How to get the ideal seedbed
Water infiltration and a layer of fine aggregates helps
Published 24/08/2010 | 05:00
AVERAGE good tillage land offers the best pre-conditions for min till but sandy clays and loams are also ideal. Heavy soils are more critical as they are harder to handle. Mostly these soils distinguish themselves by the short periods you have to cultivate them.
The target -- an ideal seedbed
- It must allow water infiltration to avoid crusting and erosion. It has to have an upper layer of coarse aggregates and organic matter that does not crust (it has to be able to soak).
- It must have a layer beneath this of finer aggregates that will stop evaporation of water and prevent the seed from drying out and give good seed to soil contact.
- It must have capillarity from beneath to transport water from the soil up to the seed.
Trying to operate min
till in wet autumns
The preservation of the soil structure is the important target at soil cultivation.
On soils that have a weakened or compacted structure, for example on sandy soils which tend to compact, or in areas prone to temporary stagnant water, this will require the top soil loosening down to 20-30cm(8-12inches). This is required to ensure sufficient oxygen supply down to the roots.
Compaction causes changes in the vertical wetness gradient. Normally soils get wetter the deeper you go. When you have compaction it will be wetter at the surface and drier further down.
Soil with a good natural structure acts like a sponge and can hold up to 40pc water by volume. The coarse pores that exist give drainable porosity as these are nearly always free of water. They are very important and you lose these when you have compaction.