Molybdenum and legumes

Abstract

The area on which the work to be described is being conducted is a 20-acre lucerne, paddock the history of which is known since 1940. It was sown to lucerne in February 1951 after very thorough seed-bed preparation. A perfect strike resulted, but in the spring it was noticed that with the exception of one or two very small patches the plants over the whole paddock were a pale yellow-green, as if they were suffering from nitrogen deficiency. Not only this, but many of the young plants had died. The yield of material from the first cut substantiated the observation that the paddock was indeed a poor example of a young lucerne stand. It was decided to investigate possible causes of this, especially as many similar cases of failure where lucerne followed lucerne had previously come to our notice. Three possibilities were discussed: 1. A nutrient deficiency. 2. A virus. 3. A toxic root excretion from the previous lucerne crop. In this paper the work done under the first heading will be presented, and in so doing, I will digress somewhat from the main theme of molybdenum because I feel that the whole trial will be of interest. The following nutrients were looked upon as possible limiting factors-calcium, phosphorus, potassium, nitrogen, boron, and molybdenum. The whole area was treated with adequate lime and superphosphate, thus eliminating the first two from the above list. The four remaining nutrients, at one level of each, were included in all combinations and all treatments replicated twice and randomised.