Under Calauan, Laguna, Philippine conditions, tubang bakod (the local name of Jatropha curcas L.) bears harvestable fruit from April to July. Hence the harvesting for jatropha fruit is priming (harvesting the fruit as they mature). Matured fruits are yellowish and turn blackish as they dry. As presented in Table 1, four samples represented the conditions when fruits were harvested. Samples 1 and 4 were harvested at the same time and on a sunny day, hence the fruits were relatively dry. Samples 2 and 3 were harvested on a rainy week, therefore they are relatively wet. These are the weather conditions during the harvesting period of jatropha fruits.
Black- and yellow-colored fruits differ in moisture condition, with the yellow-colored having higher moisture, thus, they are heavier than the blackcolored fruits. Yellow fresh fruits at 12.34 g per fruit are 3 times heavier than black fruits at 4.52 g per fruit. Extracted seeds from yellow fresh fruits at 1.27 g per seed are also heavier than seed extracted from black fruits which weigh 0.844 g per seed. Moisture content, as indicated by the color of the fruit, is important as it determines the percent seed recovery (%SR).
If the exocarp (the technical term for the fruit cover) has more moisture as in the yellow fruit, the %SR would be lower. Yellow-colored fruits have only 10.35% SR while black-colored fruits have 20.97% SR. Fruit color or its moisture content is also related to the number of seeds per unit weight. Using 1 kg as reference weight, the number of seeds per one kg seed lot was estimated:
1.0 kg of yellow-colored fruits = 797 seeds
1.0 kg of black-colored fruits = 1,227 seeds
The seed number as influenced by moisture content status is important as it determines the equivalent quantity of fruits to obtain 1.0 kg seeds. Based on estimates, the following data were obtained:
1.0 kg seed = 9.71 kg fresh yellow fruits
1.0 kg seed = 5.11 kg fresh black fruits
1.0 kg seed = 7.41 kg of fresh fruit (average of yellow and black fruits)
These fruit yield characteristics are important data for the following reasons: (a) Field conditions at harvesting time is related to the moisture condition of the fruit and seed. The fruit moisture in turn determines the number of seeds per kilogram, the % seed extraction and the weight (in kg) of fresh fruits that yields a kilogram of seed; (b) The fruit yield data, especially the conversion from kg fruit to kg seed is important in buying jatropha fruit at the farm level; (c) Data/ technical coefficients are needed in establishing jatropha farms for production and constructing mills for processing seeds into various products (crop and mill planning).