Worthwhile Regrassing?

The decision of pasture renovation is not always straight forward, especially for those that farm on easy country with well drained soils, that will not benefit from any paddock contouring or removal of rocks.

Assessing whether there is a margin in renovating pastures can be best informed, if the farmer spends the time monitoring growth rates of individual paddocks on their farm, in order to identify under-performing paddocks. If 75% of the farm is harvesting 12T or better and 25% is harvesting under 12T you then need to assess why these paddocks are not growing the grass – providing management decisions have not disadvantaged performance. To prevent disappointment 12 months after regrassing, possible reasons for poor pasture growth need to be identified i.e.drainage, soil fertility, insect/pest damage, climate, or poor grazing management - and the problem rectified prior to sowing.

There is little data on comparing newly established pastures with existing older pasture swards of same variety, due to difficulty of research protocol and controlling factors. Most trial work by individual seed companies is done comparing old vs new varieties sown at the same time. However you as a farmer can work through your own figures as illustrated below to determine the advantage.

Should you grow an extra 2T/ha over the first 3 years after renovation, (minus 1.5 T/ha in first year as opportunity cost of renovation), at 85% utilisation equates to an additional 3.6T/ha. At 15kg DM/kg MS there is economic benefit of $960/ha after 3 years at $4.00/ kg MS payout. Cultivation costs need to be subtracted from this figure, with this being dependent on the extent of paddock development.

When deciding on what pasture species to sow, farmers should be taking a number of factors into account. Persistence - how long is the plant going to stick around for i.e. after the first flood/drought are you going to be left with just weeds and native grasses?? How much will it grow, and at what times of the year is growth really important?? Will the cows actually eat it after the effort of getting the pasture established – so is it palatable and will it provide quality pasture that will lift daily production??

Persistence relies on getting a strong healthy plant established early and then managing effectively to encourage a dense sward by protecting from pests and insects, treading damage and overgrazing, and hopefully, moisture is obliging. Growth potential is also reliant on the above factors affecting persistence. And then depending on lactation you’ll want to choose varieties which growth patterns compliment your system. For example choosing winter active for early calving or later flowering to minimise post peak decline – tailoring your species selection for when you require extra feed or improved quality. Climatic conditions will also dictate your direction of species selection and alternatives from ryegrass may be sort in extreme areas, such as fescue for summer dry areas, and annuals in highly stocked systems. You may even mix compatible species at advised proportions to give you benefits of a better seasonal spread of growth and quality.

Grazing management can have a big influence on quality – timing of grazing (rotation length) and grazing pressure. However there are varieties that will seed later and have less aftermath heading depending on your needs for your farming system. A lack of quality in pastures can have a double disadvantage due to low energy density per kg DM that can lead to limited cow intakes due to increased fibre levels. Is not difficult to work through figures of improved quality and see the potential to increase farm profit.

At a requirement of 5-6 MJME/L milk, improved pasture quality of 1 ME (10.5 – 11.5 MJME/kg DM), over 100 days at a stocking rate of 2.5-3.0 c/ha @ $4.00 payout equals $200-400/ha improvement.

In summary, the benefits in pasture renovation depend on your individual situation, but providing you are targeting poor performing paddocks it is highly likely you will generate an economic advantage within 2-3 years. It is important that species selection accounts for both DM grown (quantity) and palatability (quality), as both are important factors affecting cow performance. Choosing varieties that can handle the climate and compliment your system will also give you the best returns. Happy regrassing!!

Tracey Berquist B.Appl.Sc
Intelact Nutrition Consultant
Taranaki