Are there advantages of Cross Slot openers in wet soils?
Yes! They are equally tolerant of wet soils for entirely different reasons. And there are further advantages too (see below).
In what way are Cross Slot openers superior to other openers in wet soils?
Scientists have shown that when an inverted 'T' (or horizontal) shaped slot is created in a wet soil, the placement of crop residue over the slot provides a ready source of food for earthworms, which actively colonise the slot zone. This in turn leads to an increased oxygen supply to the seeds because of their tunnelling. Further the tunnelling also increases the rate of infiltration of rain (or irrigation) water into deeper layers of the soil.
The brown colouration is low-oxygen soil The red colouration is medium-oxygen soil The orange colouration is high-oxygen soil
Double and triple disc openers create a compacted zone of low oxygen soil around the seed.
Cross Slot openers retain high oxygen soil close to the seed.
What opener types are worst in wet soils?
Double (or triple) disc type openers, because of their wedging action, produce sidewall compaction, which discourages earthworms from colonizing the slot zone. Further, by compacting the soil they exclude oxygen and push residue down into the slot allowing seed to become lodged in this residue.
The latter problem is known as hairpinning (because the straw gets bent over like a hairpin) and is explained below.