farm soil

Soil testing at the new property - part 2

Jul 04, 2012by Farmer Liz

I have to apologise for being totally slack in updating you on our soil test results. It was a crazy time of ploughing, buying seed, buying organic fertiliser, spreading the seed and waiting for rain. I will also warn you in advance that I'm still not sure what to do with these test results, so this is more of an update post on what I know now, but I still have an awful lot to learn.

the oats have started to grow!

When we did soil testing at eight acres, it was to see what minerals were likely to be missing from the animals' diets so that we could supplement what they weren't getting naturally. In that case it was quite easy to analyse the results, and we didn't take any action to improve the soil as such. This time we wanted to know if our crops would grow and that made things more complicated.

After we did the initial tests on the Cheslyn Rise soil samples (see part 1), we fully intended to also test for dispersion and slaking but we didn't get around to it, if you're interested, I've explained more below. We sent the samples that we chose from part 1 to the APAL lab and we received the mineral analysis results in a couple of weeks.

(Dispersion and slaking describes the "structural stability of soil aggregates upon wetting". Slaking is when a soil aggregate falls apart as it is wet, whereas dispersion is the clay dissolving in the water itself. Both properties are undesirable as they lead to formation of a hard crust on the soil surface and poor transport of water and oxygen in the soil due to blocked pores. As far as I can tell, both properties can be improved by sufficient organic matter, and are not helped by excessive soil cultivation.)

APAL provides the results in a table and graphical format, with a very good information sheet to explain what everything means. If you pay extra they will work out quantities of minerals to spread on your land per hectare, but we didn't want to do that, so I only paid for the basic analysis.

When I looked at the results I thought they were pretty terrible, with the calcium and magnesium totally out of balance, and low potassium and phosphorous, however when I sent it away to a few organic fertiliser producers, they said it looked ok. I suppose that is compared to some of the really bad results that they've seen! One point to remember is be careful who you go to for advice. Someone at work told me that the local produce will analyse the samples for free. Great deal! But they don't give you the results, they just tell you how much fertiliser to buy. And even some organic fertiliser people may tell you the wrong thing, just to get you to buy more.

I wasn't overly very happy with the advice that we got in the end. The company just told us to use 1 tonne per 10 acres, which seemed to be their standard advice and not based on the soil tests or the needs of out proposed crop of oats. We were in a hurry to get the seeds in the ground, and the fertiliser was reasonably priced, so we thought it was better than nothing and would at least get us started. Now I want to know more about soil improvement, crop rotation, hay making, and methods for broadacre cropping. I know what works on a 10m2 garden, now how do I apply that to 25 acres of cultivation?? I'd love to just pile on the compost and mulch, but that's not practical. As soon as we know what we're doing, I'll write a more detailed post! We have a sample of a bio-active fertiliser spray, which should be very interesting.

I suppose the lesson is to know what you want to get out of a test before you start. If you're testing for minerals so you can supplement your animals' feed, the test is easy to interpret. Even if you wanted to find out what's missing from your garden soil, it wouldn't be too difficult to then buy and spread around the minerals that you needed. On a larger scale, the answer is not so simple, and I'm not convinced that all the organic fertiliser companies know what they're doing either! Now its time to find out for myself....