Some growers have observed that adding phosphate fertiliser at planting time seems to improve the growth of onions, especially at early stages.
To test this, we’ve set up a small trial with our Ballance AgriNutrients partners. In each of 5 small plots, we placed the equivalent of 250 kg/ha of triple superphosphate 50 mm below and beside the onion seed.
We’ll track development of the plants in the treated plots and in corresponding neighbouring plots to see if there is a significant difference.
Why five plots?
Having replicated plots means we can better understand if any differences are “real” or “due to chance”. We know there is always variation in any paddock in any crop, so how can we tell if our treatment (added P) caused any difference we see?
In crude terms: If the difference between our “Plus-P” plots and our “No-P” plots is greater than the difference between the different “Plus-P” plots, we can assume the difference is real.
Generally four replicated plots would be OK for a first look at something like this. It lets us run an ANOVA test to check statistical differences. We put five plots in, partly to cover the chance of one being damaged by field operations including turning our irrigator.
Check out the LandWISE/FAR “On-Farm Trial Guide” series for explanations and templates if you want to do a trial that you can really learn from. It includes a downloadable spreadsheet that will do your ANOVA stats and interpret the result for you.