Onion is a temperate crop but can be grown under a wide range of climatic conditions such as temperate, tropical and subtropical climate. The best performance can be obtained in a mild weather without the extremes of cold and heat and excessive rainfall. However, onion plant is hardy and in the young stage can withstand freezing temperature also. In India, short-day onion is grown in the plains and requires 10-12 hours day length. The long-day onion is grown in hills requiring 13-14 hours day length. For vegetative growth, lower temperature combined with short photoperiod is required whereas relatively higher temperature along with longer photoperiod is required for bulb development and maturity. The optimum temperature for vegetative phase and bulb development is 13-24˚C and 16-25˚C, respectively. It requires about 70% relative humidity for good growth. It can grow well in places where the average annual rainfall is 650-750 mm with good distribution during the monsoon period. Areas with low (< 650 mm) or heavy rainfall (>750 mm) are not particularly suitable for rain-fed crop.
Onion can be grown in all types of soils such as sandy loam, clay loam, silt loam and heavy soils. However, the best soil for successful onion cultivation is deep, friable loam and alluvial soils with good drainage, moisture holding capacity and sufficient organic matter. In heavy soils, the bulbs produced may be deformed. Onion crop can be grown successfully on heavy soil with application of organic manure prior to planting and preparation of the field for onion cultivation should be very good. The optimum pH range, regardless of soil type, is 6.0 – 7.5, but onion can also be grown in mild alkaline soils. Onion crop is more sensitive to highly acidic, alkali and saline soils and water logging condition. Onions do not thrive in soils having pH below 6.0 because of trace element deficiencies, or occasionally, Al or MN toxicity. The threshold electrical conductivity of a saturation extract (ECe) for onion crop is 4.0 dS/m. When the ECe level exceeds this, crop yield starts declining.
Sowing, transplanting and harvesting timings of onion in different regions of India
|Season||Time of seed sowing||Time of transplanting||Time of harvesting|
|Maharashtra and some parts of Gujarat|
|1. Early Kharif2. Kharif3. Late Kharif4. Rabi||Feb.-Mar.May-JuneAug.-Sept.Oct.-Nov.||April-MayJuly-Aug.Oct.-Nov.Dec.-Jan||Aug.-Sept.Oct.-Dec.Jan.-Mar.Apr.-May|
|Tamil Nadu, Karnataka and Andhra Pradesh|
|1. Early Kharif2. Kharif3. Rabi||Feb.-AprilMay-JuneSept.-Oct.||April-JuneJuly-AugNov.-Dec.||July-Sept.Oct.-Nov.Mar.-Apr.|
|Rajasthan, Haryana, Punjab, UP and Bihar|
|1. Kharif2. Rabi||June-JulyOct.-Nov.||July-Aug.Dec.-Jan.||Oct.-Nov.May-June|
|West Bengal and Orissa|
|1. Kharif2. Late Kharif3. Rabi||June-JulyAug.-Sept.Sept.-Oct.||Aug.-Sept.Oct.-Nov.Nov.-Dec.||Nov.-Dec.Feb.-Mar.Mar.-Apr.|
|1. Rabi2. Summer (Long day type)||Sept.-Oct.Nov.-Dec.||Oct.-Nov.Feb.-Mar.||June-JulyAug.-Oct.|
Proper nursery management and transplanting are important operations in the onion crop. About 0.05 hectare nursery bed area is enough for getting seedlings to transplant in one hectare. The field should be ploughed 5-6 times to break clods and well pulverized to hold water. The debris of previous crops, weeds and stones should be removed before bed preparation. Apply half ton of well decomposed farmyard manure (FYM) at the time of last ploughing in 0.05 ha and mix well with soil. For raising nursery, raised bed of 10-15 cm height, 1.0 – 1.2 m width and length as per convenience may be prepared. The distance between beds should be at least 30 cm, so that water movements are uniform and drainage of excess water is possible. Raised bed is recommended for nursery because in the case of flat bed, water moves from one end to the other and there is a possibility of washing away of seeds. Drainage of excess water is also a major problem with the flat bed method of raising seedlings. Application of pre-emergence herbicide pendimethalin @ 0.2% is recommended to control weeds in nursery. About 5-7 kg seeds are required to raise seedlings for one hectare. Before sowing, seeds should be treated with thiram @ 2 g/kg of seed to avoid damage from damping off disease. Application of Trichoderma viride @ 1,250 g / ha is also recommended to manage damping off and raise healthy seedlings. Seeds should be sown in lines at 50 mm to 75 mm apart to facilitate the removal of seedlings for transplanting, quick weeding, spray of pesticides etc.
