Every Drop Is Money: The New Precision Irrigation Rules Everyone Needs to Know

Every farmer knows that irrigation is not just turning on the pump. If you water too little, the plant stops growing; if you water too much, you wash the fertilizers into the soil and accumulate unnecessary energy costs.

The key to balance lies in a number called Kc (the crop coefficient when watering). In 2026, the data for it is more accurate than ever. Here's what you need to know to water effectively.

1. One level, four different needs

The plant is not equally “thirsty” throughout its life. According to the latest guidelines, we should look at the field in four phases:

• Start (Initial):From sowing to 10% green cover. At this stage, the roots are shallow, and the bulk of the water is lost to evaporation from the earth itself.
• Growth (Development):The period when the leaves quickly increase in size. Here the thirst of the crop begins to grow sharply.
• Peak (Mid-season):The culture is in full force and covers the soil as much as possible. Then the needs are highest and any drought hits directly at the yield.
• Ripening (Late season):The plant prepares for harvest and naturally reduces water consumption.

2. How much do corn and sunflower “drink” exactly?

The new standards give updated odds for over 100 crops. The higher the Kc, the more water evaporates the plant relative to the standard grass:

• Corn (for grain):In its peak period, it has a coefficient 1.20. This means that it evaporates 20% more water than the reference area.
• Sunflower:A healthy and “thirsty” plant with a peak coefficient 1.15.
• Orchards:With apples and pears, things are specific — if you have fertilization between the rows, the water needs are much higher than if you keep the soil clean.

3. Why is the “Double Factor” important for your pocket?

In modern agriculture, we already divide water losses into two parts: Kc = Kcb + Ke.

• Kcb (Transpiration):This is the water that actually passes through the plant to make it grow.
• Ke (Evaporation):This is the water that is lost from the surface of the wet earth after rain or watering.

Why do you care about this?If you water with a pivot system or have frequent rainfall, the soil surface is often wet. If you do not account for evaporation from the ground (Ke) separately, you can easily be deceived and flood the levels, which only brings losses.

4. The weather outside changes the rules

Standard numbers from tables do not work the same everywhere. You need to adjust irrigation to your microclimate:

• IN hot areas with strong windand low humidity plants “sweat” much faster. There you need to water more than prescribed in the general tables.
• IN quieter and wetter areasneeds are lower and you can save a resource.

Source: FAO Irrigation and Drainage Paper No. 56, Revised Edition 2025.