- During establishment stage of mango in the field, sub-soil irrigation through pitcher buried 10 cm from the plant, 1 foot below ground level, covered by a plastic plate and fed through a 3 cm diameter pipe with 1.25 liters of water applied/plant/day and mulched with sugarcane thrash mulch (1.0 kg/basin) results in better establishment.
- Black polyethylene film (100 micro thick) helps in conservation of moisture and increase in root growth, flowering, fruiting and minimum fruit drop with enhancement in yield.
- Rain water harvesting through opening of circular trenches around trees at a distance of 6 feet and width at 9 inches, as well as depth and mulching the trenches with dry mango leaves, helps in retaining sufficient moisture in the soil during flowering and fruiting and increase in yield.
- Drip irrigation along with crop residue mulch helps in water saving. Drip irrigation with 0.6 volumes of water and plastic mulch significantly increases the yield. The water stress immediately after fruit set increases fruit drop in mango. Hence, protective irrigation is essential during the fruit development period.
- Due to high temperature stress in many areas leaf fall is observed. To overcome the leaf fall and to enhance the turgidity spray 0.2 % cent Potassium Sulphate.
Monsoon is delayed by 15 days : - No adverse impact as fruits are already matured in early and mid season varieties ; fruit size and quality will be affected in late maturing varieties viz., Chausa, Mallika and Amrapali. But irrigation and mulching is required to be followed. .
Monsoon is delayed by 30 days : No adverse impact as fruits are already matured in early and mid season varieties ; incidence of shoulder browning (fruit blemishes , tear stain ) and post-harvest diseases will be minimum ; fruit quality will be good; fruit size and quality will be affected in late maturing varieties like, Chausa, Mallika and Amrapali etc., ; impact severity will increase. Further increased temperature, relative humidity during July-September will lead to telescoped harvests, market gluts , increased incidence of jelly seed formation (internal breakdown of pulp matrix ) following rainfall. irrigation and mulching.
Rainfall deficit at vegetative phase : Impacts adversely the production of vegetative shoots (potential fruiting wood of the ensuing season). But irrigation and mulching is required to be followed.
Rainfall deficit at reproductive stage: Favourable during fruit bud differentiation (FBD) stage. But irrigation and mulching is required to be followed.
Terminal drought : Crop prospects of ensuing season will be affected especially in light soils ; recurrent droughts lead to crop failure. But irrigation and mulching is required to be followed.
- The soil moisture deficit stress in banana during vegetative stage causes poor bunch formation, lower number and small sized fingers. The water stress during flowering causes poor filling of fingers and unmarketable bunches and reduced bunch weight and other growth parameters.
- Providing irrigation through drip helps in reducing the adverse effects of water stress.
- Plant Protection Measures - High temperatures along with low humidity are congenial for flare up of sucking pests like thrips and mites in fruit crops viz., mango, grapes, and pomegranate. Proper monitoring and timely spraying of recommend pesticides will bring down the severity of incidence. For thrips, insecticides like thiamethoxam 25WG@ 0.25 g/L or Acephate 75SP @1.5 g/l or spinosad 45 % SC @ 0.5 ml/l will bring down the thrips infestation. For mite management, dicofol 18.5 EC @ 2.5 ml/l or fenpyroximate 5SC @ 0.5 ml/l.
If monsoon is delayed by 15 days/ 30 days :
- In most of the banana growing areas, usually planting of suckers / tissue culture plants should be taken up after the on-set of monsoon.
- Since banana crop is not monsoon dependent, planting can be done according to the on-set of monsoon.
Rain deficit at vegetative and reproductive phase :
- In the scenario of rain fall deficit during the vegetative stage, farmers are advised to go for drip irrigation to conserve the water and also to provide the required water at root-zone to increase the water use efficiency
- As a mitigation measure, 0.1mM salicylic acid (140 mg/litre of water with surfactant) foliar spray can be given to the plant @ 250 ml/plant
- Foliar application of Kaolinite (5%) during vegetative state reduces the transpiration water loss.
