Dr. Ajay Kumar Srivastava is an Agro meteorologist at the College of Agriculture, JNKVV,Tikamgarh, Madhya Pradesh
Article explains frost events, agro-climatic zone and its impact on crops in Bundelkhand.
A number of crops grown in the winter season (December to February) in Central India are typically affected by winter frost and dense fog. The frost event in Bundelkhand Agroclimatic zone of Central India has increased over decades. Vegetables, pulses, oilseed and fruits are quite sensitive to the frost, while cereal crops are relatively less affected. Frost damage is observed more in the lowlands /sloppy area in this zone. There are the cases; where crop produces are partially or completely ruined due to excessive frost in the winter. Mostly, the likelihood of frost is usually occurs from last week of December to end of January in central India, however, owing to the sequence of weather events like the passage of a cold front, followed by cold northwesterly winds and the presence of high pressure along with light winds and clear skies during night it may occur from December to the end of February. Frost impact is also influence by the crop type, crop stage, frost duration, surface structure, water on the crop surface and sudden drop in air temperature. The effect of frost and fog has been impacted the produce quality and production of crops yield.
Frost
Frost implies a thin layer of ice on a solid surface and is formed, when the temperature of the solid surface close to the ground falls at 0°C or below the freezing point of water. Under clear night skies and calm weather conditions, the grass on the ground emits more radiation than they receive it from the sky or other objects and if the temperature of the grass gets cold enough and in the presence of sufficient amount of water vapor in the air, frost forms on the grass. It has been observed and reported that during winter season, when the minimum temperature was recorded <2 or 1-2°C then the frosts were observed on the ground surface (Bureau of Meteorology, 2019), therefore, in the present study, less than 1-2° Celsius of air temperature considered as frost day.
Bundelkhand Agroclimatic Zone
The Bundelkhand Agroclimatic Zone of Madhya Pradesh lies between 240 40’ north latitude and 760 80’ and 800 50’ east longitude and spreads over 22.82 sq. km, The elevation of zone ranges from 266 to 560 meter above mean sea level. The topography of the area is characterized with flat land, up to 5 percent slope and small hillocks spreading over major part of the zone. Three districts namely Tikamgarh, Chhatarpur and Datia are there under Bundelkhand Agroclimatic zone of Madhya Pradesh. This zone is primarily drought prone area, which is also affected by extreme weather events like frost during rabi season.
The decadal variability of frost occurrence in Bundelkhand Agroclimatic Zone is shown in table 1. It is clear from the table values that the frost events had occurred in the different decades in this region. These recurrent frosts have badly affected the crops and income of the farmers. However, if the information about the occurrence of such weather events is received at the right time, then to a large extent, economic loss can be avoided by adopting preventive measures.
Frost events in Bundelkhand Agroclimatic zone
Quite a few incidences of frost have been recorded in the past years in the Bundelkhand agro-climatic zone of Madhya Pradesh resulted into massive impact on the rabi crops. The frequency of occurrence of frost during past 41 years in Tikamgarh district is shown in figure 1. During the recent past, the moderate frost event had occurred during 4-6 January 2011 and shown in figure 2, when the minimum temperature was recorded -1.8°C at Tikamgarh. This type of negative departure in minimum air temperature was observed in past 42 years. The duration of minimum temperature below 0°Cduring the two consecutive days (5th and 6th January) was greater than 3hours (Fig.2). During the current year (2023), ground frost (Fig.3) was observed on 8th January, when the minimum temperature is recorded 1°C ( Fig.4) at Tikamgarh district.
The decadal variability of frost occurrence in Bundelkhand Agroclimatic Zone is shown in table 1. It is clear from the table values that the frost events had occurred in the different decades in this zone.
These recurrent frosts have badly affected the crop yield and income of the farmers. However, if the information about the occurrence of such weather events is received at the right time, then to a large extent, economic loss can be minimized by adopting preventive measures.
Effects of frost on crops
There are three type of damage and the effect of frost damage on crops depends on crop stage and moisture on the crop leaves as well as departure of the minimum temperature below1-2°C and its duration. However, the cold damage on the crop generally started below 4°C.
Cold damage: It occurs, when crops are exposed to temperature less than 4°C to -2°C.
