Lucerne gives good results with careful management

Press, 29 May 1981, Page 19

Lucerne gives good results with careful management

The acccompanying item on a session on lucerne at last week's Lincoln College farmers’ ■> conference has been con- i tributed by JOHN GOULTER, journalist on the staff of Lincoln College.

The ' Lincoln College farmers’ conference was told last week that with careful management and the use of appropriate varieties lucerne can still give good results. . There was a guarded optimism at the Wednesday morning session on the future of the crop. It followed a review of the past, in which scientists and advisers from the Ministry of Agriculture and Fisheries, the Department of Scientific and Industrial Research and Lincoln College had outlined the difficulties involved in growing lucerne. Both sessions were held in association with the Agronomy Society of New 7 Zealand.

The Wednesday morning session opened with a farmer's view. Mr John Lewthwaite, of Mount Somers, told a story which reflects the enthusiasm for lucerne in the early seventies. followed by a sharp decline in its stakes as problems developed. After taking over the farm 12 years ago. three problems were apparent: poor -lamb thrift, dry summers, and grass grub. Mr Lewthwaite decided that lucerne might be the answer and the success of early trials carried out on his farm by Winchmore Irrigation Research Station convinced him.

A cropping rotation from grass through turnips and wheat to barley undersown with lucerne gave" high qual-

ity summer feed, and even in September the lucerne was producing 20 per cent more feed than pasture. “My mind was made up. All three of my initial problems had been solved by lucerne. It supported a high stocking rate, right from the first year. Lambs were all going away prime, and grass grub problems were a thing of the past.” Eventually 70 per cent of the grazing area of the farm was in lucerne, with ewe fertility increasing and a lambing percentage of around 135 per cent. “The only problem of any consequence was redgut. This usually caused 10 to 20 deaths in the January to March period. Watching lambs closely and shifting them off lucerne at the first sign of the problem made it more of an annoyance than an economic problem. It was more than offset by other advantages.” But five or six years ago Mr Lewthwaite noticed that his Wairau lucerne was yellowing in early summer. The problem increased with the production loss coinciding with the time of peak feed requirements. He put it down to Sitona weevil, and says that this was the factor which led him out of lucerne altogether. “We now have gone the full circle and are facing the same problems we had 12 years ago. but now we have double the number of lambs to fatten.” Mr Lewthwaite says that he would go back to lucerne if the problems he blamed on the Sitona weevil could be overcome. “In the meantime I must stick with grass, with its limitatons, while waiting for the scientist to come up with an economic answer.”

Mr Trevor Trought, a scientist with the Ministry of Agriculture at Lincoln, confirmed the weevil infestation in Mr Lewthwaite’s lucerne, but he considered that other factors contributed to the un satisfactory growth. In a paper on insect control. he said that the Sitona weevil can bring about almost total defoliation of a stand, but its numbers are likely to be deceptive. Farmers are most likely to notice the weevils in the December-January peak in adult numbers. But Mr Trought said that this peak collapses rapidly and the damage done is short-lived.

It is the larval numbers that are important. Laying begins in April and peaks in August. Control in late May through sprays and stocking management'looks like being the most effective. Mr Trought said. There are now new adults coming in at that period, and eradication of the larvae can do a lot to ease the problem later on.

In the discussion Dr R. B. Wynn-Williams, of the D.5.1.R., said that the Sitona weevil problem needs to be kept in perspective. "The damage it has done has been sporadic in Canterbury. Defoliation occurs when the. lucerne plants are depleted and carrying little food, anyway. The weevil is present in Australia, but it is not regarded as a pest in lucerne.”

Earlier in the morning Mr T. P. Palmer gave a paper he had prepared with Dr Wynn-Williams on cost savings that could be made in growing lucerne. He said that more money was being spent than was needed in lucerne growing, and one of the areas where savings could be made was with sowing rates. He said that many farmers were sowing lucerne more densely than necessary with no increase in yield. With seed at $8 to $lO per kg the difference in cost between a sowing rate of 1 kg per hectare and 10 kg per hectare was considerable. A sowing rate of 5 kg per hectare gave around 100 plants per square metre: more than enough for the 10 to 30 plants needed for optimum yield. The use of cover crops could also make lucerne a more economic crop, bringing in an income while the lucerne was establishing. Work done at Winchmore research station had shown that cover crops, such as peas or barley, did not lead to less lucerne plants developing, The plants were initially smaller, Mr Palmer said, but they recovered quickly. “In most Canterbury soils lucerne does not produce much in the first year so a cover crop can be a very economic course for the farmer to take.”

