Soil moisture and spontaneous vegetation in different dead vegetable mulch submitted to irrigation depths

Abstract

This study evaluated the behavior of spontaneous vegetation in seedbed conditions, under different soil mulches and irrigation depths. The plant residues used as soil mulches were Gliricidia (Gliricidia sepium), Pigeon pea (Cajanus cajan), Cameroon grass (Pennisetum purpureum), and Bamboo (Bambusa vulgaris “vitata”), besides seedbed without mulches. The irrigation depths were characterized as T5, T4, T3, T2 and T1, corresponding to approximately 117%, 100%, 72%, 59% and 38% of reference evapotranspiration (ETo). Samplings were made 26, 64, 92, 124 and 152 days after the disposal of the plant residues. The main species identified were Cyperus rotundus, Commelina benghalensis, Digitaria horizontalis, Panicum maximum and shoots of previous crops. Plant residues led gravimetric moist urelevels in soil layers of 0.10 and 0.20 m on average 2% over the exposed soil. After the 92nd day, the dead mulching with legumes residues showed levels of soil moisture inferior to the one observed for grass residues. All studied dead mulches were able to reduce the total number of weeds emerged, but the relative frequencies and densities were similar. Cyperus rotundus presented in all treatments relative frequency above 50% and relative density above 70%, given that the residues of legumes had higher population densities and dry mass. The irrigation depth did not influence weeds relative frequencies, densities and dry mass, with the exception of Cyperus rotundus, both in time and the different mulches with plant residue.