COMPOST
Photo 05: Damp rises from the straw.
Photo 06: Different qualities of straw in one load.
acts as a water and nitrogen buffer. But how can we ensure all those properties of straw are utilised to their full potential? The art of composting is found in some important details, including pre-wetting. Or, as we used to call it, the ‘flat windrow’ No one actually seems to know what this crucial process involves. People refer to it as a, yet to be opened, black box. But we do know that the micro-organisms must breakdown the waxy layer surrounding the straw blades. This layer protects the straw from moisture and mould while the cereal is growing. If we want to use cereal straw as a nutrient source for our mycelium, we must ensure the waxy layer is decomposed.
Micro-organisms
The micro-organisms are activated automa- tically when the straw is wettened (photo 05). The temperature will rise to approxima- tely 45 - 60 degrees Celsius. To promote good micro-organism activity - but above all to sustain it - three factors are important: • Nutrients: as the straw is the nutrient source, it is always present.
• Water: the straw must be wet, but not with free running water. It should feel wet, but you shouldn't see the water.
Schematic image of a microlife drop.
• Oxygen: sufficient oxygen must be present. So how do you check these three factors are accounted for? By measuring the tempera- ture in the straw. If the straw has a tempera- ture of 45 – 60 degrees Celsius, you can assume that the micro-organisms are hard at work. This can only be measured with a
34 PADDESTOELEN
long probe that reaches to the core of the straw bale. If the temperature is lower, something else is wrong. The problem is not the nutrients, but maybe too much or too lit- tle water, or oxygen. Too much water: Make sure that after wet- ting, the water can drain well from the straw. Do not apply water to the straw continuo- usly. Place the straw bales vertically, to allow water to drain from the bale more quickly. These are some ways to prevent excess water. Too little water is an increasingly common issue: Straw bales today are becoming hea- vier as they are baled under higher pressure. This higher density and compaction make it increasingly difficult for water to penetrate to the core of the bales. After two-four days, wet the bales again by dipping them, or wet them with plenty of water using a large slurry tank. After this treatment, the tempe- rature in the bales should start to rise again. Oxygen: If the straw bales are pre-wet out- doors, I don't often notice any problems with anaerobic patches in the straw. But when pre-wet is done indoors, this can be an issue, on some companies the bales are even aerated.
Assessing straw
Getting pre-wetting right is not difficult, but you have to assess the straw properly. With harder and drier straw (circled red in photo 06), it takes much longer before the straw is decomposed. For example, this straw has been cultivated and harvested under drier
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