Sincronismo de liberação de potássio de resíduos de Urochloa ruziziensis e sua absorção por cultivares de algodoeiro

Abstract

Potassium (K) is not associated with any organic structure, allowing it to be applied in the predecessor crop in direct seeding system. The objective of this work was to evaluate the timing of K release by Urochloa ruziziensis straw and its absorption by cotton cultivars under different managements of potassic fertilization. The experimental design was in a 2x6 factorial scheme with five replicates, consisting of two cotton cultivars, one early (FM 913GLT) and one late (FM 983GLT) and the management of K: 0 K-SB - Without K and without brachiaria; 0 K-CB - Without K and with brachiaria; 140 K in B -140 kg of K2O applied in the brachiaria; 70 K in B and 70 K in A-70 kg K2O applied in the bracharya and 70 kg of K2O in the cotton (30 DAE); - 140 K in A-SB- 70 kg of K2O at 30 DAE and 70 kg K2O at 45 DAE in cotton without brachiaria; 140 K in A-CB- 70 kg of K2O at 30 DAE and 70 kg K2O at 45 DAE in the cotton with brachiaria. Most of the potassium is released from the residues of Brachiaria (Urochloa ruziziensis) in the first 30 days after forage desiccation. There is a synchronism with the absorption by the cotton, but no effect of the cotton cultivars on the recovery of the leached potassium in the soil profile. In soils with low potassium and organic matter, the potassium dose applied to the forage species should be split in the forage and half in the cotton so that there is no significant loss of productivity. New studies should be conducted to highlight the negative effect of forage presence on cotton development and to find alternative forms of management since in light soils and with low water retention capacity the soil cover is fundamental for agricultural sustainability.