On-row or edge row sowing means sowing a new crop immediately alongside or in the previous crop row. Grain crops are usually sown inter-row (between the old crop rows).
On-row sowing for phosphorus
On-row sowing can make use of last year’s phosphorus (P) fertiliser. Phosphorus is not a very mobile nutrient in the soil. If it is not removed in grain or hay, P tends to remain close to where it was placed in the soil.
The dry 2018 season seen by many growers means a significant amount of last year’s P fertiliser could still be in the soil. Sowing close to the stubble line of the previous crop maximises the potential for the seed to access residual P.
Still apply starter P as young crops aren’t good at getting residual P out of the soil. Do a soil test to check P stocks. P is more likely to be available in neutral soils than calcareous soils. P availability in acid soils will vary based on inherent soil properties. Grain yield is very sensitive to P rate when soil pH is below 5. Ideally, drill the fertiliser with or below the seed.
On-row sowing and nitrogen
There could be more potential for nitrogen (N) lock-up (immobilization) when sowing on‐row. N lock-up is associated with the breakdown of stubble. For each tonne of cereal stubble, about 10 kg/ha of extra N fertiliser is needed to compensate for N lock-up. Mid-row banding of N fertiliser may help crop establishment and uptake of N fertiliser.
On-row sowing in non-wetting soils
On-row or near-row sowing can improve crop establishment in non-wetting sands. The crop row is usually less water repellent than surrounding soil. The intact root system of the previous crop provides a pathway for water infiltration. Trials in WA found that plant emergence improved from 112 plants/m2 with inter-row sowing to 158 plants/m2 with on-row sowing.
Risks of on-row sowing
On-row sowing requires a high level of sowing precision. Risks include:
- greater disease risk of stubble born diseases
- hair-pinning, where stubble is pushed into the seeding slot reducing seed-soil contact and germination rates
- poor seed placement reducing plant establishment, especially in small-seeded crops like canola.