The best time to irrigate farmland depends on various factors, including the crop type, soil type, weather conditions, and local climate. However, there are some general guidelines to consider:

1. Early Morning or Late Evening: It is often recommended to irrigate during the early morning or late evening when temperatures are cooler and evaporation rates are lower. This allows the water to penetrate the soil effectively and minimizes water loss through evaporation.

2. Avoid Midday Irrigation: Irrigating during the hottest part of the day, typically midday, should be avoided as the high temperatures and strong sunlight can cause excessive evaporation and water loss. It can also lead to increased stress on the plants.

3. Consider Plant Water Needs: Different crops have different water requirements, so it's crucial to consider the specific needs of the plants you are growing. Some crops may require more frequent irrigation, while others can tolerate drier conditions. Consult agricultural experts or reference materials specific to the crops you are cultivating for guidance.

4. Soil Moisture Monitoring: Regularly monitor the soil moisture levels to determine when irrigation is needed. This can be done through visual inspection, using soil moisture sensors, or employing techniques like the "feel and appearance" method, where the soil is assessed for dryness.

5. Water Conservation: While ensuring adequate water supply to the plants, it's important to practice water conservation techniques. This may involve using efficient irrigation methods such as drip irrigation or employing technologies that measure soil moisture and automatically adjust irrigation schedules.

Remember that local conditions and specific crop requirements play a significant role in determining the best irrigation practices. Consulting with agricultural extension services, local farmers, or agricultural experts familiar with your region can provide more precise recommendations based on your specific circumstances.