Pasture growth can decline over time due to a number of factors – and the most successful approach to this is often complete pasture renewal.
Benefits of pasture renovation include increased total pasture yield – of 18t DM/ha/yr to 8t DM/ha/yr; increased milksolids production if the extra growth is eaten, and improved pasture quality.
Renovation can make pasture management easier by using late heading varieties to minimise the drop in pasture quality as seed heads appear in late spring. It can also help reduce animal health problems.
To get a return from investment in pasture renovation requires the identification of under-performing paddocks and estimating the potential extra pasture production. For example, where the yield can be increased by 2t DM/ha the return is about 130kg MS/ha. The return will be greater if the extra growth occurs at a time of the season when animal demand exceeds pasture growth.
Estimating paddock pasture production can be done from grazing records or pasture cover assessments from farm walks.
With grazing records farmers can calculate the performance of individual paddocks by adding up the number of cow grazing days during the year. This needs to be corrected for any silage made, from extra growth, and silage fed out. Because if cows eat silage, they eat less grass.
The best paddocks can show a farm’s potential to grow pasture. The worst paddocks are identified for possible renovation. The difference between the best and worst paddocks gives an idea of the potential pasture production to be gained from renovation, provided these are similar in soil, drainage etc.
The profile for the farm will give quantitative information with which to develop an appropriate pasture renovation strategy. As a rule of thumb, the breakeven return on investment is where renovation can improve pasture production by at least 1.5t DM/year.
The breakeven point will differ between farms depending on the cost of renovation and any other benefits from the renovation such as better stock health from selecting a new endophyte like AR1, or improved paddock contour.
Reasons for poor pasture
Once poor producing paddocks are identified, successful pasture renovation involves identifying reasons for poor pasture production and rectifying possible problems.
These include low soil fertility and/or incorrect soil pH; poor drainage; pasture pests such as grass grubs, black beetle, clover root weevil and porina; excessive pugging, soil compaction and, or, overgrazing; and weeds and unproductive grasses, or a lack of ryegrass.
For more information, go to: www.dairynz.co.nz