Порівняльна оцінка вмісту рухомого фосфору в різних генетичних горизонтах чорнозему звичайного на ріллі відносно цілини в умовах північного Степу України

Abstract

Доведено, що реальна природна забезпеченість фосфором орного шару чорноземів звичайних відповідає межі низької і середньої забезпеченості цим елементом живлення рослин, що підтверджується відомими емпіричними даними про високу ефективність фосфорних добрив на цих ґрунтах. Підвищеним або високим рівнем забезпеченості фосфором характеризуються лише орний шар ґрунтів, що містить залишкові фосфати добрив, а також верхній гумусовий горизонт цілинних ґрунтів. Al on with nitrogen, phosphorus is the second most imp or taint mineral nutrient element which is in the majority of cases limiting the further growth of grain yield actually in all agricultural crops without exception. It is connected with the fact that in most types of soils phosphorus is present in slightly soluble mineral form and organic form not available to plants. This is due to low content of phosphorus available to plants in soils the payback of phosphoric fertilizers is rather high; on average, 1 kgof P2O5 guarantees the gain of 4–5 kg of grain. Because of decrease in content of phosphorus in soil, the crop rotations’ productivity reduction in years to come would reach 2,2 grain units (Medvedev, 2000).The task of monitoring the changes which occur in mobile forms of phosphorus and comparing the degree of their mobility in ordinary chernozems on the tilled field compared with virgin soils necessitated the relevant studies.Methods. The arable layer of soil contains 3,8–4,1 % of humus (Tyurin method), 0,22–0,23 of gross nitrogen, 0,12–0,13 of phosphorus, 2,0–2,1 % of potassium. Level of nitrate nitrogen after 7-day composting varied from 31 to 52 mg/kg of soil, mobile phosphorus (following the Chirikov method) – 110–112 mg/kg, mobile potassium – 105–130 mg/kg. Neutral reaction of soil solution (рНwater = 7,0) was observed.In order to identify the changes having occurred with mobile forms of phosphorus in ordinary chernozems under the in fluency of their long-term use in agricultural production, two soil sections were made, each of2 mdeep,3 mwide and6 mlong: the first one on the virgin soil area in the locality. and the second one at the distance of300 mfrom the first section. Starting from the upper part of sections, in each5 cmthroughout the depth, soil samples were taken for mobile form soft phosphorus which content was determined following the Chirikov acid method and Karpinsky-Zamyatina salt method.Results and discussion. Changes in the content of total phosphorus in soil on virgin soils and arable lands are found only in the upper (0-10 cm) layer – 0,164 and 0,148 %. As from the soil layer of 10–20 cm and deeper on the profile, its reserves were on the same level. Therefore, investigations were focused mainly on mobile forms of phosphorus which in most cases is a limiting factor for growth, development of plants and formation of yielding capacity of agricultural crops.Content of mobile phosphorus in cenoses of the ordinary chernozem under study is somewhat higher than the level of dynamic balance of phosphate systems of soils ‒ 0,17–0,19 mg of Р2О5/l on tilled field and 0,13–0,14 mg of Р2О5/l 10 cm layer ofvirginsoil. For the tilled field this increase is explained by availability of residual phosphates of fertilizers; itmeansitislow-fertilizedsoil. Phosphatestate of the lower horizons of both cenoses is actually the same and corresponds to the level of dynamic balance. Higher content of mobile phosphorus in the individual layers of soil (0,10–0,12 mg of Р2О5 /l) is created owing to availability of calcium carbonates. Since these compounds appear, neutral value of salt extract (рН 5,8) is shifting to alkali side, which enhances its extracting ability. Therefore, investigations carried out with the use of modern method so soil diagnostics haves how fundamentally low natural availability of phosphorus in ordinary chernozems of the Northern steppe ofUkraine which restricts obtaining highly wilds of agricultural crops. As a result, the sessile seals ore quire application phosphoric fertilizers, as the other soils ofUkraine.Conclusion. Ordinary chernozems on the loess of heavy soil grading of the Northern steppe of Ukraine contain increased amount of apatite-like compounds. Because of this, usage of any acid methods including that according to GOST 26204-91 (the Chirikov method) results in consider able artifice a lover statement of phosphate state of soils (by 40–80 mg of Р2О5/kg of soil).Actual natural provision of chernozem top soil with or dinar y phosphorus corresponds to the limit of low and medium availability of this nutrient element to plants which is confirmed by the known empirical data concerning high efficiency of phosphoric fertilizers on the assoils.