Clover Up project

Concern among farmers throughout NZ over the lack of clover in pastures led AgResearch Grasslands scientist John Brock to form a group of 16 farms into a Clover Up project, funded by Sustainable Farming Fund (MAF) and Agricom, to look at inconsistency of results when sowing new pastures from crop or when renewing pastures, grass to grass.

The project was a series of farm-based studies over a three year period over Manawatu, southern Hawkes Bay and Wanganui. The first year of the project established that average clover (and grass) emergence was well below potential. The results after sowing were generally poor. It also showed the general difficulties of meeting the needs of clover with modern sowing methods like minimum and no-tillage. Year two saw more detailed analyses of new pasture establishment methods, concentrating on clover, and year three was given to a demonstration site to illustrate the lessons learned.

Brock said the agronomic principles of establishing clover are well-known and well-tested and were common knowledge among farmers several decades ago, but now they seem to have fallen out of use, particularly on high-producing properties, because of other pressures for quick results. There appears to be a generation gap in farmers knowledge when it comes to establishing clover-rich pastures properly. There is a lack of appreciation of how clover plants grow. To some extent it is a failure of agronomic extension, with the scientific world assuming that former generation of farmers would have passed on the clover establishment knowledge, but not necessarily. The Clover Up project showed that the tried and true clover establishment methods still work and provided guidelines for todays generation of farmers and contractors to follow.

Brock says that farming has moved on quickly during the past 20 or 30 years, with new cultivation methods, better soil fertility, more emphasis on quick-performing grass in pasture, intensification of pasture use and particularly nitrogen fertilisers. Clover is no longer the core of production as its importance in supporting the soil fertility cycle declines and farmers now get wide variation in clover establishment. Grass grows much faster when it is wanted and competes strongly with clover. Even in low fertility situations, grass grows four to six times faster than clover, and in high fertility the grass growth rate can be up to 20 times faster. Yet clover is still seen as an essential part of pastoral farming in NZ, providing high quality feed important to animal production. White clover consistently has a higher feed energy level than grasses and is the cheapest form of high-quality feed available.

The problems

The aim for a successfully established mixed pasture sown in autumn should be 30% clover in the first year, when clover is tap-rooted and has its greatest potential for growth and spread. It must be given every encouragement in year one.

Research has shown that a successful clover component is 80-90% germination, or around 300+/sq m clover seedling emergence at six to eight weeks after sowing. This is best achieved where the soil has been cropped to reduce available soil nitrogen, sprayed out, ploughed, cultivated and firmly consolidated before being broadcast sown, chain harrowed and rolled. The emerging pasture is then rotationally grazed for the first year to control grass growth to give the clover light and allow the stolons to run and form a strong base in the pasture.

The first year of the survey of the actual results on 16 farms showed average seedling emergence of 125/sq m (35% germination vs 85% target). Was poor germination caused by poor seed or establishment techniques?

Clover emergence was related to seedbed preparation when fine and friable, clover strike was good and was more easily achieved in sandy soils compared to heavier clay soils. Clover emergence was also better when a crop had preceded the pasture sowing.

The survey also looked at plant survival and growth after 9 months (in summer) compared with 6-8 weeks from sowing (winter). It was evident that fewer clover seedlings emerged and survival of plants was poorer under the grass to grass approach to renovation as the old resident clover recovered from the Roundup spray.

So it is worth asking whether farmers are gaining any benefit from drilling clover into old pasture without killing the resident clover first. Once emerged, management factors such as pugging, a problem with cattle, use of nitrogen and/or lack of grazing control of the grass were the major problems.

Overall, it was estimated that the Clover Up group of farms achieved around 20% of potential, because not enough plants emerged at sowing and survived past winter.

The results confirmed the inconsistency in clover establishment which had been reported. They also demonstrated that the most important factor to white clover establishment is to get enough plants emerged and surviving the first 1-2 months.

Sowing is critical. The aim should be for at least 200 plants/m2. Once that is achieved, the emphasis switches to applying the correct management to capture the potential of the tap-rooted plants and encourage their spread to colonise as much area of the pasture as possible in the summer months. Here, management is critical.

Brock asked: We used to be able to do it in the past, so why now has it become such a problem?

Solutions

White clover is slow to establish and a poor competitor with ryegrass, so farmers need to make allowances. Care is needed with seedbed preparation to make sure clover seed is not lost down the cracks. Seedbeds must be firmly consolidated and the seed only lightly covered. Once emerged, the competition for light and nutrients from the more aggressive companion plants must be controlled. Reducing the amount of grass seed being sown will help. Research has shown that 8-10kg/ha of ryegrass seed is sufficient to establish a good grass component. Reducing the available soil nitrogen is also of benefit.

Further trial work on seedbed preparation and sowing showed that heavy Cambridge rolling before the drill gave the best results. The V roller tends to cut deeper rather than consolidate and places the seed too deep on loamy soils.

Brock also recommends that dairy farmers graze down to residuals of 800-1000kgDM/ha because clover grows in the pasture based and needs light. A consequence is denser pasture, better turf strength and less treading damage.