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.

Table 3. Fertilizer schedule for onion (per ha)

Schedule

N

P2O5

K2O

Organic manures

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 or

Poultry manure- Approx. 7.5 t/ha or

Vermicompost – 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 or

Poultry manure- Approx. 7.5 t/ha or

Vermicompost – 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 or

Poultry manure- Approx. 7.5 t/ha or

Vermicompost – 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. Application of 30 kg S/ha is sufficient for growing onion crop in soils having sulphur level above 15 kg/ha while 45 kg S/ha is needed for soils having sulphur level below 15 kg/ha for optimum production of onion. Soil application of 50 kg S/ha is recommended for long day onion crops. Sulphur is applied as basal dose at the time of transplanting. Foliar application of Zn @ 0.5% at 45 and 60 days after transplanting improves nutritional quality of onion bulbs. 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.

Biofertilizer

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.