Potassium leaching from black oat and pearl millet straw after chemical desiccation

Abstract

Potassium leaching from black oat (Avena strigosa) and pearl millet (Pennisetum glaucum) straw as affected by simulated rainfall at different moments after chemical desiccation was evaluated. Cover crops were grown in pots, in Botucatu, State of São Paulo, Brazil. Fifty days after emergence, plants were sprayed with herbicide. Three, 6, 9 and 15 days after the desiccation the straw received simulated rains corresponding to 5 and 10 mm, considering a mulch of 8 t ha^-1. The amount of K leached from plant residues increased after the desiccation. Fifteen days after the desiccation, a rainfall of 10 mm leached 11.1 kg ha^-1 of K. The higher potential of black oat straw to leach K was observed with 10 mm of rain. The amount of K released by rains from black oat straw is greater from the pearl millet with 5 and 10 mm, and this difference increases according to the loss of water of the tissues.