Desiccation damage: It occurs; when ice forms on the crop surface on the leaves at temperatures from 0°C to -2°C. The moisture is drawn from the leaves surface leaving them dry and brittle.
Freezing damage: It occurs, when temperatures below -2°C then there is rapid ice nucleation and ice crystals form within the crop tissue. The ice crystals physically rupture cell walls and membranes within the cells causing physical damage of crop.
The damage is usually evident 7-8 days after the occurrence of frost event. To see the damage first examines the lower parts of the crop and if it is found damaged, further observed the higher or upwards parts. This observation on the crop should be done on frost affected areas at least 10 -15 places in the crop field.
Frost damage to the crops is resulted not simply from cold temperature but chiefly from extracellular ice formation inside crop tissue that causes injury to the cells. The amount of frost injury increases as the temperature falls. Freezing injury during winter season is disastrous to fruit, vegetables and seed crops because of the high sensitivity during reproductive phase. Frost damage may either affect the entire crop or only a small part of the plant tissue, fruits, which reduce yield, or produce quality. Frost can also take place on grasses, crops, on soil and other objects and affects vegetables (Figure 5), legumes, pulses, oilseed ( Figure 6), forage crops, cereals, root crops, horticultural and ornamental crops. Damage is quite apparent due to the destruction of leaves, twigs and stems and premature falling of fruits and flowers. The affected crop loses its green color and the color of the leaves resembles the color of the soil (Figure 7 and 8). In such a situation, the outbreak of bacterial diseases increases due to rotting of the leaves of the crops. Insect-pest and disease infestation increases due to frost damage on crops. It is reported that due to frost occurrence, crop gets damaged to the tune of 80 to 90 per cent in vegetables (tomato, chilli, brinjal cumin, coriander, fennel, opium etc. etc.), 60 to 70 percent in pulse crops (peas, gram, tur, linseed, mustard, cumin, coriander, fennel, opium etc.) and 10 to 15 percent in cereal crops (mustard, wheat and barley etc.).
Remedial Measures to protect crops
Frost damage may be minimized by adopting protection methods in view of weather forecast. The Government of India through India Meteorological Department issuing frost forecast at district and block level across the country during winter season. The forecasted weather information may be used to minimize the crop loss by adopting the protective method of frost management.There are primarily two curative measures namely passive and active protections for avoiding frost damage. The passive protection method includes the proactive actions implemented before the advent of frost to minimize the impact of frost on crops. The main passive methods include site selection, managing cold air drainage, crop selection, crop nutritional management, proper pruning, crop covers, avoiding soil cultivation, irrigation, removing cover crops, soil covers, trunk painting and wraps and change in sowing date of crops. The active protection method includes use of heaters, wind machines, helicopters, sprinklers and surface irrigation.
Light irrigation to the crops increases the temperature of the soil by 1 to 1.5 degree centigrade, which reduces the impact of frost (Fig.-9). Garbage burning in the north-west direction of the fields during the night is a traditional measure to avoid damage, when there is a possibility of frost. A spray of 2 to 3 per cent solution of urea on the crop is also advisable.
Spraying of 0.1% solution of sulfuric acid on the crops should be done on the days when frost is forecasted. For this, a solution of 1 liter sulfuric acid in 1000 liters of water is made and sprayed it in one hectare area. If the possibility of cold wave persists even after this period, the spray of sulfuric acid is repeated at an interval of 15 days. Spraying of sulfuric acid on crops like mustard, wheat, potato, peas not only prevents frost, but also increases iron content and enhanced the chemical activity in plants, which increases disease resistance and improves crop yield (Fig.-10). As a long-term measure to save the crops, wind barrier trees like Mulberry, Shisham, Acacia, Khejri, and Jamun etc. should be planted on the north-western ridges of the field and at appropriate places in between so as to avoid frost and cold wind. On the night, when there is a possibility of frost, smoke should be done by burning garbage or other wastes to raise the temperature of the crop microclimate. Crude oil can also be used along with the above substances to smoke. Nursery plants and field gardens/cash vegetable crops should be covered with sackcloth, polythene or straw. Airtight structure “Tatiya” should be tied to the edge of the beds in the direction of the wind to pass up and avoid the frost damage.
