19, 4 Reinking and Groff: Siamese Seedless Pummelo All 
growing along the borders of the dikes, casting their shade 
across the beds nearest to them. Tall betel palms, scattered 
throughout the planting, towered high above the citrus and 
banana and provided a condition of semishade which seemed 
highly advantageous (Plate 8, fig. 3). In still another grove 
twenty- to thirty-year-old pummelo trees, which apparently had 
outgrown their usefulness, were severely trimmed back and 
were being intercropped or replaced with young betel palms. 
Another form of intercropping which is commonly followed 
is to grow rice in the ditches, a row or two down either side 
of the citrus beds. The rice is set out at the beginning of the 
rainy season and not only utilizes what would be otherwise 
wasted space, but helps to keep intact the sides of the beds. 
How this practice might well be followed can be noted by observ- 
ing Plate 9, fig. 1. Doubtless these growers are unconsciously 
working out methods that should be of future value in indicating 
the lines along which scientific citrus culture should be conducted 
in the Tropics. 
CULTIVATION 
Clean culture is practiced on the orchard beds of Nakorn 
Chaisri. Little difficulty is experienced with weeds, for when 
the orchards are once clean there is practically no source of 
contamination. Rarely is any effort made to maintain an earth 
mulch, but the mulch which has been cleaned out from the 
trenches and smeared over the surface of the beds is allowed 
to crack during the dry weather. The constant supply of water 
in the trenches makes unnecessary any effort to prevent evap- 
oration. During the dry season there are always at least 30 
centimeters of water in these trenches, whereas during the wet 
weather the water will often rise to within 30 centimeters of 
the surface of the beds. During seasons of exceptional floods 
the water has been known to flow over the dikes and to cover 
the beds to a depth of 60 centimeters. All growers recognize 
the ill effects of these floods, especially when the roots are sub- 
merged for too long a period. During recent years the citrus 
industry has suffered very severely from floods. This system 
guarantees the proper amount of moisture for the roots of the 
trees and shows how remarkably well the waters are controlled. 
About the only implements of culture are the specially constructed 
Chinese spade, used for removing earth from the ditches; and 
a two-pronged hoe, which is sometimes used for weeding 
the beds. 
