IRRIGATION REGIME EFFECT ON SOIL AND PLANTS

摘要

It is well known the positive effect of irrigation on the produced biomass quantity and quality. At the same time the physical and chemical properties of soil change under irrigation conditions and the soil productivity as well. This requires to choose the irrigation regime to provide high quantity and quality of the accumulated plant biomass without causing significant changes in the soil properties. Field experiments with alfalfa, fodder maize, grain maize, tomatoes, pepper, wheat, barley, soybean were conducted on meadow-cinnamonic soil in the Experimental station of the ISS 'N. Poushkarov' in Tzalapitza, Plovdiv region, and with sunflower on leached cinnamonic-forest soil in the Experimental base of Institute of Melioration and Mechanisation in Chelopechene, Sofia region. Furrow irrigation was realised with 7 variants: non-irrigated and irrigated with relative irrigation depths 0.3, 0.6, 0.8, 1.0 and 1.3, all in 3 replications. Furrow and sprinkler irrigation was realised in Tzalzpitza and drip and micro-irrigation in Chelopechene. Soil samples from depths of 0-30 cm and 30-60 cm in the vegetation season end, samples from irrigation water before and after irrigation season and samples from accumulated biomass and fruits from the non-irrigated and the most irrigated variants were collected. For determination of soil volume density soil samples were collected from non-irrigated, irrigated with the highest irrigation depth, realised by different irrigation technique. The electric conductivity of the soil solution, pH, humus content, the content of P_2O_5, K_2O, NH_4~+-N, and NO_3~--N were determined. The electric conductivity, pH, the content of N, HCO_3-, Cl, K, Na, Ca, Mg, were determined for irrigation water before and after irrigation season. For accumulated biomass were determined the content of macro- and microelements and NO_3- in leaves, stems, and fruits for tomatoes during ripening at the variants with 0. 3 and 1. 3 irrigation depths, in leaves, stems and corn-cob for maize during milk-wax ripeness and for the alfalfa biomass after 5 different cuts. The soil volume density increased more under sprinkler and micro-sprinkler irrigation conditions than under drip- and furrow irrigation conditions. The electric conductivity of the soil extracts (soil: water = 1:5) and irrigation water do not exceed the standard norm of FAO for the studied crops. The NO_3~- content did not exceed the permissible concentration limit (PCL). The results of the chemical analyses allow us to conclude that the soil, water and plant biomass chemical composition did not change significantly after the applied irrigation regimes.