A herbage test is a cost-effective way to find out the nutritional value of your pasture and crops so you know what your livestock are eating.
Do you soil test? If you do, then you already practice smart nutrient management by only applying fertiliser based on what your soil actually needs.
However, a soil test is only part of the picture. While it tells you about the nutrients available in the soil, it can’t tell you if the plants that grow there are actually taking them up.
That’s a problem because you still might be under- or over-applying fertiliser leading to plant deficiencies, or environmental (and economic) wastage. And if you don’t know the nutritional value of your pasture, you don’t really know what your livestock are eating.
However, getting a herbage test along with a soil test is a simple way to get a fuller picture.
Herbage tests aren’t new
Although we don’t currently herbage test as much as we soil test, herbage testing is not a new practice. For well over a century, scientists have been measuring pasture quality. Nowadays, herbage tests can report on a wide range of nutrient levels for mixed pasture, clover, and forage crops like lucerne, maize and turnips. Because plants may not show visible symptoms until it’s too late, testing regularly is good practice.
Herbage tests tell us a lot
Herbage tests analyse plant tissues for nutrient deficiencies, toxicities, and imbalances that can affect plant growth and livestock health. They excel at identifying deficencies of trace elements such as copper, selenium, cobalt, iodine, and sodium. This is because, as stated before, what can be measured in the soil does not directly relate to what plants absorb.
Two other trace elements successfully measured by herbage tests are boron and molybdenum. These traces are required by the rhizobial bacteria in legumes like clover to fix nitrogen. So if your clover and mixed pasture isn’t thriving, testing the clover is well worth it.
Apart from trace elements, herbage tests can clarify what is happening with major nutrients like nitrogen and sulphur. Because nitrogen is mobile in the soil (it moves through quickly), it is difficult to get a precise picture on any given day of how much is available to plants. For sulphur, it’s more about the accuracy of tests to measure what is available and what is stored in the soil. So measuring the actual levels of nutrients in the herbage helps sort these kinds of issues out.
Some labs have extra tests that measure chloride and crude protein levels of the pasture sampled along with its digestibility and metabolisable energy level. Forage crops can be measured for feed quality in terms of soluble sugars, starch, and crude fats.
So if this information is so useful, why don’t we herbage test more often?
Herbage tests aren’t costly
If you’ve wondered about herbage testing but you’re concerned about the added expense, you needn’t be.
Some fertiliser companies offer sampling services at no cost, so you only pay for the lab analysis. A good basic herbage test, analysed specifically for NZ conditions in a NZ laboratory, costs around $175.00 + GST, so it’s relatively inexpensive when compared with the information you get.
Herbage sampling is simple
Since the best time to herbage test is in early spring and autumn, you might be thinking that a herbage test is an extra demand on your time which you just don’t need.
However, your company field rep, trained in lab protocol, can collect the samples for you at the same time they soil test. So herbage testing needn’t be an extra job.
Herbage tests add value
Of course, getting the sampling done is just the first step. You need to interpret the results. Once again, this is where your local field rep can help. They will explain the results and more importantly, work out how the findings can be integrated with your soil test and your own visual assessment of what is happening on your farm. This means you get the best possible value from your fertiliser spend.
So get your local field rep to take herbage samples when they’re out there collecting soil samples and find out what your cows are really eating!
This article was published in the Coast & Country News.
