How do we encourage crops to make a final sprint?

How did it stand the past few weeks?
"In April and May, we had incredibly dry weeks. This means that the leaf wet period was virtually zero, which meant that fungal pressure was low and treatments against these pathogens were virtually unnecessary. As a result, we were still spared problems with phytophthora and downy mildew. If you then look at weed control and insecticide application, that was a challenge. In general, it was far too dry for these agents to work properly. Soil herbicides actually needed irrigation to do their job properly. For insecticides, there was too much radiation during the day, causing the active ingredients to break down immediately."

And how did this affect heat stress?
"Potatoes often still had it under control in the month of May because the plants did not have a lot of foliage yet and evaporation was limited. Beets and onions did have a bit more difficulty. Onions, of course, have a less extensive root system and then they quickly find themselves with moisture deficiency."

Are there techniques available to reduce heat stress?
"One system that works very well is the use of a mulch of chopped plant residues between the rows, such as green manures, which reduces moisture loss from the soil. In Germany, this is being used more and more. Non-inversion tillage can also already produce partly the same effect for soil water management. This obviously requires a different way of working, but I think it could fit in the Netherlands, especially if you look to the future. There is less and less water available for irrigation. Limiting evaporation could be a solution. In addition, this way of working keeps weed pressure low, because where there is organic material, weeds do not germinate."

What can we do now?
"If it's dry and you can irrigate, do it. Get things ready. In addition, make sure you keep crops disease-free, whether the weather is dry or wet. Decision support systems contribute to that. After all, it may seem like a dry day, but the nights have higher humidity than you think. Then mold pressure is still high. In this case, it can be interesting to monitor the weather by means of a weather station. Using currently measured weather data, you then get an overview of the infection pressure of various plant diseases. Then in an app you can read the ideal spray timing and compare different treatment options, including how effective these options are. This is a good way to keep a finger on the pulse and not be surprised by a sudden high infection pressure. After all, timely spraying, weed control and crop irrigation are important to get crops through the latter part of the growing season in the best possible way."

This article appears in the Akkerbouwkrant - Innovation & Ondernemen, a publication of www.akkerbouwbedrijf.nl