Efeitos de sistemas de preparo do solo na erosão e na produtividade da acácia-negra (Acacia mearnsii De Wild.)

Abstract

Black wattle plantations are not always settled in soils adequate for the species sometimes due to land value or due to industry distance. Different soil tillage systems can improve soil conditions to plant growth, avoid erosion problems and reduce costs. In areas belonging to TANAGRO S.A. e SETA S.A., in two different counties, Piratini and Butiá, RS, and two distinct soil types – litholic and red yellow podzolic – soil tillage systems with different levels of soil disturbance were tested in growing black wattle: planting in holes with no-tillage and planting after subsoiling with two, three and five shranks and harrowings. Plant height and DBH were taken annually, and after seven years samples of the trunk were obtained at six different positions for specific gravity analyses. Soils were characterized chemically and physically on their surface layers. Soil losses were greater where soil was prepared with a five-shrank-subsoiler, and they were measurable until 18 months after planting. These soil losses are very important for sustainable production of the litholic soil, constituted in around 80% of stones. Reduced tillage system, with planting holes opened manually and mechanically, did not decrease black wattle growth on both soils studied. However, plant growth increment at the initial stage was smaller on reduced tillage system, and this difference to the other tillage systems tested remained until 24 months after planting.