Maize-bean cropping tipped to see huge growth in Germany
© MGA More German growers are companion-cropping maize with beans to address astronomical ammonium nitrate and protein costs, saying the dry matter and protein performance of the resulting silage outweighs the energy hit.
Maize-bean acreage in Germany increased from virtually nothing in 2018 to cover 30,000ha (74,000 acres) last year.
See also: Why a Dorset farmer is undersowing maize with field beans
Heike Molenaar, research and development leader at bean and pea seed house Van Waveren, predicts maize and beans will cover 4.25% (about 500,000ha or 1.23m acres) of Germany’s arable land by 2028.
She pointed to German research in 2020 and 2022 showing that maize-bean silage beat maize alone on protein and calcium, and ensiled well.
However, it was slightly lower in energy at 7MJ/kg net energy lactation level (methane conversion factor), compared with 7.2MJ/kg for maize alone (see table).
Comparison of maize silage and maize-bean silage |
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|
Analysis |
Maize silage |
Maize-bean silage |
|
Crude protein (g/kg) |
72 |
81 |
|
NXP g/kg YM (available to the duodenum) |
138 |
139 |
|
Net energy lactation MJ/kg YM |
7.2 |
7 |
|
Calcium (g/kg dry matter) |
2 |
3.5 |
|
pH |
3.7 |
3.6 |
|
Source: Jilg et al, 2020. Note: YM = Methane conversion factor |
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Market necessity
Dr Molenaar told Farmers Weekly that high soy and ammonium nitrate values had forced a change at farm level, with dairies seeing the merits of a legume.
“It’s not just the dairies,” she said. “The farms growing for biogas plants are using beans too because they are so convinced with the benefits of the system.”
She said the technique was a step towards the old method of growing the “three sisters” – maize, beans and pumpkins – together in the same field.
German fertiliser market
Latest market intelligence from the third quarter of 2022 showed the following trends:
- Nitrogen fertiliser sales fell 18% to 238,000t
- Phosphate fertilisers have halved (–50.6%) to 14,000t
- Sales of calcium fertiliser were unchanged (–0.1%)
Source: Desastis
Low-input success
Peer-reviewed trials found that maize-bean yields were equal to and occasionally beat maize yields in a high-input (165kg N/ha) setting, and consistently outperformed maize-only in low-input (85kgN/ha) conditions (see graph).
Dr Molenaar said estimates of the nitrogen fixation rate of the bean as a legume were 20-40kg N/ha, with different varieties potentially fixing different amounts. However, more research was needed.
Why German farmers like maize and beans
Dr Molenaar told Farmers Weekly why external factors were encouraging the practice to take hold.
- Subsidy payments are available for crop diversity
- Arla has started paying a milk price bonus to farms cutting the amount of mineral nitrogen used.
She summarised the other agronomic and nutrition benefits of growing maize and beans:
- 20-40kg N/ha is fixed by the beans
- Balances a high-energy maize crop with home-grown protein in the beans
- Natural weed control
- Helps decrease soil erosion and increase ground cover
- Plant diversity helps soil structure due to different rooting depths
- It is seen as an additional crop to maize in the rotation, adding flexibility and productivity.
What works in Germany
- Drill date 15 May is standard advice as the late continental frost (known as the “iceman”) can affect germination in late April and early May. Soil temperatures of 12C are needed for the bean. Early genotypes have been used and drilled as early as 20 April with good results in favourable conditions.
- Seed size Maize and bean seeds are sold pre-mixed, are similar sizes and can be sown together.
- Drill depth 6cm is a workable compromise between bird predation and a warm enough soil temperature to allow germination. In practice, farms drill at 2-8cm.
- Herbicides A pendimethalin or pendimethalin/dimethenamid-p combination is an option to use for both crops for pre-emergence control. Care should be taken when using herbicides that suit both crops. Geoxx (RAGT) is the only cycloxydim-resistant maize variety, allowing for further herbicide treatment in post-emergence.
- Bird tactics Some farming communities have commited to drill their maize and beans all together on the same day, so the crop grows as one and the birds are shared out across the district. This stops bird populations attacking one farm at a time as different farms drill and crops germinate.
- Density Beans are drilled at a rate of five seeds/sq m to ensure four plants/sq m, and at a ratio of 8:4 maize to bean seeds
- Maize varieties Mid-early varieties generally work best for German growers, such as Benedictio and Figaro (KWS); Haiko (Agromais); Geoxx (RAGT); Farmurmel (Farmsaat) and LG32257 and LG (Limagrain).
- Strong maize Strong, sturdy varieties tolerant to lodging and with strong roots are required as the bean plants grow up them like scaffolding. A biomass yield of 200t/ha can be grown.
- Bean varieties Late-maturing varieties tend to work well. Beans naturally contain lectin, which can cause bad diarrhoea and even kill animals. Selecting beans with low phasin content helps manage this risk.
- Harvesting Beans can produce a large biomass cover. Rape cutters and scissor cutters on harvesting equipment can help gather and cut the crop. Harvested is at the optimal time for maize.
Maize-bean cropping in the UK
Growing beans with maize brings the same benefits as it does in Germany, but the UK has some specific challenges, according to MGA agronomist Jon Myhill.
He said the companion-cropping aspect ticked a box for the Sustainable Farming Incentive (SFI), but there were three big obstacles for UK growers:
- No post-emergence herbicide There is no product available in the UK to control post-emergence weeds that is safe for both maize and beans. With maize being a minority crop anyway, it is unlikely that a licence will be issued to get UK growers parity with German farmers. The MGA is engaged in lobbying the government to change this.
- Seed mixing German growers buy pre-mixed seed in the same bag. UK farmers must source two lots of seed, often leading to drilling maize first, then beans. Double drilling increases compaction risk, time spent and diesel used, and risks moisture loss.
- Temperature challenge of beans Waiting for soil temperatures to be at 12C for bean germination could cost four weeks in the UK. Maize needs 8C, so that by May, the farm could be facing dry conditions that will limit the growth of the beans.
Mr Myhill said UK farmers were also trying to lower nitrogen inputs, with some cow/poultry manure systems cutting out synthetic nitrogen completely on maize-only crops. He added:
- About 70% of the nitrogen maize needs is for the pre-tassling and tassling period in July, which can be accessed largely from mineralised forms of nitrogen in the soil
- Farm reports and trials show no yield loss from dropping nitrogen rates from 150kg N/ha to 120kg N/ha
- Many farms now manage with 50-100kg N/ha in total (synthetic and manure) and some with no synthetic N at all.