There are at least 4 configurations for disk seeders. 1.- One disk '/'. 2.- Two equal diameter paired disks configured in a parallel "V”. 3.- Two equal diameter paired disks, but one approximately half an inch behind the other 'Y'. 4.- Two paired disks, configured in parallel but one is half an inch larger than the other, that way achieving the same effect as in configuration 3 'Y’.
1- What are the advantages and inconveniences of each of the four systems, and is there any ideal configuration for each soil type or condition?
2- In configurations 3 and 4, where one disk is in front of the other (because it is effectively in front of the other (3), or because it is of a larger diameter (4)), would it be better if this disk had a double or simple edge, or does it matter? Thanks.
Firstly we have to consider the characteristics of the seeds to be seeded (size and way of germination) to understand the different configurations of the seeders. With cereals like wheat and barley the furrow can be small, so the recommended option is to use only one disc slanted in regard of the advance direction. This system needs less vertical force to penetrate the ground. This is the solution used by the majority of manufacturers for seeding with winter cereals.
A double disk marks a V that ensures the seed is at the bottom of the furrow, and which is needed for cereals like corn or soybean. Generally speaking this is the systems used by single-grain seeders. The use of two equal diameter paired disks has one inconvenience: with wear, the V of the furrow becomes a W, which means that the precision in depth of the seeding is not guaranteed.
There are two possibilities to resolve this: use two equal diameter disks one behind the other, or one disk larger than the other placed at the same height. They seem to be equivalent solutions, although the option of different diameter disks in mechanically simple and does not need any modification of the machine body.
There is a fifth option, which combines a seeding boot with the disks, this guarantees maintaining the V, although it is more expensive as it has more components. It adapts to soil with less surface residue. Regarding the edge of the disks, there are no references to experimental results that give advantage to any of the alternatives. It seems there are no significant differences.