Photosynthetic activity and productivity of durum wheat (Triticum durum Desf.) affected by certain preparations and various terms of sowing

Abstract: In 2019-2020, in the experimental field of the Field Crops Institute, Chirpan a field experiment with durum wheat cultivar Predel (Triticum durum Desf.) was conducted. Three sowing dates were tested: Early sowing (05 – 10 October), Normal sowing (20-25 October – standard) and Late sowing (05-10 November). In early sowing, 2 retardants were studied: Cearon 480 SL – 1 l/ha and Medax top – 1 l/ha and 2 insecticides: Proteus 110 OD – 625 ml/ha and Mageos – 100 g/ha, as well as the mixtures between them. During late sowing, 2 stimulants were studied: Naturamin plus – 1.5 l/ha and Raiza mix – 750 ml/ha and 2 foliar liquid fertilizers: Mix for cereal SC – 1.5 l/ha and Trimax SC – 1.5 l/ha, as well as the mixtures between them. These preparations and fertilizers are applied after stage 3-4 leaves of durum wheat, in the so-called “Closure of crops”. In the case of early sowing variants, this stage occurs in autumn, and in the case of late sowing variants, the stage occurs in spring. In the early sowing of durum wheat, the leaf area, photosynthetic potential, biological and economic yield are the greatest in the combinations of retardants Cearon and Medax top with the insecticides Proteus and Mageos. In the late sowing of durum wheat, the leaf area, photosynthetic potential, biological and economic yield are the highest in the combinations of the stimulants Naturamin plus and Raiza mix with the leaf fertilizers Mix for cereals and Trimax. In these variants, the leaf area dies faster during the milk development stage. The net photosynthesis productivity in the combinations is lower than in the independent use of the respective preparations and fertilizers. The harvest index in the late and normal sowing variants is higher than in the early durum wheat sowing variants.