Field Problems and their Solutions in Kharif Rice Production

In securing optimum yields from high yielding varieties of rice specific diagnosis of field problems and adoption of good management practices is the best solution apart from breeding suitable varieties and judicious plant protection. The following are some of the field management problems and solutions in kharif rice production.

1).  Selection of suitable variety

Mashuri, the popular local variety, is tall growing and susceptible for lodging and kharif pest complex.

It is usually caught in rains at maturity and germinates institute. Available high yielding varieties without these two bad characters should be selected depending on the agroclimatic situation.

2).  Field problems in the nursery

i) Preference

Prefer certified seed from a recognised source. Ensure seed treatment before sowing. Examine whether nursery was sown thin to obtain sturdy and healthy seedlings. Densely sown seedbeds tend to give weak and lanky seedlings which are prone to get transplanted in bunches, leading to delayed establishment and low tillering and give scope for excessive weed growth. Broadcasting on a drained bed @ 50-70grams of seed per square metre (depending on seed size and germination) is ideal.

ii) Wetland seed beds that have been just sown

Check for smooth level, evenness of sowing and depth of sowing. Puddle should settle down for a day prior to sowing of sprouted seeds. The seed should just sink in the bed and not buried. Unevenness of levelling results in suppression of germination both in high and low level areas and leads to patchy nursery. If the nurseries are patchy and gappy, inspite of proper levelling, and management of water, the problem might be either due to bad seed or improper broadcasting of seed.

iii)   Seed bed after 8-10 days of sowing

In dry seed beds check the seedlings whether they are normal green or turning pale and white. In black soils with high pH or lime content and in red soils with low organic matter, dry nurseries are liable to be affected by iron chlorosis.

In the region comprising Guntur, Prakasam and Nellore districts chlorosis in rainfed rice and upland nurseries is common. This may be due to iron or manganese deficiencies or both. In both the cases interveinal chlorosis in the young leaves can be seen.

In the case of iron deficiency spray 0.5% Ferrous Ammonium or Ferrous Sulphate (5 grams Ferrous sulphate or Ferrous ammonium sulphate plus 0.75 grams citric acid per litre of water) repeatedly at 4 to 5 days interval till the chloratic leaves turn normal green.

iv)   Wet land seed bed ready for uprooting within 5-6 days

Pullout a few and check the seedlings. They should have 4-6 leaves and this is the optimum stage for transplanting seedlings. This stage is reached in 20-25 days in summer and kharif and 30-40 days in cool weather in Rabi.

Remember that physiological age is more important than chronological age.

Seedlings should not be pale yellow in colour, which indicates N deficiency. Arrange for application of N at 0.3 to 0.6kg N per 100 square metres six days before pulling the seedlings in the form of a quick acting fertilizer like urea. If transplantation is expected to be delayed, let seedlings remain yellow and postpone fertilization until a week before transplantation. Seedlings should not exhibit leaf lodging which indicates over management of seed bed. No further application of N should be suggested in such cases.

v)   Seed bed ready to uproot

     The seed bed should be flooded a day earlier so as to prevent root damage while uprooting. Some damage to roots may be inevitable. If the soil is heavy the damage to root system is likely to be more. This may be overcome by adopting a high seed rate. Careful uprooting not only minimises gap filling but also helps quick establishment and improved tillering. If the soil of seed bed tends to be sticky, advise incorporation of paddy husk to facilitate easy uprooting of seedlings or else the stickiness may form clumps and cause breakage at the collar.

Uprooting should be preferably done in the evenings and should be transplanted within 24 hours. They should not be allowed to wilt in any case.

vi)   Overaged seedlings

When seedlings are overaged potential for tillering is reduced, specially with short duration varieties than late maturing ones.

To compensate loss in tillering recommended closer, planting and heavier fertilisation. Minimise nursery fertilisation.

3) Management in Main field :

i)    Main field ready for transplantation:

Thorough puddling is essential to reduce excessive water percolation and loss of applied fertilizer due to leaching and easy transplantation. This should be done 2 to 3 weeks before transplantation (specially in cooler season) to save seedlings from the harmful effects of decomposing organic matter applied.

Allow 3 weeks time for decomposition of green leaf manures if puddled in wetlands, keeping them submerged under water. Level the field uniformly after puddling.

Advise the farmers to keep the field flooded from first ploughing to transplanting time. Otherwise nitrogen will be lost due to denitrification.

