Fruits like apples, almonds, peaches, plums, pears, and cherries require a chilling temperature between zero and seven degrees Celcius for the spring growth of their dormant buds. This cold is generally required in varying amounts by different fruits to break dormancy and exhibit normal growth. Winter temperature and precipitation, especially in the form of snow, are very crucial for the induction of dormancy, bud break, and ensuring flowering.
Early snow or rains in November, December, and January are considered good for meeting chilling requirements. But unfortunately, during November and December 2023, Himachal Pradesh experienced 85 per cent deficit rains and no snow. At present, the state is experiencing sunny days and very cool nights.
The temperature, in the range of zero to -1 degree Celcius is recorded during night time, whereas during daytime it goes up to 20 to 22 degrees Celcius. The high temperature during the daytime may trigger early flowering in stone fruits and head formation in wheat which may affect the production adversely.
The prevailing dry weather will also affect the vegetables, especially in their flowering stage. During the coming few days, there is no possibility of good rains which may further affect the crops and the planting of new fruit plants. The dry weather has resulted in low moisture in the soil and led to water stress which may affect the growth and development of all crops.
Moreover, due to the present weather conditions, frost events have increased which may also affect the crops adversely. Farmers are therefore advised to give life-saving irrigation to Rabi crops. Orchardists should suspend the application of fertiliser and manures in the orchards. They should apply mulch and life-saving irrigation. Fogging by sprinklers may help in combating frost injury to crops. Farmers are advised to follow weather forecast-based agro advisory issued bi-weekly by both the universities of the state.
In temperate and sub-temperate regions, snow in winter serves the crops as white manure by supplying water slowly as per the infiltration rate of the soil and helping the plants to meet both chilling and water requirements. In case of prevailing long dry spells, the orchardists should mulch the plant basins and also the open area between rows in vegetable crops to conserve the soil and maintain optimum hydrothermal regime. The thermal insulation by the application of locally available mulches helps in reducing the cooling rate of the soil surface and keeps it warm.
The clear sky and large gap in day and night temperature is resulting in increased frost events which has adverse effects on plants and animals. Frost occurs when night temperatures drop sufficiently causing condensation and freezing of water vapours on plant surfaces and damaging plant tissues especially tender parts like leaves and buds leading to cell rupture and tissue death. Sprinkler irrigation is recommended for crops which by releasing latent heat of fusion to the surrounding air through condensation of water droplets helps to reduce the frost effect.
In the prevailing conditions to protect crops from chilly winds, farmers should go for mixed cropping in vegetables by growing both tall and short crops to provide necessary shade against cold waves.
Shelterbelt plantations on the windward side are also recommended to protect the crops against chilly winds. Farmers should also keep animal sheds warm to protect them from severe cold. Monitoring weather forecasts and taking timely action to shield crops from cold and water stress are crucial steps to mitigate potential damage.
(The author is Head of the Department of Environmental Sciences at Y S Parmar University of Horticulture and Forestry, Solan)
