Abstract
Intensive tillage (CT) application in Mediterranean olive orchards has threatened soil quality and led to soil degradation. No tillage with bare soil (NT+H) has been considered as an alternative practice to this management system; however, there are discrepancies in the literature on the results of the application of this practice. Our main objective was to assess the impact of continuous tillage and zero tillage on soil aggregate stability, SOC and SON stocks. The study was conducted in a Mediterranean rainfed olive grove under semi-arid conditions in a Calcaric Cambisol, for 16 years evaluating complete soil profiles (0–120 cm depth). In the long-term, the management practices CT1 and NT+H significantly affected aggregate particle size by reducing the percentage of macro-aggregates (>250 μm) and promoting a higher number of micro-aggregates (<250 μm). Nevertheless, NT+H affected the Bw and BC horizons with the increase in the large macroaggregates (>2000 μm) percentage. In relation to these results, the soil structural stability indices showed a significant decrease in both Mean Weight Diameter (MWD) and Geometric Mean Diameter (GMD) values with losses of more than 50% with respect to the initial period (CT0) in the first two horizons. In the long term, both in CT1 and in NT+H, higher SOC concentrations were found in deep horizons showing a C redistribution in depth and important losses in TN values—while, in CT0, macroaggregates contained the highest CPC values, after the long-term both management practices (CT1 and NT+H) affected the C dynamics and were characterised by higher C pool in the microaggregates than in the macroaggregate fractions. Therefore, long-term NT+H and CT1 showed an SOC storage deterioration and increased susceptibility to decomposition, CO2 emissions and fertility losses. This trend i.e., decreases in SOC stocks following NT, confirms previous studies on the subject and points to nutrient balance impacts.
Highlights
Introduction iationsThe intensification process of the agricultural farming system is a response to the world population growth and the new food consumption pattern in recent decades [1,2].In order to increase the crop productivity, a series of changes in mechanisation, the use of fertilisers and pesticides, and the establishment of mono-cropping have been implemented with the aim of maximised production [3,4]
This study focused on the particle size distribution of soil aggregates and the physical fractions of soil organic carbon (SOC), and Total Nitrogen (TN) associated with the aggregates to understand the effect of long-term management practices in a calcaric Cambisol soil under a rainfed olive orchard in semiarid conditions
When we focus our attention on the two sizes of macroaggregates separately, related to the large macroaggregates (>2000 μm), we obtained in the Ap horizon the highest percentages under collected in 2004 (CT0) with 12.9% with regard to those found in No tillage with bare soil (NT+H) (4.5%) and CT1 (4.7%)
Summary
The present study was conducted in an experimental olive farm in Torredelcampo, a municipality located in the west of the province of Jaén (Andalusia, Spain, 37◦ 460 26.000 N, 3◦ 540 41.500 W) (Figure 1). The farm where the study was carried out covers an area of 10 ha. The history of this farm is characterised by a long agricultural activity with small hills and unirrigated conventional olive trees Map of of (green colour) and Torredelcampo municipalitymunicipality (point yellow and(point black). 493.2 mm, with 27 a maximum thehistorical autumn mean and early spring months, mers an average of over °C in July. The annual precipitawhile thearea summer months493.2 are characterised a drought. The autumn and spring (2004–2020), the summer average annual of by theaexperimental areaDuring was 16.7 months, while the monthsair aretemperature characterised drought period. Riod studied (2004–2020), the average annual air temperature of the experimental area was. 16.7 °C, and the mean annual precipitation was 451.9 mm
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