Mar 27, 2017

Stemilt compost program helps grow apples, cherries

The compost project at Stemilt was featured at the Tilth Conference in Wenatchee, Washinton. The compost facility is located in the center of the company’s farm, where the cultivation of apples and cherries primarily occurs.

The nutrient cycling process begins from the production of cherries and apples, then after harvest goes to sorting, packaging and marketing. There are a lot of fruits that do not conform to the specifications for marketing and are sorted and returned to the compost facilities for inclusion in the composting process. Compost ingredients, including sawdust, the remains of apples, cherries and a little gypsum are combined by mixing machines. The composting process depends on microorganisms to enhance decomposition.  Microorganisms require appropriate aeration, moisture, particle size, and a sufficient source of carbon and nitrogen. Pile oxygen content and temperature are maintained by stirring two to four times per week, depending on the temperature inside the piles.

Biological activity depends on the temperature; as low temperature slows down the microbial activity. Temperatures contributes to the destruction of weed seeds and disease organisms inside the heap.  The ideal temperature should be between 110° F to 160° F, depending on the number of days. It can maintain the temperature for several days before stirring is needed for more ventilation.

Dry manure is not effective in the decomposition of organic material in the compost pile, so moisture constitutes a fundamental and effective factor in the process. Water is added periodically during the stirring process by machines, and is monitored carefully to ensure over-watering does not occur. Excess water may lead to anaerobic conditions that slow down the decomposition process and could cause odor, so the balance between drought and excess moisture is required.

Disintegration of large particles of organic material can be difficult and take longer to degrade, so it is grated into small sized pieces that can be consumed by microbes. Chopping of organic materials is advantageous to convert the organic material into fertilizer.  It can be seen at the beginning of the fermentation process with the presence of large pieces of organic matter which is then turned into very small pieces through the grating process each time they are mixing organic materials.  The finished compost product is used to fertilize the company’s orchards and is also sold to other nearby farms.

— Adel Almesmari

Source: Washington State University CAHNRS