A chemical reaction

If clover is gold then the application of agrichemicals to poor-quality hill country pastures could be considered alchemy.
Tuesday, 13 March 2018

The strategic application of sprays combined with management practices has, over four years, increased the clover composition in areas of uncultivable hill country pastures on the Craw family’s Banks Peninsula farm to 40 per cent of the total sward. Four years ago, clover made up less than five per cent of a sward dominated by poor quality native species.

Hamish and Annabel Craw are Beef + Lamb 必威手机下载版 ’s Canterbury Innovation Farmers whose Innovation Farm project was to grow an additional three tonne of drymatter on uncultivable hill country by increasing the legume content of the sward to 40 per cent. Achieving this would allow them to increase revenue from their existing stock by growing lambs to heavier weights or running a higher-earning stock class. Potentially they could also increase the stocking rate on this hill country.

Faced with an impenetrable thatch of low quality grasses such as browntop, crested dogstail and Yorkshire fog, the Craws looked to agrichemicals to open up the pasture to allow existing and introduced clover species, particularly annual clovers such as subterranean (sub) clover, to flourish.

Increasing the clover content of the sward would, by fixing 30kg of N per one tonne of drymatter grown, also reduce and eventually eliminate the need for nitrogen fertiliser.

Over three years the couple, working alongside a team including farm consultants, agronomists, a fertiliser representative and an AgResearch technician, carried out plot, then paddock-scale trials to determine the best chemical and management protocols to achieve the desired outcome.

While the active ingredient haloxfop-p was used in the first three years of the programme, due to changes in withholding period labelling, they are now using Centurian Xtra. While the agrichemicals  have been used to open up the pasture, the timing of sprays, over-sowing and season-specific grazing management have emerged as critical factors.

This spring and summer have proved to be both rewarding and challenging. In spring, the established trial areas were with thick with clover, providing high quality for lambing ewes. The couple elected to shut the area off to allow the sub clover to reseed, but given the growth rates, fuelled by rainfall and increased nitrogen in the soil fixed by the legumes, the grass did get away in late summer.

Ideally cattle would have been ideal to control pasture growth while allowing seed-set, but they didn’t have the numbers on-hand due to a change in cattle policy. While autumn and winter grazing will allow them to reduce pasture cover in time for spring, Hamish says in future they won’t close the area up completely, rather they will use cattle to graze it lightly and regularly observe pasture cover to ensure stock are not eating the clover flowers. It is estimated that this pasture-cover band (to allow seed-set) will be 1500-2500kg DM/ha

The couple point out that the management protocols they have refined- which will be discussed at a field day later this year- are applicable to farms such as theirs where the soils, altitude, aspect and climate and native species are conducive to the formation of thatch.

Similar sub clover trials on steep, dryland hill country in North Canterbury have showed that grazing alone will allow annual clovers to flourish because of the more open nature of the region’s hill country pastures.

As sheep and beef farmers are increasingly aware of the need to better manage existing and introduced clovers in order to increase productivity of hill country pastures, these trials highlight the need to seek the right management advice for specific environments.

Beef + Lamb 必威手机下载版 is running a legume-focused Innovation Farm programme on three North Island east coast hill country farms. Each farm has a different focus, but information and results will be shared between the farmers and the wider farming community.