Variation of some chemical indicators in forage of annual winter pure and mixed crops cultivated in Central Balkan Mountains (Bulgaria)

The aim of this experiment was to determine the variations in some important chemical indicators of annual winter cereal and legume pure and mixed crops for green forage production under the conditions of the fore-mountain regions of the Central Northern Bulgaria (Troyan region). In pure crops the crude protein content had fewer values compared to mixed crops. The cereals accumulated less crude fat in comparison with legumes. In mixed crops the crude fat was from 1.99 to 2.82%, with a relatively lower coefficient of variation in comparison with pure crops. More crude fibre was indicated in winter barley, triticale and winter vetch. All pure crops displayed a low coefficient of variation (from 7.21% to 10.26%). The lowest values of crude fibre were in the mixed crops with winter pea and they had a lower coefficient of variation compared to pure crops. In regard to crude ash content the legumes exceeded the cereals. In the legume pure crops a low coefficient of variation was established, while in cereals it was a medial value. On the whole all mixed crops had a low coefficient of variation. In legumes the calcium content was higher but with a low coefficient of variation than cereals. In mixed crops irrespective of whether it had a cereal or legume component the calcium content in forage varied from 0.530 to 0.870%. In mixtures the calcium variation was mostly with a medial value. The phosphorus content had lower values in forage of pure and mixed crops. The least variation (as a medial value) was observed in winter vetch and winter barley. In mixed crops with winter barley this indicator had a low coefficient of variation. The most favorable proportion between calcium and phosphorus for pure crops was found in cereals (triticale and winter barley) - respectively 2.46 and 2.23 and for mixed crops - in Winter barley+winter pea and Winter barley+winter vetch - from 1.76 to 2.57.