Rezerve i redukcija organske materije u zemlјištu

Abstract

Uprkos četiri veka istraživanja organske materije u zemljištu, opšte prihvaćena, standardizovana definicija još uvek nedostaje (Kleber i Johnson, 2010). Organska materija u zemljištu je, nakon okeana, najveći rezervoar ugljenika na Zemlji (dvostruko veći od atmosfere i tri puta veći od biotičkog ugljenika). Time predstavlja mogućnost ublažavanja klimatskih promena izazvanih gasovima staklene bašte, od kojih je jedan CO2. Pravilnim upravljanjem zemljištem (prvenstveno u poljoprivrednoj proizvodnji) moguće je vezivanje ugljenika u organskoj materiji zemljišta, čime bi se izbegao njegov negativan uticaj u atmosferi. Iako organska materija predstavlja samo oko 5% ukupne zapremine zemljišta (kao deo čvrste faze uz mineralni deo i gasovitu i tečnu fazu zemljišta), ona predstavlja njen najaktivniji deo. Ona je od značaja za uspostavljanje optimalne strukture i vodnog, vazdušnog i toplotnog režima zemljišta (Miljković, 2005). Gubitak organske materije je prepoznat kao degradacioni proces i jedna od najozbiljnijih pretnji zemljištima u svetu (Stolte et al., 2015; Pierzynski, 2017), kao i kod nas (Vasin i sar, 2021), zbog ključne uloge koju organski materijal ima na mnoge funkcije zemljišta, kao što su proizvodnja hrane i biomasa, skladištenje i filtriranje, biološko stanište i genska baza itd.

Besides parent material, relief, time and anthropogenic influence, climate and living organisms are soil-forming factors with the most profound effect on the content of soil organic matter. Humans can contribute to soil quality improvement by humization and other soil management practices (green manuring, adequate crop rotation, sustainable soil cultivation). However, a decline in the humus content is the prevailing effect of human activity on soils. Organic matter reserves in soils of Serbia have been monitored extensively and an approximate 0.38% decline in the humus content in cultivated soils poses a threat to future agricultural production. This negative trend accelerated in the 1990s and in the first decade of the twentieth century, resulting in a 0.5% decline in soil humus content in 2011-2013. The decline in humus content depends on the soil type, and it is most dramatic in chernozem soils for several reasons: reduced organic fertilization (manuring), inadequate tillage (frequency, depth), burning or unplanned removal of crop residues, etc. Soil organic matter decline is not only directly caused by soil management practices, but also by global factors, particularly climate change. To increase the content of humus in soils, the chapter proposes other management practices besides livestock increase, such as the use of organic compost from the food industry and urban organic waste, and subsidies to farmers by the state authorities in the form of green manure, adequate mechanization and equipment for shredding and incorporation of crop residues into soils.