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Yield Constraints of Mango Orchards in Thailand 
C.A.J.M. de Bie and D. Rugege 
deBie@ITC.NL 
Agriculture, Conservation and Environment Division 
ITC, Enschede, The Netherlands 
Keywords: sustainable land use, yield gap analysis, yield constraints, mango, 
Thailand, land evaluation, land use planning. 
Abstract 
Farmers in Phrao, North Thailand, planted a large number of mango orchards on a 
“trial and error” basis and with varying success. In 1993, a Comparative 
Performance Evaluation (CPE) of 45 mango orchards was made to identify land 
and management aspects that condition the level of productivity. 
The orchards are situated on podzolic soils on hills, footslopes, and terraces that 
dry out deeply during the dry season. They contain a mix of mango, lychee and 
longan trees. Yields are expressed in farm-gate prices since middlemen purchase 
the produce from farmers 'on the tree'. With many orchards having 'low' yields and 
18 having ‘zero’ yield, the yield data have a loglinear distribution. A model to 
estimate ‘when yields can be expected’ was developed by logistic regression, as 
was a linear multiple regression model for logarithmic transformed yields of the 
‘non-zero’ group. A model to estimate Ln(Yield+1), using data from all sites, 
estimates individual contributions to the total yield gap by specific yield 
constraints. The model suggests that yields increase if: 
e It is not an ‘off year (caused by biennial bearing behavior of mango; use of 
growth regulators may remedy this). 
e The orchard is situated on a hill or on soils with a relatively high pH or poor 
water holding capacity (mostly shallow soils with SCL as topsoil; water stress 
causes crop dormancy and induces flower initiation). 
e The possibility exists to apply supplemental irrigation. Orchards having a 
growth flush or in a fruit bearing stage require adequate water management 
including supplemental irrigation. 
e In established orchards weeding by tractor leads to root pruning that affects the 
tree’s physiological cycle. 
e Pruning is practiced (this is normally also done to remove branches damaged 
by stem boring caterpillars; all orchards suffered from this serious problem). 
e Spraying by motor sprayer dispenses pesticides (preferably Azodrin) deep into 
the canopy. 
The model suggests that environmental factors (location and pH) account for 
some 30% of the yield gap, management factors for 49% and the year effect 
(species attribute) for 21%. Management of mango orchards must always use up- 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 
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