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No Tillage Preceded by Subsoiling in the Mediterranean climate area of Central Chile


Titre : No Tillage Preceded by Subsoiling in the Mediterranean climate area of Central Chile

Pays : Chili

Localisation  : Chile (’secano interior’)

Durée : 1999-2011

In the Mediterranean climate area of Central Chile, in particular the non-irrigated area ("secano interior") of central Chile (30° - 37°S), soil degradation and desertification are actually the main environmental problems. Most of these 2 million ha is occupied by a traditional agricultural system that combines livestock activities with the production of cereals. As a result of the prevailing land use systems, about two thirds of "secano interior" soils are badly eroded and soil organic matter and microbial biomass are very low in many places. The soil shows severe water erosion. 75% of the area has a slope of over 15% and most soils are moderately to severely eroded. The area has a sub-humid Mediterranean climate with an average annual precipitation of 695 mm (80% concentrated in winter), with five months of drought. Soils are Alfisols of the Cauquenes type, classified as Ultic Palexeralfs. The soil is made up of materials of granite origin with moderate acidic conditions and low organic carbon. Soil clay content is 15% between 0 and 18 cm depth, below this depth it is higher than 44%. Topography is a hillside with 10 to 20 % slope and the main traditional crop rotation is oat-wheat or wheat-natural pasture.

Subsoiling before zero tillage agriculture mitigates water erosion compared to the traditional tillage. In heavy rainfall events, zero tillage reduced soil loss by more than 72% compared to conventional tillage. In addition, the runoff coefficient during the rainy period was 70% lower with zero tillage. These results show the importance of conservation tillage and crop stubble management for decreasing erosion, especially in years when extreme rainfall events lead to a high potential for soil erosion. In relation to soil compaction comparing the resistance to penetration in the soil profile, the traditional tillage system showed a strongly compacted layer at a depth of 10 cm (>1300 kPa), which increased to over 2000 kPa at depths of 15-20 cm. In contrast, no tillage preceded by subsoiling showed less compaction, beyond 20 cm below the threshold of 2000 kPa, defined by several authors as the critical threshold for radicular growth. Moreover, cereal production showed higher biomass and grain yield. It is concluded that subsoiling before no tillage agriculture with stubble retained on the surface was the best option to mitigate soil erosion. Subsoil tillage is performed with a three-pointed 50-cm chisel, without turning the soil. Subsoiling is needed every five years to break the hard pan after soil compaction. Then crops are directly seeded without any tillage and with stubble left on the field.

The main disadvantage of the system is that the farmer requires more capital to lease machinery, which in the traditional system is done with animal traction, and the horses or oxen are from their own property. However, the improved yield covers the machinery lease costs.

The studies will contribute to the rehabilitation and development of one of the most economically depressed areas of the country, with high levels of rural poverty and degradation of the natural resources.

Résultats attendus
In particular, it is expected that appropriate technologies for the sustainable management of these fragile soils will be transferred to farmers and associations, institutions and technical staff involved in soil conservation and local governments. A concrete contribution is expected in the area of the development of production systems through the incorporation of cover crops and agroforestry systems with multi purpose trees and pastures, and the development of new crop systems and crop rotations with incorporation no tillage of cultivation systems. Besides, studying how to improve agronomic practices would allow increasing soil fertility and the productive potential of this extensive area of the country

Organismes impliqués : Instituto de Investigaciones Agropecuarias. Centro Regional de Investigación Quilamapu (INIA Quilamapu),

World Farmers Organisation

Page publiée le 15 juillet 2016, mise à jour le 6 mai 2018