Take care while cultivating paddocks
Following the wettest winter on record, farmers are currently cultivating their paddocks for pasture or crop rotation.
As they do so, it’s important to be aware of and manage the associated environmental risks.
Sediment and nutrients from farming operations, along with erosion generally, are some of the most important causes of reduced water quality and cultivation increases the potential for problems.
Top soil erosion, especially in hill country, of bare or cultivated land leads to the loss of valuable nutrients. It also disrupts infrastructure and increases the costs of maintenance activity, such as cleaning culverts and drains.
The time of greatest risk can be at times like now when the protective plant cover is lost through cultivation of soils for pasture renewal and crop establishment.
However, there are a range of measures farmers can take to help mitigate the environmental risks associated with cultivation, and with erosion generally, while at the same time protecting soil resources.
Contour cultivation, sowing at right angles to the prevailing wind, sediment retention, diverting overland flow, and reducing runoff are recommended for minimising soil loss.
Satisfactory results are achieved when cultivation is carried out at a suitable soil moisture content and at a suitable depth.
If good precautions are observed, a two-pass cultivation is often all that is needed to prepare a seedbed.
Other soil conservation cultivation techniques include the suite of practices known as minimum tillage or no tillage.
When soil has been continuously cultivated for many years, the structure is likely to be poor because cultivation reduces soil organic matter levels.
No-tillage will not repair the damage overnight but, with residue retention, it will eventually.
Chemical spraying followed by direct drilling is an option on light erodible soils.
Sediment and some nutrients, particularly phosphorus, are carried to streams primarily in the overland flow of water. Dissolved nutrients such as nitrogen and other materials (including dissolved organic carbon) can also move through the soil in underground flows and contaminate watercourses.
The area beside waterways is called the riparian margin. This area is a crucial buffer between land use activities and the natural waterway.
To help prevent the transfer of sediment and nutrients to waterways, an effective filter strip needs to be established and maintained where overland water enters these water bodies.
Healthy riparian vegetation in these areas, as well as grass margins, should be maintained to improve bank stability, increase water quality, reduce stock losses, filter surface run-off and provide habitat for wild life.
-Bala Tikkisetty is a sustainable agriculture co-ordinator at Waikato Regional Council and is available at 0800 800 401 or bala.tikkisetty @waikatoregion.govt.nz.