Lesser Yam (Dioscorea esculenta)
Nitrogen (N)
Symptoms
- Leaves turn yellow or pale green starting from older leaves to younger leaves
- Veins remains green where interveinal areas become pale green
- Overall growth of plants become stunted with shorter stem, smaller leaves with thinner texture
- Plant exhibit delayed or reduced flowering.
- Reduced the vigour of the plant.
- Development of suckers are reduced.
Management
- For determining the severity of the deficiency, soil analysis has to be done
- Application of quick releasing nitrogen fertilizer like urea, according to the results of the soil test.
- Apply urea as a foliar spray (10 gram per litre of water) once every 15 days .
- Frequent application of organic growth boosters is also beneficial
Phosphorus (P)
Symptoms
- Areas of the leaf margins become yellow and turn brown.
- Older leaves often turn darken green colour
- In some cases leaves turn purple or red colour on margins & tips of leaves particularly on underside of leaves.
- Shallow & poorly developed root system are noticed.
- Tuber size will be reduced.
Management
- Ensure that recommended amount of fertilizer is applied on regular time.
- For determining the severity of the deficiency, soil analysis is to be done
- Use fertilizers such as single superphosphate for quick correction and bone meal or rock phosphate for long-term correction.
- In the pH range of 6.5-7.5, phosphorus is readily absorbed by the roots.
- Addition of biofertilizers including phosphorus solubilizing bacteria along with organic manure helps to increase the availability of phosphorus
Potassium (K)
Symptoms
- Browning or scorching in margins of leaves & burnt appearance in leaf edges are observed.
- Curling of leaf tips also noticed.
- Yellowing & browning noticed particularly on the leaf edges between veins
- In severe cases entire plant show yellowing & Interveinal chlorosis
- Deficient plants exhibit stunted growth with shorter & weak stem, reduced size of leaf blades, smaller leaves
- Small sized tubers are developed due to the deficiency
Management
- In the pH range of above 6, Potassium is readily available.
- Maintain pH by addition of lime/dolomite
- Improve the soil fertility by adding organic matter and wood ash.
- For determining the severity of the deficiency, soil analysis is to be done
- Use Muriate of Potash (MOP) according to the results of the soil test. Split application is preferable.
- Apply foliar sprays of sulphate of potash (SOP) (10 g/litre of water) and wetting agents in the morning as an immediate remedy
Calcium (Ca)
Symptoms
- Symptoms seen on growing points and younger leaves.
- Leaf deformation such as, curling & distortion observed.
- Leaf margin become irregular or wavy.
- Necrotic spots or lesions seen on leaves, particularly on tips & edges
- Tip burn is also another symptom
- Poor root development
- Stunted growth with shorter stems & smaller leaves
Management
- Check the pH of the soil. If the soil is extremely acidic (pH between 3.5 and 4.5), apply lime (3.4 kg/cent in two split doses). In areas of moderate acidity (pH between 5.5 and 6), apply lime (1 kg/cent).
- High phosphorus levels leads to calcium deficiency.
- In alkaline soil application of Gypsum is preferable
- Boron is needed for calcium utilization.
- So a boron deficiency can also lead to calcium deficiency.
Magnesium (Mg)
Symptoms
- Major symptom is dark green veins with yellow areas between the veins (interveinal chlorosis).
- Margins of leaf blade become brown & die
- Wilting, leaf curling is noticed in deficient plants
- Necrotic spots develop on leaf tips & margins of deficient plants
- Premature leaf fall
- Tuber yield is reduced
Management
- Do the soil analysis and confirm the deficiency.
- Addition of Magnesium sulphate (320 gram /plant or 32 kg/ acre) in bands near plants.
- Long-term usage of dolomite will reduce magnesium deficiency
- Magnesium and potassium fertilizers should not be applied together
Sulphur(S)
Symptoms
- Interveinal Chlorosis occurs between veins of deficient plants
- Yellowing occur uniformly across the leaf or in patches
- Delayed leaf formation
- Leaves become small & narrow
- Stunted growth with Smaller leaves & shorter stems
- In severe cases, Entire plant turn to yellow
Management
- Application of sulphur-containing fertilisers, such as Factamfos, Ammonium sulphate, Single superphosphate, etc., reduces the deficiency.
- In sulphur deficient soils , apply sulphur dust (100 gram per plant or 10 kilogrammes per acre).
- Deficiency in alkaline soil can be reduced by application of gypsum
- Addition of organic material improves sulphur availability.in the soil .
- Burning of organic waste leads to sulphur deficiency
Boron (B)
Symptoms
- Deficiency causes abnormal shapes including twisting, crinkling along the veins.
- Leaves may become brittle & show irregular growth patterns.
- Yellow or browning of tips & margins of deficient leaves
- Lesions or necrotic spots appear on leaves
- Stems become brittle.
- Tuber development is affected.
Management
- Analysis of soil to confirm the deficiency.
- Addition of borax (4 kg/ acre) into the soil
- Application of borax (1 gram / litre of water) as foliar spray.
- Avoid the combined application of Boron and calcium.
- Application of borax with ammonium fertilizers should be avoided.
Iron (Fe)
Symptoms
- Interveinal chlorosis starts from younger leaves and progress upwards
- Leaves may become pale or almost white due to extensive chlorosis
- Reduced growth of entire plant
- In extreme conditions leaf tip exhibit necrosis by becoming dry & brown.
- Normal shape or curling
Management
- Iron content in Kerala soils is often high. So, get a soil test to determine the reason for the problem
- Low potassium levels leads to iron deficiency
- Addition of Ferrous Sulphate (60 gram/plant or 6 kg/ acre) into the deficient soils.
Manganese (Mn)
Symptoms
- Symptoms appear on leaves just reaching their full size.
- Leaf discolouration & brown spots appear on tips & margins of deficient plants
- Deficiency make upward or inward curling and cupping of leaf edges.
- Interveinal chlorosis between the veins and the veins remains green in colour
Management
- Soil Analysis
- Application of Manganese Sulphate (5 gram per litre of water) as foliar spray
Zinc (Zn)
Symptoms
- Symptoms are more prominent in the early stages of growth.
- Interveinal chlorosis between the veins are noticed.
- Delayed leaf development
- Underdeveloped root system
- Leaves become smaller in size & distorted in shape with a rosette appearance
Management
- The optimal pH range for zinc availability is 5 to 7.5.
- Confirm deficiencies by doing soil testing.
- Apply zinc sulphate to deficient soils (800 g /plant or 8 kg/ acre)
- Avoid the application of Zinc and phosphate fertilizers at the same time
- In severe cases, foliar spraying of Zinc sulphate (2 gram/litre of water) with Calcium carbonate (2.5 gram/litre of water) can be advocated in morning hours.