On the problem of weeds in lucerne, Mr Palmer said that winter weeds may in fact produce valuable feed. But he said that the weeds generally come in after a disease in the lucerne or mismanagement of grazing. "If there’s plenty of lucerne you don’t get weeds — the lucerne will push the weeds out. It’s when there are empty spaces that the weeds come in.” In contrast to Mr Lewthwaite’s paper, Mr Mike Brosnan, who farms in the Hakataramea Valley, outlined the continuing success he has had with lucerne. With 200 of his 570 hectares in lucerne, he has gone from 1100 ewes to 3000 and managed to come up with surplus hay to sell.

"Lucerne has done everything I have asked of it,” Mr Brosnan said. "In my view if drought and light soils are a limiting factor, lucerne is well worth the trouble.” Dr Jim White, of Lincoln College, outlined some of these difficulties, and their solutions from a grazing management view. He said that a long spelling period was vital for good production, and without it a plant's reserves could become seriously depleted.

Dr White said that lucerne needs to produce 30 per cent more dry matter than pasture to be a reasonable alternative, and such a figure is well within the possibilities of many New Zealand areas. Lucerne yields on the pumice soils of the North Island are 50 per cent higher than pasture, and on the college's Ashley Dene farm lucerne outyields pasture by 100 per cent. In dry; climates, particularly, lucerne can lead to all-round increases in returns.

A paper from Dr K. T. Jagusch, of Ruakura, on stock performance with lucerne. showed that lucerne can be used for flushing ewes, as long as it is free from leaf spotting fungi and aphids. He said that research had established that the oestrogen problems associated with flushing on lucerne only arose with diseased or aphidinfested stands. Healthy lucerne is high in protein, he said, and may, in fact, provide a lambing bonus over pasture or other alternatives. Closing the session Dr M. W. Dunbier, of the D.S.I.R. at Lincoln, spoke on the longer lives of lucerne crops, associated with newly developed varieties.

He said that New Zealand lucerne growers have experienced a number of diseases and pests over the last decade.

“They should not. however, consider that their position is unique in the number of problems they have to contend with, either in terms of the climate or diseases and pests. Some other countries have more pest and disease problems and a less favourable climate than New Zealand, but with resistant cultivars and good management they obtain good performance from lucerne.” Dr Dunbier said that bacterial wilt was now the major factor to be considered in choosing a cultivar. In the United States bacterial wilt resistant cultivars were routine and the adoption of these cultivars in New Zealand would make the problem insignificant here also. Except for the standard Wairau. most cultivars such as Saranac and Washoe are resistant to the wilt, but the D.S.I.R.'s Rere, bred for its resistance to blue-green and pea aphid, shows only moderate resistance to bacterial wilt. He said that the most serious lucerne pest or disease in North Otago and parts of Canterbury is the stem nematode. Infestation can be rapid, especially where the nematodes are carried in irrigation water' and they can dramatically affect a lucerne stand. Chemical treatment is effective but costly, and Dr Dunbier said that resistant cultivars, such as ASI3R and Washoe, were the answer.

He said that lucerne breeding programmes in North America, particularly in producing resistant cultivars for aphids, had been "spectacularly successful.” Ultimately though, cultivars suited for local conditions would have to be developed within New Zealand. He outlined the D.S.I.R.'s programmes at Lincoln and Palmerston North, which are aiming for strains resistant to bacterial wilt and the blue-green and pea aphids. Imported cultivars, he said, had overcome some of lucerne’s problems and the New Zealand-bred cultivars will overcome more.

"Good management of these cultivars will give excellent results to the grower. The challenge is to choose the correcct cultivar for the situation.”