How often has a hobby farm sprung up where there was once a dairy? An old market garden? Or even an orchard – long neglected. The legacy of scattered out-buildings and established trees remind us of days gone. But what about the soil?
Well, the history of a farm can give us a few hints about the condition of the soil, as can a few other tell tale signs. It might be worth getting to know a few local old timers around the place who can fill you in on what happened there in past generations. Sometimes these farms have had years of neglect, where they were agisted and overgrazed. Heavy hoofs have compacted the ground and opportunistic caretakers have taken a few cuts of hay.
Hay paddocks, old dairy day paddocks and other blocks used for intensive agriculture can often have nutrient deficiencies. Repeatedly cultivated soils can have structural problems and are often low in organic matter. These nutrient deficiencies can manifest themselves in many ways as I will discuss later, but it’s often a case of removing nutrients, usually in the form of meat, milk and plant material, and not replacing it. Even when there is a history of fertiliser application, often it was done “the way Dad did it”, with key nutrients being overlooked.
One nutrient that often gets overlooked on these blocks is potassium (K). This is probably because deficiencies may not appear if it is in combination with a phosphorous (P) or nitrogen (N) deficiency. But potassium is very important for plant growth and it also helps legumes (clover and lucerne) fix nitrogen to the soil. Potassium deficiencies can often be mistaken for nitrogen deficiencies, with grasses appearing pale and yellowing, with retarded growth. Weeds are generally abundant, and lush green growth is observed where stock has urinated.
If you think your pasture could be potassium deficient, now is a good time to test it. Pastures need potassium the most when they are actively growing (i.e. spring). A test strip is a useful tool in evaluating this. Simply buy a garden sized (1kg) bag of muriate of potash, and throw it out in a strip based on a 125kg/ ha. application rate. (That’s a bag to the acre, in the old money). My maths says a strip 50cm wide and 2.5m long would give the right area for 1kg.
Keep your strip away from troughs and fences (where nutrients tend to accumulate) and pick an area that you believe best represents the average of the paddock. Steer clear of urine patches too, if they are evident. If you see a result in the ensuing weeks and months, you might consider a one-off application. A Silvan super spreader hooked up behind the trusty SOTA Kubota would fit the bill here.
A bit of advice, before you engage the PTO – muriate of potash can burn establishing seedlings, so if you are renovating your pastures, apply well before or after you sow. High applications of potassium can increase susceptibility of stock to grass tetany and other metabolic disorders in some circumstances. For those who are organically inclined, poultry manure is an excellent source of potassium, as well as phosphorous, sulphur and organic matter. Application rates are usually a lot higher. Stock may be exposed to botulism if not removed from the paddock.
One of the best ways to get rid of weeds is an aggressive pasture. Having a soil in good condition provides the best medium for pasture plants to grow vigorously and outcompete undesirable plants. Combined with sustainable stocking rates it is possible to have a pasture that compliments the rest of your farm’s improvements.