After sowing, the seeds should be covered with fine powdered farmyard manure or compost followed by light watering. Application of water through drip or micro sprinkler irrigation system helps in saving irrigation water (Fig. 2). Foliar spray of benomyl @ 0.2% is recommended to control soil borne diseases in the nursery. When the severity of thrips infestation is high, foliar application of Fipronil or profenopos @ 0.1% is recommended. Seedlings are available for transplanting in 35-40 days after sowing (DAS) for Kharif and 45-50 DAS for late Kharif and Rabi seasons.
Land preparation for main field
Prior to transplanting, field should be ploughed and disked properly to eliminate debris and soil clods. Organic manures equivalent to 75 kg N/ha (approximately FYM 15 t/ha or poultry manure 7.5 t/ha or vermicomposting 7.5 t/ha) should be incorporated at the time of last ploughing and beds with appropriate size should be prepared after leveling. Mostly, flat beds of the size 1.5-2.0 m width and 4-6 m length is formed. However, flat bed should be avoided to prevent water logging during Kharif or rainy season. Water logging favours Anthracnose disease which is most devastating during Kharif season. Broad bed furrows (BBF) of 15 cm height and 120 cm top width with 45 cm furrow are formed to achieve proper spacing and population density. It is suitable for drip and sprinkler irrigation as well. BBF is the best method for Kharif onion production because the excess water can be drained out through the furrow. This improves the aeration and helps in reducing the incidence of Anthracnose disease.
Proper care should be taken while selecting seedlings for transplanting. Over and under aged seedlings should be avoided for better establishment. At the time of transplanting, one third of the seedling top should be cut to get good establishment. The onion seedling should be transplanted after dipping roots in carbendazim solution (0.1%) for two hours to reduce the incidence of fungal diseases during the establishment. The optimum spacing is 15 cm between the rows and 10 cm between plants.
Fertilizers and manures
Nutrient removal by onion crop mainly depends upon bulb yield, variety, quantity of fertilizers applied, soil condition and season. The results of the experiment carried out at DOGR, Rajgurunagar showed that onion crop removes about 90-95 kg of N, 30-35 kg of P2O5, and 50-55 kg of K2O to produce 40 t onion bulbs/ha. Therefore, it is necessary to apply plant nutrients in a balanced manner externally through different sources for sustainable onion production and soil health. Based on the results of field experiments conducted at DOGR, recommended doses of organic manures and fertilizers have been standardized and presented in Table 3. Fertilizer requirement of long day onion (grown in the hills) is higher than the short day onion crop due to its longer crop duration and yield potential.
Fertilizer schedule for onion (per ha)
|Kharif onion (Yield potential – 25-30 t/ha)|
|Basal||25 kg||40 kg||40 kg||Organic manures equivalent to 75 kg N(FYM – Approx. 15 t/ha orPoultry manure- Approx. 7.5 t/ha orVermicompost – Approx. 7.5 t/ha)|
|30 DAT||25 kg||–||–||–|
|45 DAT||25 kg||–||–||–|
|Total||75 kg||40 kg||40 kg||–|
|Late Kharif and Rabi onion (Yield potential- 40-50 t/ha)|
|Basal||40 kg||40 kg||60 kg||Organic manures equivalent to 75 kg N(FYM – Approx. 15 t/ha orPoultry manure- Approx. 7.5 t/ha orVermicompost – Approx. 7.5 t/ha)|
|30 DAT||35 kg||–||–|
|45 DAT||35 kg||–||–|
|Total||110 kg||40 kg||60 kg|
|Long day onion (Yield potential-100 t/ha)|
|Basal||60 kg||60 kg||70 kg||Organic manures equivalent to 75 kg N(FYM – Approx. 15 t/ha orPoultry manure- Approx. 7.5 t/ha orVermicompost – Approx. 7.5 t/ha)|
|30 DAT||60 kg||–||–|
|60 DAT||60 kg||–||–|
|Total||180 kg||60 kg||70 kg|
One third of recommended N and full dose of P2O5 and K2O are applied at the time of planting while remaining two third N is applied in two equal splits at 30 and 45 days after planting.
