PASTURES affected by flooding and severe waterlogging need extra care to re-establish healthy productive pastures.
Focus on soil testing, soil temperatures, seed depth, irrigation, weed control and grazing management, to help pasture re-establish.
Soil testing is highly recommended. After flooding sandy soils can have issues with leaching of various nutrients, such as sulphur, potassium and nitrogen. In heavy soils inundated for prolonged periods, denitrification can occur.
Fertiliser applications may need to be adjusted. The soil test may also indicate the need for gypsum to help build and protect soil structure.
Soil temperature is critical in pasture establishment. The ideal soil temperature for sowing varies depending on the species. For ryegrass and clovers, the ideal soil temperature for germination is 20 to 25°C; Persian and Shaftall clover can withstand higher soil temperatures up to 35°C; oats have an ideal soil temperature range of 10 to 25°C, while wheat and barley prefer a couple of degrees lower. A good rule of thumb for ryegrass and clover is to sow when daily maximum air temperatures for five consecutive days average less than 25°C. Above that seed establishment is reduced significantly and pastures may need to be resown.
The sowing depth of seed is proportional to the seed size. Generally, the depth should be twice the length of the seed. For example, ryegrass seed should be sown at 1-2 cm deep. Sowing too deep increases emergence time, or failure to emerge.
For a dense, productive pasture aim for plant densities of 600 seedlings/m2 (measured one week post emergence). A pasture count lower than 80% will require more drastic action.
Newly established seedlings are more susceptible to moisture stress than established plants. Depending on the season, the first irrigation will typically use 1.5 ML/ha with subsequent irrigations of 0.5 ML/ha, depending on soil type and irrigation layout.
After the pasture sward is established, the first grazing is crucial to get right. Pasture should be 10 cm high and at least at the two-leaf stage; check the root system is developed enough, by using the ‘pluck test’ – take a tiller between your fingers and pull in a motion to mimic a hungry cow’s bite. If it tears without pulling the plant out of the ground, it is ready to graze.
Graze pastures to a residual height of 4-6 cm, to help promote tillering and minimise damage to the pasture. On-off grazing should be used to help achieve residuals of 4-6 cm when first grazing new pastures.
It is vital to get the basics of pasture establishment and grazing right to ensure the best result possible and produce healthy productive pastures.