- Foliar fertilization with five sprays of 3% Polyfeed (19:19:19), i.e., 30g litre-1 of water along with surfactant at 15 days interval during vegetative stage is recommended.
- Mulching of the soil surface either with black polythene or with plant material / leaves of banana etc. can be spread around the basin to reduce the water loss.
- Growing green manure crops around the plant and mulching is recommended.
- Application of 5kg Rice husk ash or composted coir pith in the pit at the time of planting is recommended to increase the water holding capacity in the rhizosphere.
- Instead of open irrigation, sub-surface irrigation is recommended.
Terminal drought : In the case of terminal drought, growing of banana with sub-surface irrigation, plastic mulching, mitigation with salicylic acid, foliar spray of water soluble fertilizer and leaves retaining with 5-6 leaves is recommended to help in overcome the drought situation.
If monsoon is delayed by 15 or 30 days and rain deficit at vegetative phase:
- Crop residue recycling to build organic carbon reserves to improve soil health and water holding capacity to cope with dry spells
- In-situ moisture conservation using organic or inorganic mulches should be practiced with immediate effect. Locally available organic plant wastes or plastic mulches (white/black/ pervious mulches)
- Avoid applying fertilizer till sufficient soil moisture is available or fertigation may be adopted for efficient use of limited available/harvested rainwater.
- Reduce intercultural operations to minimize the loss of moisture
- Removing suckers and water sprouts
- Conserve the stored water in ponds and earmarking for use of life saving irrigation in critical stages of the crops.
- Make raised ridges along the rows around the plants.
- Apply Hydrogel in the root zone of the plant below drippers. Mix 500g hydrogel in 5 Kg fine sand/soil; apply 20 g of this mixture/tree
- Take sprays of abamectin 1.95 EC @0.5ml/l if mite infestation is seen due dry conditions
Rain deficit at reproductive phase:
- Spray Gibberelic acid (GA) 10mg/l+ 0.5ml/l spreader sticker at full bloom
- Spray boric acid 2g/l + 0.5ml/l spreader sticker within 20 days of fruit set in the evening. Repeat after 1 month.
- Next day spray N-(2-chloro-4-pyridinyl) phenyl urea(CPPU) [common name for chlorfenuron] @5ml/l +0.5ml/l.
Terminal drought: In addition to the measures mentioned above the number of fruits should be reduced depending on assured water available with the farmer. Sprays of 2,4-Dichlorophenoxy acetic acid (2,4-D) 10mg/l in plants below 4 years repeat after 10 days if required may be taken in case of fruit dropping. In plants above 4 years 1 spray of 20mg/l may be sprayed.
Monsoon is delayed by 15 days : Early winter crop will be affected, therefore, supplementary irrigation and Mulching should be done.
Monsoon is delayed by 30 days : Rainy season crop will be affected (reduced fruit size and quality); prospects of winter crop gets affected / delayed winter crop but crop size and quality may improve. Supplementary irrigation and mulching be provided.
Rainfall deficit at vegetative phase : Delayed winter crop. Supplementary irrigation and mulching be provided.
Rainfall deficit at reproductive stage : Rainy season crop will be affected; Delayed winter crop. Supplementary irrigation and mulching be provided.
Excess rainfall leading to flooding : No adverse effects; incidence of diseases and pests may increase. Management of pests and diseases is important.
Terminal drought : Total crop output will be affected. Irrigation and mulching should be provided.
Monsoon is delayed by 15 days :Fruit size and development gets affected. Supplementary irrigation and mulching be provided.
Monsoon is delayed by 30 days : Fruit size and development gets affected. Fruit drop may occur. Supplementary irrigation and mulching be provided.
Rainfall deficit at vegetative phase : Gets affected. Supplementary irrigation and Mulching be provided.
Rainfall deficit at reproductive stage : Not applicable as it occurs during March-April.
