‘molly’ isn’t needed in large amounts, but legumes like clover need it to help fix nitrogen.
6YouAnimals don’t put nutrients back into the soil evenly. This is why your pasture will be different heights, as there will always be more growth above a dung or urine patch.
But a healthy pasture will be composed of a constant amount of clover right through the pasture, and the colour should be a uniform dark green. When Doug goes onto a farm as a consultant, he groups paddocks by their similarities, based on topography (eg steep, flat) and other similarities, then marks out soil test sites so he can recheck the same places every year. While he’s testing the different areas, he’s also making a note of the quality of the clover using a clover-only herbage test where it is struggling (not near urine or dung patches). The two combined give a much better story of what is going on in the soil than just a soil test.
Doug says having a monitoring programme of some kind like annual soil tests, and clover leaf and mixed herbage tests, is a very small cost in relation to an annual fertiliser spend, but can make a huge difference to the health of livestock, soil fertility, and the profitability of the land. When you do a soil test there are all sorts of things you can choose to test for: • ph • phosphorus • potassium • calcium • magnesium • sodium • sulphate sulphur
But Dr Edmeades says one of the most important to include is the test for organic sulphur, the major test for measuring long-term sulphur requirements (as it makes up 95% of sulphur in soil). Instead people tend to tick the box for available sulphate sulphur which varies hugely and only represents around 5% of what’s immediately available to plants. Reactive phosphate rock (RPR) was introduced in the late 1980s as a cheap (by 30% per tonne) and effective alternative to soluble fertilisers like super phosphate. The theory was, it takes longer to break
When Doug is developing a nutrient programme for a farm, he creates what he calls an economic optimisation plan and it’s always based on how much phosphate a property requires as it’s the most expensive ingredient (about $3/ kg). He checks the Olsen P range, and then brings all the other nutrients up to the level where they’re not limiting the expression of the phosphate. Molybdenum (pronounced mol-lib-denum) is a trace element and isn’t needed in large amounts, but legumes like clover need it to help break down nitrogen gas into protein as part of their nitrogenfixing abilities.
But put too much on and it prevents utilisation of copper in livestock. When molybdenum was first discovered, farmers put on a little, got a great response and so quickly increased the amounts they used. When they got copper deficiencies, they then went back too far the other way and stopped using it. Doug says it’s only now that farmers are rebounding back to the correct use of ‘molly’.
The best way to test for molybdenum is to take clover and mixed herbage samples.