THE EFFECT OF MIXED PLANTING OF BIRDSFOOT TREFOIL, SAINFOIN, SUBTERRANEAN CLOVER AND TALL FESCUE ON NODULATION AND NITRATE REDUCTASE ACTIVITY IN SHOOTS

A pot trial was carried out at the Institute of Forage Crops, Pleven, Bulgaria (2011 - 2012) to study nodule biomass, nitrate reductase activity and biochemical composition of birdsfoot trefoil, sainfoin, subclover and tall fescue, pure and in mixture. The tested treatments were as follows: birdsfoot trefoil (100%); sainfoin (100%); subterranean clover (100%); tall fescue (100%); birdsfoot trefoil + tall fescue (50:50); sainfoin + tall fescue (50:50); subterranean clover + tall fescue (50:50); birdsfoot trefoil + subterranean clover + tall fescue (33:33:33); sainfoin+ subterranean clover + tall fescue (33:33:33). It was found that birdsfoot trefoil and subclover in binary mixture with tall fescue formed by 15.1 and 15.4% more nodules as compared to the nodulation in pure crops. However, tall fescue inhibited nodulation of sainfoin by 25.0%. When the third component (i.e. subclover) was included in the mixture the number of nodules significantly exceeded pure sainfoin (by 18.5%). Nitrate reductase activity in the leaves was increased in all legumes tested, except tall fescue decreased.

Total content of plastid pigments in mixtures of birdsfoot trefoil with tall fescue was decreased, while in mixtures of sainfoin and subclover with tall fescue was found to increase. Crude protein content was the highest in aboveground mass of birdsfoot trefoil (15.07%). Water soluble carbohydrates in mixtures were significantly higher as compared to pure legumes and lower as compared to tall fescue.