When is the best time to collect a soil sample for testing?

Timing does matter. The best time to collect a soil sample is after the previous crop is harvested and before you apply fertiliser or manure for the next crop, usually a few weeks before sowing. That way the report reflects the true status of your soil and you get the card in time to plan the next crop's fertiliser. Avoid sampling right after you have applied fertiliser, manure, lime or gypsum, the readings will be distorted, wait until the next cycle or several weeks later. Also avoid sampling when the field is very wet or freshly irrigated, slightly moist or dry soil is easier to sample and dry. Sampling well ahead of sowing also gives the lab time to test and return the card before you need to buy fertiliser. So the simple guide is, after harvest, before any fresh inputs, and with enough lead time before the next sowing. Plan it around your block's sampling drive if you are getting the free card.