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(3) Bulk piles are woefully inefficient due to poor aeration and generally high amounts of anaerobic conditions.


fill and that requires an increasing percentage of area to extend the process. Indeed I have worked with farms that were doomed to limited productivity due to insufficient area necessary to process a year’s worth of tough straw.


Composting systems Beyond the area/space factor, the dynamic that affects the amount of time required to compost various types of straw is process. By process I mean what compos- ting systems are used to compost the raw materials within any length of time. The options in descending order of efficiency generally are bunkers, conventional ricks, bulk piles, and prewet/dipped bales. Bunkers (1) are the most efficient composting system, since they compost the straw the quickest per unit time. Why? Because of the uniformly high temperatures achieved through a high percentage of the mass. Ricks (2) pro- vide less decomposition per day than bunkers because there is more exposure to the ambient environment and more anaerobic area. Aerated ricks can improve the efficiency of ricks if managed correctly. Next bulk piles, (3) whether in ‘A’ piles or flat heaps, provide some composting benefit but are woefully inefficient due to poor aeration and generally high amounts of anaerobic conditions. Finally bale prewet or dip (4) can be considered more a preparation period whose main purposes are to provide initial moisture and to develop a microflora to drive the rest of the process.


Processing raw materials Now is where the art comes in, orchestrating the com- posting process over the time necessary to cure the raw materials into a productive Agaricus growth me- dium. First it must be understood that each mushroom farm may not have all the systems available mentioned above. It is therefore up to the manager to use what is available to get the job done properly. Some randomly devised examples follow: • If the straw is weathered, partially dewaxed, and chaffy (short) a few days in prewet, a couple days in bulk piles along with a 2 or 3 bunker periods (of 3 to 4 days duration) might be sufficient (2+2+8).


• Moderate raw material might take 4-5 days in bulk


(4) Bale prewet or dip can be considered more a preparation period which main purpose is to provide initial moisture and to develop a microflora to drive the rest of the process.


(5) Very tough, waxy straw.


piles and then 3 X 3-day bunker periods. Alter- natively 10 to 13 days in ricks (if it didn’t shorten the straw too much) or a combination of ricks and bunkers. (4+9 or 4+12).


• Very tough, waxy straw (5) can take forever! I recall dealing with desert cultivated irrigated straw one year when 4 weeks in a combination of prewet, bulk piles, and ricks were required. However, if more efficient bunkers were available the time could have been cut to 3 weeks or less. (6+14 or 7+18).


Environmental factors complicate the issue even further. Areas of high environmental sensitivity due to odor or other factors may require the entire compos- ting area to be under cover, aerated, and even filter exhaust. In these cases economics and technology take an even greater part in the composter’s options. In a case such as this space/area (additional time) can be prohibitively expensive, however these examples are outside the scope of this paper. The point is the com- posting process and time can be manipulated to match any straw being composted provided there is sufficient space and systems.


Delaying straw use Another strategy of dealing with tough waxy straw is to ‘cheat the system’. That is to contract for more straw than the annual requirement to delay usage until well after harvest. In this case newly harvested straw can sit and weather for months before integration into the composting process, therefore requiring less on site composting time than if it was used directly out of the field. It is not uncommon to find compost operations contracting enough straw so that freshly harvested straw can sit for 2 to 6 months before use, although there is risk involved. What happens if the straw is low quality that year? In reality making composting is a very easy pro- cess - it’s making suitable and productive Agaricus mushroom compost that is difficult. Here we review how a good composter may make required adjustments for variable straw, which is just one part of the ‘art of composting’. Choose your own examples.◗


Most photos courtesy of J-M Farms, Oklahoma, USA. Others from Adelaide Mushrooms, Australia.


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