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Accueil du site → Doctorat → Espagne → 2000 → INFLUENCIA DEL SISTEMA DE LABOREO Y DEL BARBECHO SOBRE LA DINAMICA DEL AGUA EN EL SUELO Y EL CRECIMIENTO DEL SISTEMA RADICULAR EN CONDICIONES DE SECANO SEMIARIDO

UNIVERSIDAD DE LLEIDA (2000)

INFLUENCIA DEL SISTEMA DE LABOREO Y DEL BARBECHO SOBRE LA DINAMICA DEL AGUA EN EL SUELO Y EL CRECIMIENTO DEL SISTEMA RADICULAR EN CONDICIONES DE SECANO SEMIARIDO

LAMPURLANES CASTEL JORGE

Titre : INFLUENCIA DEL SISTEMA DE LABOREO Y DEL BARBECHO SOBRE LA DINAMICA DEL AGUA EN EL SUELO Y EL CRECIMIENTO DEL SISTEMA RADICULAR EN CONDICIONES DE SECANO SEMIARIDO >

Auteur : LAMPURLANES CASTEL JORGE

Université de soutenance : UNIVERSIDAD DE LLEIDA

Grade : TESIS DOCTORALES 2000

Résumé
The objective of this study was to investigate the effect of tillage system and fallow on the soil physical properties related with water storage and root growth. An experiment was established in La Segarra (Lleida) in two soils of different depth. The deep soil was a Fluventic Xerocherpt of 120 cm depth, typical of valleys. The shallow soil, was a Lithic Xeric Torriorthent of 30 cm depth, and was usually found in the high platforms. The experimental plots were arranged in three strips : a central strip continuous cropped with barley and two lateral strips that alternated each year between fallow and cultivation. Three tillage systems were compared in the deep soil (subsoil tillage, minimum tillage and no-tillage or direct drill) and two in the shallow soil (minimum tillage and no-tillage). Water content in the soil, root length density and biomass were determined at meaningful crop development stages. Yield was determined at the end of the crop cycle. Bulk density, penetration resistance, hydraulic conductivity at different potentials, percent of soil covered by residues and surface roughness were also determined. In the continuous cropped strip of the deep soil, no-tillage system maintained the soil wettest and allowed a more active growth of the root system than the subsoil or the minimum tillage systems. The mean yields were greater under no-tillage (3605 kg ha -1 ) or minimum tillage (3508 kg ha -1 ) that when subsoiler was used (3371 kg ha -1 ). In the shallow soil the results depended on the year though there were not differences between tillage systems in mean yield (1867 kg ha -1 for no-tillage and 1806 kg ha -1 for minimum tillage). The fallow efficiency for water accumulation did not surpass 18% in the deep soil and 7% in the shallow soil. During the July to February period, the fallow without tillage showed a greater efficiency that the tilled fallow. In the February to October fallow period no-tillage showed the lowest efficiency. Mean yield increase by the use of fallow was 128 kg ha -1 in the deep soil and 371 kg ha -1 in the shallow soil. Bulk density was greater in no-tillage (1.34 Mg m -3 ) that in minimum (1.27 Mg m -3 ) or subsoil (1.22 Mg m -3 ) tillage systems, but did not reach limiting levels for root growth. Penetration resistance reached values greater than 2 MPa in all tillage systems, especially under no-tillage, but this was not reflected in a worse root growth. Fallow contributed to reduce penetration resistance even in the no-tillage treatment. In the first years after tillage suppression hydraulic conductivity of the no-tilled soil was reduced with respect to that of the tilled one (5 vs. 15 cm day -1 ). This effect was counteracted by a greater percent of soil surface covered by residues under no-tillage, giving as a result a greater water accumulation in this system. During the fallow the quantity of residues covering the soil reduced drastically from February to the sowing of the following crop, leaving the soil insufficiently protected against summer evaporation. No-tillage (or direct drilling) is a valid alternative for the semi-arid rainfed cropping systems in the Mediterranean area. No-tillage increases the quantity of available water for the crop, favours root growth, and yields obtained are similar or superior to that obtained when tillage is accomplished. Initial damage of the soil physical properties (bulk density, penetration resistance, hydraulic conductivity) observed in this system is recovered in a few years. Fallow increases water availability for the crop in deep soils and increases yield of the next crop but does not compensate the year without production. The potentially better system of performing fallow is no-tillage. Nevertheless, this system should be combined with an only superficial pass of cultivator when the quantity of residues that cover the soil descends below of the optimum level for water and soil conservation. Fallow improves soil physical properties, consequently it may be interesting to accelerate the recovery of the soil in the first years after no-tillage introduction

Mots clés : CIENCIAS DE LA TIERRA Y DEL ESPACIO ; EDAFOLOGIA ; FISICA DE SUELOS ; CIENCIAS AGRARIAS ; AGRONOMIA ; PRODUCCION DE CULTIVOS ; COMPORTAMIENTO DEL SUELO EN CULTIVOS ROTATORIOS ;

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