Soil characteristics under legume and non-legume tree canopies in signalgrass (<i>Brachiaria decumbens</i>) pastures

Abstract

Tree canopies can change soil environments. Our study looked at soils 10%, 50%, 100% and 150% the distance from tree trunk to canopy edge of leguminous sabiá (Mimosa caesalpiniifolia Benth.) and espinheiro (Machaerium aculeatum Raddi) and non-legume cajueiro (Anacardium occidentale L.) and jaqueira (Artocarpus integrifolia L.) in a signalgrass (Brachiaria decumbens Stapf) pasture. Composite soil samples were collected from the 0 to 10 cm soil layer. Clay concentration increased (P ≤ 0.05) with distance from tree trunk to full sunlight, whereas CO₂ emission, phosphorus, and organic matter from soil collected under tree canopies were inversely proportional (P ≤0.05) to distance from the tree trunk. Soil under the canopy of espinheiro had greater (P ≤ 0.05) concentrations of exchangeable cations than the non-legume trees. Pearl millet [Pennisetum americanum (L.) Leeke] grown in soils collected under tree canopies had 24% greater (P ≤ 0.05) dry matter (DM) yields than those grown in full sunlight. Soil collected under cajueiro grew 100% greater (P ≤ 0.05) pearl millet DM yields than jaqueira, whereas soil collected under sabiá produced the least (P ≤ 0.05) pearl millet DM. Tree canopy had a positive effect on soil fertility and leguminous tree canopies tended to improve soil properties more than non-legumes.

Keywords: CO₂ emission, extractable phosphorus, shade, silvopasture, soil organic matter

African Journal of Range & Forage Science 2014, 31(1): 37–42