Diversity of plant families is key: When considering seed mixes, ensuring a diversity of plant ‘functional groups’ or ‘families’ is critical.²¹Species that share morphological, phenological, and physiological traits, such as in the case of plant families) are more important than total species diversity. See research from the Jena Experiment https://the-jena-experiment.de/ While some farmers use a set number of plant families, others recommend a range (e.g. 4 to 6 different families). Plant families are often selected for specific desired characteristics (e.g. medicinal properties for livestock, breaking down hard soil pans, or including certain root exudates that can facilitate phosphorus availability) and to bring in diverse and complementary root systems. Different plant families can also be used for summer or winter planting depending on the farm context (e.g. in low rainfall areas, some farmers only sow summer mixes when soil moisture is adequate and terminate the crop before peak flowering to conserve soil moisture). Seed mixes can be sourced from a commercial supplier tailored to your needs and season, or you can source your own seed and start with a smaller mix of what’s locally available. Depending on their context, enterprise mix, rotation goals and end use (e.g. cash crop or cover crop), many farmers choose to begin with annuals.

Choose plants that are right for your context and aims: When choosing plant family combinations and species, start by investigating the issues and constraints that are preventing you from achieving your goals. What are the current limitations to your soil health? Think about soil structure, biology and nutrients. For example, do you have compaction, high aluminium levels or little signs of soil life? Choose plants that are likely to help you address those constraints. Also think about plants that would do well in your environment. Take into account what’s already in the paddock, and try to choose plants that complement what’s already there. In the case of weeds, it’s worth trialling beneficial plants from the same family as the dominant weed species in a bid to outcompete them while also fulfilling the ecological role of that weed. If the weed is doing well in your soil conditions, a more desirable plant from the same species may well thrive.  See Episode 7 of the Soils for Life podcast.

Choosing plant mixes can be complex and imprecise, and something that many farmers report getting better at over time with observation and monitoring. If unsure, go for diversity. It’s often advised to choose a mix of plants suited to your environment from a minimum of four different plant families, preferably six. Another way to create diversity is to choose plants that have different canopy heights and leaf structures to support greater photosynthetic capacity and biomass production within the crop (see Appendix 1, 2 and 3 for common annual plant families for different seasons). And make sure to consider whether annuals or perennials are right for your context (see Annuals and perennials section below).

Summer and winter mixes: Deciding whether to plant summer (also called warm season) or winter (cool season) mixes (or both) depends on your context. While multispecies crops can be more drought resilient than monoculture crops, you still need to consider soil moisture.

Rotations: Whether your multispecies crop is part of a set rotation or not depends on the function of the multispecies crop, your system and whether you need to be opportunistic with rainfall and soil moisture.

Like any other crop, multispecies cropping benefits from a good start, with timely planting for seasonal breaks and available moisture. When preparing a paddock, you might want to weigh up weed management options and nutritional and biological support. Other considerations include soil-to-seed contact, protection from wildlife, sufficient moisture, suitable temperature and pest/disease control.

Preparing your paddock: Two common approaches to weed management when preparing a paddock for a multispecies crop are mechanical (e.g. grazing, tillage, slashing, roller crimping) and chemical (e.g. application of a knock down herbicide prior to sowing).

Managing herbicide use: When using herbicide as part of their multispecies crop rotation, some farmers have found ways to use less or buffer its impact.

Seeding ratios and rates: Once you have chosen a mix of plant species, you need to figure out how much of each seed is required. Like many other aspects of multispecies cropping, this can depend on your context and may require some trial and error. Seeding rates of a species can vary, with Grant, Rob and Ian seeding at rates that range from 0.5 kg/ha to 21 kg/ha (see Tables 1, 2 and 3).

When it comes to seeding rates, less is often more to ensure plants aren’t overcrowded and can reach their optimum structure and physiology. Visualise what you want a square metre of your multispecies cover crop to look like (e.g. how dense do you want it? What kinds of plant dynamics?) and then work back to figure out your seeding rate. It is often a matter of trial and error to figure out what suits your context.

Seeding rates might need to be adjusted to the conditions, including climate, season and soil type. In dry conditions, many farmers have found high seeding rates can work better because the plants cool the soil down and work together to access moisture. For example, 30–40 kg/ha might be suitable in dry conditions, whilst 10–15 kg/ha might be more suitable in wet, heavy clay soils. Latitude and corresponding climate can also affect seeding rates, with lower seeding rates being suitable in warmer climates. Seeding rates may need to change depending on how you are seeding, as well. For example, broadcasting may need a higher rate than direct drilling.

You may also need to consider ratios for each type of seed in the mix (e.g. agronomist Dr Ademir Caligari recommends chenopodiaceae make up less than 1% and brassicaceae less than 5% of your total mix if you’re trying to improve arbuscular mycorrhizal fungi) and the per hectare seeding rate for each seed type. 

Mixing the seed may be required depending on how you source your seed, your method of seeding and the seed mix (see Sowing the seed and equipment section below). Rob finds that using a chaser bin with scales is handy for weighing out each individual variety before putting it into one bin for mixing (60 tonne field bin). Knowing the weight is also useful for measuring out the volume of biological seed treatment required, if using. Rob saves most of his seed so this process is useful.

Biological seed treatments: Each of the example farmers treat their seed with a biological treatment and also apply nutrition when sowing.

Sowing the seed and equipment: When sowing a multispecies crop, you need to ensure your seeding equipment is capable of handling seeds of different sizes and sowing them at the depths required. For example, some farmers will utilise the small seed box of their seeder to plant the smaller seeds at surface level. Others will utilise the fertiliser box where appropriate, and some farmers simply mix all their seed together and utilise the planter box.

Foliar sprays are a common way to support the growth of a multispecies crop. Farmers might respond to visual cues from the crop (e.g. yellowing, purpling, stunting, leaf curl), use a brix meter to gauge plant health and photosynthesis or use plant tissue or sap testing to determine if and when they need to apply a nutrient or biostimulant foliar application.

When to harvest, utilise or terminate the crop really depends on how the season is going, your rainfall, whether you’re responding to an opportunistic market and the function of the multispecies crop (i.e. whether it is grazed, harvested for fodder or a cash crop or used purely as a cover crop to be mulched in).