In addition to NPK, sulphur is also an essential plant nutrient important for onion crop for improving yield and the pungency of onion bulbs.
• Sulphur is recommended as basal dose at the time of transplanting.
• Application of 15 kg sulphur/ha is sufficient for growing onion crops in soils having sulphur level above 25 kg/ha while 30 kg sulphur/ha is needed for soils having sulphur level below 25 kg/ha for optimum production of onion.
• Soil application of 50 kg S /ha is recommended for long day onion crops.
If the soil test shows a deficiency of any micronutrients, besides NPKS, the deficient micronutrient should also be applied to correct the deficiency. If the plant is diagnosed with micronutrient deficiency during growth stages, the deficiency should be corrected by either foliar or soil application of concerned nutrients, immediately.
• ZnSO @ 10 kg/ha as basal is recommended in areas having Zn deficiency.
• Borax @ 10 kg/ha is recommended for areas having boron deficiency.
• FYM @ 15 t/ha is recommended in areas having multi-micronutrient deficiency along with foliar application of micronutrient mixture (Fe: 2.5%, Zn: 0.3%, Mn: 1%, Cu: 1.0%, B: 0.2%) at 45 and 60 days after transplanting for increasing onion productivity.
• Application of micronutrient increased bulb yield by 7-15% compared to control.
Foliar application of nutrient in onion
- If the crop growth is poor, foliar application of water soluble NPK fertilizers (20:20:20 or 19:19:19) in onion @ 5g/liter at 30, 45 and 60 days after transplanting is recommended for improved yield.
Biofertilizer is a substance which contains living microorganisms. The biofertilizers can be used either for seed treatment or soil application. When applied to seed or soil, the microbe colonizes the rhizosphere or the interior of the plant and promotes growth by increasing availability of primary nutrients to the host plant by biological nitrogen fixation, phosphorus solubilization and stimulating plant growth through the synthesis of growth-promoting substances. Based on the experiments carried out at DOGR, biofertilizers @ 5 kg/ha each Azospirillum and phosphorus solubilizing bacteria are recommended for onion crop. The addition of Azospirillum improves soil nitrogen through biological nitrogen fixation while application of phosphobacteria solubilizes unavailable phosphorus present in soil and makes them available to plants and improves the efficiency of applied P fertilizer.
Weed management Frequent irrigation and fertilizer application to onion crop favour severe crop-weed competition. Weeds compete with the onion crop for water, soil nutrients, light and space. Onion crop exhibits a greater susceptibility to weed competition than most other crops, mainly due to its slow growth at initial growth stages and inherent characteristics such as short stature, non-branching, sparse foliage and shallow root system. Control of weeds at the initial growth stages is essential for getting high marketable bulb yield. Because of labour scarcity, chemical control of weeds along with cultural methods is inevitable. Application of Oxyflurofen @ 23.5% EC (1.5 -2.0 ml/L)/ Pendimethalin @ 30% EC (3.5-4ml/L) before transplanting or at the time of transplanting followed by one hand weeding at 40-60 days after transplanting is recommended for efficient weed control.
Garlic being a very shallow-rooted bulb crop needs frequent irrigation. It is very sensitive to moisture stress particularly during bulb initiation and bulb development. Garlic crop should be irrigated immediately after planting and subsequently at 7-10 days interval depending upon the soil moisture. In general, kharif crop needs 5-8 irrigations and rabi crop 12-13 irrigations. Irrigation needs to be stopped when the crop attains maturity (10-15 days before harvest). Excess irrigation is always harmful and dry spell followed by irrigation will result in the splitting of the outer scales in garlic. Avoid waterlogged conditions at all stages as these lead to development of diseases like basal rot and purple blotch. Similarly, continuous irrigation towards maturity leads to secondary rooting which, in turn, produces new sprouts and such bulbs cannot be stored for long. With flood irrigation water loss is too high due to conveyance, seepage and percolation losses.
Modern micro-irrigation techniques such as drip and sprinkler irrigation help in saving irrigation water and improve the marketable bulb yield significantly. In case of drip irrigation, seed cloves need to be planted at a spacing of 15 x 10 cm in a broad bed furrow (BBF) of 15 cm height and 120 cm top width with 45 cm furrow. Each BBF should have two drip laterals (16 mm size) at 60 cm distance with inbuilt emitters. The distance between two inbuilt emitters should be around 30-50 cm and the discharge flow rate of 4 l/hr. The drip irrigation system helps in water, labour and fertilizer saving, and improves bulb yield by 15-25% over flood irrigation system.
