Adding legumes to your crop rotation? Things you need to consider
With so much talk about sustainability in agriculture these days, the spotlight is back on legumes.
If you’re looking to add legumes to your crop rotation you no doubt have lots of questions. How do they work? What should we be looking for when choosing a species and what are the biggest traps? Nick Eyres, Elders Agronomist in the Mid-West region of WA answers all your questions and more.
Legumes are a critical part of the farming system and have been for the history of agriculture. The ability to ‘fix’ local atmospheric nitrogen (which makes up 79 per cent of our atmospheric gases) and put it either in the ground, in our animals mouths or in a grain bin has a magnitude of benefits for the system, and is mostly accepted as the ultimate in sustainability.
These days, high protein foods such as grain, meat, poultry or milk are in demand. The protein in all these products is made of Amino acids of which nitrogen is an element. That nitrogen must come from somewhere.
Before the days of synthesized nitrogen fertilisers (or even super phosphate) planting legumes was the most convenient and most popular way to get nitrogen on farm.
When growing legumes you need to be alert for chemical residues and nutrition in the soil.
Highly residual products always have a risk of carryover and some of the biggest offenders are our group B’s and lontrel. There are however, other residual products which can give sometimes randomly occurring responses 12 months down the track.
Beware if using strong residual products in your system.
It is incredibly important to have adequate long-term nutrition for all crop species. While they can be different between species, broadly speaking a good nutritional program provides good options.
Nutrition is often confused for nitrogen (N). While nitrogen is often the ‘squeaky wheel’ getting the attention, the whole package becomes increasingly critical when we start introducing legumes to the party. Given that legumes have to find their own N (arguable, as it’s the little guys in the root nodules doing this handy little trick for them – more on this in a tick) any kind of hindrance to energy production for either the plant or the bacterial colonies in the roots will significantly reduce N assimilation and hence availability to the plant, protein production, overall growth and rotational benefits.
A good example of this is vetch on sandplain, likely be very responsive potassium (K) applications, whereas something deep rooted like a serradella is more likely going to be phosphorus responsive due to its incredible root system able to find deep K.
Do adequate soil testing, know the paddock and get a good interpretation of the results for whichever species is being grown.
Know your limits
This applies to all forms of farming, but is particularly relevant when delving into new areas.
There are people out there with specific information for your local region. Find them, ask them questions and critically assess the fit for your system. Your local Elders branch is a great place to start.
Remember there are only so many places you can be at once. Focusing on more than one area brings distractions and increases the risk of a failure. Understand the limitations of your working capital, manpower and networks. Some gear is suitable for some things not others. It’s important to identify these before we set out to implement action, or the learning curve becomes very steep, very quickly.
Don’t reinvent the wheel
There are a huge range of legume species, all with their own attributes which we should be exploiting. For example, Narrow Leaf Lupins love acid sand, Chickpeas don’t.
Choose your legume rotation carefully, both species and in most instances, varieties, based on a variety of factors:
- rainfall zone
- pest species (insects, weeds, disease)
- paddock/rotational history
- soil types and tests (for legumes its worth testing P, K, CEC and ExCa as a minimum before you start)
- non-wetting characteristics.
Once you’ve determined what the most limiting constraints are, you can narrow down on species and systems that are worth trying based on individual species characteristics.
Making money from the crop
While growing protein is thrilling and improving soil condition is good, it won’t strictly pay your overheads. Here are a few ways the protein you’ve accumulated can be turned into cash:
- Harvest seed and sell as a high protein commodity or specialty product – if selling protein as a pulse, you can get more $/kg N by growing high value pulses over commodity pulses, even where gross margins may be a little out in total production.
- Grow meat and/or fibre through a well-managed grazing program – turning high protein pastures into meat and/or wool has a significant effect on the protein assimilation in the soil and produce and therefore on next year’s available N.
- Manage risk and put a value on cash flow – known as cover cropping, the practice is gaining momentum around the world. Trying to find the value to replace the lost income is the tricky bit with cover crops, and in particular legume cover crops, particularly when there are no sheep in the system to graze the country immediately afterwards. Knowing however, that you’ll have a crop worth harvesting next year has a different value to each individual.
Implement your plan
Once the plan is worked out, preferably before the day of seeding, it’s important to do your best to follow it. Following a plan (where appropriate) makes it much easier to alter and improve it in future years.
Implementation is critical, as with any cropping species. Often, it’s on the worst section of our farm that we want to plant something that we can ignore, yet will grow like a weed because we can’t grow any other crops there.
If you have such country, it is even more important to give it a chance to perform. If something fails when it had the best chance, then it’s still a clear outcome.