AGROCHEMICAL EVOLUTION OF THE CHERNOZEMIC SOIL IN THE SUPERFICIAL HORIZON BY DIFFERENTIATED NITROGEN FERTILIZATION

Soil fertility, upon which plant growth and hence crop yield and quality depend, embraces its content of plant food (nutrients), its organic matter content, its structure, its ability to supply water and its depth. Excessive use of fertilizers with nitrogen products of ion nitric accumulation in the soil (temporary) and in plants, which disturbs the balance of photosynthesis, causes the appearance of necrosis and burns on leaves, severe intoxication and even death by asphyxiation phenomena and cyanosis at ruminants, children and old people. One of the ways of soil pollution through agricultural technology is over-fertilization and, in particular, the administration of high doses of nitrogen fertilizers. Excess of nitrogen fertilizers, as well as their empirical application, have negative effects on harvest quality. The main aim of this study was to determine the effect of five nitrogen levels and different type of fertilizers on the agrochemical evolution of the chernozemic soil in the superficial horizon. Field experiments were conducted at the Agricultural Research and Development Station (ARDS) Suceava, Romania, in two growing seasons (2017 and 2018) with five nitrogen levels (80 kg/ha, 120 kg/ha, 160 kg/ha, 200 kg/ha and 240 kg/ha) and two type of nitrogen fertilizers (ammonium nitrate and urea).

Biological activity of typical chernozemic soil under different systems of main tillage and crops fertilisation of a short crop rotation

The influence of four main tillage systems and four fertilization systems on biological reactivity of a plow layer of typical chernozemic soil under agrophytocenosis of five crops was investigated during four year research (2016–2019) of the stationary field grain row crop rotation. Loss of mass of flax linen in a plow layer of soil during two months of the study characterizing the intensity of cellulose-decomposing microorganisms under beard, beardless, differential and disc tillage made correspondingly 24.5; 22.7; 23.4 and 23.3 % – for soybeans; 16.3; 15.7; 15.9 and 16.2 % for winter wheat, 24.1; 22.8; 24.7 and 22.6 % – for sunflowers, 27.7; 24.1; 25.1 and 23.7 % – for spring barley, 21.9; 19.9; 22.4 and 19.0 % – for corn. Steady surface and beardless tillage strengthen the differentiation of a plow layer according to the intensity indices of flax linen decomposing while the beard one tillage decreases. The most heterogenic plow layer was observed under beardless tillage; it was a bit lower under disk tillage in a crop rotation. The intensity of flax linen decomposing on the top of a plow layer (0–10 cm) is the highest under beardless tillage and the lowest under beard tillage, while in the bottom (20–30 cm) of a plow layer an inverse relation can be observed. The intensity of carbon dioxide production by the soil under soybeans, winter wheat and spring barley is the highest under beard tillage and the lowest it is for soybeans under beardless and differential tillage, for winter wheat, sunflowers and spring barley under beardless tillage and for corn under disc tillage. For sunflowers and corn this index is higher under differential rather than under beard tillage in a crop rotation. The biological reactivity of a plow layer of a typical chornozemic soil increases as the fertilizers application rates increase. Crop rotation productivity is almost at the same level under beard and beard-beardless tillage in a crop rotation. Systematic beardless and surface disc tillage decreases this index significantly. Key words: soil, crop, crop rotation, tillage, fertilizers, flax linen, carbon dioxide, plow layer, heterogeneity.