Sowing date affects the success of pasture establishment and persistence.
Right sowing date
Sowing date is particularly important in summer-dry areas. In autumn, sow early so individual plants have time to develop and reach over 20 tillers in size, prior to the following (potentially dry) summer.
Late sowing means slower establishment due to the cooler temperatures.
Also, the potential to pug and damage new pastures in winter and spring is greater, and smaller, weaker plants are less tolerant of a potentially dry summer because they have fewer tillers and a weaker root structure.
Slower establishing species such as brome and tall fescue must be sown early when soil temperatures are consistently >12oC.
A firm seedbed greatly improves pasture establishment, particularly for clover.
Seedbed consolidation conserves moisture and allows a seed drill to achieve the right sowing depth.
Research in the Manawatu showed sowing with a V-roller into a well-consolidated seedbed gave 50% better white clover and 25% better ryegrass establishment than sowing into a poorly consolidated seedbed.
In this case a Cambridge roller was weighted with concrete posts, to compact the soil until the roll form held under normal walking pressure. This research also highlighted the bad practice of using rubber wheeled rollers, which do not compact the soil well.
The particular consolidation technique for every seedbed will vary, depending on soil type, cultivation and soil moisture.
Drilling method is a critical decision when establishing a new permanent pasture. Good ground cover, or density, at sowing improves clover establishment and gives much better weed control.
Sometimes a drill or method can be modified to get better ground coverage. If row drilling, for example, remove the tubes from under the seed box so seed simply sprinkles on the ground. Welding a ^ shaped angle iron under seed box can help seed spread. If direct drilling, sprinkle clover seed and 1/4 of ryegrass seed through a small seed box (with tubes removed) ahead of the main drill. Main drill coulters will help cover and sow this seed.
Sow ryegrass/white clover seed mixes at 5-10 mm deep to get the best establishment. White clover seed is very small and sensitive to sowing depth and establishes much faster sown at this depth. Ryegrass is less sensitive to sowing depth and still establishes well sown at 20 mm. At a depth of 50 mm neither species establishes well.
The exception to sowing shallow is in dry conditions, when it is sometimes better to drill seed a little deeper into better soil moisture. In these conditions white clover may struggle.
A consolidated seed bed is critical to allow good depth control with a seed drill. In a soft seedbed wheel tracks are pushed down, and coulter depths vary, leading to both uneven sowing depth and establishment. The same effects can occur when drilling too fast, causing uneven sowing depth.