ORGANIC MATTER AMENDMENTS TO A SILT LOAM AND A LOAM SOIL ON 'O'NEAL' BLUEBERRY ORCHARDS IN SOUTH URUGUAY

Abstract

Highbush blueberry (Vaccinium corymbosum L. hybrids) growth is limited in South Uruguay since soils do not meet their requirements of: good drainage, low pH, and without compaction. The addition of organic matter to the soil could overcome some of these limitations. The objective of this study was to determine the effect of different organic amendments on some soil physical and chemical properties, and Higbush blueberry 'O'Neal' growth. Two trials arranged in a randomized complete block design with three replications were conducted, one in a fine silty Typic Argiudoll (trial 1), and the other one in a fine loamy Typic Argiudoll (trial 2). In trial 1, treatments were rice hull, eucalyptus sawdust and rice hull mixture, eucalyptus sawdust, and pine sawdust and pine bark mixture, at rates of 31, 36, 41, and 45 mg.ha -1 of dry matter, respectively. In trial 2, treatments were, rice hull, eucalyptus sawdust, Lithuanian peat, eucalyptus and pine sawdust mixture, and pine sawdust and pine bark mixture; at rates of 47, 61, 65, 67 and 70 mg.ha -1 of dry matter, respectively. A control without amendment was included in both trials. All amendments increased soil organic carbon and particulate organic matter as compared to the non-amended control. After 10 months of amendments application there were no differences among treatments. In trial 1, bulk density was lowered by rice hull alone or mixed with eucalyptus sawdust for the first ten months. Lithuanian peat resulted in lower pH values for the first six months, afterwards the effect dissapeared. Contrary to the excpected, pine sawdust had any acidification effect. In trial 2, all amendments improved shoot length respect to the control. Root volume exploration was almost doubled by the sawdusts mixture at 67 mg.ha -1 one year after being transplanted. Eucalyptus sawdust had no allelopathic effect, being promising for use as amendment for cultivating blueberries on mineral soils.