On-row versus inter-row sowing
Seeding on the previous year's row as opposed to the previous year's inter-row has been shown to enhance soil water content. The remnant root systems of the previous crop are thought to provide pathways for water into the soil.
Dead plant crowns and root systems from a previous crop, if left undisturbed, seems to improve the wetting of repellent soil by rainfall after harvest and into the next growing season. It appears that rain wets-up a thin layer of topsoil and flows into channels remaining from the previous crop roots.
It is possible the dead root systems may provide a habitat for soil microbes which can consume more of the hydrophobic organic matter causing water repellence, however more research is required to support this assertion.
Plant establishment was improved when seeds were sown on the previous year’s row compared to the previous inter-row.
In a wetting agent trial in 2011, at Balla near Northampton, banded wetting agents were applied at the same time that lupin was dry-sown using knife points. The wetting agents improved seedling establishment where seeding was on the previous year’s inter-row, but much greater improvements were measured by seeding on the previous season’s wheat rows (see Figure 1).
Figure 1: Dry sown lupin establishment when sown either between, or on the
previous year’s wheat rows, and with or without (Nil) banded-applied wetting
agent at Balla on deep yellow water repellent sand in 2011.
Figure 1: Dry sown lupin establishment when sown either between, or on the previous year’s wheat rows, and with or without (Nil) banded-applied wetting agent at Balla on deep yellow water repellent sand in 2011.
This method requires a suitable tractor guidance system to maintain the sowing position consistently on or very close to the old row. A fully matched controlled traffic system may allow such methods to perform better by avoiding other traffic running over the old rows and perhaps compromising the wetting-up by following rain.