Grams Per Day: Determining Cannabis Yield Success by Weight
Whether you’re a small-time home grower or large producer, evaluating crop performance affects critical decision making when it comes to the bottom line. But how does one account for flowering time and weight yielded to obtain a value for crop output? Ben Burkhardt shines some light on how he devised an analysis of true yield results.
The key metric in cannabis cultivation is yield of dried flowers and it is the primary focus for every gardener regardless of whether they are growing boutique, small-batch artisan cannabis, or large-batch, low-cost flowers. A crop’s output largely dictates the cost to grow it, which is to say that a large yield typically trumps the other variables within a cost of goods analysis.
One would use this data analysis process to determine, for example, if a particular costly supplement is worth it, or what the return on investment might be on a state-of-the-art lighting technology, or whether a particular genotype (clone) might be suitable for increased production in the garden.
The Problem with Flowers per 1,000-W Flowering Light
For years cannabis cultivators would speak of their yields in terms of how many pounds or kilos they produced of dried, processed flowers per 1,000-W flowering light. A good crop might have led the happy gardener to say, “I got two pounds per light!” Although this method of measuring a batch’s (or crop’s) result does give some indication of what was achieved, it does not account for the wide window of different genetics’ flowering times.
While the right cut of Sweet Tooth No. 3 might finish in 42 days of flowering, a Super Silver Haze may take as long as 84 days, doubling the flowering time, thus it would have to yield double the dried grams per crop as the Sweet Tooth to yield the same when accounting for the time that the space was used to grow the batch.
Measuring Cannabis Yield Using Grams Per Day Average
In order to account for both the flowering time and the weight yielded from a particular batch, I developed a simple and useful system of data analysis of true yield results and trends. First, the number of 1,000-W lights used in the batch is determined. Then the total grams of dried manicured flowers and the days of flowering time are assessed. The equation is as follows: Yield in grams ÷ number of lights ÷ days in flower = GPD average.
Here’s an example: 1,000 grams yielded ÷ 1 light ÷ 70 days in flower = 14.29. So this single light’s crop had a gram per day (GPD) average of 14.29. No matter how large or small a crop is, it can be measured as such, allowing an equal playing field of crop analysis irrespective of crop size or time it takes to flower particular genotypes. Here’s another example from a larger batch: 58,453 grams yielded ÷ 75 lights ÷ 67 days in flower = equals 11.63 grams per day.
Upon examination, most batches yield between six and 16 grams per day. Anything below is essentially crop failure, anything above is phenomenal. I consider any garden operating at 10 or above acceptable, with 12 as a target. At that point there is potential to increase yield through tweaks to the environment, nutrient regimens and genotype (strain or cutting) selection.
The GPD model can be used to assess anything from the yields of a specific time period from a specific section of the garden, to an individual gardener’s effectiveness, or to assess the profitability of different genotypes from a batch of seeds.
It can be used to compare facilities, finely adjust strain-specific nutrient regimens, or even to determine the ideal temperature and humidity levels for different genetics. As the long as the data gathered is accurate, it can be the best tool to maximize a garden’s performance, which is the ultimate engine of profitability.
An Effective Model for Monitoring Cannabis Yields
The GPD yield analysis model is the most effective method to monitor yield trends in your garden, whether you operate with a single light in a closet or manage a million watts. GDP provides clarity to the decisions that impact the bottom line on a daily basis. As the cultivation industry becomes more sophisticated, high level operators will need to use tools like the GPD yield analysis model to inform critical decisions.