A complex assessment of mineral fertilizers with humic substances in an agroecosystem of acid soil
This study aimed to evaluate the impact of total humic extract (THE) and complex mineral fertilizer N 5 P 15 K 25 enriched with humic substances (HS) 0.5% on moraine loam soil properties and crop productivity. The field experiment was performed in Western Lithuania (55°43ʹ N, 21°27ʹ E) at Vėžaičiai Branch of the Lithuanian Research Centre for Agriculture and Forestry in 2015-2017. Experimental object: THE 16.5%, which contains 13.2% humic acids, 3.3% fulvic acids and 5.5% potassium oxide (K 2
... assium oxide (K 2 O), and complex mineral fertilizer N 5 P 15 K 25 enriched with HS 0.5% consisting of humic and fulvic acids. The soil of the experimental site was moraine loam Bathygleyic Dystric Glossic Retisol. The experiment included the following treatments: 1) unfertilized (control), 2) NPK + THE 20 L ha -1 , 3) NPK traditional, 4) NPK 400 kg ha -1 with HS 0.5% and 5) NPK 200 kg ha -1 with HS 0.5%. The experimental data indicated that the application of NPK + THE 20 L ha -1 or complex mineral fertilizers NPK 400 and 200 kg ha -1 with HS 0.5% additives tend to mitigate moraine loam soil acidification and to contribute more to the formation of water-stable aggregates in the topsoil compared with NPK traditional. The both rates of mineral NPK fertilizers enriched with HS 0.5% significantly (by 1.8-2.1 times) increased the content of water-soluble phosphates in the topsoil compared with unfertilized soil. The highest amount of water-extractable organic carbon and the greatest soil biological activity were determined in the soil after incorporation of 400 and 200 kg ha -1 of mineral fertilizers enriched with HS 0.5%. In terms of crop yield, soil enrichment by mineral fertilizers (400 and 200 kg ha -1 ) with HS 0.5% additives and by the NPK + THE 20 L ha -1 was superior to NPK traditional fertilization.