Excess rainfall leading to flooding : Excess vegetative growth resulting in reduced reproductive growth ; prolonged flooding situation may result in death of plants; incidence of thrips and rust increases. Improving drainage; pests and diseases management is important.
Terminal drought : Reduced yield arising from fruit drop, low fruit size. Irrigation and Mulching should be provided.
Monsoon is delayed by 15 days : Sowing of kharif crops will be delayed. Irrigation and mulching should be provided.
Monsoon is delayed by 30 days and at vegetative phase : Already sown rhizomatous (turmeric, ginger), tuber (Amorphophallus), get affected. Supplementary irrigation and mulching be provided.
Terminal drought :Adversely affected
- Litchi being an evergreen plant, the maintenance of optimum soil moisture is critical for growth, development and fruit production.
- It is adapted to warm subtropics, cropping best in region with brief dry frost free winters and long, hot summers with high rainfall and humidity.
- If rainfall is evenly distributed, litchi is grown successfully and supplementary water requirement depends upon cultivar and evaporation demand.
- To achieve faster growth of the plant, no water stress should be permitted, while in the reproductive phase water stress is beneficial at the time of panicle emergence, flowering and fruit bud differentiation (February-March).
- Light irrigation but at frequent short intervals during summer months and cleaning of the basin is advocated (April-May).
- Certain physiological disorders like poor sex ratio, poor fruit set, heavy fruit drop and high fruit cracking and sunburn of the fruit are more intense under water deficit in the rhizosphere and can be minimized with proper water management (March–May).
- Early flushing, proper vegetative growth and shoot development are very much influenced by the timely onset of monsoon, without any additional irrigation (June-September).
- Intercultural operations, pruning and training operation and summer ploughing is followed just after harvesting of the fruits, dependent on cultivars (June -July).
- Arrival of monsoon brings, great change in weather conditions, immediately the atmosphere becomes saturated with moisture and relative humidity goes high (>90 %). It also marks disappearance of dry heat, scorching loo, winds and appearance of wet and cold air, thunderstorms, cumulus clouds having overhead, which give a good boost to vegetative growth of litchi.
- The phase change i.e. vegetative to reproductive stage require induction of cool/low temperature with mild stress condition with restricted or no supplemental irrigation.
- Fruit development, fruit yield and quality require regular monitoring of nutrients and moisture with good management practices during pre - monsoon period for economically viable harvest.
If monsoon is delayed by 15 days :
- New litchi fruit plantations, under area expansion programme, which is generally associated with onset of monsoon, will be delayed.
- Cost of handling and maintenance of planting material will increase.
- In case of early varieties (cvs. Shahi, Rose Scented) cost of two irrigations will increase while in case of late varieties (cvs. China, Late Bedana) cost of at least one number of irrigation will increase.
- The adult plant of litchi (>10 years), which is supposed to be drought tolerant and can survive 4 - 12 weeks without water will start developing its adaptive a biotic stress tolerance mechanism like shading of leaves, delay in flushing, curving/dropping/bending of leaflets and will force the plant to go in resting phase with restricted overall vegetative growth and vigour.
- Overall, the exhausted commercial bearing litchi plants/trees need immediate application of nutrition and irrigation, just after the harvesting of fruits, will be less effective under the conditions of delayed monsoon.
- The required pruning and training operations followed just after the harvest of fruits, which cause decrease in the canopy density, needs immediate application of manures and fertilizers for early emergence of new flushes will be affected and influence the next season fruiting due to non or late emergence of current season shoots.
- In case of delayed monsoon, atmospheric humidity remains very low consequently, evapo -transpiration rises considerably during this period (June), the root activity and nutrient use efficiency are badly affected, ultimately affecting the overall vegetative growth and vigour of plant, ma y lead towards declining phase and revival will take time during that annual cycle.
If monsoon is delayed by 30 days :
- Area expansion programme by new litchi fruit plantations which is generally associated with onset of monsoon, will be delayed.
- Cost of handling and maintenance of planting material will increase.