In case of sprinklers, the distance between two laterals (20 mm size) should be 6 m with a discharge rate of 135 l/hr.
Fertigation is an effective and efficient method of applying fertilizers through drip irrigation which is used as the carrier and distributor of irrigation water and crop nutrients. Application of 30 kg nitrogen as basal dose at the time of planting and the remaining in seven equal splits at weekly days interval from planting to 60 DAP through drip irrigation is recommended. Application of nitrogenous fertilizers through drip irrigation system reduces nitrogen losses by leaching into ground water, as in fertigation, fertilizer nutrients are applied in root zone as per the crop requirement thereby improving efficiency of applied fertilizer.
Cropping system Garlic is a shallow-rooted crop suitable for various cropping patterns including intercropping and sequential cropping, depending upon location, nature of soil and climatic conditions. Garlic may not efficiently utilize all the mineral nutrients applied to soil. The unused mineral nutrients may be leached down along with irrigation or rain water. These unused mineral nutrients present in subsoil can effectively be used by growing deep rooted crops in succeeding season. Based on the findings of field experiments, legume followed by garlic sequence is recommended for higher yield, better utilization of nutrients and for improving soil health. Legume based cropping sequences like groundnut in summer season followed by garlic in rabi season improves the soil fertility status and provides better monetary returns to the farmers.
Intercropping is the practice of growing two or more crops in proximity. The most common goal of intercropping is to produce a greater yield on a given piece of land by making effective use of resources without affecting the yield of the main crop. Onion crop is best suited for intercrop with paired row planting of sugar cane (Nov.-Dec. Planting) under drip irrigation system. Ridges and furrows of 90 cm distance need to be prepared for planting sugar cane. Sugarcane sets with the single bud need to be planted at 30 cm apart in the bottom of the ridges. After every two rows of sugar cane, flat bed of 180 cm need to be prepared for planting onion crops. Onion seedlings should be planted at time of sugarcane planting. Additional fertilizer nutrients required for onion crop need to be calculated and applied as per requirement. Onion crop can be harvested after 120 DAT(Days after transplanting). Sugarcane-onion intercropping system with drip irrigation saves 25-30% water.
Garlic is mainly a rabi crop harvested during March and is required throughout the year for consumption. Hence, garlic bulbs should be stored properly to meet the supply year round. Well cured (dried neck and outer skins), clean bulbs firm to the touch can be stored for 5-6 months at ambient temperature in ventilated storage structures, but with low relative humidity (< 70%). Bulbs should be graded before storage and 20-25 plants tied in bundles along with tops. The tops should be divided in three segments and interwoven tightly. Such bundles are kept in upright position in shade for curing for 15 days and hang them in dry and well-ventilated area or use forced air to dry bulbs. If the large quantity of bulbs needs to be stored, these should be arranged in 4 feet diameter circle and to a height of 3 feet. The heap diameter should be reduced gradually from 4 feet bottom to 3 feet at top while arranging the bulbs. There should be a gap between two heaps for good ventilation.
High humidity in the stores favours mould growth and rooting. Mould growth can also be a problem if the bulbs have not been well cured before storing. During storage, bulbs will eventually become soft, spongy and shrivelled due to water loss. Excessive exposure of bulbs to direct sunlight should be avoided as it causes sloughing due to excessive shrinkage.
For long-term storage, garlic can be best stored in cold store at temperatures -1°C to 0°C with low relative humidity (60-70%). Application of excess nitrogen and irrigation 15-20 days before harvesting favours sprouting of bulbs in the field. Early planting of garlic also causes sprouting. This can be prevented by optimum supply of nitrogen and stopping irrigation about 15-20 days before planting. Irradiation with 2-6 krad of cobalt 60 gamma rays has been recommended for controlling sprouting in storage. The irradiation given to bulbs within 8 weeks of harvesting (before sprout initiation) can inhibit sprouting effectively, reduce weight loss and prolong storage life for about one year. Doses higher than 10 Kr reduce diallyl disulfide content which gives typical garlic flavour.
For seed garlic, pre-harvest spraying with 0.1% carbendazim and disinfection of stores before storage reduce post-harvest losses particularly decay loss.