Staking and trellising
Bitter gourd grows very fast and vines elongate rapidly within two weeks after planting. Thereafter, the plant sends out lateral stems. Staking and trellising will increase fruit yield and size, reduce fruit rot, and make spraying and harvesting easier. Pandals are the most common trellising system used in Kerala. For this, pandals of 1.5 m height are erected using bamboo poles, wooden stakes, GI pipes or other sturdy materials when the plants start vining. Steel wires/strings, preferably coated with rust proof materials like plastic are used to connect the stakes, and to which coir or plastic ropes are tied in a crisscross manner so that horizontal coir/plastic ropes run across on the top forming a net. Vines are supported by bamboo stakes, which help vines freely climb and reach the top.
Other improved methods of trellising are also available. The trellis can be arranged either in a lean-to or tunnel structure. For the lean-to type, the stakes are joined between two adjoining beds forming an A shape structure. Horizontal stakes are installed at the top joining all other beds. The stakes support the climbing vines and lateral stems. Strings are used to secure adjoining stakes. The trellis should be 1.8-2.0 m high, constructed from stakes 1.2-1.8 m apart. For the tunnel type, plants are grown inside an arch shape structure made of either PVC or galvanized iron pipe. Plants are supported by bamboo stakes where vines freely climb and reach the top, which will then grow along the structure.
Pruning
Bitter gourd develops many side branches that are not productive. To improve yield, remove lateral branches until the runner reaches the top of the trellis. Leave 4-6 laterals and cut the tip of the main runner to induce early cropping. Removal of lateral branches in the first 10 nodes has a positive effect on total yield. Where consumers want their bitter gourd straight rather than curved, tie a pebble at the end of a long piece of string to the flower end to weigh down the fruit and keep it from curling.
Manuring
Balanced fertilization is essential for high yielding and good keeping quality of the fruits. Fertilizer dosage depends on soil type, fertility level, and soil organic matter. Apply FYM @ 20-25 t/ha as basal dose along with half dose of N (35 kg) and full dose of P2O5 (25 kg) and K2O (25 kg/ha). The remaining dose of N (35 kg) can be applied in two equal split. A fertilizer dose of 70:25:25 kg N:P2O5:K2O / ha in several splits is recommended in Onattukara region. The fertilizer dose per pit would be 28:10:10 g N:P2O5:K2O.
Irrigation
Bitter gourds do not tolerate drought. Maintain good soil moisture in the upper 50 cm of soil where the majority of roots are located. During the initial stages of growth, irrigate at 3-4 days interval, and alternate days during flowering/fruiting. Furrow irrigation is the ideal method of irrigating. But in high tech agriculture, water use efficiency can be improved by using trickle or drip irrigation. During rainy season, drainage is essential for plant survival and growth.Irrigation at 15 mm CPE (app at 3 days interval for sandy loam soils) are more economical than irrigating once in 2 days especially during summer months for water economy.
Hormone application
In bitter gourd, male and female flowers are borne separately on the same plant, and male flowers normally exceed the females by about 25:1. Spraying vines with flowering hormones after they have six to eight true leaves will increase the number of female flowers and can double the number of fruits. For example, one application of gibberellic acid at 25-100 ppm increases female flowers by 50 % and can work for up to 80 days. Application of ethrel (an ethylene releasing compound) has been found to increase femaleness in bitter gourd.
Pollination
Bitter gourd is a cross pollinated crop. Insects, especially bees, pollinate flowers. Pollination can be a problem during the wet season since bees are less active during overcast conditions. Introduction of beehives ensure good pollination and avoid the need for hand pollination.
Weed control
Conduct weeding and raking of the soil at the time of fertilizer application. Earthing up is done during rainy season. Hand or hoe weeding can be performed as needed. Mulching is commonly used for bitter gourd crops grown on raised beds. Use organic or plastic mulch depending on availability. Mulch can be laid down before or after transplanting and after sowing.