PRE-COMPACTION AND ORGANIC CONDITIONING FOR THE RECULTIVATION OF A COARSE-TEXTURED SOIL (TYPIC XEROCHREPTS) DISTURBED BY SAND EXTRACTION

Abstract

Subsoil extraction of subsurface sandy layers causes damages to soil structure, decreasing its loading capacity. A study was conducted in central Chile in order to reclaim an agricultural soil (Typic Xerochrepts, sandy loam) disturbed by subsurface sand mining. The study was conducted in pots of 20 L, and treatments with two factors were established: pre-compaction (without and with two increasing levels), and the addition of organic amendment (broiler litter in doses of 0, 15, 30 and 60 Mg ha-1). The effect of the treatments was evaluated on soil physical properties (bulk density, pore size distribution, mechanical strength, aggregate stability and water repellency), dry matter yield and pod production of green beans (Phaseolus vulgaris L.). The replenishment of soil after the
extraction of subsurface sand generated a condition of high coarse porosity, low water retention and low loading capacity. The combination of the organic amendment in doses lower than 30 Mg ha-1 and the absence of pre-compaction promoted excessive soil settlement, decreasing the macroporosity and increasing the mechanical strength. However, pre-compaction until reaching levels of bulk density between 1.05 and 1.15 Mg m-3 and the amendment dose between 15 and 30 Mg ha-1, promoted the best physical soil conditions, resulting in a high aggregate stability, and maximum dry matter production and yield of commercial pods.