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Today we are going to talk about using spent coffee grounds in your garden and what benefits are. Lab Report: http://www.albertaurbangarden.ca/wp-content/uploads/2015/02/150208_AlbertaUrbanGardenCertificateofAnalysis-RevistedReport.pdf Programs like Starbucks grounds for your garden provide spent coffee grounds for use in your garden at no cost. These grounds can provide a number of benefits to your garden that help build your soil and feed your plants. Spent coffee grounds are high in nitrogen and also have phosphorus, potassium and a number of other trace elements considered to be beneficial or essential for plant growth. My local Starbucks was kind enough to provide samples of used and unused coffee grounds for analysis to take down to Maxxam Analytics.  These samples will tell us the pH, the immediately available N-P-K and the total available and unavailable trace elements. A common concern about using coffee grounds in the garden is that they will change the pH of the soil. Fast changes in pH can negatively impact the nutrient cycle in your soil impeding plants ability to absorb nutrients. The pH of the unused coffee grounds was reported at 5.88 and the used grounds at 5.4. These numbers fall on the lower end of the optimal range for plant growth according to Dr. Perry with the University of Vermont. [1] If used in the creation of compost over time the acid will become neutralized as the material breaks down. [5] When used as mulch generally you are applying small enough quantities that any transfer of acidity to the soil will be neutralized by the soils natural buffering capacity. [7] Now that we know using coffee grounds in the garden don’t change the pH let’s talk about the use of used coffee grounds to add nutrients to the soil. In order to compare used coffee grounds to commercial products and other samples I have run we will present the results in N-P-K and leave the trace elements in mg/kg. The lab results represent what is immediately available to the plants. The lab uses a weak acid wash to replicate soil conditions and isolate the available organic nitrogen, phosphorus and potassium. The N-P-K of used coffee grounds is: 0.00083 -- 0.2016 -- 0.771 And the N-P-K of unused coffee grounds is: 0.00036 -- 0.3208 -- 2.41 References: Optimal pH for plant growth: http://pss.uvm.edu/ppp/pubs/oh34.htm Nitrogen Cycle: http://en.wikipedia.org/wiki/Nitrogen_cycle Atomic mass: http://en.wikipedia.org/wiki/Relative_atomic_mass The Chemical Composition of exhausted coffee waste: http://webcache.googleusercontent.com/search?q=cache:0ChFgQV_POYJ:www.researchgate.net/publication/257418689_The_chemical_composition_of_exhausted_coffee_waste/links/00b495253eabc2623c000000.pdf+&cd=1&hl=en&ct=clnk&gl=ca The evaluation of coffee grounds in compost: http://www.researchgate.net/publication/255578345_Maturity_Indices_as_an_Index_to_Evaluate_the_Quality_of_Compost_of_Coffee_Waste_Blended_with_Other_Organic_Wastes Unverified Analysis of Grounds for your Garden Results http://www.sunset.com/garden/earth-friendly/starbucks-coffee-compost-test Do Coffee Grounds Acidify your Soil? http://www.gardenmyths.com/coffee-grounds-acidifies-soil/ Conversion Calculation https://en.wikipedia.org/wiki/Labeling_of_fertilizer#Converting_nutrient_analysis_to_composition thumbnail Credit: http://www.brucesbrew.com/coffee-storage.html#axzz3R4wI6QbT