A farmer weeds her garden. PHOTO | COURTESY
Green gram is a leguminous crop that is widely cultivated in Uganda and several Asian countries.
Green gram is a source of protein, fibre, iron, and vitamin C and has many health benefits.
Green gram can be consumed as whole grains, split pulses, sprouts, or flour. Green gram is also used as a green manure crop, as it can fix atmospheric nitrogen and improve soil fertility. Green gram is a short-duration crop that can fit well in many cropping systems.
Soil requirements
Green gram can grow in a wide range of climatic conditions, but it prefers warm and humid weather with a temperature range of 25°C to 35°C.
It can tolerate moderate rainfall of 85 to 100 cm, well distributed throughout its growing period of 100 days. However, waterlogging and cloudy weather are harmful to the crop.
Green gram can be grown on a different types of soils, from sandy loam to black cotton soils, having good drainage capacity.
Saline, alkaline soils are not suitable for green gram cultivation. Green gram is very sensitive to waterlogging conditions. The optimum soil pH for green gram cultivation is 6 to 7.
Land preparation
The land should be prepared well for sowing by one or two plows followed by two or three crosses, harrowing, and planking. The field should be well-leveled and free from weeds and stubbles. The seed rate for summer green gram cultivation is about 15-20 kg per hectare. The seed selection should be done carefully by choosing healthy, uniform, and disease-free seeds.
The sowing should be done by broadcasting or drilling method at a depth of 3 to 4 cm and a spacing of 30-45 cm between rows and 10-15 cm between plants.
Irrigation management
Irrigation is the application of water to the soil for crop growth and development. The frequency, rate, amount, and time of irrigation are different for different crops, types of soil, and seasons.
The irrigation requirement of green gram depends on the soil type, climate, crop stage, and rainfall. Generally, green gram needs 4-5 irrigations during its growth period. The first irrigation should be done when about 20-25 percent of plants have germinated or about 20 days after sowing. The second irrigation should be done at the time of flowering, which is about 35-40 days after sowing. The third irrigation should be done at the pod formation stage, which is about 50-55 days after sowing. The fourth irrigation should be done at the pod-filling stage, which is about 65-70 days after sowing. The fifth irrigation may be given if there is no rainfall during the pod maturation stage, which is about 80-85 days after sowing.
Pest and disease management
Green gram cultivation faces a myriad of challenges posed by various pests and diseases, each capable of significantly reducing yield and quality. Among the prominent adversaries is the gram pod borer, known for its polyphagous appetite attacking leaves, buds, flowers, and pods, causing considerable damage and a potential 50 percent yield loss when unchecked. Another formidable foe is the spotted pod borer, inflicting up to 30 percent yield loss by weaving its destructive web on buds, flowers, and pods. The spiny pod borer targets green gram pods, leaving longitudinal slits and compromising seed quality, with a potential yield loss of 20 percent in its wake. The blue butterfly and grass blue butterfly pose threats by causing leaf skeletonisation and flower drop, respectively, leading to yield losses of up to 15 percent.
Nematodes, including cyst nematode and root-knot nematode, invade green gram roots, forming galls or cysts and impeding nutrient and water uptake, potentially causing significant 50 percent yield losses if uncontrolled.
Fertilisation
Green gram is a legume crop that can fix atmospheric nitrogen in the soil using Rhizobium bacteria. It requires minimal nitrogen fertiliser but requires phosphorus, potassium, sulfur, and micronutrients for optimal growth and yield. Recommended fertilisation practices include applying 10 tonnes of well-decomposed farmyard manure or compost per hectare.
Weed control
Weeds, unwanted plants, can significantly reduce the yield and quality of green gram crops by up to 50 percent.
To ensure successful cultivation, use clean and certified seeds, prepare the land well by plowing, harrowing, and leveling, and sowing seeds at the recommended spacing and depth.
Apply pre-emergence herbicides such as pendimethalin or oxyfluorfen within three days of sowing to control annual grasses and broadleaf weeds.
Hand weed or hoe the crop at 20 and 40 days after sowing to remove escaped or perennial weeds.
Mulch the crop with straw, leaves, or plastic sheets to suppress weed growth and conserve soil moisture. Avoid intercropping or mixed cropping with green gram to avoid increased weed competition and interference with weed control operations.
Harvesting
Green gram crops are ready for harvest when 80 percent of the pods turn yellowish-brown and dry. Harvesting time depends on variety, sowing time, climatic conditions, and market demand. Seeds should be stored in a cool, dry, well-ventilated place from direct sunlight, moisture, and rodents.
The harvesting process involves cutting the plants manually or mechanically, threshing, and separating seeds from pods, chaff, and dust. Seeds should be dried to 8-10 percent moisture content, avoiding direct sunlight exposure.
Seeds should be cleaned by hand or using graders or separators. Fungicides like thiram or carbendazim can prevent fungal infections during storage.
