Today, we are going to look at how to calculate seed yields. This information will help you set your prices and will be useful in crop planning. We will look at
- Using your harvest data to calculate yield
- Consulting (and interpreting) reference material for yield data
This post is one in a series on seed economics that begins here. Quick Review of previous posts:
- Seed profitability can be evaluated as $/bedft.
- Small scale growers should average $2.50/bedft to $5.00/bedft
- Profit in space is calculated by : Seed yield (g/bedft) x seed price ($/g) = $/bedft
A warning – I mix and match metric weights and evil imperial distances with reckless abandon. Take heed …
Calculate yield from harvest data
This is done after you have harvested a seed crop. Weigh your total seed harvest and divide that amount by the area in which it was grown.
- Let’s say I grew 100bedft of Tatsoi and harvested 2.5kg.
- My yield would be: 2500g / 100bedft = 25g/bedft
- Columns F, G and H are the relevant columns to calculate yield.
- I keep track of rows/bed and inrow spacing to compare what happens when these variables change. (I posted on plant spacing and yield here.)
- The number of plants is important when considering whether your plant population size is adequate.
As you grow a variety to seed multiple times, you will discover the yield range you can expect. Here are some yield ranges we have measured on our farm:
*Tomatoes sometimes grown 2 rows/bed to augment number of plants in population.
**These lettuce yields are much lower than what growers in better climates can get.
Consult Reference Materials for Yield Data
These two books have yield information for most seed crops and some varieties:
- Connolly, Bryan. The Wisdom of Plant Heritage: Organic Seed Production and Saving. NOFA. 2004
- Patrick Steiner, Small-Scale Organic Seed Production. Farm Folk City Folk.
You’ll quickly notice that these yields are not presented as g/bedft. You’ll have to convert the yields before you can use them with the equations I have provided. This isn’t always easy:
1. If the yield is in weight/acre then convert to g/bedft similar to what was done with $/acre here)
- Tatsoi in Brian Connolly’s book: Brassica Rapas are 1200-2400 lbs/acre
- 1200lbs/acre x 454g/lb ÷ 28 beds/acre ÷ 300 bedft/bed = 65 g/bedft
2. If the yield is in rowft (or rft) then you have to assume how many rows/bed the grower planted:
- Weight (g) x Rows/Bed ÷ Rowft = g/bedft
- Tatsoi in Patrick Steiner’s book: 25 lbs for 1500 rowft
- Assuming 3 rows/bed: 25 lbs x 454g/lb x 3 rows/bed ÷ 1500 = 23 g/bedft
3. If the yield is in # of plants, you will need to assume rows/bed and inrow spacing
- Weight (g) x rows/bed ÷ inrow spacing (rowft/plant) ÷ plants = g/bedft
- Mustard in Patrick Steiner’s book: 1lb for 40 plants
- Assume 3 rows/bed and 1ft per plant: 1 lb x 454g/lb x 3 rows/bed ÷ 1 rowft/plant ÷ 40 plants = 34 g/bedft
4. If the yield is in the number of fruit (melons, squash, … ) … well this one I will let you work out yourself.
Using Yield Data
- Remember data from reference materials is not from your farm.
- Yield varies from crop to crop, variety to variety, farm to farm, and season to season.
- When there is a range of yield data, use the lower values. If you harvest more than this, you can revise your prices and future planning yields .
- Until you are familiar with a crop and what you can expect it to yield, don’t overcommit yourself. Grow small amounts at first and increase gradually.
Next, we’ll look at setting prices.