The common mistake in the case of black soils is to transplant without allowing the puddle to settle. In a freshy puddled field planting tends to be deep resulting in low tillering. Advise the farmers to allow the puddle to settle for two days before transplanting. In the case of red soils the farmers can rush to transplant or else the puddle settles down and makes transplantation difficult later.

If the field is not evenly levelled the transplanted seedlings may sink at lowest place. The water and nitrogen management will be very defective and the crop will not grow uniformly.

ii)    Is algae a problem in the area?

In such cases skip or minimise basal N dose or delay by 10 days. Keep the water at minimum level till the seedlings are established. In severe cases apply 1 to 2 kg copper sulphate per hectare mixed with sand. Dry the field alternatively by which algae would settle down and turn brown.

iii)   Zinc deficiency

If the crop is not thriving inspite of proper fertilization, if it is patchy and unhealthy the problem is most likely zinc deficiency. Zinc sulphate at 50kg/ha once in three seasons is the general recommendation. In saline and alkali soils zinc deficiency is more serious than in normal soils. In such soils zinc sulphate is to be applied every year.

Do not mix zinc sulphate with phosphate fertilizers. Apply them separately with 2-3 days gap.

iv)   Mainfield planted the previous day:

The seedlings should be planted shallow i.e., not more than 3cm deep. Deep planting results in delayed establishment and results in poor tillering and yield.

In case the total N proposed is 80-100kg per hectare, spacing should be 20x15cm. If the seedlings are over aged or fertilization is medium level or if the varieties are low tillering close spacing of 15x10cm can be adopted.

Planting of more than 2 seedlings per hill is not desirable.

Advise the farmers to reserve some seedlings in the nursery for gap filling.

v)    Mainfield ten days after planting

Establishment of the plant is indicated by the resistance offered when pulled. Advise farmers to keep not more than 2-3 cm film of water.

Gap fill twice, once 7 days after planting and second time within 10 days after planting. Loss of production is more serious than disturbance to plants due to gap filling.

vi)   Main field 20 days after planting

There should be 200 tillers per square metre in a field where 20x15cm spacing is adopted i.e., 6 tillers per hill under good management. Check for nitrogen, phosphate, potash deficiency, sulphide injury, salinity and alkalinity problems and correct them.

For BPH prone areas and the susceptible varieties recommend planting of seedlings 30cm in rows apart which may help in minimising BPH incidence. This further makes easy the spraying of insecticides.

vii)  Water Management:

Keep water not more than 5cm deep throughout tillering period i.e., upto 45 to 55 days after planting and at 5cm from P.I to flowering. Never dry or drain the field except to top dress fertiliser. Avoid continuous flow of water in the belief that water should be periodically changed. A field flooded with a thin film of water would retain available soil nitrogen in a stable ammoniacal form. If the field is subject to drying and reflooding, soil nitrogen would be oxidised into nitrates and lost by leaching during subsequent flooding. Therefore alternate drying and wetting causes significant loss of nitrogen leading to poor growth of crop.

viii)  Fertilizer Management

In delta areas fertilizer doses should be determined based on soil test results.

Split application of N have proved to be far better as the efficiency of applied N with split application is above 30% under transplanted conditions. Extra yield of 13% in Kharif and 23% in Rabi have been recorded due to split application.

In NSP area P2O5 has to be applied at a higher dose. In canal areas of Nellore district nitrogen has to be applied at the rate of 40kg N/ha as the response is very poor.

ix)  Main field 50 days after planting

Tillering would have been nearly complete. Check there should be 350-400 effective tillers per square metre.

x)   Main field at flowering

Examine whether there is protracted flowering. If so this may be due to retarded growth, delayed top dressing, improper spacing, deep planting etc. Advise the farmer to adopt proper management practices in the next season.

4. Harvesting

High yielding varieties maintain greenness due to their habit of slow senescence. Do not wait till the crop is completely dry. Harvest when the stems are green (karra patchi) stage. This will avoid grain shattering and also breakage in milling. Breakage in milling is the result due to hasty over drying rather than a varietal characteristic etc.

5.  Save Paddy caught in rains with salt treatment

Harvested sheaves with panicles if dipped in 5% salt solution prevents grain germination and spoilage of straw. If threshed paddy can be heaped on straw in a place with slope and 4kgs salt can be sprinkled for every 100 kg paddy, prevents grain germination. Thus every quintal paddy can be saved from spoilage with only two rupees.

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