Legume micro nutrient

Dear All, 16th March
Evaporation 10 to 16th March: 6,7-1,1-10,2-3,2,2,3-1

When we were at Dan Green’s about three weeks ago we noticed a wild legume growing in his grass leys. I have been trying to get Mike Bingham to identify it, but, in the meantime I went to his excellent website on the Zambian Fauna – Google Flora of Zambia. I think it is a sub species of what I knew as Dolichos axillaris but is now called Macrotyloma axillare. When I returned from University (before the Rinderpest) this legume used to be so vigorous that it would smother the grass in a great ocean of legume. It (and all my other legumes) have declined over the years until I reckon they are only producing (at best) about 25% of those levels. I was uncertain whether it was because of a shortage of bacteria innoculant, or some micro-nutrient. I think this year I have satisfied my self that it is probably Molybdenum and, to a lesser extent, Boron. (My innoculant experiment showed NO difference, but a field where I applied extra micro-nutrients during the two years that I cropped tobacco, now has that ‘ocean’ effect.) I actually believe that, if we are to grow significant legumes we ought to fertilise those fields with all the other nutrients – if the legumes add 100-200kg of N per ha per year, then we need to maintain the rest of the other nutrients, otherwise the extra growth (stimulated by the N) just burns it’s way what nutrients are there until one (or more) becomes seriously limiting.

This MIGHT be the reason why my Phosphate levels are so low. The other theory is possibly that it is being bound up by the lime. This is an area where I hope to learn more over the next few years.

I repeated last year’s Vydate trial and got positive results all round. I also did a Tabacpac trial …and got negative results. But: DISCLAIMER, neither trail was a true random replication. Although this year’s trials were better than last year’s trials they were NOT properly randomised – so don’t take this result seriously. If a job is worth doing, it is worth doing well – so I hope my Tabacpac trial in 2014/15 will be ‘proper’.



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