- Soil becomes very hard affecting aeration, nutrient take up through lack of water, water holding capacity and microbial activity
- Vigour of plants is affected
- Very slow if any recovery after grazing. Essentially the pasture is permanently damaged
- Bare ground becomes evident allowing weeds to take over
- Erosion now highly likely
Wet and muddy conditions
- Soil becomes pugged which means plants become damaged affecting plant density by as much as 50%
- Resulting bare space allows weeds to invade
- Soil porosity is reduced affecting aeration, water holding capacity, microbial activity
- Earthworm population is depleted
- Erosion and nutrient run off are now more likely
In the case of intense rotational grazing, direct seeding immediately after grazing is considered a worthwhile practice. Rather than wait for a pasture to fall behind in production it is assumed at some level the pasture has been damaged, especially in congested areas such as gateways. Oversowing at a reduced rate will ensure the paddock remains in optimal condition for the next grazing rotation.
Renovation should assist with some or all of the following:
- Restore plant density per square metre back to a level where grazing will support an acceptable level of production
- Improve the soil biology to a level where the pasture is able to be resilient and optimally take up the available nutrients
- The pasture is maintained at or near peak production
Ripping and subsoiling
If it is established that compaction is excessive then consideration needs to be given to remedial action. The most effective method is to assist natures work by subsoiling.
The intention of sub soiling is to create vertical cracks and shatter the soil. This mechanically reintroduces porosity achieving better air movement, water penetration and microbial activity. It also allows a plants roots to grow and travel more freely thereby accessing moisture and nutrients.
Timing is everything – if the soil is too wet it will more like plasticine and won’t shatter. If there is a hard pan then setting the machine depth is critical to get below the pan to break it up.
The soil’s surface has suffered from hoof indentations as a result of pugging – harrows can tear the surface allowing soil to fill in the indentations. The soil needs to be dry enough to break up.
Harrowing will cause some further damage to plant density. The broadcasting of seed will overcome this and improve pasture recovery.
Harrowing will not however improve soil biology. Consideration needs to be given to either subsoiling or cultivation if improvement of soil biology is the desired outcome.
Cultivation and re seeding
Where pasture damage is severe the option is to cultivate, which is expensive, however for optimal results it is regarded as the most effective. Soil conditions need to be dry enough for the soil to become friable as a result of cultivation. Restoration of the soil biology will be improved and return to production will happen earlier.
Once cultivated the pasture can then be resown. An option at that time is to go over the paddock twice on the diamond ( diagonally opposite) at a half rate. This will get maximum coverage of plants per square metre.
Direct drilling seed into existing pasture
Direct drilling can be useful in the following situations:
- In the context of renovation – restoring a pasture back to peak production. Again it is assumed that grazing has to some degree damaged the pasture
- Alternatively it may be that the introduction of another crop at certain times of the year will offer better ground cover and quality grazing fodder
- It’s also possible that a pasture has been stressed due to lack of rainfall and good rains are forecast. As a result an opportunity presents itself to top renovate the pasture with fresh seed
- Intensive rotational grazing as mentioned above
For direct drilling Double disc drills with heavy duty frames have proved to be effective in terms of penetration and accurate seed placement