Efecto de mejoradores físicos, químicos y biológicos de la compactación de suelos bananeros bajo sistemas de riego

Abstract

Compaction, considered as the hidden enemy of the farmer, causes soil degradation, since it results in a loss of soil porosity and the hardening of upper soil horizons. The general objective of this work was to analyze soil compaction under pressurized irrigation systems, and the effectiveness of physical, chemical and biological treatments to ameliorate soils condition in Machala city, Ecuador. The study was conducted from May 2015 to April 2017 on three farms with subfoliate and suprafoliar irrigation systems. A total number of 360 soil samples were collected and analyzed. In each irrigation system, the tested treatments were: control, gypsum applied on soil surface, tilling, and the establishment of a vegetation cover. Organic matter content and several physical properties, including specific surface (SS), were measured and correlated with moisture contents at low water potentials of the retention curve. Moisture content was measured using frequency domain reflectometry (FDR) probes; optimal hydric interval (OHI) was determined at 5 levels of compaction with bulk densities of 1.1; 1.2; 1.3; 1.4; and 1.5 g cm-³. Laboratory compaction tests were used to determine soil critical density (SCD) and optimal water content, which showed that soils resistant to compaction had compaction curves with low slope. Water retention curves (WRC) were determined using Richards apparatus. Penetration resistance was lower after the different treatments, probably due to their ameliorating effect on soil structure or by the effect of precipitation. The evolution of infiltration rate (irrigation rate 12.7 mm.h‾¹˃ soil infiltration rate 2.8mm.h-¹) suggests that suprafoliar irrigation tends to produce soil sealing and crusting in the upper layers. Uniformity coefficient (CU), distribution of uniformity (DU) and coefficient of variation (CV) of applied irrigation showed high variability, indicating a poor distribution of water. Thickness of water drops (3.5) was considered as very big in the suprafoliar irrigation system. Structural stability index (<5), and crusting index (1.96) indicated that these soils are degraded soils or at risk of degradation. The most effective treatment to alleviate soil compaction was tilling (506,9KPa), followed by gypsum (554,7KPa), whose effect was evidenced after 90 days, and finally the establishment of a vegetable cover (790,5KPa). Key words: compaction, tilling, frequency domain reflectometry (FDR), sealing, crusting, optimum water interval (IHO), critical soil density (DSC).