate
throughout the study area, so the negative
effect of rainfall on fertilizer use during this
season is probably related to problems of
runoff and leaching in areas of excessive
summer rainfall.
Fertilizer use is less likely in households
that own more livestock. This may be because
manure provided by livestock serves
as a substitute or because households with
a clear-cut interpretation of the results which are therefore not reported here (but available from the authors on
request). Similar to the regressions for mulching and manure, the “other inputs” regression results are still used
to determine predicted values of the probability of use of “other inputs,” which are used as instrumental variables
in the IV estimation of equation (1) in Chapter 3 (and discussed later).