Soybean: the keys to good planting
Unlike other species, the planting of soybean will condition 70% of the success of the crop. To succeed in this stage, care must be taken with the selection of the plot, the preparation of the soil, the sowing date and the use of certified seeds.
Water, weeds and soil type: factors for choosing the plot
Three elements must be taken into account when choosing the plot: water availability, soil type and cleanliness. Water is needed from flowering to the end of seed maturation and is essential for soya cultivation. This is why irrigable plots must be preferred on soils with limited water availability. Without irrigation, plots with a very good water availability will be chosen. Soils with a limestone content of more than 10% are to be avoided because they can harm the development of the crop. In general, it is necessary to pay attention to weeds that are very competitive and difficult to destroy.
For tillage, look for structural deterioration
In the case of a plot with well-structured soil, all preparation techniques are possible. Deep work, on well-dried soil, can be considered but remains optional if intercrop residues are degraded. Direct seeding is also practised, making sure to clear the seeding line and to sow the seed in fine soil.
In the case of structural soil deterioration, tillage is carried out up to 20 cm, by ploughing or scraping, before or during winter for clay soils. Fragile soils, such as compact silt, are prepared in winter or just before sowing, in order to prevent rainfall from drenching fine soil.
The preparation of the seedbed is a decisive step for the success of the crop yield. Using tools with moderately deep teeth, such as a harrow, work is carried out on dry ground while limiting the number of passages to limit settling. In compact soil, the bed must be thick enough to avoid the formation of a compact crust. In clay soils, rolling after sowing will ensure good contact between the seed and the soil.
Sowing, depending on the variety’s earliness
Seeds are sown in sufficiently warm soil, at more than 10°C for 3 consecutive days. The seed is deposited at a depth of 2 cm in early sowing or on compact soil; at 3 or 4 cm in late sowing or on hot, dry or clumpy soil. The sowing speed must not exceed 6 km/h, adapting spacing to the earliness of the variety: between 18 and 30 cm for group 000, 18 and 50 cm for group 00 and 25 to 60 cm for groups 0, I and II. For early varieties, sown with a cereal seed drill, very narrow spacings of 15 cm, show better results. If the plot presents a risk of sclerotinia, seeds must be sown sparsely at 50 to 60 cm, to ensure good aeration of the vegetation cover.
The seed dose then depends on the earliness of the variety, germination, sowing conditions and water features of the plot. Below is an explanatory table sourced from Terre Inovia:
The use of certified seeds facilitates sowing thanks to controlled and known data. The germination level makes it possible to adjust the sowing dose as closely as possible in order to avoid the effects of over-density. The thousand seed weight makes it possible to hone seed density. Calibrated, certified seeds offer a real comfort to ensure even planting.
