Drought and local showers: what to do with irrigation?

After the weeks without precipitation came together from April, precipitation came in the last weeks of May. Locally, 50 millimeters fell in a single weekend, with the monthly sum still rising to 80 millimeters in the following days. A total of 40-50 millimeters is representative of most of the country.

Good news, because moisture has returned to the surface immediately after a period of drought. At least, for now. Is there going to be another period of irrigation?

Niek van Andel is a meteorologist and keeps a close eye on things. He warns against too much optimism: "There is still no question of a large water buffer and it is precisely on the surface that the moisture will be extracted immediately after a number of dry days", according to the meteorologist of AgroExact† "Depending on the temperature, 20 -30 millimeters can evaporate in a week - not to mention high summer conditions with a lot of sun. Crops may need moisture again sooner than expected, especially now that most crops still shallow rooting." Van Andel expects that sprinkling or other irrigation options will soon be looked at again. Certainly not an easy choice due to the fuel prices this year.

Not irrigating is of course an option. No irrigation costs in this case, but this will irrevocably be at the expense of yield. And certainly with the current prices, it can sometimes turn out well to grab a nice harvest and to irrigate it. But when is the right time to start again? With what amount? And when should I water again next time?

'Just more than enough' reel turns of 30 mm or more on a fixed schedule is still a tried and tested strategy, but not the most economical this year. Van Andel: "Every extra millimeter that washes away to deeper layers will not increase the yield, in fact, minerals wash out and with a bit of luck the ground closes so that the next natural rain or thunderstorm quickly creates large puddles on the land. rather than filling a gap." And of course: every millimeter more, costs more money.

In this case (a great desire to achieve a good yield, but at high prices for irrigation), the use of irrigation advice based on a soil moisture sensor is the ideal solution, according to Van Andel, who is also the founder of AgroExact† "We came out on top in the WUR test, both in terms of accuracy and the possibilities of the platform." The sensor measures the suction pressure of the soil every half hour, ie how hard a plant has to 'pull' to absorb moisture from the soil. If it is too high, the plant will fail to grow. The sensor measures this value in the root zone. The crop can be entered on the application, so that a message is sent when the values ​​increase from optimal (code green) to sub-optimal (code yellow) to critical (code red). The ideal window to start irrigation is between the sub-optimal conditions and the critical conditions (code orange). By filling in the depth of the root zone and the soil type, it also follows directly from the range of maximum amount that can be applied.

"During the development in 2018, 2019 and 2020, we gained a lot of experience in how the sensor is used in practice. We know from users that in practice they start irrigating earlier, but with smaller amounts. Because we focus on the root zone this often results in net fewer millimeters in order to still keep the sensor 'in the green.' Both literally on the field and the values ​​on the app."