How Does Abnormal Heat Affect Crops?

The risk becomes especially serious when high temperatures are combined with low soil moisture, dry winds, or sensitive growth stages such as flowering and yield formation.

There is no single critical temperature that applies to every crop. The level of damage depends on the crop species, variety, growth stage, soil moisture, and the duration of the heat.

The problem: the plant’s natural cooling system is disrupted

Plants absorb water through their roots and release part of it through tiny openings on their leaves called stomata. This process helps cool the plant.

When the soil becomes too dry, the plant closes its stomata to reduce water loss. This creates several problems at the same time:

•  natural leaf cooling decreases; 
•  the intake of carbon dioxide required for photosynthesis becomes limited; 
•  leaf temperature may rise above air temperature; 
•  plant growth and development begin to slow down. 

When heat stress occurs together with drought, the impact on the plant becomes much more severe.

Consequences: what signs can be seen in the field?

1. Leaves wilt and develop heat damage

When a plant loses more water than its roots can absorb, the leaves may begin to droop, curl, or dry along the edges.

Prolonged heat can cause:

•  leaf yellowing; 
•  sunscald and leaf burn; 
•  loss of green colour; 
•  premature leaf ageing; 
•  slower plant growth. 

2. Flowering and pollination are disrupted

Flowering is one of the most heat-sensitive stages of plant development.

High temperatures can reduce pollen viability and interfere with pollination and fertilisation. As a result:

•  flowers may fall; 
•  young fruit may fail to develop; 
•  the number of grains per head may decrease; 
•  fewer fruits may form; 
•  final yield may decline. 

Heat tolerance can vary considerably between varieties. Choosing varieties adapted to local conditions is therefore highly important.

3. Grain filling and fruit development are shortened

High temperatures accelerate plant development, but they also shorten the time available for the crop to build yield.

As a result:

•  grains may not reach their full weight; 
•  fruits may remain small; 
•  market appearance may deteriorate; 
•  crop quality and storage life may decline; 
•  total yield may decrease. 

Heat is especially dangerous during grain filling, fruit development, and crop maturation.

4. Young seedlings face greater risk

Dry, uncovered soil heats up quickly under direct sunlight. Young seedlings have shallow and underdeveloped root systems, making them highly sensitive to heat and moisture shortages.

This may lead to:

•  reduced seed germination; 
•  rapid drying of the upper soil layer; 
•  damage to young leaves; 
•  delayed development; 
•  the death of individual plants. 

Solutions: what should farmers do?

Before the heat arrives

Farmers should monitor the weather forecast in advance and identify the most vulnerable parts of the field.

Priority should be given to crops that are at the following stages:

•  seedling emergence; 
•  flowering; 
•  fruit set; 
•  grain filling; 
•  fruit growth and maturation. 

Before a hot period, farmers should:

•  inspect the irrigation system; 
•  assess available water reserves; 
•  check soil moisture; 
•  determine the irrigation priority for different fields; 
•  use mulch where appropriate; 
•  prepare temporary shading for seedlings and sensitive vegetable crops when possible. 

Mulch helps reduce soil surface temperature and moisture loss through evaporation.

During the heat

The main goal is not simply to provide as much water as possible. It is to maintain stable moisture in the root zone.

Excessive irrigation can also be harmful. It may cause waterlogging, reduce oxygen around the roots, wash nutrients out of the soil, and waste water.

Recommended actions include:

•  irrigating early in the morning or in the evening; 
•  delivering water directly to the root zone; 
•  considering the soil’s water absorption rate; 
•  avoiding prolonged soil drying; 
•  prioritising crops during flowering and yield formation; 
•  using drip irrigation when available; 
•  regularly inspecting leaves and young shoots. 

When high temperatures, dry winds, and low soil moisture occur together, the plant’s ability to cool itself becomes severely limited. Field monitoring should be intensified during such periods.

After temperatures decrease

Once the hot period has passed, the field should be inspected and the condition of the plants assessed.

Farmers should check for:

•  leaf burn; 
•  yellowing and wilting; 
•  fallen flowers and young fruit; 
•  the condition of new growth; 
•  soil moisture; 
•  signs of diseases and pests. 

Large amounts of fertiliser or crop protection products should not be applied immediately based only on visible symptoms.

Yellowing, spots, and wilting may be caused by several different factors:

•  heat stress; 
•  water shortage; 
•  nutrient deficiency; 
•  disease; 
•  pest damage; 
•  improper irrigation. 

The likely cause should be identified first. Measures should then be selected according to the crop, its development stage, and the specific field conditions.

In future seasons, planting dates should be planned so that sensitive stages such as flowering and yield formation do not coincide with the hottest period of the year whenever possible.

Farmers should also select locally tested varieties with greater tolerance to heat and drought.

Systematic crop monitoring with UFarmer

During abnormal heat, a single irrigation event or one field inspection is not enough. Air temperature, soil moisture, and plant condition may change throughout the day.

For this reason, farmers need continuous and systematic monitoring.

Daily tasks in the Agro Calendar

The Agro Calendar in the UFarmer application helps farmers plan daily activities according to the crop and its development stage.

During hot weather, these tasks may include:

•  checking soil moisture; 
•  scheduling irrigation for the morning or evening; 
•  inspecting leaves for wilting, burn, and yellowing; 
•  monitoring flower and young fruit drop; 
•  checking the condition of young shoots; 
•  completing necessary agronomic activities on time. 

This approach helps farmers avoid missing important tasks and manage crop care consistently.

Weather-based recommendations

Weather information and alerts in UFarmer help farmers learn about approaching heat, strong winds, or rainfall in advance and adjust their work plans.

When a sharp rise in temperature is expected, the application may remind the farmer to:

•  check soil moisture; 
•  revise the irrigation schedule; 
•  pay closer attention to sensitive crops; 
•  monitor plants during flowering; 
•  prepare for possible heat stress. 

This allows preventive action to be taken before serious damage appears on the plants.

Continuous monitoring of crop condition

The crop monitoring function helps farmers track changes in the field regularly.

Farmers can identify the following signs at an early stage:

•  leaf spots; 
•  yellowing; 
•  leaf curling; 
•  heat damage; 
•  wilting; 
•  slower growth; 
•  changes in fruits and stems. 

When unknown spots, yellowing, or signs of damage appear on the leaves, the plant can be checked using the Scanner section in UFarmer.

The application helps assess possible causes and provides practical recommendations for the next steps and preventive actions.

During abnormal heat, UFarmer therefore serves as more than a weather information application. It becomes a digital assistant that:

•  creates a daily work plan; 
•  reminds farmers about important tasks; 
•  provides recommendations based on weather conditions; 
•  supports continuous crop monitoring; 
•  helps identify possible problems earlier; 
•  promotes more systematic field management. 

Conclusion

Heat cannot be stopped, but its impact on the crop can be significantly reduced.

Farmers need to monitor weather forecasts in advance, conserve soil moisture, organise irrigation properly, and inspect plant condition every day.

The three main rules are:

1.  Prepare for heat before it arrives. 
2.  Give priority to crops during flowering and yield formation. 
3.  The right amount of water at the right time is more important than simply applying more water. 

With the UFarmer Agro Calendar, farmers can plan daily tasks, receive weather-based recommendations, and continuously monitor changes in the field.

Protecting the harvest does not begin after a problem appears. It begins with recognising the risk early and taking action at the right time.