Factors In Poor Lucerne Establishment

Press, Volume CIX, Issue 32215, 6 February 1970, Page 8

Factors In Poor Lucerne Establishment

A combination of factors in the early stages of lucerne establishment appear to be affecting the survival of the plants.

Dr I. D. Blair, reader in microbiology at Lincoln College, said this week that while a recently-published report had indicated there appeared to be no disease or pest markedly affecting the growth or yield of lucerne, this had referred to previously - recorded diseases and pests. There was, however, a condition or disease organism that existed and which seemed to be extremely important if it were associated with soma other factors. In the course of an agronomic survey, which has been referred to on these pages recently, Dr Blair said, it had been found that in mature stands the lucerne plant population rarely covered more than 80 per cent of the ground in rows and in many cases the coverage was much below this level. In that investigation, he said, the work had been confined to mature stands but studies were now being directed at recently-sown stands—mainly those sown in October and November of last year.

Seedling emergence had been measured over foot lengths on about 100 sites in a paddock. It had been found, as a result of these investigations, that seedling emergence varied from 0 to 30 a linear foot. What was the optimum level of seedling establishment still required to be determined, he added. Discussing the wide variation demonstrated in establishment, Dr Blair said that one factor involved was the well-known problem of irregular seed distribution through the standard drill, particularly in rough seed beds. Still another factor was the germination of lucerne seed in general. Mr A. V. Lithgow, superintendent of the seed industry, had provided figures showing that of 79 germination tests only 15 per cent showed better than 80 per cent germination. Furthermore, there was the problem of hard seed. According to Mr Lithgow it was highly variable. Hard seeds ranged from 15 to 25 per cent in a line, but the

percentage could be as high as 40. These were seeds that did not germinate in the period of the official test, but they were said to frequently germinate later and so far as he could make out were responsible for weak seedlings in a stand. In their latest investigation of newly-sown stands they had returned two months later when they found a tremendous range in growth of seedlings. In a typical measurement, seedlings varied from being no more than a half inch tall up to others that were six inches high and tillering. It was his view that the stunted plants were the product of hard seed and these also tended to be more diseased. It had been observed that these stunted seedlings had a poor root system, had no nodules about the roots and were more clearly marked about the roots with a brown decay. From these decayed areas they had isolated the fungus which was commonly referrod to as fusarium. Two species of this genus had been identified and in tests Dr F. R. Sanderson, of the Crop Research Division of the Department of Scientific and Industrial Research, had shown that they were highly pathogenic, being able to produce this wasting form of seedling. This had also been confirmed by himself. These fungi were naturally soil inhabiting and widespread in the soil and were part of the complex that was contributing to poor seedling emergence. It was not only causing the deterioration of seedlings but preventing other seedlings from emerging at all. Dr Blair said that prevalence of fusarium was directly related to the closeness of the lucerne to a grass crop and this would be particularly the case where the seed bed for new lucerne after grass had been poorly prepared and not all grass turf was distintegrated. Where there was no fallow after grass poor seedling growth might be expected. In these circumstances, he said, farmers might well pay more attention to the place of lucerne in rotations and they might also bear in mind that as lucerne was an expensive crop to establish it needed a good start if it was going to subsequently produce well. If it was sown after grass then a fallow, probably summer, would be desirable. In order to get a satisfactory strike when lucerne seed was not naturally of high germination and also had a hard seed problem, it was also probably necessary to sow at a fairly high rate. Dr Blair said that while sowing lucerne with a cereal crop such as barley or oats had the attraction of providing an immediate return, it seemed to him false economy when the subsequent lucerne was so poor as he had seen this season.