- In case of early varieties cost of four numbers of irrigation will increase while in case of late cost of two numbers of irrigation will increase to maintain th e annual growth and reproductive cycle of the fruiting trees.
- Delay in the emergence of early flushing will influence the vegetative growth, shoot maturity, flowering and fruiting of the coming season.
- Shoot growth and vegetative growth will be slow.
- Drying of newly emerged flushes and shoot tip burning may occur.
- The adult plants/trees of litchi (>10 years) will start developing stress tolerant mechanism to be in resting phase to overcome the stress condition created due to delayed monsoon and ultimately affecting the due vegetative growth of the season.
- Litchi has low ability to transport water from root to leaves and in case of delayed monsoon and lack of moisture in the root zone may seize many physiological and metabolic processes of the plant body. As wet soil alone with applied irrigation cannot prevent the development of tree water stress. Rain deficit at vegetative phase :
- Establishment of new plantations will be a difficult feature.
- During critical crop growth stages, too many days without ra in can adversely affect the proper vegetative growth, may lead to crop failure during the coming season.
- Shoot growth and canopy spread will be slow.
- Litchi trees may undergo the process to develop stress tolerant adaptive mechanism to remain in resting phase rather than to go for normal vegetative growth during the season and will affect the health and fruit production of the crop.
- As mentioned above, that litchi has low ability to transport water from root to leaves, the proper management practices (application of organic manures, use of mulching) with supplementary irrigation through efficient and effective methods may reduce the ill effect of the situation created due to deficit rainfall.
- The important factor i.e., a high rate of relative humidity (RH), which favours fast vegetative growth, is lacking in the situation of deficit rain during the vegetative phase, always an important factor can be managed by providing an adequate supply of water through irrigation.
- On the whole, litchi appears to suffer moisture stress on hot, dry, windy days of low RH, require timely implementation technologies with proper management practices.
Rain deficit at reproductive stage :
- The phase change i.e. vegetative to reproductive stage is very crucial for litchi fruit production, which require induction of cool/low temperature in conjunction with the conditions of low moisture in the rhizosphere as well as low humidity in the atmosphere, hence deficit rain with no supplemental irrigation creating mild stress condition is beneficial for better transformation into reproductive stage in litchi cultivation.
- The mature shoots developed form the early appeared flushes only undergo in resting phase and bring floriferous condition with created mild stress condition during winter season.
- Practices of withholding irrigation two months prior to the expected time of panicle emergence, no intercultural operation, no pruning and training operation, mulching beneath the canopy spread area etc. is recommended and had proved beneficial during this initiation (period) of reproductive stage.
Terminal drought :
- Drought is a major abiotic factor, which excessively limits growth and vigour of the litchi plants/trees in general and limits fruit production.
- In case of litchi production system in India the critical period for irrigation is from the end of March to the onset of monsoon i.e.June as that is the time when fruit development and vegetative growth occur, drought condition may be managed through proper irrigation management through various improved systems of irrigation.
- One of the major consequences of drought condition is inhibition of metabolic functions, reduced rate of photosynthesis and reduced root activity in rhizosphere. Consequently, nutrient use efficiency is decreased, resulting decline in quantum of fruit production and quality of fruits.
- From March onwards, when temperature starts rising in the places and the atmospheric humidity remains very low consequently, evapo - transpiration rises considerably during this period and if the litchi orchard is not frequently irrigated during this period, there may be occurrence of many physiological disorders (fruit cracking, sunburn and fruit drop).
- As mentioned that litchi has low ability to transport water from root to leaves, he nce, to overcome the drought condition, proper watering of the orchard to the level till it regains capacity to effectively run the metabolic processes with reduced cell turgor (as visible from leaflets vigour), management practices (application of organi c manures, use of mulching), proper pruning and training operation to keep the reduced height of the trees and spreading canopy along with supplementary nutrition and irrigation through improved and efficient methods, may reduce the ill effect of the situ ation created due to drought.
Source : NHM