Influence of mineral nutrition on sunflower yield under trickle irrigation

In field experiments, the effect of different doses of fertilisers (ammophoska and ammonium nitrate) depending on the irrigation regime was studied on the development and yield of sunflower in a nine-field crop rotation system, on ordinary medium-deep clay loam chernozem. In general, on the plots without fertilisers and at all fertilizer doses, the nitrate content in the soil arable layer tends to rise. With increasing doses of fertilisers, the content of mobile phosphorus in the soil increased as well: from 44 to 72 mg/kg of soil (no irrigation) and from 39 to 63 mg/kg (irrigation). The trend of exchangeable potassium content is also positive, increasing from 296 to 406 mg/kg of soil (no irrigation) and from 302 to 369 mg/kg (irrigation). The fertilizers had a positive effect on sunflower plant development, but it was less significant than from irrigation. On fertilised plots the plant development indicators (leaf width, capitulum diameter, leaf length, plant height) were, on average, 7-29% higher than on unfertilised variants. The maximum yield level (5,6 t/ha) was obtained under the irrigation regime with a pre-irrigation soil moisture level of 90% of the lowest moisture capacity, on N120P90K90+N45 background.