Soil acidification and liming in grassland production and grassland soil fertility in Slovenia | Zakisanje tal in apnjenje v travništvu ter rodovitnost travniških tal v Sloveniji

English. This paper reviews the evidences on grassland soil acidity and liming in relation to soil processes and herbage production. There is also an outline of the present state of soil acidity and acidity-related traits – contents of organic matter (OM), phosphorus (P) and potassium (K) in Slovene grassland. In grassland, soil acidification is an ongoing process under humid climate conditions. It is mainly driven by leaching of nutrients, net loss of cations due to retention in livestock products, use of physiologically acid fertilizers, acid rain and N2 fixation. This process is reduced by strong pH buffering capacity of the soil and by physiologically basic fertilizers. Acid grassland soils in Slovenia are widely distributed in spite of the fact that 44% of the total land has developed from a carbonate parent material. Of the 1713 grassland soil samples analysed during 2005-2007 45% were regarded as acid ones (pH < 5.5; in KCl), 57% as soils with very low P status (˂ 6 mg P2O5/100 g soil) and 22% as soils with very low K status (˂ 10 mg K2O/100 soil). Increased content of soil organic matter was identified for alpine pastures (˃ 10 % OM in 44% of samples), mainly as a result of low decomposition rate. Liming of acid grassland soils did not always reflect in a higher herbage yield. The cause for this inefficiency is plant composition of grassland. Thus, many grassland plants with relatively high production potential have adapted to acid soil conditions. To illustrate the inconsistent liming effect three researches are reviewed. In the first two researches liming along with fertilizer application did not increase the yield comparing to the fertilized control while in the third research the increase amounted 26 %. Liming improves considerably botanical composition of the acid grassland (e.g. sward where Common Bent – Agrostis tenuis Sibth. – prevails) and thus indirectly affects palatability and nutritive value of herbage. Grassland liming has a weak direct effect on herbage quality – it usually increases content of Ca and sometimes decreases Mg in herbage. The latter effect is rare. In Slovenia, ameliorative liming is advised for grassland soils with pH < 5.0 and maintenance liming for grassland soils with pH < 6.0 (pH in KCl or CaCl2).

Slovenian. Pregledni članek obravnava kislost travniških tal in apnjenje v povezavi s procesi v tleh in pridelavo travniške krme. Dodan je zgoščen prikaz kislosti ter s tem povezane vsebnosti organske snovi, fosforja in kalija v travniških tleh v Sloveniji. Zakisanje travniških tal je v vlažnem podnebju stalen proces, ki je odvisen predvsem od izpiranja hranil, negativne bilance hranil zaradi odvzema, uporabe fiziološko kislih gnojil, kislega dežja in biotske fiksacije N2. Zakisanje tal po drugi strani pomembno zmanjšujejo puferski mehanizmi v tleh in nekatera gnojila. Razširjenost kislih travniških tal v Sloveniji je velika, kljub temu, da ima 44 % zemljišč karbonatno podlago. Od 1713 vzorcev travniških tal je imelo 45 % pH vrednost pod 5,5 (v KCl), 57 % zelo malo fosforja (˂ 6 mg P2O5/100 g tal) in 22 % zelo malo kalija (˂ 10 mg K2O/100 g tal). Vsebnost organske snovi je povečana na planinskih pašnikih (˃ 10 % OS v 44 % vzorcev) predvsem zaradi slabe razgradnje. Apnjenje kislih travniških tal vedno ne poveča pridelka krme. Razlog za to je v travniških rastlinah, ki dobro prenašajo kisla tla, a imajo obenem razmeroma velik rastni potencial. V zvezi s tem so predstavljene tri raziskave, v dveh apnjenje skupaj z gnojenjem ni povečalo pridelka v primerjavi z gnojenimi kontrolami, v enem pa je pridelek povečalo za 26 %. Apnjenje pomembno izboljša botanično sestavo acidofilne travne ruše (npr. ruša s prevladujočo lasasto šopuljo – Agrostis tenuis Sibth.) in s tem posredno vpliva na okusnost in hranilno vrednost krme. Neposredni vpliv apnjenja na kakovost krme je razmeroma majhen – običajno poveča vsebnost Ca v krmi, lahko pa tudi zmanjša vsebnost Mg. Slednji vpliv je redek. Za Slovenijo stroka priporoča meliorativno apnjenje travniških tal s pH < 5,0 in vzdrževalno apnjenje tal s pH < 6,0 (pH v KCl ali CaCl2).